GROWTH OF UPLAND RICE IN DIFFERENT POPULA TIONS AND SUPPLEMENTAL IRRIGATION

Four experiments were carried out on cerrado soil in order to study th e effects of three row spacings (0.3; 0.4 and 0.5 m) and three seed de nsities (50, 100, and 150 seed.m(-2)) on growth of two rice (Oryza sat iva L.) varieties with and without sprinkler supplemental irrigation. Two experiments were carried out with the Araguaia variety (medium gro wth duration) and two with the Guarani variety (short growth duration) . The growth rates of leaf area index (LAI) and total dry matter (DM) were adjusted to quadratic and exponential regressions. Irrigation inc reased DM, LAI, crop growth rate (CGR) and leaf area duration (LAD) in both varieties. The Guarani variety had higher DM, showing higher val ues of CGR, and reached fastly the maximum LAI, with high capacity to exploit the available surface than the variety Araguaia. The increasin g of the spacing showed a decrease in LAI, LAD, and CGR in both variet ies. LAI and DM per tiller were positively correlated with the grain y ield with higher coefficient correlation in 30 and 10 day before flowe ring in the varieties Araguaia and Guarani respectively, without irrig ation and in the final flowering under supplemental irrigation.