Location: Soil, Water & Air Resources Research
Project Number: 5030-12210-004-006-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Aug 15, 2024
End Date: Aug 14, 2028
Objective:
Determine gains in nitrogen use efficiency and identify changes in underlying plant processes that benefit crop growth with different modes of humic product application in Iowa corn and soybean fields.
Approach:
To test whether humic product application promotes crop growth and hence fertilizer use efficiency, Core funding has supported a field experiment of continuous corn cropping with multiple rates of liquid nitrogen fertilizer application. Each rate has subplots with and without humic product application. At the higher nitrogen application rates, earlier results confirmed greater nitrogen use efficiency and grain yield with humic product application. But at lower, deficient nitrogen fertilizer rates, the humic product caused a loss in grain yield. This complex grain yield response was reproduced in measurements of leaf soluble carbohydrates, which were funded by a previous grant with this same funder. More process-level measurements are needed to untangle the likely causes of the adverse effects that humic products may have on grain yields when applied at deficient fertilization rates. Proposed renewal of funding will provide laboratory supplies for additional in-season crop measurements. These same measurements of nitrogen use efficiency and physiological processes will also be conducted in a separate field trial of a corn-soybean rotation that will compare different modes of humic product application: Analysis of both field trials will provide unique insights and guidance on how different modes of humic product application at varying crop growth stages can favorably modify crop nitrogen use efficiency and grain yields, and further explore the unusual crop responses at deficient nitrogen fertilization rates.