Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fall 2014
15 The Fluid Journal Fall 2014 support previous work, indicating that continuous corn systems result in lower yields than corn--soybean rotations and that the yield penalty associated with continuous corn is partly the result of stover accumulation. During average and poor growing seasons, corn/soybean rotations are more likely to support high plant populations than continuous corn. Partial stover removal did not overcome the continuous corn yield penalty in strip-tillage systems, but it did overcome the yield penalty in conventionally tilled systems and was especially beneficial in High Technology treatments in 2011. We believe stover removal will be even more effective under favorable growing conditions. This datum indicates that stover removal may require additional fertilizer application, especially under high density planting conditions. 2012 Hybrid trait, specifically insect resistance traits, played a critical role in protecting corn yields from yield loss during the drought of 2012. Yield data directly support previous work from this research group, indicating that the yield penalty associated with continuous corn is much greater under drought conditions. Reduced plant populations and omission of fungicide also improved crop yields during the severe drought of 2012. P, S, and Zn fertilizers had generally positive results when applied to the TRAD package, increasing yields by an average of 6 bu/A-1, but N, P, S, and Zn applications actually reduced grain yields when applied to the high- population, high-input HT package. During poor growing seasons like 2012, corn/soybean rotations are more likely to support high plant populations than continuous corn. Stover removal was effective for high-population, conventionally-tilled continuous corn systems, but did not provide a yield advantage to other systems under the poor growth conditions of 2012. Surprisingly, reduced surface residues in corn/soybean rotations appear to have made soil moisture penetrate the residue/soil interface and move deeper in the soil profile, as evidenced by soil moisture readings at five depths in four Management Systems in the study. During a severe drought, such as 2012, accumulation of residue on the soil surface appears to have made rainfall less root-available by sequestering the moisture in the residue where it was more vulnerable to rapid evaporation. Dr. Gentry is Director of Water Quality Research for the Illinois Corn Growers Association and Adjunct Assistant Professor in the Department of Natural Resources and Environmental Sciences at the University of Illinois, Urbana-Champaign, and Dr. Below is Professor of Crop Physiology in the Department of Crop Sciences, University of Illinois 2013 A late planting date, late-season drought, and extensive plant lodging resulted in lower yields and a muted effect of technology and stover management treatments. Averaged over other treatments, intensively- managed treatments did not produce significantly greater corn yields than the conventionally-managed environment, despite substantially greater inputs. These results are in contrast to 2011 and 2012 when intensively-managed environments yielded 15 and 19 percent greater than conventionally-managed environments. Yield data from 2013 were unique in a number of respects, owing to weather, late planting date, and late- season drought. There was no significant continuous corn yield penalty observed in 2013, meaning that yields were essentially the same between continuous corn and corn following soybeans. When stover was removed in 2013, treatments consisting of lower plant populations and higher levels of P, S, and Zn inputs (i.e., +FERT) resulted in greater yields than other treatments, whereas treatments consisting of high plant populations and/ or lower levels of P, S, and Zn inputs (i.e. TRAD, HT, -FERT) demonstrated reduced yields. These data suggest that the drought during pollination, coupled with fertility lost from stover removal, proved detrimental to crop yields. Full retention of stover may have proved beneficial by reducing evaporative soil moisture losses during the drought in August. There was essentially no stover removal effect in 2013, with one notable exception. It appears that higher plant populations and lower levels of P, S, and Zn resulted in reduced yields when stover was removed. One entire system, CC/Stover Removed/Strip Tillage, had to be omitted from the study as a result of severe lodging in two replicates, which was the result of the location of the split plots along wind-affected field edges that were impacted by a strong wind event. We do not believe that the lodging was the result of a treatment effect due to strip tillage, since other plots were similarly impacted but fortunately did not result in loss of entire reps. As in 2012, Hybrid was the most influential technology factor in 2013, followed closely by P-S-Zn application. Replacing the triple-stack, insect- protected hybrid with the same hybrid without the Bt traits and keeping other Technology factors at the advanced level (-HYBRID) resulted in a 6 percent yield reduction relative to the HT treatment, averaged over all systems. A 5.5 percent yield increase was demonstrated when the triple-stack hybrid replaced the non-Bt hybrid when other Technology factors were applied at the standard level (+HYBRID) relative to the TRAD treatment. Summing up This study demonstrated that: • The combined application of commercially available and proven technologies increased yields above the standard treatment by 15 percent in 2011 (moderate drought), 19 percent in 2012 (severe drought) and 9 percent in 2013 (late planting with dry mid-season conditions) • The effects of various management factors are highly dependent on growing season and no single factor is consistently the most beneficial to crop growth. The most influential factors were nutrient applications in 2011, crop hybrid in 2012, and crop hybrid and nutrient applications in 2013. • Continuous corn production yielded significantly less grain than corn following soybeans in 2011 and markedly less grain during the drought of 2012 (37 percent reduction). In 2013 no yield penalty was observed for continuous corn • As demonstrated in 2012 and 2013, application of strobilurin-containing fungicides can be beneficial even during dry growing seasons when most fungal pressure is low. However, if late-season conditions during grain fill and afterwards are poor, fungicide can actually reduce grain yield.