Effects of Soil Moisture Depletion at Different Growth Stages on Yield and Water Use Efficiency of Bread Wheat Grown in Semi Arid Conditions in Ethiopia

Abstract

A field experiment was conducted at the Malkassa Agricultural Research Center (MARC) in Ethiopia, during the off season of 2009 from January to April. The purpose of the study was to evaluate the effect of soil moisture depletion at different growth stages on yield and water use efficiency of bread wheat (Triticum aestivum L.) variety “Hawi” grown under semi arid conditions. Three soil moisture depletion (SMD) levels and 4 growth stages of SMD were used as the main- and sub-plots, respectively, and were arranged as split plots in a randomized complete block design with 4 replications. Irrigation was applied when the soil moisture was depleted by 50% (D1; control), 60% (D2) and 75% (D3) of available soil water (ASW) at 4 growth stages: 1) vegetative (V), 2) heading (H), 3) flowering (F) and 4) grain filling (G). All the plots were irrigated to field capacity after planting. Soil samples were taken before and after each irrigation event for the first 3 wk after planting. Thereafter, irrigation frequency was established according to treatments. All the treatments were irrigated when 50% of ASW was depleted for the whole growing season, except for the growth stages where SMD treatments were imposed. The SMD levels significantly affected dry matter, grain yield (GY), water use efficiency (WUE) and thousand seed weight (TSW) of the “Hawi” bread wheat. The 50% SMD gave the highest GY, TSW, spike length, plant height and WUE at each growth stage. Increasing the SMD level significantly reduced the yield and yield components of the “Hawi” bread wheat. Grain yield reduction was 26.6 and 30.8% for D2 and D3, respectively, compared with D1.