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Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Fall 1994 Soybeans. The five varieties tested in the system were selected for their excellent yielding ability, but significant yield differences occurred. In 1991, five varieties averaged 56 bu/ A with irrigation and 46 bu/A without. Similarly, MEY systems showed a significant yield increase over conventional systems. Our results showed that maturity was delayed about four days by irrigation, with a beneficial lengthening of the seed- filling period. Row spacing is another important cultural practice that has a significant effect on double-cropped soybean yields. We used spacing of 15 inches in our studies, with a seeding rate of six seeds/ft or about 209,000 seeds/A. Several fertility practices have been studied. One variable is direct fertilization of the soybeans. Results to date, where high soil test levels for P and K are maintained, show that farmers have the option of applying the total two-crop P and K requirement to wheat. We continue to experiment with N applications on soybeans. Rotations Rotation studies conducted at Poplar Hill to evaluate several cropping systems have shown that no-till corn planted into a wheat and double- cropped soybean stubble continuously produces the best yields. This includes yields of corn planted into a winter cover crop of hairy vetch. This is significant. No expense is involved for the wheat/soybean stubble, which provides a natural mulch following harvest of the two crops. Compare this to the cost for establishing a legume winter cover crop. Rotation also provides a wheat crop following corn, which takes up around 30 to 35 lbs of residual N not used by the corn. Mulford is manager of the Poplar Hill Facility in Quantico, Maryland, and Dr. Kenworthy is professor of agronomy at the University of Maryland. Figure 1. Yield comparisons, Delmarva Peninsula average versus three-crop/ two-year systems ap- proach, Mulford/ Kenworthy, Maryland. Figure 2. Yield response of corn hybrids to row spacing, three-crop/two-year systems approach study, Mulford/Kenworthy, Maryland. 15" Row Width 30" 130 150 170 190 210 230 Yield (bu/A) Top Hybrid Bottom Hybrid Corn Wheat Crop Soybeans 20 40 60 80 100 120 140 160 180 200 220 Yield (bu/A) Delmarva Peninsula Avg. Systems Approach
Fluid Journal 1996-1998