RHS Level 2 Certificate

Week 19 – Outdoor food production. Vegetables – crop rotation, intercropping and successional cropping

Learning outcomes

1.1 Describe the methods used to advance and extend the productive season of outdoor food crops; including the use of polythene, mulches, fleece, ‘enviromesh’, low tunnels, cloches and cold frames.

1.2 Describe propagation methods used in the production of vegetable crops, including direct sowing and raising plants in seed beds, blocks and modules

2. Crop rotation etc 2.1 State the benefits and limitations of using crop rotation. 2.2 Describe a four-bed system of crop rotation. 2.3 Explain how successional cropping can be achieved for a NAMED

crop by using sowing and planting dates, choice of cultivars and environmental protection.

2.4 Explain how intercropping can be used to maximise production. 2.5 Describe the effect of plant spacing on a named crop. 2.6 Describe what is meant by ‘cut and come again’ vegetables

Extending the season for food crops

Using protection – cloches, greenhouse, poly-tunnel - at the beginning and end of the season.

Using varieties that are suited to the stage of the growing season. For example Peas (Pisum sativum) can be picked from May to September if the right varieties are chosen.

Sow in succession – so that there are new plants ready to harvest as one batch finishes.

Successional cropping

Sowing different varieties – early, mid-season and late

Sowing a few seeds at regular intervals so that the plants do not all reach maturity at the same time. For example, hearting lettuce (such as Cos) take 8 -14 weeks to reach maturity. Sowing half a row each week-10 days from late March until late July gives continuity of harvest May to October.

Propagation methods for vegetables

Seed – sown outside or sown in pots under cover. Modules or soil blocks to minimise root disturbance. Seed beds for brassicas that will be transplanted.

Plants – young vegetable plants at planting out stage can be purchased from mail order suppliers who will deliver in the correct week for planting.

Roots, slips and sets – Asparagus (Asparagus officinalis) is supplied as a root, Sweet potatoes (Ipomoea batatas) as slips (shoots with part of the root tuber – a bit like propagating Dahlia) and onions (Allium sativum) as sets (juvenile bulbs).

Intercropping and other intensive cropping approaches

Intercropping – growing rows or plants of a quickly maturing vegetable between those of a slow growing one.

Catch cropping – growing a quickly maturing crop on soil left vacant by a harvested crop or set aside to be planted later.

Mixed cropping – growing several vegetables together that benefit each other and are harvested at the same time (e.g. ’the Three Sisters’: sweet corn, beans and squash).

‘Cut and come again’ and ‘baby’ veg.

Cut and come again – takes advantage of the fact that leafy vegetables will re-grow if the growing point/roots are not removed by harvesting. Either involves removing a few leaves at a time or harvesting the head and stimulating re-growth.

‘Baby’ vegetables – quick maturing cultivars sown at close spacings so that the competition encourages smaller plants that grow rapidly to maturity and can be harvested small and early.

Crop Rotation – basic principles

Three or four groups (excluding permanent planting) depending on plot size. More groups = longer cycle (the longer the cycle the better).

Four group cycle – legumes, brassicas, alliums, roots. (For a three group – put alliums with roots).

Legumes are generally followed by brassicas. Root crops (include potatoes if space does not

permit a separate area) tend to be followed by alliums (the cultivation required for roots minimises weed competition).

Crop rotation – rotation groups

Vegetables divided into five groups – permanent planting (perennials like Asparagus); Brassicas; Legumes; Alliums; root crops.

Salad crops and some others like Sweet Corn and squash do not fall into a rotation group

The principle is not to grow the same group on the same soil two years running.

Crop Rotation – benefits and limitations

Benefits Limitations

Minimises plant problems – pests, diseases and deficiencies

Most pests and diseases are mobile or have long persistence

One crop can benefit the next in the rotation – nitrogen fixing legumes; potatoes suppress weeds

Personal taste is vital on a small scale – the grower might like brassicas but not carrots.

Planning the rotation also enables planning succession

Inflexible – intercropping, catch cropping or mixed cropping do not fit well

Learning outcomes

1.1 Describe the methods used to advance and extend the productive season of outdoor food crops; including the use of polythene, mulches, fleece, ‘enviromesh’, low tunnels, cloches and cold frames.

1.2 Describe propagation methods used in the production of vegetable crops, including direct sowing and raising plants in seed beds, blocks and modules

2. Crop rotation etc 2.1 State the benefits and limitations of using crop rotation. 2.2 Describe a four-bed system of crop rotation. 2.3 Explain how successional cropping can be achieved for a NAMED

crop by using sowing and planting dates, choice of cultivars and environmental protection.

2.4 Explain how intercropping can be used to maximise production. 2.5 Describe the effect of plant spacing on a named crop. 2.6 Describe what is meant by ‘cut and come again’ vegetables