Effect of corn stover harvest and winter rye cover crop on corn nitrogen fertilization

Pantoja, Jose
Major Professor
John E. Sawyer
Committee Member
Journal Title
Journal ISSN
Volume Title
Research Projects
Organizational Units
Organizational Unit
Journal Issue

Improvement in N management to optimize corn N fertilization requirement and minimize NO33--N loss from agricultural fields is an ongoing need for continuous corn (Zea mays L.) and corn-soybean [Glycine max (L.) Merr.] production systems. This is especially important in Iowa as this state has the largest corn production across the U.S.A. The present dissertation includes two projects that evaluated corn response to N application and optimal fertilization rate. The first project evaluated the effect of corn stover harvest (SH) in continuous corn and the interaction with chisel plow and no-tillage systems; and the second project evaluated the effect of a rye cover crop (RCC) in no-till corn-soybean. For the RCC project, an additional in-field experiment was conducted to help understand the N cycling.

Results of the corn SH project showed that across tillage systems and fertilizer N rates, corn grain yield was 7 and 10% greater with 50 and 100% SH compared to no harvest, respectively. Corn grain yield was also 9% greater with chisel plow than with no-tillage. At the economic optimum N rate (EONR), yield was not influenced by SH with chisel plow, but was 6% greater with each SH rate in no-tillage. The EONR was the same with both tillage systems, but decreased by 22 and 45 kg N ha-1 with 50 and 100% SH, respectively. Results indicate, at least on a short term basis, that suggested N fertilization rates should be adjusted when stover is harvested in continuous corn production.

Results of the RCC project showed that the reduced corn grain yield by 6% at the EONR, and increased RCC biomass production resulted in lower corn yield. The EONR was the same with no-RCC and RCC. Soybean yield was not affected by the RCC. The RCC N cycling experiment showed that RCC biomass degradation and N recycling after rye control consistently decreased over time (total of 105 d after control), following an exponential decay. Nitrogen recycling was faster and more N recycled with RCC following soybean than following corn (22 vs. 14 kg N ha-1, respectively), and was influenced by the RCC C:N ratio. This research indicates that corn N fertilization rate should be the same with or without a RCC system, mainly due to the RCC not recycling a large amount of N. Since there was low RCC N uptake, reduced corn yield, and no change in EONR, improvement in the RCC system or management practices are needed for RCC to become viable in a no-till corn-soybean rotation.