EFFECTS OF SALINE WATER AND IRRIGATION INTERVAL ON SOYBEAN (GLYCINE MAX) YIELD AND ALTERING SOIL PHYSICO-CHEMICAL PROPERTIES

Abstract

The declining availability of fresh water has become a worldwide problem, which maintains the development of alternative, secondary quality water resources for agricultural use. Several studies recommend that the need of attention for selected crops that can tolerate water and salinity stresses when saline water is used for irrigation. In this study, the effects of different irrigation intervals and salinity levels of irrigation water on Soybean yield and their impacts on soil physico-chemical properties were investigated using three irrigation intervals (I1 =3days, I2= 4days and I3= 5 days) with four salinity levels (S1= 4dS m-1 , 5dS m-1 and 6 dS m- 1 ) in a factorial combination using CRD with three replications. The result showed that salinity, irrigation interval and their interaction had shown highly significance effects (p<0.001) on number of pod per plant, number of seed per plant and grain yield of Soybean. The highest number of pod number (88.33), grain yield (2.31ton/ha) and number of seed per plant (172.33) was recorded from Soybean which was irrigated with the first salinity level, i.e. fresh water (S1) with irrigation interval of (3 days), S1I1;while the lowest pod number per plant (6.67), number of seed per plant (12.67) and minimum grain yield (0.034 ton/ha) were obtained from Soybean irrigated by salinity level four (S4) with 5 days irrigation interval (S4I3).Statistical analysis showed that salinity ,irrigation interval and their interaction showed highly significance effects (p<0.001)on electrical conductivity of soil. Irrigation with highest salinity level (S4) with five days of irrigation interval resulted in the salt accumulation in the root zone from 0.41 μS m -1 (before sowing) up to 13.73 μS/cm at the end of growing period and exchangeable Sodium of 0.2 cmol/Kg was found before sowing while 0.82cmol/kg was found after harvesting. Therefore, based on soil salinity and crop yield, irrigation interval of 3 days at lower levels of irrigation water salinities (up to 3 dS m-1 ) is suitable for soybean production in the study area. The study also showed that salinity and irrigation interval significantly affected the soil nutrients (p< 0.001) despite their interaction were not significantly affected on soil nutrients. Increasing the concentration of salt in irrigation water reduce availability of nutrients in the soil. Soil which was irrigated by salinity level four (S4=6dS/m) had lowest Organic Matter, Organic Carbon, Nitrogen (N), Phosphorus (P) and Potassium (K) content. Highest Organic Matter, Organic Carbon, N and P content were observed at soils which were irrigated by fresh water. This indicates that there is a need for giving attention for management of soil besides achieving Soybean yield production when saline water is used for irrigation.