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Fluid Journal : Fluid Journal 1993-1995
3 Fluid Journal Fall 1995 and 3:1 N:P2O5 ratios shortened the period between emergence and mid- bloom by 6 and 7 days, respectively. Effects of planting date Yield. No significant planting date x starter fertilizer interaction occurred in any year of the test, indicating that grain sorghum yield response to starter fertilizer is independent of planting date. In other words, starter effects were similar regardless of the time the crop was planted. Yields, however, were lower with the June than the May planting (Figure 3). This was probably due to the effects of lower than optimum temperatures on grain fill. Dry matter production was not affected by planting date. P uptake. When averaged over three years, P uptake at the 6-leaf stage was 19 percent greater for the May planting than for the June planting. Leaf concentrations. Leaf N and P concentrations were not affected by planting date. Methodology Soil. Our studies took place near Belleville, Kansas, on a Crete silt loam soil. Soil pH was 6.1; organic matter content was 2.4 percent. Bray-I P and exchangeable K in the surface 6 inches of soil were 24 (medium-high) and 380 (very high) ppm, respectively. Plots. Experimental design was a split-plot replicated four times. Plots consisted of four rows 42 feet long and 30 inches apart. Whole plots consisted of planting dates (mid-May and late- June). Subplots were combinations of N and P starters (0, 10, 30, or 90 lbs/A of N, with or without 30 lbs/A of phosphate, plus a check (no fertilizer) and broadcast NP treatment. Placement. Starter fertilizer treatments were knife-applied at planting in a band 2 inches to the side and 2 inches below the seed. Immediately after planting, surface broadcast applications were made to all plots, except the unfertilized plots, to bring the total amount of fertilizer applied to 90 lbs/A of N and 30 lbs/A of phosphate Fertilizer. Fertilizer combinations consisted of 28% UAN, ammonium polyphosphate (10-34-0), laboratory grade phosphoric acid (85% H3PO4), and water. Each combination was mixed separately and diluted so that 40 gal/A of material was applied, regardless of N and P rates. Planting. Pioneer 8699 was planted each year at 50,000 seeds/A using a New Idea 9700 air planter equipped with Buffalo row cleaning units. At planting, crop residue was cleared from an 8- to 10-inch wide area centered on the old row. No additional tillage occurred. Planting dates were mid-May/ late-June in 1991, mid-May/mid-June in 1992, and late-May/late-June in 1993. Tissue samplings were collected at the 6-leaf stage for analysis of dry matter, arid N and P concentrations. Leaf samples (leaf below flag leaf) also were collected at bloom stage for analysis of N and P concentrations. Harvest occurred in mid-October of each year. Grain yield was determined by combine harvesting of a 5- by 40- foot area and corrected to 14 percent moisture. Weather. Extreme drought conditions in July and August of 1991 caused delayed and erratic heading as well as plant leaf tissue damage. Because of drought effects, leaf nutrient concentrations, mid-bloom notes, and yield components in 1991 were not reported. Dr. Gordon is associate professor and Dr Whitney is professor in the Department of Agronomy at Kansas State University. !
Fluid Journal 1996-1998