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Fluid Journal : Fluid Journal 2002-2004
2 Fluid Journal Winter 2003 wide application range. IF applications of 2 to 8 gal/A of Ca(NO3)2 increased yields when compared with the check. Yield increase on a Loring soil was comparable with the yield from IF applying 1.5 gal/A of 11-37-0 (Table 1). The wide application range (allowing for possible calibration errors), plus the increased yield, makes calcium nitrate solution a feasible IF starter material. The primary disadvantage for calcium nitrate would be for those situations where P and/or K is needed as a starter component. N fertilization Nitrogen fertilization of cotton affects yield, earliness, and lint quality. For perennial cotton, applying optimal N is essential and may differ within a production area due to climatic and soil differences. An optimal N rate should maximize yields, while excessive or inadequate N applications may reduce cotton yields. High N fertilization may produce excessive vegetative growth, delaying maturity and harvest. These conditions may reduce yield and lint quality during years of early frost or prolonged Fall rain. Crop maturity is a critical production consideration for cotton producers along the northern edge of the U.S. Cotton Belt. Nitrogen deficiency causes premature senescence and reduced yields. Research conducted on three loess-- derived soils indicates that broadcasting 60 to 90 lbs/A of N was sufficient for NT cotton production (Table 2). Winter covers for the three soils were winter weeds on the Loring silt loam, winter wheat on the Lexington silt loam and corn stover on the Memphis silt loam. In this research, increasing N rates (30 to 120 lbs/A) were either broadcast as ammonium nitrate (AN) or injected as urea-ammonium nitrate (UAN) solution. These materials were applied immediately after planting. Injecting UAN reduced earliness, reduced ratio of first picking to total lint yields in certain years (all characteristics of excessive N availability), and did not improve yields, which contrasts to research conducted in other states. This research indicates that N immobilized by surface residues was small since yield differences between the two application methods (broadcasting or injecting ) were not significant. This was surprising when compared with reduced yields resulting from surface N applications for NT corn production. Based on these data, broadcast N application for NT cotton may be effective with low amounts of surface residues on the loess-derived soils. Additional N research was conducted, evaluating N application rates and application timing for CT and NT cotton produced on loess-derived soils. N rates of 40, 48, and 80 lbs/A were broadcast at planting. An additional 32 lbs/A was sidedressed to the cotton approximately four weeks after planting on those plots receiving 48 lbs/A of N broadcast at planting. Splitting N applications increased NT yields on two of the three soils when compared to broadcasting all of the N at planting. The response to sidedressing was limited to NT production. Broadcasting only 40 lbs/A of N lowered CT and NT yields in five of six site-years. Research conducted in 1999 and 2000 on a Loring silt loam at Milan indicated that 90 lbs/A of N was optimum for ultra-narrow row cotton (Figure 2). This rate is slightly higher than the current N recommendation for cotton production. Potassium fertilization Fast-fruiting cotton cultivars have exhibited K deficiencies beginning at bloom. Foliar applying low K rates three to four times, beginning at bloom, partially corrects these deficiencies. These fast-fruiting cotton varieties may exhibit K deficiency on new leaf growth in the top third of the plant rather than on the older mature leaves. Soil and foliar applied K was examined on three soils of varying extractable K. Mehlich-I extractable K was high on two soils and low on the third. Both CT and NT production systems were used. Four-year average CT yields produced Table 1. Effect of starter sources and application methods on NT cotton produced on Loring silt loam and Collins silt loam at Milan and Jackson (1994-1997). Broadcast Starter Yield Treatment Placement N P2O5 N P2O5 Loring Collins ------------------lbs/A------ ------------------ Check 8040 00 9821,116 Ca(NO3)2 IF 78 40 2 0 1,116 1,206 Ca(NO3)2 IF 76 40 4 0 1,131 1,193 Ca(NO3)2 IF 72 40 8 0 1,141 1,190 Ca(NO3)2 IF 68 40 12 0 1,073 1,133 11-37-0 SB 70710341,188 11-37-0 IF 7935271,138 ________________________________________________ IF = in furrow SB = surface band
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