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Fluid Journal : Fluid Journal 2005-2007
Winter 2005 Proper Nutrient/Water Input--- Key To High-yielding Cotton Dr. Daniel Krieg Summary: Proper management of production inputs (nutrients and water) is essential if maximum cotton yield is to be achieved within the constraints of the physical environment we experience in Texas. The recommended rates of applied nitrogen (N) and phosphorus (P) will ensure that deficiencies do not occur during the early stages of fruit development, thus maximizing fruit retention while avoiding over-applying and wasting money so critical to assuring the highest possible profits. Through funding from the Fluid Fertilizer Foundation (FFF) and the Foundation for Agronomic Research (FAR) we clearly have demonstrated proper and efficient nutrient management strategies for center-pivot irrigated cotton on the Texas High Plains. We believe the principles are transferable to all parts of the cotton-producing world. Management of nutrient supplies, especially nitrogen and phosphorus, ensures deficiencies will not occur during early stages of fruit development. Fluid Journal 1 W ater and nutrient manage- ment under both rain-fed and irrigation conditions has been the focus of my research over the past 35 years in West Texas where we grow 35 percent of the U.S. cotton acreage. Our results suggest that 24 to 26 inches of water are required to grow the crop if the risk of water stress reducing produc- tivity is to be minimized within the constraints of the typical evaporative demand on the Texas High Plains. Water supply and growing season length moderate the genetic influence with respect to both main-stem nodes and fruiting sites on a fruiting branch. A "typical" cotton plant in today's varieties will initiate fruiting branch formation at the sixth to seventh node and progress upward at a three-day interval for 50 to 60 days, producing 22 to 24 main-stem nodes and 15 to 16 fruiting branches. Fruiting sites. Depending on plant density and available environmental resources, a typical cotton plant can produce 30 to 50 fruiting site in 60 days. Each main-stem node and fruiting site on a branch is associated with a leaf. Each fruiting site requires approximately 500 heat units (HUs) from initiation to flower concurrent with expansion of its subtending leaf. Therefore, each fruit develops under slightly different weather conditions; however, the need for mineral nutrients is the same for each seed it contains. The capsule and each seed increase volume very rapidly follow- ing flowering, reaching maximum volume in 18 to 20 days. Development. The embryo develops rapidly during this period and its major demand is for reduced carbon, reduced organic N compounds, and P for energy metabolism and membrane structure. Potassium (K) is the primary inorganic osmoticum provid- ing the driving force for water influx to increase the volume of both the capsule and seed. Large quantities of K are accumulated from 10 to 15 days after post-anthesis. The indi- vidual fibers are initiated from epider- mal cells on the seed-coat and elongate for 18 to 20 days coincident with volume increases in the boll and seed. K also provides the inorganic osmoticum for water influx into the fiber, allowing elongation to occur rapidly.
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