Water use efficiency and yield response factor of common bean subjected to deficit irrigation strategies: a case study in Brazil

Water-saving strategies are important to cope with water shortages that affect irrigated agriculture. To determine the water use efficiency (WUE) and yield response factor (Ky) of common bean (Phaseolus vulgaris L.) grown under different deficit irrigation strategies, a rain shelter experiment was conducted. Common bean was subjected to five water replacement levels: 100% of field capacity (FC) throughout the growing season (M1; the reference treatment); 75% (M2) and 50% (M3) FC, starting at 20 days after sowing until the end of the growing season; and 75% (M4) and 50% (M5) FC at flowering. Grain yield (GY), yield components, WUE, and Ky were evaluated. Water use efficiency under M3 and M4 was comparable to M1, the highest WUE obtained (1.55 kg·m-3). However, M3 significantly reduced GY (42%), which was mainly caused by the decrease in the number of pods and grains per plant. Therefore, limiting water at 75% FC during flowering (M4) could be viable to avoid yield gaps and maintain higher WUE in water scarce regions. Yield response factor of common bean revealed that the greatest water savings were obtained with the M3 irrigation strategy, reducing crop evapotranspiration by approximately 70%.