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Fluid Journal : Fluid Journal 1993-1995
1 Fluid Journal Spring 1993 Dr. E.C. Varsa and Stephen Hnetkovsky Effects of Residue Density on Corn Yield Research Spans three-year period at two southern Illinois locations. Summary: Soil temperature decreased with increasing residue levels. Increasing levels of residues at mid- season crop development resulted in significantly higher soil moisture. Corn yield remained unaffected by increasing levels of residues in 1989 and 1991. Corn yield from injected UAN was 20 bushels per acre greater than that obtained from dribble-placed UAN and over 40 bushels per acre greater than that obtained from broadcast urea. NEPT (urease inhibitor) addition resulted in about a 4-bushel per acre increase over an unamended UAN. Split application of UAN resulted in corn yields about equal to those obtained with dribbled UAN.Experiments were conducted on corn from 1989-9 1 at two southern Illinois locations. Study sites were the Belleville Research Center and the Carbondale Agronomy Research Center on Iva silt loam and Stoy silt loam soils, respectively. The previous crop was no-till corn at each location for each year of the study. The objectives of our research were to study the effects of different residue density levels on performance of urea ammonium nitrate (UAN) solution, urea, and urease inhibitor additives on no-till corn. The urease inhibitor studied was NBPT. Treatment comparisons also included placement and timing strategies. We established four residue levels each year of the study by removing residues from the 0-level residue plots and adding those residues to existing stubble on other plots to give a 200 percent residue level. Other plots had about one-half of the residues removed to result in a 50% residue cover. The 150 120 90 60 30 0 0 50 100 200 Residue density level (%) Yield (Bu/A) O-N UAB(Dr) UAN+NBPT(Dr) UAN (NW) Urea(Br) = Split Figure 1. Effect of N and inhibitor on no-till corn yields at different residue levels, Belleville, 3-year averages (1989-1991). remaining plots, designated as 100% residue cover, remained undisturbed. Except for the "weed and feed" treatment, fertilizer treatments were applied at approximately the 2- to 3- leaf stage. Table 1 describes the fertilizer treatments reported in this article. We planted Pioneer brand 3471 in 1989 and 1990 and Pioneer brand 3394 in 1991. Yield results mixed We saw considerable variation in the grain yield as affected by residue levels. At Belleville, increasing residue level lowered yield in 1989. However, in 1990, grain yield was higher at the higher residue levels at both locations. The 1990 growing season was very unusual in that excessive rainfall delayed planting until mid June. Additionally, heavy rains in May caused considerable surface soil compaction. The beneficial effects of the 200% residue level resulted in nearly a 20-bushel per acre yield increase over the 0% residue level at Carbondale. At Belleville, the highest residue level increased yield only 10%. At Belleville (Figure 1), clearly UAN injection was superior to dribble placement, regardless of the use of NBPT. Also, broadcast urea was clearly inferior to all other fertilized treatments. Higher residue levels had a more negative effect on yields for the urea and control treatments than all others at Belleville. This was probably the result of higher nitrogen immobilization of urea and 0-N treatments as well as higher ammonia volatilization losses with the urea N source in the presence of higher residues. Inclusion of NBPT
Fluid Journal 1996-1998