Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 13, 1997
Publication Date: N/A
Interpretive Summary: Crops grown in rotation often have higher yields than those grown on the same land year after year. This yield difference is called the rotation effect. There is only limited information about the rotation effect of the many crops and cropping systems that could be grown in rotation with corn. When corn follows legumes, such as alfalfa and soybeans, at least part of the rotation effect is caused from the atmospheric nitrogen fixed by the legume crop and left in the soil. This effect is called the nitrogen rotation effect. Rotation effects that are not caused by increased soil nitrogen are called non-nitrogen rotation effects. This study was conducted to investigate the influence of several annual and perennial crop species grown alone or in combination (called cropping systems here) on subsequent corn production. The cropping systems grown before corn did not affect the physical condition of the soil or the amount of measurable nitrogen left in the soil. However, when corn was subsequently grown, yield increases over corn following corn occurred for 8 of the 13 cropping systems investigated. Even when the effect of nitrogen was removed, 5 of the 13 cropping systems still resulted in higher corn yields than when corn followed corn. This information will be of most use to individuals interested in sustainable agriculture including farmers.
Technical Abstract: Thirteen cropping systems were grown for 6 yrs on a typic Calciaquoll soil in central Iowa with varying rates of N fertilizer. Perennial plant species were then killed and corn was planted to test residual effects. Within each plot, half the corn was fertilized with 224 kg N ha**-1 and half was left unfertilized. Plant analyses showed that the perennial C4 species, switchgrass and big bluestem, consistently removed the least amount of N of any of the species. There was little difference for soil total-N, NH4-N, or NO3-N concentrations to a depth of 1 m among reed canarygrass, switchgrass, sweet sorghum, and alfalfa. Residual NO3-N concentrations were higher to a depth of 1 m for subplots fertilized with 280 kg N ha**-1 for 6 yrs than for plots fertilized with less N. Aggregate stability did not differ following reed canarygrass, switchgrass, sweet sorghum, or alfalfa. Without N during the 7th yr, corn following sweet sorghum produced the lowest yield (7.5 t ha**-1), whereas the highest yiel following a nonlegume crop was for corn after big bluestem (11.8 t ha**-1). For comparison, corn without N following soybean yielded 11.1 t ha**-1 and that following alfalfa yielded 13.6 t ha**-1. Fertilizer N reduced the rotation effect, but reed canarygrass, big bluestem, alfalfa, soybean, and sorghum intercropped into alfalfa still resulted in significantly higher corn yields than corn following corn (13.0 t ha**-1) with yields of 14.1, 14.2, 15.7, 14.2, and 15.3 t ha**-1, respectively.