Second-year corn after alfalfa often requires no fertilizer nitrogen

Matt A. Yost, Thomas F. Morris, Michael P. Russelle, Jeffrey A. Coulter

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Terminated alfalfa (Medicago sativa L.) often provides N to at least 2 yr of subsequent corn (Zea mays L.) crops, but the variability in fertilizer N guidelines for second-year corn in the midwestern United States needs to be addressed. In several states, fertilizer N guidelines are the same for second-year corn after alfalfa as they are for continuous corn, whereas other states recommend reducing fertilizer N rates to second-year corn by 25 to 145 kg N ha-1. Experiments were conducted at 28 farms in Iowa and Minnesota to determine fertilizer N requirements of second-year corn after alfalfa. Second-year corn in half of the trials showed no response to fertilizer N and the economically optimum N rate (EONR) for corn grain yield in the 14 responsive trials ranged from ≤67 to 196 kg N ha-1. Furthermore, in 10 of 19 trials there was no response of grain yield to fertilizer N in both first- and second-year corn. These results indicate that current university fertilizer N guidelines for second-year corn after alfalfa often are unreliable. At the widely adopted critical concentration of 21 mg kg-1, the pre-sidedress soil nitrate test (PSNT) correctly identified only 63% of the trials as responsive or nonresponsive to fertilizer N. When results of our experiments were combined with data from the literature, second-year corn grain yield responded to fertilizer N 55% of the time and the PSNT remained accurate only 65% of the time, indicating that more accurate forecasting of second-year corn N requirements is needed.

Original languageEnglish (US)
Pages (from-to)659-669
Number of pages11
JournalAgronomy Journal
Volume106
Issue number2
DOIs
StatePublished - Jan 1 2014

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