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Nitrogen fertilization is an important input for optimization of cotton (Gossypium hirsutum L.) production. However, due to the indeterminate growth of cotton, high N rates can cause excessive vegetative growth which ultimately decreases yield. Pix (1,1 dimethyl piperidinium chloride) suppresses vegetative growth of cotton and often enhances lint yield. Therefore, field studies were conducted in Burleson County, Texas during 1989 and 1990 to determine if nitrogen rate and time of nitrogen application interact with Pix treatment to influence cotton growth and yield. Pix treatments were a control, four early season multiple applications of 146 ml Pix/ha, and a single early bloom application of 584 ml Pix/ha. The five N application rates were 0, 45, 90, 134, and 179 kg N/ha. The two times of N application were a single (preplant) and a split application (half preplant and half at pinhead square stage). Lint yield increased as N rate increased but did not differ between the two highest N rates. Lint yield was greatest (1450 and 1374 kg/ha for 1989 and 1990, respectively) at the 179 kg N/ha rate. Conversely, lint yield per unit of applied N decreased with increasing N application rate, ranging from 7 kg lint/kg N at 45 kg N/ha to 4.28 kg lint/kg N at 179 kg N/ha. Lint yield was not directly influenced by Pix application. However, a significant interaction for Pix treatment and N application rate indicated that multiple Pix application increased the lint yield for the highest N rate relative to the control. The multiple Pix application also promoted earlier maturity and increased seed size. Nitrogen uptake was not affected by Pix treatments. However, N rate and time of application did influence the nutrient uptake of the cotton plant. Nitrogen concentration increased with N rate for all the above ground parts of the cotton canopy. Approximately 103 days after planting (DAP), total N uptakes (kg/ha) of the above ground canopy were 50 and 53 for the control (no additional nitrogen) and 208 and 155 kg N/ha for the highest N rate in 1989 and 1990, respectively. Similarly, N content in the cotton seed increased with N rate, ranging from 29 kg/ha for the control to 72 kg N/ha for the highest N rate. In all treatments, about 5 kg N was taken up by the seed for every 100 kg lint produced. Although Pix application did not affect total phosphorus uptake, nitrogen application rate significantly influenced P concentration and uptake in cotton. Phosphorus concentration in the above ground cotton canopy decreased as N rate increased, resulting in 5.5 and 3.4 g P/kg for the control and the highest N rate, respectively, at 103 DAP. A similar trend was also observed for seed P content. For every 100 kg of lint yield about 1.0 kg P was found in the seed. Potassium uptake of cotton was also affected by N application rate but not by Pix treatment. Leaf K concentration increased with increasing Iq rates but did not increase for stalks and bolls at 103 DAP or for seed at harvest. Seed K content for the control and the highest N rates were 16 and 33 kg K/ha, respectively. For every 100 kg of lint about 2.5 kg K was removed in seed. |
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©National Cotton Council, Memphis TN |
Document last modified Sunday, Dec 6 1998
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