IRRIGATION SCHEDULING BASED ON SOIL MOISTURE FOR MAIZE CROPS IN SEMI-ARID ENVIRONMENT, ARBA MINCH

Abstract

Irrigation water is scarce in semiarid environment and need to be used judiciously. Minimizing water input in crop fields such as maize will help in saving water which would increase the water productivity. Several approaches are employed to reduce irrigation water input in agricultural areas. In this particular study, soil moisture based water application has been employed to study the effect of deficit irrigation application in Arba Minch area. The study was particularly conducted on Arba Minch University demonstration farm. The aim of this study is to assess the role of different water applications and the responses of maize yield, under the semi-arid environment like Arba Minch by planting two commonly grown varieties of maize (BH-140 and BH-540). Both field and laboratory experiments were carried out to acquire important data for analysis in this study. For the analysis, AquaCrop model was employed. To carry out this, irrigation application based on current amount of soil moisture in the crop root zone with 100, 75, 50, and 25% of the soil moisture deficit is satisfied for the designed treatments. The soil moisture deficit is taken as the amount of soil moisture content between the field capacity and the current soil moisture content. The results of the study showed that large savings in irrigation can be possible using the soil moisture based approach when compared to the previous studies. As a result, yields of BH-140 was from 8.93 t/ha to 5.65 t/ha and for BH-540 from 8.84 t/ha to 5.76 t/ha. These were obtained with the overall water application for BH-140 from 417.55 mm to 268.39 mm and BH-540 was 417.13 mm to 266.09 mm. Thus, for BH-140, the model showed NSE of 0.737 and RMSE of 0.534. Whereas for BH-540, the model showed NSE and RMSE of 0.755 and 0.489 respectively. Also, water productivity based on the total supplied water ranges from 2.717 kg/m 3 to 1.353 kg/m for BH140 and from 2.920

kg/m 3 to 1.385 kg/m 3 BH-540. Comparatively, better aboveground dry biomass was observed for BH-540 in treatment T 5B . Contrarily, the grain yield was better in the case of BH-140 maize variety. Therefore, the model can effectively be used for maize irrigation scheduling in the study area using the values calibrated in this study. 3