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Fluid Journal : Fall 2016
8 The Fluid Journal Fall 2016 Table 11: Nitrogen, phosphorus, potassium, and sulfur concentrations in cotton leaf tissue during the 1st and 5th weeks of bloom at Lewiston, NC Nutrient Systems Leaf Nutrient Concentrations 1stǂ 5th N P K S N P K S ------------------------------------- % ------------------------------------- Unfertilized Control 4.03 0 .27 0.93 b 0 .64 4.02 0.31 1.10 0.85 b Broadcast Agronomic Control 3.90 0 .25 1.00 b 0 .67 4.27 0.32 1.29 0.91 ab Liquid Starter Control 4.09 0 .25 1.01 b 0.67 4.46 0.30 1.20 0.92 ab 100% 2X2 N-P-K-S 4.07 0.26 1.16 a 0.82 4.47 0.31 1.17 0.95 a 100% Deep Placement N-P-K-S 4.03 0 .26 1.03 ab 0.73 4.15 0.33 1.20 0.95 a *Values with the same letter are not significantly different at α = 0.05 ǂ Week of bloom Fig. 5: Lint yield and nutrient management systems at TAREC and Lewiston, NC. Bars with the same letter are not significantly different at α = 0.05 within location. Dr. W. Hunter Frame is Field Crops Agronomist, Department of Crop & Soil Environmental Sciences, Tidewater Agricultural Research & Extension Center, Suffolk, Virginia 23437. than all other fertilized treatments (Table 10). At Lewiston, no differences in Leaf N and P concentrations were observed during the 1st and 5th weeks of bloom (Table 11). Leaf K concentrations were significantly higher for the 100% 2 x 2 N-P-K-S compared to the broadcast agronomic control, fluid starter control and unfertilized control during the 1st week of bloom (Table 11). The leaf K concentrations at Lewiston were below current sufficiency ranges for K during early bloom of 1.5 to 3.0% K (Mitchell and Baker, 2009). The only other difference in leaf nutrient concentrations observed at Lewiston was during the 5th week of bloom when the 100% 2 x 2 N-P-K-S and deep placement systems produced significantly higher leaf S concentrations than the unfertilized control (Table 11). Lint yield. Lint yields were again exceptional during the 2015 study at both locations. The only response observed during the 2015 study was at TAREC, with the unfertilized control having significantly less lint yield compared to all other fertilized nutrient management systems (Figure 5). At Lewiston, there was no difference in lint yields among nutrient management systems indicating that N was the most limiting nutrient at that location. However, there is a trend that the unfertilized control (1,293 lbs. lint per acre) had the lowest lint yield (Figure 5). These are similar responses to what was observed in 2013 and 2014 at both locations. Summing up The results of the trial were very consistent among nutrient management systems from year to year and within each location and side-dress N management. Responses to P and K rate as well as 2 x 2 deep placement combinations were limited across all locations in terms of plant growth, petiole and tissue nutrient concentrations, and lint yield during the three years of the study. When N was deficient petiole P concentrations were artificially high, most likely due to a concentration of P in lower biomass for N deficient plots. Petiole and leaf K concentrations were not affected by N status during bloom and results indicate that broadcasting K may be more efficient, based on petiole K data in this study. Sulfur is the one nutrient in cotton where data are limited in the upper southeast coastal plain. At Lewiston, when 32% UAN was used as the side- dress N source, the 100% 2 x 2 N-P-K-S placement at planting produced higher petiole S concentration, which indicates that this placement technique was more efficient in delivering S in cotton than the other techniques. However, for the broadcast and fluid starter agronomic control, the balance of S was applied with the deep placement strip-tillage implement. More data are needed to ascertain if broadcasting S will perform similar to the 2 x 2 placement. For lint yield, N was the most limiting nutrient during the study with only lint yield differences occurring in the unfertilized control at TAREC each of the three years. Responses to P and K during the study were limited, as sites chosen were based on medium to high soil test P and K levels. Overall, the study was valuable in evaluating the performance and placement of new P and K fluid sources on cotton growth and performance in the upper southeast coastal plain.