Conservation Ag and Nutrient Use Efficiency

7/26/2019 Conservation Ag and Nutrient Use Efficiency

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Conservation Agriculture Practices in Enhancing Nutrient

Use Efficiency/ Resource Conservation

J. Somasundaram* R.S.Chaudhary and N.!.Sinha

Indian Institute of Soil Science, Nabibagh, Berasia Road, Bhopal-462038 !"#

$%&ail' so&a(a)ara&an*)ahoo+co+in

"ntroduction

Our mother soils are generally taken for granted for many uses. Most people do not

recognize the importance of soil resource. Soils are fundamental material for farming/agriculture.

Without high quality soils, agriculture production cannot e attained on sustainale asis. !hus,

con"ersion from con"entional practices to conser"ation agriculture #ill help in sustaining soil health.

$o%till/conser"ation agriculture production systems are capale of impro"ing the soil health y

increasing organic caron, aggregation, impro"ing infiltration, minimising erosion losses, etc.

&onser"ation agriculture '&() practices in"ol"e minimum soil disturance, pro"iding a soil

co"er through crop residues or other co"er crops, and crop rotations for achie"ing higher producti"ity.

!his has emerged as #ay for transition to the sustainaility of intensi"e cropping systems. !he key

features of &( include* 'i) minimum soil disturance y adopting no tillage and minimum traffic for

agricultural operations, 'ii) lea"e and manage the crop residues on the soil surface, 'iii) adopt spatial

and temporal crop sequences / crop rotations to deri"e ma+imum enefits from inputs and minimize

ad"erse en"ironmental impacts. n the con"entional systems in"ol"ing intensi"e tillage, there is

gradual decline in soil organic matter through accelerated o+idation and urning of crop residues

causing pollution, greenhouse gases emission and loss of "aluale plant nutrients. ntensi"e seed%ed

preparation #ith hea"y machinery lead to declining soil fertility, iodi"ersity and erosion. When the

crop residues are retained on soil surface in comination #ith no tillage, it initiates processes that lead

to impro"ed soil quality and o"erall resource enhancement. !herefore, conser"ation agriculture

practices may lead to sustainale impro"ements in the efficient use of #ater and nutrients y

impro"ing nutrient alances and a"ailaility, infiltration and retention y soils reducing #ater losses

due to e"aporation, and impro"ing the quality and a"ailaility of ground and surface #ater. When the

crop residues are retained on soil surface in comination #ith no tillage, it initiates processes that lead

to impro"ed soil quality and o"erall resource enhancement.

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Elements of a Nutrient #anagement Strategy in CA$

$utrient management strategies in &( systems #ould need to attend to the follo#ing four

general aspects, namely that* 'i) the iological processes of the soil are enhanced and protected so that

all the soil iota are microorganisms are pri"ileged and that soil organic matter and soil porosity are

uilt up and maintained- 'ii) there is adequate iomass production and iological nitrogen fi+ation for

keeping soil energy and nutrient stocks sufficient to support higher le"els of iological acti"ity, and

for co"ering the soil- 'iii) there is an adequate access to all nutrients y plant roots in the soil, from

natural and synthetic sources, to meet crop needs- and 'i") the soil acidity is kept #ithin acceptale

range for all key soil chemical and iological processes to function effecti"ely.

%o&ards CA'(ased Nutrient #anagement Practices

ntegrated Soil ertility Management 'SM) and ntegrated $atural resources Management '$M)

approaches of "arious types and nomenclature ha"e een in "ogue in recent years in certain sections

of the scientific community. 0enerally, such approaches are focused more on meeting crop nutrient

needs rather than managing soil health and land producti"ity as is the case #ith &( systems. (lso,

most of the #ork that is couched under the ruric of SM or $M o"er the past 12 years or so has

een geared to#ards tillage%ased systems #hich ha"e many unsustainale elements, regardless of

farm size or the le"el of agricultural de"elopment. 3nless the concepts of soil health and function are

e+plicitly incorporated into SM or $M approaches, sustainaility goals and means #ill remain

only accidentally connected, and sustainale crop intensification #ill e difficult to achie"e

particularly y resource poor farmers. We elie"e that &( systems ha"e #ithin them their o#n

particular sets of SM or $M processes and concepts that comine and optimize the use of organic

#ith inorganic inputs integrating temporal and spatial dimensions #ith soil, nutrient, #ater, soil iota,

iomass dimension, all geared to enhancing crop and system outputs and producti"ities ut in

en"ironmentally responsile manner. !here is empirical e"idence to sho# that &( ased SM or

$M processes can #ork ecause of the underpinnings of soil health and function.

ocusing on soil fertility ut #ithout defining the tillage and cropping system, as often

proposed y SM or $M approaches, is only a partial ans#er to enhancing and maintaining soil

health and producti"ity in support of sustainale production intensification, li"elihood and the

en"ironment. O"er the past t#o decades or so, empirical e"idence from the field has clearly sho#n

that healthy agricultural soils constitute iologically acti"e soil systems #ithin landscapes in #hich

oth the soil resources and the landscape must operate #ith plants in an integrated manner to support

the "arious desired goods and ser"ices 'e.g., food, feed, feedstock, iological ra# material for

industry, li"elihood, en"ironmental ser"ices, etc) pro"ided y agricultural land use. &onsequently,

successful nutrient management strategies as part of any SM or $M approach must pay close

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attention to issues of soil health management #hich means managing the microscopic integrity of the

soil plant system particularly as mediated y soil li"ing iota, soil organic matter, soil physico%

chemical properties, a"ailale soil nutrients, adapted germplasm as #ell as to managing the

macroscopic dimensions of landscapes, socioeconomics and policy. 0i"en that &( principles and

practices offer sustantial enefits to all types of farmers in most agro%ecological and socio%economic

situations, &(%ased SM and $M approaches to nutrient management and production

intensification #ould e more effecti"e for farmer%ased inno"ation systems and learning processes

such as those promoted through armer ield School net#orks.

Ado)ting a CA'(ased Nutrient #anagement rame&or+

&( has no# emerged as a ma4or 5reakthrough6 systems approach to crop and agriculture production

#ith its change in paradigm that challenges the status quo. 7o#e"er, as a multi%principled concept,&( translates into kno#ledge%intensi"e practices #hose e+act form and adoption requires that farmers

ecome intellectually engaged in the testing, learning and fine tuning possile practices to meet their

specific ecological and socio%economic conditions 'riedrich and 8assam 9::;). n essence, &(

approach represents a highly iologically and io%geophysically%integrated system of soil health and

nutrient management for production that generates a high le"el of 5internal6 ecosystem ser"ices #hich

reduces the le"els of 5e+ternal6 susidies and inputs needed. &( pro"ides the means to #ork #ith

natural ecological processes to harness greater iological producti"ities y comining the potentials of

the endogenous iological processes #ith those of e+ogenous inputs. !he e"idence for the uni"ersal

applicaility of &( principles is no# a"ailale across a range of ecologies and socio%economic

situations co"ering large and small farm sizes #orld#ide, including resource poor farmers '0oddard

et al. 9::


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nutrient management inter"entions that may e proposed can contriute to the system effecti"eness as

a #hole oth in the short% and long%term.

Conservation agriculture and soil organic car,on$

When comparing SO& in different management practices, se"eral factors ha"e to e taken into

account. (s reported, ulk density can e affected y tillage practices. f ulk density increases after

con"ersion from con"entional tillage to zero tillage, and if samples are taken to the same depth #ithin

the surface soil layer, more mass of soil #ill e taken from the zero tillage soil than from the

con"entionally tilled soil. !his could increase the apparent mass of SO& in the zero tillage and could

#iden the difference et#een the t#o systems if there is significant SO& eneath the ma+imum depth

of sampling 'AandenBygaart and (ngers 9::>). !herefore, Cllert and Bettany '1;;2) suggested

asing calculations of SO& on an equi"alent soil mass rather than on genetic horizons or fi+edsampling depths in order to account for differences in ulk density. !illage practice can also influence

the distriution of SO& in the profile #ith higher SO& content in surface layers #ith zero tillage than

#ith con"entional tillage, ut a higher content of SO& in the deeper layers of tilled plots #here

residue is incorporated through tillage 'Dantalia et al. 9::). Blanco%&anqui and @al '9:: Mg ha%1 on a dry matter asis) of

#heat stra# applied annually on SO& under zero tillage on an (eric Cpiaqualf in central Ohio.

O"erall, SO& from : to 2: cm depth #as =9.2 Mg ha%1 in the unmulched soil, ;E.1 Mg ha%1 #ith =

Mg ha%1 mulch, and 1:E.; Mg ha%1 #ith 1> Mg ha%1 mulch. !he rate of decomposition of crop

residues depends not only on the amount retained, ut also on soil characteristics and the composition

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of the residues. !he composition of residues left on the field% the solule fraction, lignin, hemic

'cellulose) and polyphenol contentH#ill determine its decomposition 'Sakala et al. 9:::). !he

solule fraction is decomposale 'Sakala et al. 9:::) and can stimulate the decomposition of the

'hemi) cellulose 'Aanlau#e et al. 1;;E). @ignin is resistant to rapid microial decomposition and can

promote the formation of a comple+ phenyl%propanol structure, #hich often encrusts the cellulose,

hemicellulose matri+ and slo#s decomposition of these components 'Sanger et al. 1;;>).

&onser"ation agriculture is not a single component technology ut a system that includes the

cumulati"e effect of all its three asic components. !he crop intensification component #ill result in

an added effect on SO& in zero tillage systems. West and Iost '9::9) reported that although relati"e

increases in SO& #ere small, increases due to the adoption of zero tillage #ere greater and occurred

much faster in continuously%cropped than in fallo#%ased rotations. Sisti et al. '9::E) found that

under a continuous sequence of #heat '#inter) and soyaean 'summer) the concentrations of SO& to

1:: cm depth under zero tillage #ere not significantly different from those under con"entional tillage.

7o#e"er, in the rotations #ith "etch planted as a #inter green%manure crop, SO& concentrations #ere

appro+imately 1< Mg haJ1 higher under zero tillage than under con"entional tillage. t appears that

the contriution of $9 fi+ation y the leguminous green manure '"etch) in the cropping system #as

the principal factor responsile for the oser"ed & accumulation in the soil under zero tillage, and that

most accumulated & #as deri"ed from crop roots. !o otain an accumulation of SOM there must e

not only a & input from crop residues ut a net e+ternal input of $ e.g. including an $%fi+ing green

manure in the crop rotation 'Sisti et al. 9::E). &on"entional tillage can diminish the effect of an $

fi+ing green%manure either ecause the $%input can e reduced y soil mineral $ release or the $ can

e lost y leaching '$OF J) or in gaseous forms '"ia denitrification or $7F "olatilization) due to

SOM mineralization stimulated y tillage '(l"es et al. 9::9). 7ence, intensification of cropping

practices y the elimination of fallo# and mo"ing to#ard continuous cropping, is the first step to#ard

increased SO& contents. educing tillage intensity, y the adoption of zero tillage enhances the

cropping intensity effect.

Conservation agriculture and Nutrient availa,ility$

!illage, residue management and crop rotation ha"e a significant impact on nutrient distriution and

transformation in soils '0alantini et al. 9:::, Ctana et al. 1;;;), usually related to the effects of

conser"ation agriculture on SO& contents. Similar to the findings on SO&, distriution of nutrients in

a soil under zero tillage is different to that in tilled soil. ncreased stratification of nutrients is

generally oser"ed, #ith enhanced conser"ation and a"ailaility 'ranzlueers and 7ons 1;;>). !he

altered nutrient a"ailaility under zero tillage compared to con"entional tillage may e due to surface

placement of crop residues in comparison #ith incorporation of crop residues #ith tillage 'smail etal. 1;;E). Slo#er decomposition of surface placed residues 'Balota et al. 9::E, 8ush#aha et al. 9:::)

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may pre"ent rapid leaching of nutrients through the soil profile, #hich is more likely #hen residues

are incorporated into the soil. 7o#e"er, the possile de"elopment of more continuous pores et#een

the surface and the susurface under zero tillage may lead to more rapid passage of solule nutrients

deeper into the soil profile than #hen soil is tilled 'ranzlueers and 7ons 1;;>). urthermore, the

response of soil chemical fertility to tillage is site%specific and depends on soil type, cropping

systems, climate, fertilizer application and management practices 'ahman et al. 9::=).

!he density of crop roots is usually greater near the soil surface under zero tillage compared

to con"entional tillage 'Kin et al. 9::E). !his may e common under zero tillage as in the study of

Mackay et al. '1;=, @am et al. 1;=2). (ccording to Schoenau and &ampell '1;;>), a greater immoilization in

conser"ation agriculture can enhance the conser"ation of soil and fertilizer $ in the long run, #ith

higher initial $ fertilizer requirements decreasing o"er time ecause of reduced losses y erosion and

the uild%up of a larger pool of readily mineralizale organic $.

!illage increases aggregate disruption, making organic matter more accessile to soil

microorganisms 'Si+ et al. 9::9, Beare et al. 1;;E) and increasing mineral $ release from acti"e and

physically protected $ pools '8ristensen et al. 9:::). @ichter et al. '9::=) reported that permanentraised eds #ith residue retention resulted in more stale macro aggregates and increased protection

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of & and $ in the micro aggregates #ithin the macro aggregates compared to con"entionally tilled

raised eds. !his increases susceptiility to leaching or denitrification if no gro#ing crop is ale to

take ad"antage of these nutrients at the time of their release 'andall and raga"arapu 1;;2,

&hristensen et al. 1;;E, Goran 1;=:). andall and raga"arapu '1;;2) reported aout 2 higher $OF%

$ losses #ith con"entional tillage compared to zero tillage. Do#kin and Schoenau '1;;=) report that $

a"ailaility #as not greatly affected in the initial years after s#itching to zero tillage in the ro#n soil

zone in &anada. Other authors reported that $%mineralization rate increased as tillage decreased*

@arney et al. '1;;). (fter 9: years of zero tillage, e+tractale I #as E9 greater at :%2 cm, ut

=%1= lo#er at 2%F: cm depth compared #ith con"entional tillage in a silt loam 'smail et al. 1;;E).

(lso 3nger '1;;1) and Mato#o et al '1;;;) found higher e+tractale I le"els in zero tillage compared

to tilled soil in the topsoil. (ccumulation of I at the surface of continuous zero tillage is commonly

oser"ed 'e.g. ranzlueers and 7ons 1;;>, Cd#ards et al. 1;;9, ollett and Ieterson 1;==, Cckert

and Dohnson 1;=2, 7argro"e et al. 1;=9). &oncentrations of I #ere higher in the surface layers of all

tillage systems as compared to deeper layers, ut most strikingly in zero tillage 'Guiker and Beegle

9::>). When fertilizer I is applied on the soil surface, a part of I #ill e directly fi+ed y soil

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particles. When I is anded as a starter application elo# the soil surface, authors ascried I

stratification partly to recycled I y plants 'Guiker and Beegle 9::>, Cckert and Dohnson 1;=2).

Guiker and Beegle '9::>) suggest there may e less need for I starter fertilizer in long%term zero

tillage due to high a"ailale I le"els in the topsoil #here the seed is placed. Geeper placement of I in

zero tillage may e profitale if the surface soil dries out frequently during the gro#ing season as

suggested y Mackay et al. '1;=). ollett and Ieterson '1;==) oser"ed either

higher or similar e+tractale 8 le"els in zero tillage compared to mouldoard tillage, #hile oldan et

al. '9::). Cd#ards et al. '1;;9), ho#e"er, oser"ed higher e+tractale &a concentrations #ith zero

tillage than #ith con"entional tillage on an 3ltisol, #hich they attriuted to the higher SOM contentunder zero tillage. !he same conclusion #as reached y Sidiras and Ia"an '1;=2) #ho found

increased a"ailale &a and Mg concentrations to >: cm depth in oth an o+isol and alfisol in Brazil.

n contrast, Ble"ins et al '1;=F) reported lo#er e+tractale &a under zero tillage than con"entional

tillage.

#icronutrient cations and aluminium$

ncreasing supply to food crops of essential micronutrients might result in significant increases in

their concentrations in edile plant products, contriuting to consumers health 'Welch 9::9).

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Micronutrient cations '?n, e, &u and Mn) tend to e present in higher le"els under zero tillage #ith

residue retentions compared to con"entional tillage, especially e+tractale ?n and Mn near the soil

surface due to surface placement of crop residues 'ranzlueers and 7ons 1;;>). n contrast,

0o"aerts et al. '9::


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&C& and nutrient a"ailaility increase in the topsoil. $umerous studies ha"e reported higher

e+tractale I le"els in zero tillage than in tilled soil largely due to reduced mi+ing of the fertilizer I

#ith the soil, leading to lo#er I%fi+ation.

References$

Baker, D.M., Ochsner, !.C., Aenterea, .!., and 0riffis, !.D. 9::


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riedrich, !. and 8assam, (.7. 9::;. (doption of &onser"ation (griculture !echnologies* &onstraints

and Opportunities. n"ited paper, A World &ongress on &onser"ation (griculture, E%< eruary

9::;, $e# Gelhi, ndia.

0alantini, D.(., @andriscini, M.., glesias, D.O., Miglierina, (.M., and osell, .(. 9:::. !he effects

of crop rotation and fertilization on #heat producti"ity in the Iampean semiarid region of

(rgentina 9. $utrient alance, yield and grain quality. Soil Till. Res. 2F*1F*12F%1>>.

@anders, D. 9::F*19F%1F9.

Mackay, (.G., 8ladi"ko, C.D., Barer, S.(., and 0riffith, G.. 1;=


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Mohamed, (., 7ardtle, W., Dir4ahn, B., $iemeyer, !., and "on Oheim, 0. 9::

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Conservation Ag and Nutrient Use Efficiency