Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fall 2016
6 The Fluid Journal Fall 2016 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 Measurements were initiated at the 4th WAP and 7th WAP for TAREC and Lewiston respectively (Tables 6 and 7). Nutrient management systems were significantly different during the 4th WAP at TAREC, with the fluid starter control having significantly higher NDVI values than the 100% 2 x 2 N-P-K-S (Table 6). From the 6th WAP to the 8th WAP the Table 9: Total Nodes and nodes above white flower (NAWF) for cotton grown under dif- ferent nutrient management systems at Lewiston, NC Nutrient Systems Total Nodes NAWF 5thǂ 6th 7th 8th 9th 10th Unfertilized Control 5.2 6.2 8.7 9.9 3.8 2.7 Broadcast Agronomic Control 5.1 6.4 7.8 9.9 4.1 2.6 Liquid Starter Control 5.3 6.5 8.3 9.7 3.4 2.9 100% 2X2 N-P-K-S 4.8 6.1 8.0 9.5 3.8 2.9 100% Deep Placement N-P-K-S 5.6 6.9 7.8 10.1 3.8 2.5 *Values with the same letter are not significantly different at α=0.05 ǂ Week after Planting Fig. 3: Nitrate-N (A), phosphorus (B), potassium (C), and sulfur (D) concentrations in cotton petioles using different nutrient application management systems during the 1st nine weeks of bloom at TAREC (*ANOVA was significant at α = 0.05 for that sampling interval). only significant differences occurred at TAREC between the fertilized and unfertilized treatments. By the 5th WAP, NDVI values were greater than 0.8 for all treatments, indicating that biomass and reflectance increased the most from the 4th to the 5th WAP at TAREC. No differences were observed in NDVI at Lewiston. One possible cause for this was that readings were initiated after sidedress N was applied and all nutrient management systems received N at sidedress (Table 7). Again, NDVI values were greater than 0.7 for all treatments at Lewiston during 2015 from the 7th WAP through the 10th WAP. No differences were observed at either location during 2015 in the total number of nodes among nutrient management systems (Tables 8 and 9). The total number of nodes was similar at both locations and increased as the growing season progressed. The NAWF were significantly different among nutrient management systems at TAREC during the 9th WAP with the unfertilized control having significantly fewer NAWF than all other systems (Table 8). No differences in NAWF were observed at Lewiston among nutrient management systems (Table 9). Both locations were below the cutout point for NAWF (< 5 nodes) during the second week of bloom, indicating that the bloom period was significantly shortened during 2015 due to environmental conditions during August. Petiole/tissue analyses. Overall petiole and tissue analyses were similar to 2013 and 2014 in the trends observed during the first five weeks of bloom. Petiole nutrient concentrations for TAREC and Lewiston are in Figures 3 and 4. At both locations, petiole nitrate N concentrations dropped quickly and were below 3,000 ppm by the third week of bloom at each location (Figures 3A and 4A). The only petiole nitrate-N concentration differences observed were at TAREC with the unfertilized control having significantly less petiole nitrate N concentrations than the fertilized treatments (Figure 3A). At Lewiston, the unfertilized controls received N at sidedress and no differences among nutrient management systems in petiole nitrate N concentrations were observed during the bloom period. For petiole phosphorus concentrations, again the unfertilized control treatments at TAREC, which received no sidedress N, had significantly higher petiole P concentrations during weeks 1 through 4 than fertilized plots (Figure 3B). No differences in petiole P concentrations were observed at Lewiston during the bloom period (Figure 4B). The elevated petiole P concentrations when N was deficient was observed in 2013 and 2014