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Fluid Journal : Fluid Journal 1999-2001
Winter 2000 than either Au86-2397D or Au86- 2397I at R1 when averaged across N rates. Dry matter. Both Au86-2397D and Au86-2397I exhibited increased plant dry matter yield with N starter, whereas Cook did not. It would appear dry matter response to the N starter at R1 stage was dependent on growth habit and cultivar. N concentration. Above-ground plant N concentration at R1 increased 5 percent when N starter was applied. Moreover, reduced nodulation owing to N starter had no negative effect on total plant N concentration at the R1 stage of growth. Cultivar selected had no effect on plant N concentration. Late-season Maturity date was not affected by cultivar selected or starter N rate applied (data not shown). Plant height. Au86-2397I had greater height than Au86-2397D at R8. Averaged across N rates, Au86- 2397I measured 27 inches while Au86-2397D measured 18 inches, only a 4-inch increase following R1. Application of N starter slightly increased R8 plant height. Lodging. Although there were statistical differences in plant lodging scores due to cultivar selected, there was little or no lodging (data not shown). Relatively short plant height (<22 inches) kept lodging scores minimal. Only when plant height exceeded 24 inches did we see increased lodging. Methodology Site. Experiments were conducted in seven southern Alabama site-year environments in 1995-96. Design was a randomized complete block consisting of six treatments, with four replications in each environment. P and K fertilizers were applied according to Auburn University Soil Testing Laboratory recommendations prior to planting of corn in early March. Planting. Soybeans were planted during July in 6-inch rows at the seeding rate of 530,000 seeds/A. Pesticides. Herbicides were applied for weed control after planting. All sites received additional postemergence applications of herbicides and insecticides for control of specific pests. Climate. Growing-season precipitation was within normal limits, and supplemental overhead irrigation was applied according to standard practice. Sampling. Prior to soybean planting, soil samples were taken. Root and plant samples were taken at the R1 developmental stage. Starling is a former graduate student; Dr. Wood and Dr. Weaver are professors in the Department of Agronomy and Soils, Auburn University. ! 30 29 28 27 26 25 24 Figure 1. Yield effects of N starter and cultivar on R8 developmental stage traits of late-planted soybeans in southern Alabama, 1995-96. 0 45 N starter -- lbs/A Yield - bu/A Cook Au 86-2397D Au 86-2397I
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