IMPROVING WATER PRODUCTIVITY BY DEFICIT IRRIGATION IN TRANSPLANTED (TP) RICE FARMING

摘要

In order to investigate the effects of deficit irrigation management on rice yield at transplanted (TP) farming a field experiment was conducted at Rice Research Institute (Mazandaran, Amol) during 2000-01 on rice, Tarom variety. The treatments included seven levels of irrigation managements. Experiment was arranged in a randomized complete block design (RCBD) with three replications. Objectives of this study were improving water productivity (WPI and WPI+P) and get reasonable yield. For economic analysis was applied the Partial Budgeting (PB) method and Marginal Benefit – Cost Ratio (MBCR). Results indicated that there was a more significant difference in yield between treatments (α ≤≤ 0.01). Maximum paddy yield was for T1 (whole submerged soil : 5 cm water) with 4373 kg.ha-1 and minimum paddy yield was for T7 (saturated soil during whole growth season) with 3943 kg.ha-1. Amounts of WPI+P and WPI for T7 were 6.1 and 7 kg.mm-1 respectively. With 42 percent reduction of water use, although, 10 percent reduced yield, but In this case, maximum net benefit per unit water use and Maximum benefit – cost ratio (2.24) was obtained. The limit of benefit for optimum level of deficit irrigation management is when total costs of water and irrigation are 0.29 US$.m-1. Results showed that it is not necessary to maintain the rice field submerged in the whole growth period. Using this method, it is possible to increase productivity of irrigated field and deficit irrigation method can be applied without noticeable yield reduction.