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Fluid Journal : Fluid Journal 2002-2004
1 Fluid Journal Fall 2002 P Starters Bump Yields In Corn/Soybean Rotations DR. GYLES RANDALL AND JEFFREY VETSCH Summary: On the low P-testing site, tillage did not affect corn yields in 2001, the five-year average, or the 1998 to 2001 soybean yields. Starters increased corn yield by 35 bu/A in 2001 and by 45 bu/A/yr across the five- year period, while soybean yields were increased by 20 bu/A in 2001 and 14 bu/A/yr across the four-year period due to the residual effects of the starter. Corn and soybean yields at the 100-lb/ A P2O5 rate (broadcast) were generally greater than the 50-lb/A starter P2O5 rate and deep-band P treatments, suggesting that band applications at a half rate are usually not sufficient in low to very low P-testing soils. Highest yields were generally found with the chisel plow system, followed by the one-pass and strip-till systems. Lowest yields were usually found with no-till. The data from these studies suggest that P management strategies are more important than tillage systems for optimizing yields on low P-testing soils. However, on high P-testing soils, tillage has a greater effect on yield than does P management. Researchers stress that optimum placement of phosphorus (P) is essential in reduced-till systems, especially in soils testing low in P. Row-crop agriculture in the Mississippi River Basin is under intense pressure to reduce sediment and nutrient losses by practicing less tillage, as well as more precise application and placement of nutrients (N and P). No-till, strip-till, and one-pass secondary tillage systems are being proposed as reduced-till alterna- tives to conventional-till. No-till corn production, however, has provided serious challenges to corn growers in the northern portions of the Corn Belt and has not been economi- cally competitive with conventional-till systems. This is especially true on the Table 1. Corn yield in a corn/soybean rotation on a low P testing soil as affected by tillage and P management strategies in 2001 and the 5-year avg. Tillage P mgt. P2O5 Yield lbs/A bu/A 2001 1997-2001 avg. No-till Check 0 107 103 Starter 50 133 139 Field cult. Check 0 101 103 Starter 50 140 151 Fall band 50 142 144 Spring b'cast 100 152 162 Strip-till Check 098 102 Starter 50 139 149 Fall band (f) 50 140 146 Fall band (r) 50 135 139 Fall band (f) 100* 146 Chisel Check 0 106 104 Starter 50 141 152 Fall b'cast 100 149 163 (f) = fixed in same position each year (r) = random and band moved 8 inches laterally each year prior to planting corn * This treatment first applied in fall, 1999. highly productive but poorly drained clay loam soils of northern Iowa and southern Minnesota, where approxi- mately eight million acres are in corn production annually. Retarded plant growth, delayed silking, greater moisture at harvest, and reduced corn yields are often associated with no-till systems that have high amounts of surface residue and cooler soil temperatures.
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