Interaction between soil moisture and nitrogen (N) levels plays a major role in determining wheat yield, according to a crop nutrition expert.
Dr Glenn McDonald, Associate Professor at the University of Adelaide’s School of Agriculture, Food and Wine, says having an understanding of the soil’s moisture holding capacity and information about changes in plant-available soil water during the growing season are important aspects of N management.
“The supplies of water and N are the major drivers of growth and yield of crops, and the two interact to determine crop yield,” said Dr McDonald, when addressing a Grains Research and Development Corporation (GRDC) grains research Update in Adelaide (SA) on nitrogen application “rules of thumb”.
“While availability of moisture is recognised widely as an important factor limiting responses to N, it is also important to realise that lack of N can be an important limitation to soil water use and particularly use of subsoil moisture.”
While much of N management focuses on improving post-anthesis growth and grain filling, it is more than likely that the effects of N and its interaction with soil moisture are influencing yield earlier by affecting grain number as well as grain size, according to Dr McDonald.
He said applying N fertiliser at the optimum rate for the anticipated yield or applying it strategically during the growing season could improve yield and grain protein.
“Applications of N up to mid-stem elongation build the foundation for yield and have relatively little effect on protein, while later applications of N can be used to maintain or increase protein, but have little or no effect on yield. Applying N between the flag leaf emergence and flowering stages of crop growth can result in greater increases in grain protein concentration.”
Dr McDonald said the demand for N was driven by crop growth rate and the pattern of N uptake would reflect the changes in growth rates during the growing season.
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