Estimation of Water Requirements and Plant Coefficient (Kc) for Cotton Plants

Cotton is one of the most important industrial plants that can produce products in different climates. This project aimed to assess the water requirements, evapotranspiration, and transpiration of cotton plants using a lysimeter device measuring 1.5×2×2 m3. The study was conducted at the Agricultural Research Station in Kashmar, Iran, utilizing soil with a silty loam texture. Before planting the type of soil, the important points of the soil moisture indicators, including the moisture in the agricultural capacity (FC) and the wilting point (PWP) were determined. The amount of fertilizer required was determined based on the soil test and the fertilizer recommendation of the Soil and Water Research Institute. The amount of irrigation water was determined in each shift. Irrigation was done when the easily accessible moisture of the soil was drained and the amount of irrigation water was calculated using the formula and was given to a maximum of 10 percent. A water drain should be created. The water given to the lysimeter at each irrigation turn was measured by the water meter and the amount of drain water was also determined after irrigation. Based on the balance equation, plant evapotranspiration (ETc) was calculated. The results showed that the average evaporation and transpiration of cotton plants in the years of implementation of the project (4 years) is equal to 1183 millimeters. This is while this amount has been estimated as 1000.4 mm in the book of estimating the water requirement of plants by Penman-Monteith's formula.