ABSTRACT
Several approaches to the management of irrigation of Upland and Pima cotton are available and developed to an extent that farm application is feasible. Consumptive use patterns provide a basis for general water needs of the crop over the course of the growing season. More recently, weather based irrigation scheduling has become practical with the use of real-time weather data from meteorological systems and weather stations for estimating crop water use rates and needs from actual conditions. Infrared thermometry has also been developed to some extent for field application as a crop irrigation management tool. The infrared thermometer is commonly used to calculate a CWSI (crop water stress index) value, which is dependent upon crop-specific baselines for interpretation and use. One of the only direct plant measurements for assessment of crop water status is that of the pressure bomb. The pressure bomb readings provide a LWP (leaf water potential) reading which is used to indicate crop needs in terms of irrigation. Soil moisture measurements are indirect means of determining crop-water conditions, but are fundamental to knowing what the extent of soil-water depletion is throughout the profile prior to irrigation. Soil moisture readings done instrumentally by use of the neutron moisture meter provides accurate, reliable information. Management of water in terms of quality is also important in irrigated cotton production. Careful management of parameters such as salinity and sodic levels are needed for estimating the full needs of the soil-plant system in terms of irrigation water, and maintaining soil conditions for maximum effectiveness of water that is provided to the crop.
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