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Fluid Journal : Fall 2016
5 The Fluid Journal Fall 2016 The last data set evaluated the different proportions of P and K applied to the 2 x 2 band and deep placement at the 100% application rate. Combinations were tested as single treatment factors using ANOVA. Differences in among treatments in each analysis were determined using the Tukey-Kramer HSD at ɑ = 0.05 level of significance. Results The 2015 growing season for cotton in Virginia was challenging as average lint yields were well below 2014 with 823 lbs. lint per acre in 2015 compared to 1,239 lbs. lint per acre in 2014. A dry August and three weeks of cloudy and rainy weather at the end of September ended the season with shed fruit and severe boll rot on the remaining fruit. Plant growth, petiole and tissue, and lint yield data followed similar trends in 2015 when compared to the two previous years of the study. For the study locations, lint yields ranged between 750 to 1,500 lbs. lint per acre at TAREC and 1,250 to 1,400 lbs. lint per acre at Lewiston, NC. Differences among P and K rates and placement (Trts. 4-9), as well as the placement combinations (Trts. 5, 8, 10, 12, and 13) were limited among all dependent variables measured at both locations. This reinforces observations made during the 2013 and 2014 studies (data not shown). As a result, only the nutrient management systems (Trts. 1, 2, 3, 5, and 8) will be discussed for this report. Growth measurements. Plant height measurements were initiated at the appearance of a fully unfurled second true leaf. The fluid starter control treatment had the tallest plants in each from the 3rd week after planting (WAP) to the 8th WAP (Table 4) at TAREC. The fluid starter control had significantly taller plants than the unfertilized control in all sampling intervals (Table 4). All fertilized plots were significantly taller than the unfertilized control from the 6th WAP through the 8th WAP (Table 4). When comparing the fertilized treatments at TAREC, the fluid starter control produced significantly taller plants than the 100% 2x2 N-P-K-S treatment from the 3rd WAP through the 6th WAP, significantly different from the 100% deep placement treatment during the 3rd and 5th WAP, and significantly different than the broadcast control during the 4th through the 6th WAP (Table 4). Table 5: Early season plant height of cotton grown under different nutrient manage- ment systems at Lewiston, NC Nutrient Management Systems Plant Height 3rdǂ 4th 5th 6th 7th 8th ------------------ in. ------------------ Unfertilized Control 3.8 7.2 8.8 13.7 21.5 26.9 Broadcast Agronomic Control 3.7 7.1 9.1 14.6 21.5 27.9 Liquid Starter Control 3.7 7.5 9.6 16.3 23.2 28.5 100% 2X2 N-P-K-S 3.5 6.9 8.5 14.5 20.9 26.6 100% Deep Placement N-P-K-S 3.9 7.5 9.8 16.8 23.5 28.9 ǂ Week after Planting Table 6: Normalized difference vegetative index (NDVI) for cotton grown under different nutrient management systems at TAREC Nutrient Management Systems Normalized Difference Vegetative Index (NDVI) 4thǂ 5th 6th 7th 8th 9th Unfertilized Control 0.38 ab* 0.80 0.83 b 0.78 b 0.78 b 0.78 b Broadcast Agronomic Control 0.41ab 0.83 0.86a 0.85a 0.89a 0.87a Liquid Starter Control 0.45 a 0.84 0.86a 0.86a 0.90a 0.88a 100% 2X2 N-P-K-S 0.35 b 0.82 0.85a 0.84a 0.88a 0.87a 100% Deep Placement N-P-K-S 0.40 ab 0.83 0.85 a 0.85 a 0.89 a 0.87 a *Values with the same letter are not significantly different at α=0.05 ǂ Week after Planting Table 7: Normalized difference vegetative index (NDVI) for cotton grown under different nutrient management systems at Lewiston, NC. Nutrient Systems Normalized Difference Vegetative Index (NDVI) 7thǂ 8th 9th 10th Unfertilized Control 0.72 0.80 0.83 0.88 Broadcast Agronomic Control 0.75 0.79 0.83 0.88 Liquid Starter Control 0.74 0.81 0.81 0.87 100% 2X2 N-P-K-S 0.76 0.81 0.83 0.87 100% Deep Placement N-P-K-S 0.78 0.81 0.85 0.87 *Values with the same letter are not significantly different at α=0.05 ǂ Week after Planting Table 8: Total Nodes and nodes above white flower (NAWF) for cotton grown under different nutrient management systems at TAREC Nutrient Systems Total Nodes NAWF 6thǂ 7th 8th 9th 10th Unfertilized Control 7.7 8.0 8.2 4.1 b 2.2 Broadcast Agronomic Control 8.3 8.5 9.5 5.9 a 3.5 Liquid Starter Control 8.6 9.2 9.5 6.0 a 3.7 100% 2X2 N-P-K-S 8.5 8.9 9.1 5.4 a* 4.3 100% Deep Placement N-P-K-S 8.2 8.8 9.9 5.8 a 3.6 *Values with the same letter are not significantly different at α=0.05 ǂ Week after planting Unlike at TAREC, the unfertilized control treatments at Lewiston were fertilized with nitrogen at match-head square. This was done to keep the Lewiston location consistent during all three years of the study. No plant height differences were observed during any sampling interval at Lewiston during 2015 (Table 5). Crop growth was slower at Lewiston than the TAREC location during the 2015 growing season. In addition to plant heights, a Greenseeker® Crop Sensor (Trimble Navigation Limited, Sunnyvale, CA) was used to measure normalized vegetative index (NDVI) for each plot.