Effect of deficit irrigation on quantitative and qualitative yield of soybean cultivars in Rasht region

To investigate the effect of deficit irrigation on quantitative and qualitative yield of soybean cultivars, an experiment was conducted as split plots based on randomized complete block design with three replications at agricultural research farm, university of Guilan, during 2009. Main factors were included four irrigation levels based on potential moisture 30-35 (I1), 50-55 (I2), 70-75 (I3) Centibar (irrigation time was determined by tensiometer) and without irrigation (I4), and sub plot factors were included seven soybean cultivars: 033, 032, Sahar (group maturity 4), L.17, Zan, Clark and Madari (group maturity 3). Results showed that seed yield of soybean had decreased in I2 I3 and I4 treatments (15%, 20% and 65% respectively). Among the studied traits, just oil and protein content have increased by drought stress. Highest (1379 Kg) and lowest (478 Kg) seed yield per unit area obtain from I1 and I4, respectively. 033 in I3 treatmenthad the highest and Zan in I4 had the lowest oil and protein yield. Also irrigation water productivity increased significantly with application of deficit irrigation treatments (13% and 33% increment in I2 and I3, respectively). Results of the present experiment showed that in soybean production in Rasht region, irrigation based on potential moisture 70-75 Centibar, moreover in economize of water use and increase in water productivity, can improve of soybean seed oil and protein percentage.