ASSESSMENT OF YIELD AND WATER USE EFFICIENCY OF DRIP-IRRIGATED COTTON (Gossypium hirsutum L.).

Climate change raises the question of demand for more economical ways to use irrigation water. Against the background of different levels of fertilization, cotton varieties have been tested. The experiment was performed under irrigated and non-irrigated conditions. The experiment was performed in the experimental field of the Trakia University, Stara Zagora during the period 2018-2020. Cotton productivity has been established under non-irrigated and irrigated conditions. The analysis of the results shows that the naturally colored variety Isabel, when realizing irrigations, on average for the period forms a yield 39.9% higher than the non-irrigated one. Under irrigated conditions, the Darmi variety increased productivity by 34.3%. An increase of 27.9% was registered for the Helios variety. The Isabel variety has the highest values of the irrigation water efficiency coefficient (0.88-1.11). Against the background of different levels of fertilization, the Darmi variety forms an efficiency coefficient from 0.9 to 1.03. Helios variety is responsive to irrigation, but on average for the three-year period stands out with the lowest values of efficient use of water resources (0.53 - 0.95). [ABSTRACT FROM AUTHOR]