This work aimed to determine the permanent wilting point of soybean, and bean crops and weeds of high occurrence in Brazilian agricultural areas. The treatments consisted of two crops, Glycine max and Phaseolus vulgaris, and four weed species: Euphorbia heterophylla (susceptible to ALS - inhibiting herbicides), Euphorbia heterophylla (resistant to ALS - inhibiting herbicides), Bidens pilosa and Desmodium tortuosum, with two water stress induction times (pre-flowering and grain filling onset). The soils in the pots were kept close to 80% of field capacity until the pre-determined water stress times were achieved. From this stage on the end of the day, the pots were transferred into a dark chamber with relative air humidity close to 100%, to confirm turgidity definitive no- return [permanent wilting point (PWP)]. A sample of the soil was collected (without roots) to determine water moisture content using the gravimetric method. Based on the soil moisture values determined for each appraised treatment, soil water potential in PWP was determined by soil moisture retention curve. At the grain filling stage, PWP for B. pilosa occurred when soil water potential was more negative than in the other appraised species, showing that at this developmental stage, B. pilosa presents a greater efficiency in soil water extraction, and, consequently, greater competitive potential than the other appraised species.
Glycine max; Phaseolus vulgaris; competition; water; water deficit
