In Brazilian Savannas, large part of irrigated common bean is cultivated under no-tillage system. The ground mulch reduces water requirement of common bean, which affects the management of irrigation. The present study was conducted to determine relative crop coefficients (Kr) under no-tillage system, related to the percentage of soil covered by mulch. The experiment was conducted at Embrapa - Rice & Bean Experimental Station, located in the municipality of Santo Antônio de Goiás, GO, in an Oxisol, in a randomized block design, with four replications. The treatments were five different percentages of soil cover with sorghum mulch: 0, 25, 50, 75, and 100%. Crop evapotranspiration (ETc) was determined using field water balance approach. Kr was determined by the relationship between ETc and reference evapotranspiration (ETo). ETo was determined based on Class A pan evaporation. The ETc decreased as the percentage of soil cover increased. The maximum Kr values were 1.25, 1.24, 1.15, 1.12 and 1.01 for the percentages of soil cover of 0, 25, 50, 75 and 100%, respectively.
Phaseolus vulgaris L.; water economy; irrigation; mulch
