Farmer’s Weekly – 09 August 2019

legumesthanwhenwheatwas

producedalone,and35%better

whentherotationincluded

onlyoneyearoflegumes.The

useofcanolaintherotation,

withoutanylegumes,increased

nitrogen-useefficiencyby9%.

Duringthepasttwoseasons,

ofwhich 2017 wasdryand 2018

hadbelow-averagerainfall,

theresearcherssetoutto

establishhowlowthenitrogen

levelcouldbereducedina

medicandwheatrotation.

In2017,wheatwasplanted

withonly12kg/haofnitrogen.

In2018,thiswasreducedto

9kg/ha.Duringbothyears,

a topdressingof30kg/ha

ofnitrogenwasapplied.

Theevaluationrevealedthat

in84%ofthetrialcamps,half

ofthemproducedhigheryields

whenlessnitrogenwasused.

A

roundtheworld,a

growingnumberof

farmersareswitching

tocroprotationduetoits

capacitytoimprovefarm

earningsthroughhigheryield

andreducedfertiliser,pesticide

andherbicideusage,while

boostingsustainability.

Long-termrotationtrialsby

theWesternCapeDepartmentof

AgricultureattheLanggewens

ResearchFarmintheSwartland

andTygerhoekintheSouthern

Capeconfirmthis.

Incroprotationevaluationsthat

startedatLanggewensin1996,

wheatmonoculturehasalways

beenthepoorestperformerof

allthecombinationsundertrial.

Butinrotationsthatincludedat

leastonetypeoflegume,suchas

lupinesormedics,theaverage

wheatyieldwas30%higher

thanwhenwheatwasproduced

ina monoculture.Theyieldsof

rotationscontainingnolegumes

wereonaverage12%higher.

Bestrotation

A medic-canola-medic-wheat

rotationconsistentlyperformed

thebest,producinganaverage

yield37%betterthana system

wherewheatwasproduced

onitsown(seetable).

Water-andnitrogen-use

efficiencyalsoimproved.Water-

useefficiencyofrotationsthat

includedcanolawas11%higher,

androtationsthatincludedone

ormoreyearsoflegumecrops

orpastureswerebetween26%

and31,6%higherthanwhen

wheatwasplantedonitsown.

Nitrogen-useefficiency

wasonaverage89%better

inrotationsthatincluded

Includingmorethanthreecropsin a cashcropsystemmaynotonlyhelpincrease yield, but

significantlyenhancethelong-termsustainability of a farm.Dr JohannStrauss of the Western

CapeDepartmentof Agriculturespoke toGlenneisKrielaboutthebenefits of crop diversity.

Fast

Facts

• thegreater
  thediversityin
  croprotation,
  thebetter.


• animalsadd
  valuetocrop
  rotation.


• Despiteits
  advantages,crop
  rotationis not
  a stand-alone
  solutiontofarm
  problems.

Crop diversity

A pillar of sustainable

production

46 farmer’sweekly 9 AUGUST 2019

soil health Crop Rotation