|Yost, Matt -|
|Coulter, Jeffrey -|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 7, 2013
Publication Date: April 26, 2013
Repository URL: http://hdl.handle.net/10113/57276
Citation: Yost, M.A., Russelle, M.P., Coulter, J.A. 2013. Nitrogen requirements of first-year corn following alfalfa were not altered by fall-applied manure. Agronomy Journal. 105(4):1061-1069. Interpretive Summary: Despite years of research, it remains difficult to estimate the amount of supplemental nitrogen a crop will need to provide highest economic returns to the farmer. This is especially true for crop rotations that follow legumes, like alfalfa, and for animal manures. Alfalfa usually, but not always, provides all of the nitrogen needed in the first corn crop. Would adding dairy cow manure help? We conducted experiments on eight Minnesota farms to determine the amount of fertilizer nitrogen needed for the first year of corn after alfalfa, both with and without manure added the previous autumn. There was no effect of manure on corn grain of silage yield, even though we found evidence that some nitrogen from manure was present in the crop at harvest. Yield of corn grain responded to fertilizer nitrogen at only two of the eight farms and corn silage yield responded at three, confirming that alfalfa often provides sufficient nitrogen to the next grain crop, but less frequently for the silage crop. Our research showed that farmers could get more benefit from livestock manure, and help prevent nitrogen losses to the environment, by spreading the manure on crops that need extra nitrogen to produce high yields. In addition, the research confirmed that alfalfa has high value as a nitrogen source for following crops, which should reassure farmers that they can reduce fertilizer nitrogen applications in this rotation.
Technical Abstract: There are no published reports on the direct effects of fall manure application on alfalfa (Medicago sativa L.) N credits to first-year corn (Zea mays L.) grown as grain or silage. Therefore, on-farm experiments were conducted at eight locations in Minnesota to test whether manure applied during fall alfalfa termination affected the rate of fertilizer N needed by first-year corn. At none of the eight locations did manure affect corn yield. At six of eight locations, grain yield also did not respond to fertilizer N, but the two remaining locations had an economically optimum N rate (EONR) of 98 kg N/ha for grain yield. The EONR for silage yield was 113 kg N/ha at these two locations plus one additional location. The presidedress soil nitrate test (PSNT) was successful at predicting the need for N fertilizer to optimize grain yield only 63% of the time in this study, but only 55% of the time when considering these and 86 site-years of first-year corn after alfalfa from the literature. The basal stalk nitrate test (BSNT) was successful at identifying the need for N fertilizer 75% of the time in this study. However, accurate critical concentrations could not be estimated when considering relative yield and BSNT data from these and 13 site-years of our previous work. These results confirm that first-year corn following alfalfa often does not require supplemental N for maximum grain yield, and that improved methods are needed to predict fertilizer N response in first-year corn.