Assessment of water use efficiency in some soybean cultivars under different amount of irrigation

Explore for optimized water use of limited water resources is a serious challenge in the agricultural sector. To achieve this strategy، it is necessary to assess the plant response to water for obtaining the highest water use efficiency. A field experiment was conducted using line-source sprinkler irrigation to evaluate effects of different water amounts on yield and water use efficiency in three soybean cultivars (Sahar، G3 and DPX) for two years (2005، 2006). Four irrigation treatments (W1، W2، W3 and W4) based on distance from the pipeline (W1 nearest and W4 farthest) as main fixed and soybean cultivars that were randomly distributed within each irrigation treatment were examined under a strip plot design with four replicates. Although، results have shown that there were similar trend in soybean yield response to water but، they had different slopes. Generally، reducing the amount of irrigation water has increased the WUE and maximum water use efficiency was obtained by DPX cultivar. Overall mean indicated that WUE in SAHAR، G3 and DPX were 5. 1، 6. 2 and 7 Kg. ha-1. mm-1، respectively. These results imply that the highest water use efficiency does not conform to the highest yield. In other words، by increasing the amount of water from the point of maximum water use efficiency may lead to increase soybean yield، so that the amount of water use efficiency reduced، but this strategy is not suitable for water shortage areas.