Kernel weight relevance in maize grain yield response to nitrogen fertilization

Abstract

Knowledge of maize (Zea mays L.) kernel weight (KW) and kernel number (KN) response to nitrogen (N) fertilization can help understand the physiological basis behind the overall grain yield response to N fertilizer, but such data are rare. To fill this gap, we studied how KN and KW respond to N fertilization. We first analyzed grain yield and its components in 23 field N response experiments (site × year combinations) from Argentina and United States. Second, we compared results to literature studies, and analyzed the contribution of each yield component to yield N fertilization response. We hypothesized that there is a range in grain yield response to N fertilization where both KN and KW explain the responses to a similar degree, but large increases in grain yield are only sustained by KN changes. Our experiments showed that N fertilization had a consistent effect over both yield components across experiments. In Argentina the average grain yield relative response ([Trait Nn – Trait N0]/Trait N0) across sites to the maximum N fertilization rate (43%) was more related to KW (23%) than to KN (17%). In the United States the average relative grain yield response across sites to the maximum N fertilization rate (82%) was more related to KN increases (52%) than to KW (22%). When comparing our results to literature studies, we found that in situations where grain yield responses to N fertilization were less than 30%, the KW response is slightly a higher contributor than KN to grain yield increases. As the grain yield response to N fertilization is higher than 30%, then KN changes are significantly more important in explaining these grain yield increases. The KW response to N fertilization increases showed a maximum response value of 34% increase, while KN continued increasing linearly. These results evidence the relevance of KW changes in maize grain yield response to N, but also the importance of KN responses when N grain yield limitations are most severe.