Closing the nitrogen supply and demand gap using legume residue combined with fertiliser nitrogen input

MUSCHIETTI PIANA, M.P.; MCBEATH, T.; MCNEILL, A.M.; GUPTA, V.; CIPRIOTTI, P.A.

Melbourne

Conferencia; VII International Nitrogen Conference; 2016

INI

In low-rainfall wheat cropping systems, lownitrogen (N) use efficiency has been linked to asynchrony between soil mineral-Nsupply and crop N uptake. This is especially true on sandy soils of SEAustralia which have a low-N supply capacity. When the N released from soil and residues areinsufficient, and/or the timing of biological supply is not well matched withcrop demand, manipulating N supply with fertiliser becomes vital to achieveyield potential. The aim of this study was to measure the timing of N supplywith crop N uptake for wheat following wheat-residues and wheat followinglupin-residues under two N fertiliser rates in a low-rainfall sandy soilenvironment. In each residue-type site, plants and deepsoil samples up to rooting depth were collected at sowing and at 5 key wheatgrowth stages. Plants were analysed for N content, above-ground biomass andgrain yield at maturity. All soil samples were analysed for gravimetric waterand nitrate-N. Thecombination of lupin residues with a high fertiliser N rate increased soil-N levels, promoted plant performance and wheat Nuptake. In a decile 3 year, the additional N supplied as fertiliser was a keyinput to support an increase in wheat yield potential. Responses in N uptakethroughout the growing season indicates that there remains a demand forfertiliser N following legume-N residue in this environment, but fertiliser Ninputs remain risky as indicated by the lack of significant yield effect.