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Fluid Journal : Fluid Journal 1999-2001
Spring 1999 affected significantly. The fact that late- season N applications had no impact on leaf N concentration suggests that fertilizer N taken up by the plant was translocated directly to the forming soybean seed and not stored in the leaf. Methodology Locations. Studies were initiated in 1994 and repeated in 1995 at four Kansas locations in Shawnee, Johnson, Reno, and Stafford counties. Soil types were Muir silt loam, fine- silty, mixed, superactive, mesic Cumulic Haplustolls in Shawnee County; Eudora silt loam, coarse-silty, mixed, superactive, mesic Fluventic Hapludolls in Johnson County; Naron fine sandy loam, fine- loamy, mixed, mesic Udic Argiustolls in Reno County; and Pratt loamy fine sand, sandy, mixed, mesic Psammentic Haplustalfs in Stafford County. Cultural practices used at each location are summarized in Table 1. At all sites, soybeans followed corn and cooperators applied needed P and K in the corn year of rotation. Plots. All sites were irrigated. Each included four replications and nine treat- ments arranged in a randomized complete block design. Individual plots usually measured 10 by 20 ft. When 36-inch rows were used they measured 12 by 20 ft. Treatments included UAN, urea, urea + NBPT, and ammonium nitrate, applied at rates of 20 and 40 lbs/A. Applications were foliar- or broadcast-applied between the R3 and R4 stages of growth. A check (no-N) treatment was included. Soil samples were taken at each site and analyzed for pH, P, K, and organic matter (Table 2). Profile N (nitrate N) was determined to a depth of 6 inches in 1994 and 24 inches in 1995. Plant tissue samples were taken two to three weeks after late-season N application by collecting the last fully developed trifoliate leaf from 10 to 12 plants in each plot. _________________________________ Wesley is extension assistant, Dr. Lamond is professor, Dr. Martin is agronomist, and Dr. Duncan is extension specialist in the Department of Agronomy, Kansas State University. ! Figure 3. Effect of late-season N application on irrigated soybean oil concentration, Wesley, et al., Kansas State University, 1994-95. 35 30 25 20 15 10 5 0 Check UAN Am. Nit. Urea Urea + NBPT % grain oil concentration 0 lbs/A 20 lbs/A 40 lbs/A Figure 2. Effect of late-season N application on irrigated soybean protein concentration, Wesley, et al., Kansas State University, 1994-95. 40 35 30 25 20 15 10 5 Check UAN Am. Nit. Urea Urea + NBPT % protein concentration 0 lbs/A 20 lbs/A 40 lbs/A
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