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Factors Affecting The Establishment And Maintenance Of An Organic Production Unit

2010

Organic Training College

of Aotearoa New Zealand

© Telford Rural Polytechnic US 21043 The Principles Of Organic Horticultural Production

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Telford Rural Polytechnic Te Whare Wanaka O Puerua

© Telford Rural Polytechnic All rights reserved. Telford Rural Polytechnic (TRP) is the owner of the copyright in this publication. Other than as permitted by the Copyright Act 1994, no part of this publication may be reproduced, copied, or transmitted in any other form, or by any other means, without the prior written permission of Telford Rural Polytechnic, Private Bag 6, Balclutha, New Zealand.

DISCLAIMER: Telford Rural Polytechnic –

Is not responsible for the results of any actions or in-actions occurring on the basis of information

supplied, nor for any omissions or errors.

While referring learners to manufacturer‟s websites, or to other resource material from specific suppliers (e.g. information pamphlets) - for reading, viewing photos or other research - is doing so in order to enhance learners‟ knowledge and awareness. Such references are not an endorsement for any particular service or product, nor are they intended to direct learners away from other services or products of a similar nature.


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Contents

Introduction ................................................................................................................................... 5

Suggested Reading .................................................................................................................... 6

Books ...................................................................................................................................... 6

Journals And Magazines ......................................................................................................... 6

Industry Websites ................................................................................................................... 6

Factors Affecting The Establishment And Maintenance Of An Organic Production Unit ....... 7

Reading ...................................................................................................................................... 7

The Relationship Between Physical Site And Crop Selection ...................................................... 7

Climate........................................................................................................................................ 7

Readings ................................................................................................................................. 8

Aspect ......................................................................................................................................... 8

Distance To Markets ................................................................................................................... 9

Past Land Use ............................................................................................................................ 9

Surrounding Land Use ................................................................................................................ 9

Other Organic Growers ......................................................................................................... 10

Boundary Integrity ..................................................................................................................... 10

Buffer Zone ........................................................................................................................... 10

Existing Buildings ...................................................................................................................... 11

Treated Timber ..................................................................................................................... 11

Irrigation Source ....................................................................................................................... 11

Sustainable Water Use ......................................................................................................... 11

Water Quality ........................................................................................................................ 11

Soil Fertility ............................................................................................................................... 12

Chemical Residue In The Soil ................................................................................................... 12

Review 1 ...................................................................................................................................... 13

The Important Elements In Successful Planning Of Organic Horticulture Production

Systems ....................................................................................................................................... 14

Biological Diversity .................................................................................................................... 14

Biodiversity................................................................................................................................ 14

Reading ................................................................................................................................ 15

Ecosystem Balance And Stability .............................................................................................. 17

Reading ................................................................................................................................ 17

Sustainable Use Of Energy ....................................................................................................... 18

Organic Horticulture Emphasizes Sustainable Energy Use ................................................... 18

Soil Protection ........................................................................................................................... 19

Fertility Management................................................................................................................. 19


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Planning For Soil Fertility ...................................................................................................... 19

Planning For Micronutrient Availability....................................................................................... 20

Soil pH And Fertility ............................................................................................................... 20

Integrated Pest And Disease Management ............................................................................... 21

Annual Crop Rotation ................................................................................................................ 21

Reading ................................................................................................................................ 21

Crop Selection .......................................................................................................................... 22

Crop Performance Monitoring ................................................................................................... 23

Review 2 ...................................................................................................................................... 24

The Importance Of Monitoring In The Management Of An Organic Horticultural Production

System ......................................................................................................................................... 25

Pest And Disease Management ................................................................................................ 25

Decision-Making ....................................................................................................................... 25

Corrective Action ....................................................................................................................... 25

Crop Performance..................................................................................................................... 25

Reading ................................................................................................................................ 26

Review 3 ...................................................................................................................................... 27

Glossary ...................................................................................................................................... 28

Answers To Review Questions .................................................................................................. 28


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Introduction

Organic horticulture produces healthy, high quality food in an ecologically responsible, sustainable

way.

Organic growing systems work with nature to avoid the need for agrochemicals and to minimise

damage to the environment and wildlife. Organic growers utilize sustainable soil and crop

management practices to maintain optimum fertility and biological activity in the system, with

particular emphasis on soil health.

Organic growers view biodiversity in the cropping area and wider environment as vital to crop

health and this is enhanced by encouraging wildlife, planting a wide range of plants, and applying

crop rotation. Biodiversity helps to maintain stable populations of natural predators, preventing

pests and diseases from reaching damaging levels.

On completing this learning programme you should be able to:

Demonstrate knowledge of planning requirements for establishment and maintenance of

an organic horticulture production system.


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Suggested Reading

Books

Australia and New Zealand Organic Gardening

Bennett, Peter

5th Edition

Brookvale, NSW

National Book distributors 1991

The New Zealand Organic Gardening year: a month-by-month guide for vegetables and flowers

Jonathan Spade; illustrated by Ulco Glimmerveen.

Spade, Jonathan

Glimmerveen, Ulco

Auckland [N.Z.]: Collins New Zealand, 1989.

The New Zealand Organic Gardening Handbook

Little, Brenda

Auckland, N.Z.: Reed Books, 2000.

Organic Gardening for New Zealand Gardeners

McLeod, Judyth

Auckland, N.Z.: Random House, 2004.

Rodale's All-New Encyclopedia of Organic Gardening: the indispensable resource for every

gardener

Edited by Fern Marshall Bradley and Barbara W. Ellis.

Emmaus, Pa: Rodale Press; [New York]: Distributed by St. Martin's, c1992

Journals And Magazines

Soil & Health Association of NZ Inc publishes Organic NZ six times a year. The magazine covers

organic growing and other issues including genetic engineering.

Industry Websites

This learning programme may refer the learner to industry websites for the purpose of research.

Please read the disclaimer carefully before continuing.


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Factors Affecting The Establishment And Maintenance Of An

Organic Production Unit

Why is there such a great emphasis on planning an organic system? As we will see, growers must

build solutions to nutrition and pest and disease control into their system to ensure that it is a

resilient ecology, which is not vulnerable to changes from outside. This does differ from a

conventional horticulture system where the grower has greater options for intervention when

problems arise. The following section outlines the important factors to take into account when

setting up an organic growing unit.

Reading

Read the article Closing the Circle from ORGANICNZ Jan-Feb 2008 about the establishment of an

organic market garden in Canterbury.

The Relationship Between Physical Site And Crop Selection

One of the fundamentals of organic growing is the choice of „the right plants in the right place‟.

More interventions are required when growing a crop that is not well suited to its site or region.

For example, pip fruit require a free draining soil to thrive. Heavy soils can be improved by ripping,

drainage or by planting the trees on mounds to improve drainage. However, the trees will be less

vigorous that those planted on freely draining soils. For organic growers, this is a significant

drawback.

When growers or farmers are converting to organic growing, there are risks of lower yields during

the transitional phase, which is two to three years. During this time, while soil biological processes

are building up, the grower relies on good planning and management to make the system work

without depending on chemical remedies. Aspect, rainfall and soil type cannot be changed while

energy systems; soil organic matter and biodiversity can be managed.

Climate

Climate is important in relation to organic growing for the following reasons:

Many crops have distinct requirements, for example capsicums and eggplants require long

hot summers while carrots prefer cool soil temperatures and peonies require winter chilling.

A favorable climate is important for the crop because a humid, wet weather pattern which

increases fungal diseases, to which the crop is susceptible, will place greater stress on the

system as the grower works to manage the diseases.


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Readings

These two extracts are from Costs and Risks of Conversion to Organic Kiwifruit and Apple

Systems by the Ministry of Agriculture and Fisheries (http://www.maf.govt.nz/mafnet/rural-

nz/sustainable-resource-use/organic-production)

They highlight the relationship between the climate and organic growing

Costs and Risks of Conversion to Organic Kiwifruit and Apple Systems

Kiwifruit

Since the early 1990s conventional kiwifruit growers have been able to overcome problems of

biennial bearing and lack of winter chilling by using a budburst enhancing product, hydrogen

cyanamide. Organic producers cannot use this product. Consequently, organic producers are

more subject to the vagaries of nature. That is, yields in one year are more heavily affected by

previous crop yields and the nature of winter and spring conditions. The use of hydrogen

cyanamide, because it extends the growing season, also has a positive impact on fruit size and

hence on reject rates. Generally, fruit less than 79gm in size is unable to be exported and is

rejected from the export crop. Organic growers tend to have lower fruit numbers and smaller fruit

size which reduces their marketable yield.

Apples

In Nelson, disease management was considered a major impediment to successful organic

production. This is due to the higher rainfall that occurs in Nelson creating a better environment for

fungal development.

Aspect

The aspect of a site describes the direction it faces. In the southern hemisphere, north-facing sites

have benefits over south facing sites. This is because they are faster to warm up in spring and

receive more sunlight during winter than south facing sites.

The aspect also influences the movement of surface water. The water and airflow patterns

of the land can affect the humidity levels, which in turn influence disease levels.

West facing sites experience the full heat of the sun in the afternoon.

A crop will mature faster and earlier if planted on a sunny north-facing site. There may also

be fewer disease problems caused by cold soil.

If the slope is significant, thought needs to given to the practicalities of planting and

harvesting safely.


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Distance To Markets

Access to the market is of prime consideration. Establishing an economically viable growing unit is

easier if it is close to the market.

This could mean proximity to any of the following:

Pack house and cool store.

Airport or port for exporters.

Supermarket or restaurant.

Farmer‟s market for small-scale growers.

Processing plant if the crop is grown for processing. For example wine grapes or process

tomatoes.

Transport costs are a factor in the crop costs and savings are made if the grower is close to the

market.

Past Land Use

Part of the process of applying for organic certification is examining the land use history of the site.

Some types of land use have a strong impact on the soil and environment of the site. The types of

uses, which are significant, are intensive factory farming such as Piggeries. Intensive farming

practices use antibiotics, broad-spectrum drenches and other animal pharmaceuticals, which are

not permitted in organic growing systems. Caged poultry is another intensive farming practice,

which may include the use of antibiotics, growth hormones and genetically modified feed. None of

these substances are permitted in organic growing systems.

Genetically modified crops such as sweet corn. Growing organic sweet corn on the site risks corn

volunteers (self sown) from the previous crop contaminating the organically grown crop. As the

genetically modified corn seeds may survive in the soil for more than a year, this risk would affect

the length of time the grower would take to become certified organic. Converting the property to an

unrelated crop such as grapes or olives may reduce the time required to convert to organic

certification.

Conventional orchard or vegetable growing where agrichemicals have been stored mixed and

used on the property. Soil tests are taken to identify where the highest levels of contamination are.

In areas of heavy contaminations, the soil may need to be removed or not used for any kind of

cropping.

Surrounding Land Use

What the neighbours are growing and how they are growing has an impact on an organic unit.

Conventional intensive farming and growing systems are heavily reliant on agrichemicals and

animals medicines, which are not permitted in organic growing. If these farming activities are close

to the organic unit, a wide buffer zone, planted in shelter species or native trees and shrubs can

mitigate some of the adverse effects of this land use.


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Risks include spray drift and surface runoff of fertiliser and animal effluent contaminated with

antibiotics and agrichemicals contaminating the soil or groundwater.

Other Organic Growers

Groups of organic growers in a neighbourhood sometimes work together to create a shared buffer

zone with their non-organic neighbours.

Boundary Integrity

The organic grower must maintain organic standards at all times.

Organic certifiers require that the organic property has:

„Distinct, defined boundaries and buffer zones such as runoff diversions to prevent the unintended

application of a prohibited substance to the crop or contact with a prohibited substance applied to

adjoining land that is not under organic management.

The handler of an organic handling operation must implement measures necessary to prevent the

commingling of organic and non-organic products and protect organic products from contact with

prohibited substances „

(Source New Zealand Food Safety Authority Technical Rules for Organic Production)

Should the property become contaminated with a substance which is not permitted, the grower‟s

produce may be rejected from export markets or even lose certification.

There are several aspects to boundary integrity, for example:

Will the neighbour‟s stock be able to wander in?

Does the property share a driveway or water supply with a conventional property?

Is the property adequately fenced?

Are there adequate shelterbelts on the organic farm?

Properties are not always in neat square parcels with one simple boundary. If a property is divided

up into several parcels, for example, which are spread around a neighbourhood, there is a very

large boundary. The boundary with conventional land use still has to be maintained. In cases

where the produce, implements or other growing material are moved about between parcels of

land, there is a risk of contamination when transiting through conventionally farmed properties. A

single parcel of land is more straightforward in terms of organic growing.

Buffer Zone

On an organic property you can protect the boundaries by putting in a living fence and a border

area of around 10 meters deep, which together creates a buffer zone. You can see that an

organic property does require more land to meet this requirement, and it is land, which is not in

production, so no income can be directly derived from the buffer zone. If the boundaries of the

property have the best land for growing this may represent a significant loss to the grower. A well-

designed living fence does have benefits to the grower, however. The shelterbelt can be part of an

integrated pest management system and even provide timber, honey and stock forage as well as

sheltering the crop.


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Existing Buildings

A horticulture property needs buildings, and what type and how many is largely determined by the

crop being grown.

Any of the following buildings may be required:

Implement sheds.

Greenhouses either plastic or glass.

Shadehouse.

Packhouse.

Coolstorage.

Storage for growing media, compost ingredients, seed.

Treated Timber

Any building or structure, which is in direct contact with the crop at any stage, must be constructed

from untreated timber. This includes climbing structures and crop supports, cold frames and raised

beds.

Irrigation Source

Water is set to become the main limiting factor in horticulture as land use intensifies and dairy

conversions increase in New Zealand.

Sustainable Water Use

Organic production relies on sustainable water use. This means water use, which can continue

without depleting the resource for future generations. Crops requiring high water inputs are not

suitable for areas where water is in short supply.

Water Quality

The water for organic growing must be free from contaminants such as pesticides or fertiliser

residues.

Water sources include:

Rainwater.

Bore water.

Town supply (which may or may not be metered).

Practices like water harvesting and recycling as an integral part of daily operations increases the

amount of water available.


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Soil Fertility

Many organic growers report that maintaining soil fertility is one of their biggest challenges. Soil

fertility is the ability of a soil to supply the essential plant nutrients. It is estimated that just over 5

percent of New Zealand„s soils are ideally suited to horticulture. These are soils that are young

and not yet depleted by leaching, or are rich organic peat soils.

Poor soils include those that are dry (arid), acid, wet, thin and unstable, or very old and leached.

Taking a look at the crops growing and stock carried in the neighbourhood is a good indication of

the soil fertility.

The store and availability of nutrients in the soil is called the Cation Exchange Capacity or CEC,

which is measured in a laboratory test.

Chemical Residue In The Soil

Chemical residues in the soil from previous farming or horticulture activities on the properties are

identified by a soil test. The more intensive the previous uses, the higher the levels of residues,

which may include heavy metals, pesticides and herbicides or asbestos. The transition period into

organic certification is designed to allow for low-level chemical residues to be deactivated by the

soil microorganisms. Where there is a major contamination problem, specialist remediation work is

essential.


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Review 1

1 Give two reasons why a grower or potential grower is careful in selecting a site to grow an

organic crop.

2 What is a buffer zone?

3 On an organically certified property, the implement shed can be made of treated timber -

true or false? Explain your answer.

4 What activities can cause contamination of the soil?

5 How could the activities of neighbouring farmers or growers affect an organic production

unit?

Give two examples.


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The Important Elements In Successful Planning Of Organic

Horticulture Production Systems

The production system, or the way that you are going to produce a crop, takes careful planning as

part of the wider crop ecology. Organic growing involves planning and managing a cultivated

ecology where problems are kept from breaking out by a network of interrelationships similar to

those of a natural ecosystem. Disease control, for example is managed by strategies such as

companion planting, which cannot be implemented when the disease appears, rather, the

companion planting and other strategies are built into the production system from the beginning.

Such systems take time and careful planning. We can identify the important elements of the

organic horticulture production systems.

Biological Diversity

A 1997 study by Massey University economists suggested that the total annual value provided by

New Zealand‟s native biodiversity to the country‟s economy could be more than twice the value of

our gross domestic product. They estimated the annual value of native biodiversity on land in 1994

at $46 billion, and valued marine ecosystem services at $184 billion – a total of $230 billion a year.

By comparison, New Zealand‟s gross domestic product that year was $84 billion.

(Source - Biodiversity New Zealand (biodiversity.govt.nz))

Biodiversity

Biodiversity includes the whole range of life on earth and in the sea, from single celled bacteria to

plants and animals. Not all of these living things are grown as crops or farm animals, so - how

come they are so important?

Apart from its intrinsic worth, the biodiversity within healthy ecosystems provide „environmental

services‟ including the production of raw materials (timber, seafood), clean water, decomposition

of wastes and recycling of nutrients, the creation and maintenance of soils, pollination by insects

and birds and the regulation of local weather patterns. Healthy ecosystems can also play a

positive role in reducing the effects of climate change through their ability to absorb carbon

dioxide.


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The layout of this property includes a pond and woodlot.

As an ecosystem in its own right, the organic production unit needs biological diversity to

achieve balance between pests, diseases and their antagonists (enemies), recycle

nutrients, aerate the soil and pollinate crops, to name just a few environmental services.

A monoculture (a crop of all one species) lacks this diversity and as a system has a much

lower natural resilience to pest and disease attack.

Biodiversity is promoted within the system by having more types of organisms and more

types of places for them to live. For example, shade trees and green manure crops provide

flowers (for food) and living spaces for useful natural enemies. Even mulch can provide

living space for natural enemies like spiders and ground beetles.

Organic systems recognize the importance of diversity within each crop species by growing

from open pollinated seeds, seed saving and growing local heritage varieties. This

preserves the biodiversity within individual species, an important strategy for maintaining a

diverse gene pool, which can buffer the crop against environmental change.

Reading

This article is from the website of Organic Inform (www.organicinform.org) at Elm Farm, England.

http://www.organicinform.org/


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24 July 2007

Organic farming restores biodiversity

A new study suggests that the harmful effects of intensive cropping on weed community

composition can be restored through organic conversion.

The research was conducted in Finland, using the results of two extensive weed surveys of spring

cereals collected in the 1960s and 1990s. The study included 131 organically cropped fields,

comprising fields from the 1960s, which had not been treated with herbicides in the preceding ten

years. These fields had then been treated with herbicides in the intervening period before

undergoing organic conversion in the 1990s. On average, the farms involved in the study had

practiced organic farming for 4.5 years.

The results suggest that the frequency of weed occurrence in the period had fallen in eight

species; risen in 19 species; remained the same in 11 species; and disappeared completely in 3

species. These different patterns suggest that different species have diverging recovery abilities.

Organic cropping was found to be most beneficial for species that benefited from conventional

inputs before conversion, and relaxation of weed control measures following conversion. However,

features of those species that did not restore with conversion included preference for low nitrogen,

grassland dominated crop rotations and susceptibility to herbicides.

The research suggests that organic cropping is beneficial for biodiversity, “at a general level”

(p388). However, in terms of promoting biodiversity through bird populations, the availability of

seed-food for birds on organically cropped farms has actually declined within the period. This

suggests that whilst organic cropping can help to restore biodiversity, the recovery period differs

between species, including species important for the diets of farmland birds.

Planning biodiversity involves incorporating as many species as possible into the production unit.

This involves;

Mixed species shelter.

Intercropping.

Companion planting.

Using groundcovers.

Native forest restoration where possible on the farm.

Encouraging a variety of habitats like wetlands and stream margins where different species

will find a home.


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Wild borage attracts and feeds bees, although in many regions it is a pest plant.

Ecosystem Balance And Stability

A balanced ecosystem is stable over time and is the best insurance against external changes such

as an influx of a pest or poor weather. The balanced ecosystem is also complex, with an intricate

food web, maintaining a flow of nutrients from plants to animals and back to the soil via

decomposers. The stability of the unit or garden ecosystem is the main defence the system has

against adverse conditions such as pest attack, or adverse weather events. The organic growing

unit is based on systems and management, which promote and enhance these beneficial

processes and interactions, just as they would happen in natural ecosystems. The stability is built

up on the inside of the system, rather than external controls like herbicides and pesticides. The

grower‟ chooses inputs which work as far as possible with natural cycles rather than trying to

control or disrupt them.

Organic farms and gardens have been shown to have a higher level of species diversity and

ecosystem complexity than conventional farms.

Planning for stability involves:

Managing external inputs carefully so that the system is not destabilised.

Introducing changes gradually.

Working as much as possible with what is already on the property.

Reading

Go to the website of the Biological Husbandry Unit and follow the links to the page listing manuals

from past workshops held by the Unit. www.bhu.co.nz/manuals.html

Read the manual “Resilient Farm Design”.

Many of the points addressing farming are also relevant to horticulture.

http://www.bhu.co.nz/manuals.html


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Answer the following questions.

1 Look at the table on pages 2 and 3. What is a system design approach to weed control?

Fast nutrient availability?

2 What are three benefits, which a well-designed shelterbelt can provide?

3 Which native plants can be planted in a beetle bank?

Sustainable Use Of Energy

'Sustainable energy' means the sourcing, transformation, use and management of energy in a

manner, which improves social well-being, while conserving physical resources, maintaining the

integrity of ecosystems, and avoiding the transfer of costs onto future generations.

Organic Horticulture Emphasizes Sustainable Energy Use

This means identifying where and how energy is used, for example glasshouses, irrigation and on-

farm packing and processing, and implementing energy efficiency strategies.

There can be opportunities on farms and orchards to produce energy from wastes, whether as

biogas from crop wastes, or electricity from small turbines on irrigation channels.

Planning for sustainable energy use includes:

Carrying out an energy audit of the production unit including buildings and vehicle use.

Considering energy efficiency when purchasing machinery or equipment.

Maintaining existing machinery at its optimum level of efficiency (regular tuning, oil and

filter changes).


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Investigating alternative energy sources such as solar heated water for cleaning.

Soil Protection

A living soil is the engine room of organic crop production. The millions of organisms in the soil,

from microbes to mites and millipedes, work on organic matter to release nutrients for plants to

use. Most of this activity takes place in the topsoil, the top 30cm of the soil. This is because the

soil is warmer and contains more oxygen near the surface. This fragile living layer is easily blown

or washed away by wind and rain. Extremes of temperature right at the surface will result in a

lower level of activity by microorganisms, which in turn decreases the rate of nutrient cycling and

soil structure improvement.

Planning for soil protection includes:

Avoiding synthetic fertilizers that depress microbial action.

Protecting the soil surface with mulches, green manures and crop cover.

Feeding the soil life with the raw materials for humus production.

Using crop rotations to replenish the soil.

Tillage of topsoil only, to avoid mixing topsoil and subsoil.

Cropping at optimal rather that maximum densities.

Fertility Management

The soil nutrients in organic production are supplied by the breakdown of organic matter in the

soil. The soil life ((fungi, bacteria and invertebrates) release the nutrients that plants need from

organic matter in the soil.

The plant macro nutrients are nitrogen, phosphorus, and potassium, sulfur, calcium, and

magnesium. The plant micronutrients include iron, zinc, manganese, copper, boron, chlorine, and

molybdenum.

You can see from this that managing the fertility of the soil is not a simple matter of supplying the

nutrients; rather, it is an on going process of creating and maintaining a soil environment where

efficient breakdown and nutrient release can happen. You must plan to have a ready year round

supply of compost, manure and other soil amendments that are permitted in organic production.

The grower supplies the raw materials as green manure crops, composts and manures, while

caring for the soil life by keeping the soil surface protected from erosion and temperature and

maintaining the above and below ground food web, which keeps up a flow of nutrients from plants

to animals and back to the soil again.

Planning For Soil Fertility

Cropping removes nutrients from the soil, which need to be replenished. Planning for nutrient

involves putting strategies in place including green manure crop, rotation, cover cropping and the

addition of organic approved manures and fertilizers:


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Nitrogen: The most common sources of nitrogen are from animal manure, either

composted or raw, and green manures in the form of legumes that fix nitrogen from the

atmosphere. Additional sources of nitrogen include blood meal, fish emulsion, fish protein,

kelp and seaweed.

Phosphorus: Sources include manure, bone meal, fish and poultry meal, and rock

phosphate.

Potassium: Sources include manure, alfalfa meal, kelp, wood ash, and granite dust.

Calcium: It is generally supplied through lime applications used to adjust acidic soils.

Sources include dolomite lime that also contains magnesium. Other sources include bone

meal, gypsum, and wood ashes.

Magnesium: Sources: Dolomite lime.

Dolomite lime

Planning For Micronutrient Availability

The grower can grow plants (some of these are weeds!), which are accumulators of trace

elements. The accumulator plants are then returned to the soil as mulches or composts for

the soil life to work on.

Deep rooting plants work in a similar way in that they extract minerals from deeper in the

soil profile, some of which are trace elements.

Keeping the soil at optimal pH levels frees up trace elements, which are unavailable at high

or low pH.

Maintaining good soil organic matter levels makes places available within the soil for the

trace elements to be held, available for plant use.

Soil pH And Fertility

It is important to manage the pH of the soil since it can affect the plant‟s ability to take up nutrients

and the microbial activity in the soil that affects the processes needed for plant nutrition.


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Integrated Pest And Disease Management

Planning for the integrated pest management on a new production unit is closely linked to the

planning for biodiversity.

The strategies include:

Growing healthy plants, which are well suited to the site. Stressed plants are more likely to

succumb to pest and diseases. Plan for some losses. It‟s wise to remove plants, which are

not thriving. Avoiding over feeding or over watering which produces weak watery growth

which is more susceptible to pest and disease attack.

Planning a diverse cropping regime to encourage a wide range of garden life. This can

include companion planting and intercropping.

Encourage the right predators to be on the property at the right time. They need a habitat

and a food source for all life cycle stages. This can include growing predator attractive

plants like phacelia, marigold, sweet alyssum and dill, all year round.

Landscaping the cropping area to include a pond, wetland, rocks and stones and if

possible native plants in a natural community. Such „refuges‟ attract and nurture the type of

insects and spiders, which are not attracted by the crop plants alone.

Research which pest and diseases are most likely in the areas where you are growing. There will

be some sprays and oils, which are permitted for limited use in the event of an outbreak

Annual Crop Rotation

Growing the same crop in the same place year after year leads to serious pest, disease and weed

problems. The soil also becomes depleted and its structure suffers from being cultivated at the

same depth season after season. To overcome this problem, growers adopt a four to five year

rotation cycle, planting different crop each season.

Crop rotation is an important tool for maintaining a healthy soil. Specific rotation systems vary, but

all are based on the principle of following a deep rooting crop with a shallow rooting one, and

including a nitrogen fixing legume such as beans in the rotation. To reduce specific crop diseases,

a minimum of two to three years must elapse before the same crop is grown again.

Planning for crop rotation involves advance planning and selecting the crops for the rotation. One

of the rotations may be a green manure crop, which is dug in, or a fallow year where the land is

allowed to revert to pasture. As neither of these last two rotations result in a saleable harvest,

allowance must be made for this in the long-term financial plan.

Reading

Go to the website of the Biological Husbandry Unit and follow the links to the page listing manuals

from past workshops held by the Unit. www.bhu.co.nz/manuals.html

http://www.bhu.co.nz/manuals.html


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Read the manual “Rotation Design” then answer the following questions.

1 What is soil sickness?

2 What is the effect of continuous cropping on the soil structure? (P7)

3 Rotation design. What is a good alternative to a pasture phase?

Crop Selection

The crop is determined largely by the site and region. As we saw, it is not sustainable to grow

commercial crops, which are difficult to grow organically. Disease and climate pressures will

require too many interventions that the crop may not be profitable.

The premiums for certified organic produce may be higher, but the crop production costs are

higher, too, especially in the transition stage. Growing a poorly performing crop will increase costs

even more, so selecting a crop which is known to perform well in your area under organic

management, is essential.

Once the crop or crops in a rotation have been selected, the crop may be planted as seed, in

which case a supply of organic certified or permitted seed is identified for the seasons order to be

made.


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Basil seedlings

Alternatively the plants can be ordered and bought in as transplants from a nursery supplier.

Planting an orchard represents significant financial investment, so time taken to source the most

suitable material is important. Locally grown trees will be better adapted than stock brought in from

outside. A large order needs to be placed with the nursery at least one season ahead.

Crop Performance Monitoring

Regular crop monitoring is used to gather information about the performance of the cultivars, and

the crop management. The information is used to make the best decisions during the current and

future growing seasons.

What is being monitored? Below are sample criteria:

Planting date.

Cultivar name and seed or plant source.

Daily weather records.

Additions, removals and returns of nutrients and organic matter to the soil as mulches,

composts, and green manure.

Soil moisture status.

Weed growth and weed type.

Pest status in the crop (number and locatiion).

Diseases (prevalence and form eg, fruiting body).

Interventions with date and type of spray used.

Crop progress indicators for example onset of flowering and ripening.

Harvest dates and yields.

Other aspects to monitor are the overall economic performance of the crop in terms of yield, crop

quality and uniformity. If the crop is being produced for export, the grower should note how well

the crop conforms to the export market criteria.


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Review 2

1 Name two ways in which disease control can be planned for.

2 What is biodiversity?

3 Why would a grower make records about their crop? Give 2 reasons.


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The Importance Of Monitoring In The Management Of An

Organic Horticultural Production System

Pest And Disease Management

Because organic growing relies on establishing a balance between pest and beneficial organisms

in order to reduce crop losses, a quick solution to pest attack is not possible. Regular monitoring

for early signs of trouble gives the grower the maximum time to consider control methods.

The following are examples of useful information:

Raised humidity around the crop. Fungal diseases favour these conditions.

Increasing numbers of pest insects such as aphids in weeds or shelterbelts.

Fungal fruiting bodies present.

Low numbers of predator and beneficial organisms.

Decision-Making

Information is crucial to effective decision making in the organic orchard or garden. This is based

on observations and data collecting over several growing seasons.

For example the best time to control many weeds is when they are at the two to four leaf stage.

For a crop this may mean that there is just a short time when the weeds will respond to cultivation.

Corrective Action

Good monitoring and record keeping throughout the growing season informs the decisions which

will avert disaster. The corrective action can involve manipulating natural processes such as

raising the level of life in the soil or planting food for predator insects. These corrections take time

to come into effect, in fact rapid change may destabilize the system and so is usually counter

productive.

Crop Performance

The crops performance gets evaluated on a number of criteria including:

Percentage of crop to reach export grade.

Crop size and yield per hectare.

Crop quality.

Date of maturity.

The spread of maturity across the season.

Direct losses to pests and disease.

Losses to weeds.


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Reading

”Monitoring for Pests and diseases”

Read this advertisement for a pest and disease monitoring service.

Organic Pipfruit Monitoring

Monitoring is a core requirement for the successful implementation of organic pipfruit production.

Organic growers rely on the balance between pest and beneficial insects being maintained.

Fruitfed Supplies' organic pipfruit monitoring service provides growers with valuable information on

pest identity, location and severity, and any beneficial insect activity in their blocks. This enables

strategies for pest control to be checked and adjusted if necessary, in a timely manner.

While pest identification and control is our primary focus, we will also alert growers to the presence

of disease. Our trained staff can identify the early stages of pest and disease development,

enabling prompt action to be taken. Ideally, pests are controlled before they cause much visible

damage to your crop. Once monitoring is completed, one of our representatives will prepare a

report detailing all findings and recommending a pest management strategy to suit your property.

In addition to this, you will be invited to attend relevant grower education programmes and

discussion groups, and be offered regular updates concerning seasonal issues.

Monitoring Details

Organic pipfruit monitoring follows the same monitoring protocols as conventional pipfruit. A full

programme of 6 rounds can be followed or a reduced programme of rounds 1, 2 and 4 (or any

other combination to suit) is also available. The following list details some of the key pests and

diseases we monitor, however this may vary according to seasonal or geographical need:

Key Insect Pests: Apple leafcurling midge, codling moth, european red mite, leafroller, pear

leafcurling midge, scale, two spotted mite, woolly apple aphid, codling moth.

Minor Insect Pests: Froggatt‟s apple leafhopper, Fuller‟s rose weevil, mealybug, noctuid moth,

pear slug.

Key Diseases: Black spot, powdery mildew.

Beneficial Insects: Aphelinus mali (WAA parasite), Phytoseiulus persimilis (TSM predator),

Platygaster demades (ALCM egg parasite), Stethorus spp, Typhlodromus pyri.


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Review 3

1 An organic vegetable grower has kept all their management, irrigation and rotation records

since 1997. What is the use of this information?

To the grower:

To their neighbour, who is thinking of converting to organic growing:


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Glossary

Arable: A farming system growing crops.

Beetle banks: Specially planted grassy beetle habitat, which encourages predatory ground

beetles.

Bacillus thuringiensis (Bt):

A naturally occurring bacterium present in soil that produces a protein toxic

to caterpillars. It is used as a biological control.

Biological control: The control of pests and parasites using other organisms.

Brassicas: Members of the cabbage family such as cabbage, cauliflower, broccoli and

kale.

Cover crop: Crops that are grown to protect and improve the soil, or control weeds and

pests.

Crop rotation: A system in which two or more crops are grown alternately in a field in a set

sequence.

Cultivation: Working the soil to kill weeds incorporate manure or areate the soil.

Green manures: Crops grown specifically to capture nutrients in the soil, and to be ploughed

into the soil to provide humus.

Herbicide: An agrichemical, which kills weeds.

Horticulture: The growing of fruit, vegetables and the care and cultivation of landscapes.

Humus: Stable end product of decomposed organic matter in the soil.

Legume: Plants of the pea family, for example peas, beans and clover - these crops

fix nitrogen into the soil.

Microclimate: Climate of a small area that is different from that of a surrounding area.

Microbe: A living organism such as fungus, bacterium or protozoan that can be seen

only with a microscope. Soil microbes help dead plants and animals to

decompose.

Microorganism: Animals and plants that are too small to be seen clearly with the naked eye.


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Mulch: A material such as straw or leaves applied to the soil to protect it from the

weather or to suppress weed growth.

Pasture: Land covered with grass or forage crops and used for grazing livestock.

Pheromone traps: These use chemicals resembling the scent of insect sex attractants to lure

the insect into a trap.

Predatory: Living by eating other animals especially by catching living prey. For

example, ladybirds feed on insects such as aphids.

Substrate: The base on which an organism lives.

Trace elements: A substance needed in very small amounts for the proper functioning of the

body. Examples include chromium, copper, cobalt, iodine, selenium and

zinc.


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Answers To Review Questions

Review 1 1 There may have been a chemical spill or contamination from a previous agrichemical store.

Neighbouring properties may be using farming practices, which will impact on the organic

property, such as spraying, growing a genetically modified crop or using GM feed.

2 It‟s a wide border between the organic growing areas and the next-door conventional farm.

In the buffer zone you may not grow a crop but rather plant shelter plants.

3 True - as it will not come into contact with the crop.

4 Use of agrichemicals, animal pharmaceuticals, soil fumigation with e.g. methyl bromide,

use of synthetic fertilizers, use of treated timber in beds.

5 Spray drift, surface runoff which is contaminated with agrichemicals.

Reading “Resilient Farm Design”.

Many of the points addressing farming are also relevant to horticulture.

1 Rotation design or competing ground cover. Fast nutrient availability. Correct position of

crop in a rotation, provision of organic material as required.

2 Crop shelter; Habitat for Predators and Parasitoids of Pests; Aesthetic Values, beauty;

Timber and Firewood; Human Food Production e.g. feijoas; Bee Foraging; Stock Feed e.g.

tagasaste; Mulching and Composting materials.

3 Native tussock grasses e.g. Poa cita and sedges e.g. Carex secta.

Reading “Rotation Design”.

1 This developed if the same crop was grown year after year and was shown as poor crop

growth.

2 Hard pans or loss of soil structure.

3 Green manures and intensive use of added organic matter/compost.

Review 2 1 By selecting healthy disease resistant plants; Planning rotations.

2 Is short for biological diversity, which describes the whole range of life, plant and animal

on earth.

3 To record weed species and how these change over time in response to management

practices; To record crop progress each season in areas like flowering onset, harvest; To

record any interventions and sprays used.

Review 3 1 To the grower.

2 Shows the success or failure of the grower‟s crop management systems.

3 To their neighbour, who is thinking of converting to organic growing.

4 Gives information about the types of crops which succeeds in the area, as well as climate,

pest and disease and soil management information.


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MODULE 10 Conversion

Topics

1. Planning 2. Conversion for Livestock 3. Getting the Soil Right 4. Weeds 5. Pests and Diseases 6. Sources of Information 7. Assess yourself 8. Review

Module objectives

On completing this module you should be able to:

1. Appreciate the difficulties in converting to organics 2. Know methods of mitigating these difficulties through planning 3. Understand the economic constrictions for conversion to organics 4. Provide useful advice for farmers considering organic conversion Introduction

Before being able to produce certified organic produce, one must take land through a conversion process. While the land is being converted there is also often a requirement for the farmer‟s way of thinking to change. Conversion is often the most challenging part of being organic with all the inherent risks of excluding prohibited products combined with limited experience and, until the official conversion process is complete, an inability to command a full organic premium. Overcoming the challenges faced in conversion is a key component to the growth and adoption of organics.

Planning

The initial conversion is one of the most challenging parts of a farm being organic. Some modern organic farms may not look as different from conventional farms as organic farms perhaps used to but nevertheless the conversion to organics involves a shift in the way the farm system works, a shift in management and a paradigm shift for the grower also. It is conversion of the farm and the farmer.

Plan in Advance

Conversion of a farm to organic certification should be planned in advance. Probably the best method is to visualize the desired organic enterprise and then identify the changes and stages that could be achieved to reach that desired goal by working backwards to the present condition of the farm. There are some advantages in keeping the plan reasonably broad and it should also be expected that things will not necessarily go to plan. But it is always best to have thought ahead and to make each new decision in the light of what you had wanted to accomplish. It is recommended to review the plan annually with the benefit of lessons learnt in the previous year and an improved perspective of the challenges faced.


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Components of the Plan

The plan will include basic information and considerations including farm size, a conversion timetable. But it should also include what part each member of the farming family and each farm worker might play. Is there adequate “buy in” by all the affected parties; this is a vital question as a high degree of commitment is likely to be required in the challenges faced during farm conversion and once fully certified organic. Converting to organics may involve diversification of farm activities perhaps even the instruction of livestock on a horticultural property or the introduction of crops onto a livestock enterprise. Many people may be able to start creating a more rounded farm that includes livestock, forage production and cash crops. Such major changes will involve new machinery and equipment requirements but also different commercial relationships and the aquiring of new personal knowledge.

Leading Up to Conversion

As well as planning for the future, it is advisable to keep a good record of the past including the last uses of substances that would be prohibited under organic certification. The date of last use of these products on the converted land will affect how quickly the transition to full organic certification can be achieved

Financial Preparation

There should be enough capital input available for any extra machinery requirement and other costs incurred in conversion. These costs need to be well thought out and the decision to convert made with the knowledge that funds will be available to meet expected costs and contingencies. There may be a strong argument for governmental financial assistance into organics if the public in general could benefit from the environmental outcomes and the nation can benefit through accessing export income on value added products. In New Zealand there has, however, been limited direct financial support like this and the process of conversion, the time of greatest risk in the decision to go organic, will need to be almost entirely funded by the farm business.

Markets

Before entering into the process of conversion, adequate thought should be given to what range of crops and other products will be produced, where these will be sold and the present and likely future state of the market. To some extent markets may be able to be developed and market research can be undertaken to assess the likely success of the proposed operation in the proposed locality.

Machinery

Often machinery related to weeding will be the largest area of attention as organic growing often involves a more mechanical approach to weed control. Weeding may previously have been largely herbicide based. There are many options available for weeding and due care should be exercised in deciding on the likely best tractor and kit options.

Labour Requirement

The likely requirement for extra permanent and casual labour for seasonal jobs should be


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assessed. Organic farming will often involve a greater labour component (e.g. hand weeding, or harvesting of diverse crops) and this can be difficult to arrange in some rural areas. Thought should be given to such arrangements as required.

1.1.8 Biting Off the Right Amount

Many organic farms have been converted from conventional in one foul swoop perhaps reflecting a personal conviction to go organic and not compromise. There are inherent risks in taking this approach and it is generally advised to take things more gradually. One of the best approaches is to convert sections of the farm over time so that any issues that arise are not going to be too economically crippling. Certification bodies allow for this though often they will want to see that there is a plan to eventually bring the whole property into organic management. A strategic way of entering a mixed cropping farm into organics is to place into conversion areas as they come into the pasture phase. The productivity of pasture is least likely to be affected in the short term by the decision to go organic. The pasture can be cultivated for cropping once the transition period into full certification has passed and a full premium can be achieved for crops that will be growing in relatively fertile, low weed burden and low disease burden paddocks. In the lead up to the first organic crop, skills in organic cropping can be practiced on neighbouring conventional crops with reduced risk of crop failure.

1.1.9 Farm Design

There haven‟t always been text books on conversion to organic farming and many farmers have learned the hard way that the adoption of organic farming is not just the sudden exclusion of chemical fertilisers and pesticides. Thought should be given to alternative soil fertility management, crop care and animal health etc following the principles outlined in these 12 Modules. A key component in cropping will often be rotation design which, although flexible, should be worked out to provide some of the best preventative actions against weeds, pests and diseases.

Conversion for Livestock

One of the most important aims in converting a livestock farm to organics will be to ensure that animal health is optimised through good farm management. The key features here will be reduction in potentially stressful management or conditions and the provision of good balanced nutrition.

Some fundamental changes in farm operations may be required to achieve lower stress levels including reducing stocking rate, increasing the age of weaning, keeping family type groups, operating mixed ages and providing more shelter.

Seasonal feed deficits may alter if the farm has been used to using strategic nitrogen fertiliser applications to overcome e.g. early spring or autumn feed deficits.

Organic feed for intensively kept livestock such as poultry can be expensive and difficult to organise so sources, alternatives and costs should be factored into a conversion plan.

Many farms use trace element supplements. In an organic farm the requirement for such supplements needs to be established by evidence of historical issues, animal tests, plant tissue analysis or veterinary advice. There may be scope in the plan to include plant species, grazing management or other techniques for improving the utilisation of certain trace elements by the livestock.

Intensively kept livestock may also require some housing in which case the plan should


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include the design of housing to ensure sufficient space, ventilation, hygiene and layout for healthy animal production.

Some of the specific categories that should be included in a conversion plan are…

Pasture Design including tonic plants such as chicory and plantain, optimal grass mixes for livestock health and strategic seasonal dry matter production, appropriate legume choice for adequate nitrogen fixation.

Grazing Strategy including prevention of internal and external parasite issues as well as maintenance of diverse pasture mixes.

Breeding Programmes including the introduction of lines hardy to parasite and disease issues and the progressive culling of unsuitable livestock.

Nutrition including feed budgets and any supplementary feed that might be required.

Animal Health Strategies for any identified or potential issues on the farm including preventative measures, curative measures and the ability to quarantine off animals that may have to receive prohibited inputs and be removed temporarily from organic production.

Getting the Soil Right

As part of the Conversion Plan you will need to assess the nutritional requirements of the crops and pasture and where these nutrients will come from. If composting is going to be practiced, a system needs to be designed and the appropriate equipment obtained. Large-scale composting can be a daunting process and inadequate equipment can make it several times more difficult than it needs to be.

For intensive cropping a suitable design may be to rely on an area of pasture or semi-waste ground to provide herbage that is then composted or simply added to the cropping area. A suitably large area needs to be set aside for this with the realisation that there will be little direct economic return from this area and that there is likely to be a requirement to replace the nutrients harvested from this area (e.g. with mineral fertilisers). For such a design, there may be a requirement for machinery such as a forage harvester.

Potential fertiliser sources should be identified and a suitable fertiliser programme developed. There is now much choice available even for organic farms. Attention should be paid to adding sufficient major nutrients to replace produce losses as well as being able to strategically obtain good plant growth at key times perhaps with the use of biofertiliser stimulants. Certified products need to be located and information sought on them.

Organic farming is very dependent on soil processes so as outlined in Module 4, steps should be taken to improve and maintain soil organic matter levels and soil biological activity.

Weeds

Before entering conversion an assessment of weed potential should be made. In some cases there

may be a perceived requirement for herbicide use to reduce potential for future problems that will

take longer to correct by organic means. This can be an individual moral judgement. Another


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example of such a decision is the establishment of tree crops. It is a not uncommon practice to

establish tree crops conventionally using herbicide (ensuring fast even tree establishment without

root competition from grasses and weeds) and then converting to organic three years before the first

expected economic harvest.

If the farm is being converted to organics in portions, there is a strong argument for converting the

most weed free areas first since weeds are often the single biggest challenge to successful organics.

Once an area is converted to organics, full attention must be paid to weed management. It is often

in the conversion period that weed management is too relaxed and weeds are allowed to set seed.

While you might still get a crop, the harvest will be more difficult and more to the point the weed

seed burden has the potential to cause serious weed issues for years to come.

Pests and Diseases

As early as possible in the conversion process, attention should be paid to improving biodiversity and habitat for prevention and biological control of pests and diseases. There may be the ability to look at strategic intercropping (or mixing of livestock species) or the improvement of field margins for providing some of these resilience benefits to crops. There may also need to be consideration for reducing the density of plantings to allow better airflow (reduced humidity) and to reduce the epidemic spread of diseases and pests.

There may be a choice to move towards more hardy varieties or even species of crops or pasture plants. Planning should also include what pests and diseases are likely to be problems in each of the chosen crops, pastures and livestock. Preventative actions and remedies should be investigated and prepared for.

Sources of Information

For the individual farmer there may be good value in employing a consultant to plan the process of conversion with them. Such a consultant should have a good understanding of organic principles and practice and operate a broad approach to the planning process.

It will be valuable to talk to, meet and visit existing successful organic farmers or growers of a similar farm type. In some cases there are active organic discussion groups for farmers and growers. For particular crops it can also be valuable to belong to grower associations even if they are both conventional and organic people involved – there will still be useful information and contacts.

There is a large amount of information available in magazines, agricultural papers, websites, email newsletters, books, and scientific publications. Skills should be aquired for sourcing information and discerning useful and reliable points relevant to the farms operation

Assess yourself

Questions

1. What are some of the financial considerations in during the conversion period?


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2. What are the advantages of converting a farm portion by portion to organic farming (and can you think of any disadvantages)?

3. What sort of changes might be expected in a livestock enterprise converting to organics and why?

4. Why should conversion to organics not be simply a cessation of use of fertilisers and pesticides?

5. What sources of information might be useful to a converting farmer?

Review

Field Trip for Module 10

The Single Overriding Communication Objective (SOCO) for Module 10 was that Broadacre Agriculture by definition reduces the scope for biodiversity and the adherence to some principles of organics – BUT that with the right approach (and a different approach from more intensive growing) it is possible to improve system design beyond large monocultures. We went to Kowhai Farm and observed a few examples of the issue of going large scale. 1) Bumblebees were used as an example. The accommodation shortage for bumble bees was being addressed by the provision of “bumble bee motels” but the remaining limiting factor was food source for the bumble bees which probably partly explains the low occupancy rate in the motels. Tagasaste was in flower but only present in a small patch at the entranceway. Ideally the presence of tagasaste would be extended to bring some stock shelter, bee fodder, nursing of other shelter trees, and other potential benefits. 2) We looked at the shelterbelts and saw that the lack of shelter was not due to lack of planting but rather lack of planting of the right species. We observed that present shelter was inadequate and likely to be limiting stock performance and some crops (beans especially benefit from good shelter. The macrocarpa and pines present in some areas were deemed too short to give good shelter over the large (broadacre after all) paddocks and that of any of the tree present it was only the poplars that were tall enough to give shelter to a reasonable proportion of the paddock. It was suggested that taller trees be established as primary shelter. And with the size of the paddocks it was necessary for such tall shelter to be present all around the existing shelter areas. With initial provision of shelter it was assumed that the slower growing and less hardy native species would have a better chance at establishing and be able to grow faster giving more aesthetic and other benefits than when growing alone. 3) Onions are a major income earner on the farm and typically are managed with intensive weeding (and hence a mostly bare soil). There was a question about the use of small clovers as an intercrop with onion. Whereas it was judged that the clovers would not compete strongly with the onions and would bring benefits of covering the soil, providing habitat for beneficial insects and fixing nitrogen, a strong negative point would be that it would preclude weeding operations (interrow cultivation) and this would be too high a risk on a broad acre scale (weeds could establish and cause competition, pest and harvesting difficulties. The method may well be suitable on an intensive scale where harvesting is going to be by hand anyway and problem weeds can be dealt with intensively as they arise.


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4) I commented on the problems experienced with thrips on the onions last year. And we observed the large field prepared for onions. What lessons were learnt from last year and what could be put in place now to reduce the thrip issue this year? The class considered that crop rotation was important and this is correct. In fact attention should be paid to what crop goes into the old onion area to ensure that it is not a host to the overwintered thrips likely to be present in and around that field. As had been commented in a previous class it might be a good idea to not have this years onions in a paddock adjacent to last years onions – fortunately this years crop is diagonally opposite but perhaps it would be better still separated further to reduce the potential pest pressure from thrips. The rotation as it is keeps onions away from the same paddock for six years and this is more than sufficient to address the rotation requirement for thrips. From Module 6 of BIOS 072 we have the following relevant paragraphs on management in onions (I have omitted a couple of paragraphs on more intensive methods of thrip management).

Onion Pest Management - Thrips

Thrips are the main pest issue in onion growing. There are at least two thrip species commonly attacking onions, these being the onion thrip (Thrips tabaci) and the western flower thrip (Frankliniella occidentalis). They rasp the leaf surface leaving a characteristic silvery appearance. Sucking on plant sap, they can reduce crop yields significantly when the infestation is during mid season and bulb formation has just begun. They also increase the susceptibility of onions to disease such as botrytis (see below). Thrips have a life cycle of several flightless instar larvae all of which feed on plants and a mature phase capable of flying. If populations build up, this can result in serious damage to the crop and even complete crop failure. In unsprayed conditions, the levels of natural enemies may be able to build up. The natural enemies present in New Zealand include predators and parasites. Numbers of thrips are also affected by local sources of thrips and host condition. In a similar way to weed management the options for thrip management can be expressed in a gradient from systems based such as crop rotation and provision of refuges for biological control agents down to intervention control with spraying again generally reflecting an increased cost from systems to interventionist approaches. Rotation

Onion thrips are a problem on a wide variety of crops. Onions should not be for instance planted into areas that have had a winter cover crop of ryecorn or wheat for example but rather for example oats, which does not host the thrips. Surrounding areas and crops

Attention should be paid to the surrounding area. Ideally there would be refuges such as beetle banks for spiders, spider mites, ground beetles, lacewings, pirate bugs, ladybirds etc (though many of these control agents have difficulty accessing the thrips hidden in amongst onion leaves). On the other hand areas of weeds and old crops that may serve as a source of thrips should be tidied or onions planted elsewhere. Bad thrip infestations can result from a nearby thrip infested crop that has been left to mature. When the infested crop starts to dry out, the thrips will transfer over to the onions. Flower provision Some thrip predators and parasites will be improved in number and activity if there is the provision of suitable


38

flowers for providing pollen and nectar. For example the pirate bug eats thrips and mites but also derives food from pollen of open flowers e.g. buckwheat. Hoverflies attracted and boosted by phacelia, buckwheat and other flowers can also aid the biological control of thrips.

Crop Condition

A stressed crop will be more prone to thrip infestation. A common issue is shortage of soil moisture and irrigation should be kept up to ensure healthy growth without summer dry stress. Crop nutrition is also important with a desire for uninhibited growth with adequate provision of calcium and possibly boron. Excess nitrogen should be avoided as this can provide an easy and desirable food source for thrips. Spray Avoidance

Spraying with insecticides reduces natural enemy levels (a problem even for some of the organic restricted sue sprays). Also spraying with fungicides to control onion diseases can reduce the level of fungal biological control of thrips. Therefore a reduced spraying regime say based on monitoring of thrip numbers and disease presence can assist biological control of thrips. Protective Spray

Spraying with a protective kaolin clay film (SurroundTM

– available in New Zealand but use on certified organic properties would have to be with specific permission) appears to offer some protectant effect against thrips, reducing their ability to feed on the onion leaf surface. Sprays

There are a wide variety of sprays available on a restricted basis for organic control of thrips but their use on onions is only with moderate success as they are not very systemic or in some cases are active entirely by contact. Options include neem (especially the oil products), garlic/pepper sprays, garlic/pyrethrum sprays, sulphur sprays, insecticidal soap and diatomaceous earth. The problem is that the thrips largely hide within onion leaves and contact spraying is severely impeded by this. Many of the sprays can have a negative impact on natural enemies too and use should be on a confirmed need basis.

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