Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2012
Publication Date: 8/13/2014
Citation: Riedell, W.E. 2014. Nitrogen fertilizer applications to maize after alfalfa: grain yield, kernel composition, and plant mineral nutrients. Journal of Plant Nutrition. 37:2026-2035. DOI:10.1080/01904167.2014.911892.
Interpretive Summary: Because farmers often apply excess N fertilizer to maize after alfalfa, information is needed that explores crop and yield responses to reduced N fertilizer in maize after alfalfa. The hypothesis tested was that reducing the amount of N fertilizer applied to maize after alfalfa will not significantly reduce grain yield nor have negative effects on kernel composition. Because N has an effect on maize root system morphology, which in turn may alter the uptake of essential mineral nutrients in addition to N, it was also of interest to determine the effects of N fertilizer reduction on other essential mineral nutrients in plants and grain. Results of this study show that application of N fertilizer to first year corn after alfalfa did not result in increased grain yield but did increase kernel concentrations of protein, P, K, and Zn. The observation of increased kernel protein concentration in the absence of increased grain yield further suggests that, in this study, N fertilizers were applied to maize after alfalfa in excess of that needed to increase yield. Application of N fertilizer with no resulting yield benefit is a production practice that will lead to increased input costs, reduced profitability, and increased potential for environmental contamination if N fertilizers move outside the root zone. Based upon these results, application of N fertilizers to first year maize after alfalfa is a crop production practice that should be avoided in the northwestern corn growing region of the U.S.
Technical Abstract: Farmers often apply greater rates of nitrogen (N) fertilizer to first-year maize (Zea mays L.) after alfalfa (Medicago sativa L.) than are needed to attain maximum yields. Fertilizer N applications that do not result in increased grain yield will lead to increased input costs, reduced profitability, and increased potential for environmental contamination if N moves outside the root zone. Thus, information is needed that explores grain yield, grain composition, and shoot organ mineral nutrient responses to reduced N fertilizer in maize after alfalfa. The effects of N fertilizer treatments (no N fertilizer, 73 kg N ha-1, or 135 kg N ha-1) on maize shoot organ dry weight and shoot mineral concentrations (N, P, K, and Zn) at the tassel (VT) development stage, grain yield, and grain components (protein, oil, starch, P, K, and Zn) were investigated on maize after alfalfa in a 2-year study conducted at Brookings, South Dakota, USA. Fertilizer N application to first year corn after alfalfa resulted in increased N concentration in leaves, leaf sheaths, and stems of plants at the VT development stage during both years of the study as well as small but significant increases in the leaf P concentration in one growing season characterized by warm air temperatures and above average precipitation. Fertilizer N applications did not result in increased grain yield but did increase kernel concentrations of protein, P, K, and Zn concentrations and reduced starch. Increased kernel protein concentration in the absence of increased grain yield was another indicator that applying N fertilizer to maize after alfalfa in this study increased soil N in excess of that needed to increase yield.