Leaf area index and yield of upland rice. I. Limiting levels

Abstract

The relationship between leaf area index (LAI) and yield of upland rice was studied in 12 field experiments during five years, using IAC 47, a medium growth duration cultivar. There was great growth variation among experiments, with maximum LAI Ranging between 1.5 and 8.3, and leaf area duration (LAD) during reproductive stage ranging between 49 and 339 days. In the absence of environmental stresses, yield increased with LAI up to the level of 4,000 kg/ha at a LAI of 4.5. LAI levels below 2.0 minimized the risk of yield losses due to water stress, but yield potential was restricted to 1,500 kg/ha. Yield losses due to water stress during the reproductive stage were higher than 40% when LAI was higher than 3.0. LAI values higher than 6.0, associated with high rainfail and nebulosity during the reproductive stage, resulted in yields below 2,500 kg/ha. The possibility of using LAI as a factor of increase of mean upland rice yield in regions of both risky and favorable rainfail distribution is discussed.