Ecological intensification of corn based cropping systems: soil quality changes impact yield

WALTERS, DAN T.; CASSMAN, KEN; DOBERMANN, ACHIM; SPECHT, JIM; YANG, HAISHUN; WINGEYER, ANA B.

Conferencia; Fluid Fertilizer Foundation Symposium; 2009

More intensive N management strategies that focus both on improving crop N use efficiency and residue carbon management also contribute to reducing nitrogen input over the longer-term through increases in soil organic matter and N storage that can increase the indigenous soil N supply capacity. Herein we will report on corn yield, N use efficiency (NUE) and changes in both soil C and N over the course of the Ecological Intensification experiment and the residual effect of changes in soil quality on corn yield in 2008. Average crop yields in this experiment were close to the yield potential of soybean and corn at this location and significantly higher than the national or state average. Corn yields were generally in the 215 to 287 bu/a range or within 84 to 97% of the simulated yield potential. Corn following soybean yielded about 5 to 11% higher than continuous corn primarily due to fewer problems with stand establishment and fewer pest and disease problems. Since the start of this experiment, large amounts of crop residue have been returned to the soil in all four management systems, but with significant differences among them in terms of dry matter amounts and composition. Corn returned 75 to 100% more residue than soybean, but with a much wider C/N ratio. Both residue C and N input were highest in the CC-int system, exceeding the more commonly practiced CS-rec system by 30 to 40%. Although corn yields and N use efficiency were higher for the intensive corn-soybean rotation, this excellent performance was achieved at the cost of exploiting C and N reserves. These observations lead us to conclude that the N-credit attributed to corn-soybean rotations appears to be due to mining of soil N reserves. The elevated indigenous N supply mineralized from the CC treatment that had received the M2 N rate as well as post-harvest fall applications of N to residue prior to plowing was approximately 30% greater than the other (rotation by fertilizer management) treatments.