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Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Spring 1993 resulted in an average increase of 4- bushels per acre (Figure 2). Figure 3 shows the effects of residue levels on N fertilizers, inhibitor and placements at Carbondale. Severe summer dryness greatly reduced yields in both 1989 and 1991. Consequently, the yield differences due to inhibitor and placement strategies were small. Figure 3. Effect of N and inhibitor on no-till corn yields at different residue levels, Carbondale, 3-year averages (1989-1991). 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 • = split • Yield (Bu/A) Figure 2. Effect of N and inhibitor on no-till corn yields over all residue levels at Belleville and Carbondale, 3-year averages (1989-1991). N Rate: 150 lbs N/Acre O-N UAN UAN UAN UR 120 90 60 30 0 O-N UAN UAN UAN UR + NBPT DrDrINJBr Belleville + NBPT DrDrINJBr Carbondale 40 116 120 135 92 39 868389 78 Note that split UAN application was the highest yielding treatment at the 100% residue level density. Broadcast urea resulted in the lowest relative yields (Figure 2). Other variables Increasing levels of residues resulted in higher amounts of soil moisture. The 0-4 inch depth showed the greatest differences with smaller differences found at the 4-8 inch depth. Soil strength as measured by penetrometer resistance in the 0-2 inch depth was also significantly lower at higher residue density levels. We think that at the lowest residue level rainfall caused compaction on the bare soil. Figure 4 shows that increasing residue levels significantly decreased soil temperature during the period of measurement. The 200 percent residue level averaged nearly 4 degrees cooler than residue-free plots. A lower temperature would delay germination, emergence and early root development. Additionally, lower temperature would reduce rates of microbial activity and might impact such processes as nitrification, denitrification and N immobilization. Residue Impact Crop residues occurring at the soil surface in a no-till system have a significant impact on the physical, Table 1. Fertilizer treatments applied over O, 50, 100 and 200 percent residue levels at Belleville and Carbonadale in 1989-1991 experiments. Treatment N N Source/Inhibitor/ No. Rate1 (Placement) 2 10 2 150 UAN* 3 150 UAN + NBPT* 4 150 UAN** 5 150 UREA*** 6 150 UAN**** * Dribble ** Inject *** Broadcast **** Split---!Weed&Feedand! Sidesdress-dribble 1 includes N from 50 lbs. of ammonium sulfate per acre applied over all treatments. 2 UAN source was 28-0-0. NBPT was applied at 1.0 lb. per acre as a mixture with UAN. Dribble placement was approximately 6 inches from 30-inch spaced corn rows. Injection was to about 5 inches depth at about 6 inches from corn rows using an apparatus similar to that described by Benjamin et al., (1988). Treatment No.6 also included 7-21-7 as a "starter" at planting and was applied only to the 100% residue level.
Fluid Journal 1996-1998