Response of two rice cultivars to levels of water in the soil

Abstract

Experiments were carried out with rice cultivars, to evaluate their behavior when exposed to water stress. The treatments were: 1. soil at field capacity and soil subject to rainfall only during emergence until before flowering and also from final flowering until maturation; 2. irrigated based on of 100, 75, 50, 25 and 0% of maximum evapotranspiration at the flowering stage during the period of 15 days before to 15 days after flowering initiation for CNA-791041 upland. For IR-50 irrigated cultivar this period started 30 to 48 days before flowering. Irrigation started when soil water potential of the reference treatment at 15 cm of depth was -0,010 to -0,015 MPa. Water deficits in the soil was ensured by the use of rain shelters. The results showed: 1. correlation of the yield with the levels and criteria of irrigation as well as the different stage of development when submitted to water deficiency also influenced the results; 2. the cultivar IR-50 showed more negative values of leaf water potential and higher of diffusive resistence to water vapor flux during the period of water stress, presented higher sensibility to water stress.