Cotton yield response to water and nitrogen interaction under various inrrigation practices

The Texas High Plains region is characterized as arid and has variable growing condition. Due to the weather unpredictability, economic productivity of cotton is below the US national average level. Excessive water extraction and limited aquifer recharge is the main cause for the decline in the Ogallala Aquifer, which is the only major source of water in THP.

Farmers in this region are facing problems due to limited irrigation and high nitrogen prices, which result in reduced cotton production. Irrigation and nitrogen are the two most important factors for maximizing cotton production. In this research, I attempt to make an efficient and effective evaluation of utilization of these factors. During the study, various water and nitrogen treatment levels were simulated with the Cotton2k crop simulation model for center pivot irrigated and dryland cotton to see the response of cotton yield. Thirty years (1975-2004) of cropping season weather data from four high plain counties, Crosbyton, Muleshoe, Plainview, and Seminole, were used for the simulation. Factorial combinations of various treatments were made. For dryland 0, 1.8, 3.7, 5.5, 7.3, 9.2, 11.0, and 12.8 kg/ha (0, 10, 20, 30, 40, 50, 60, and 70 lbs/acre) of different levels of nitrogen were used and for center pivot irrigation, total water of 4.6, 9.2, 13.8, 18.4, 23, 27.6, 32.2, 36.8 inches was combined with 0, 4.6, 9.2, 13.8, 18.4, 22.9, 27.5, and 32.1 kg/ha (0, 25, 50, 75, 100, 125, 150, and 175 lbs/acre) of nitrogen level.

The yield results were analyzed and the results showed that, for rainfed condition, best yield of 882 kg/ha were found with the application of 60lbs/acre. For center pivot irrigated field, when 175 lbs/acre of nitrogen was applied, maximum yield occurred with dose of 83 cm of water. Further study should focus on economic analysis.