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Fluid Journal : Fluid Journal 1993-1995
1 Fluid Journal Fall 1993 1400 1200 1000 800 600 40 20 0 Dryland Limited Irr Rainfall Full Irr Rainfall 11-15" + 5-6" Irr + 10-12" Irr Lint Yield - lbs/A 33" row 40" row 9% 18% 16% Figure 1. Lint yield response of narrow (30") and conventional (40") row spacings.Yields are averaged across three cultivars from 1983- 1989. Summary: Maximizing Water-use efficiency must be the goal of every cotton production system on the semi- arid High Plains of Texas. Compared to current average yields that are highly variable from year to year and from region to region, cotton yields can be almost doubled through a systems approach to management. The system includes: 1) population density management to minimize the risk of excessive plant water stress, 2) partitioning a greater percentage of the water supply to plant use, rather than losing water through free soil evaporation, 3) irrigation scheduling based on crop water requirement, and 4) potential evapotranspiration/ nutrient management---especially N based on growth and yield responses to water supply. To reach cotton's capability of producing 50 pounds of lint per inch of water requires 5 pounds of N and 0.4 pounds of P2O5 to use water with maximum efficiency. Proper timing of input applications rep-resents the key management strategy for increasing yields within the limits of environmental constrains. Achieving consistently high yields requires a systems approach to management, especially on the semi-arid High Plains of Texas. The first component involves water management strategies. Under high evaporative demand conditions, the goal of any water management strategy must be to reduce soil evaporation (E) and maximize plant transpiration (T). Only the water that goes through the plant has any chance of contributing to crop yield. Two basic approaches have been used to reduce E and increase T in crop production. Dr. Dan R. Krieg Maximizing Water-use Efficiency Key In Cotton Production Yields nearly double through systems approach to management. Narrower rows. Row spacing experiments across various soil types in the area, which range from clay loams to loamy fine sands, have produced a consistent 10 to 15 percent yield advantage of narrow rows (30-inch) over traditional (40-inch) row patterns (Figure 1). The narrower row yield advantage occurred across all water supplies, revealing the importance of summer rainfall to crop production. Narrower rows resulted in faster canopy closure, reducing soil E and partitioning a greater percentage of the water supply to plant T. This produced greater crop yields with the same water usage. Ground cover. Wheat sown in the late fall after cotton harvest has been terminated in mid-to-late April. Cotton is then planted into the standing residue. The terminated wheat serves as ground cover to minimize wind erosion throughout the spring. Young seedlings are protected from wind and blowing sand in May and June as the wheat deteriorates. The straw reduces radiant energy reaching the soil surface and also minimizes soil evaporation by increasing resistance to wind movement. Major concerns Two major water-related concerns exist relative to widespread adoption of this system.
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