Growth and yield of rice cultivars sowed on different dates under tropical conditions
Rice plants are susceptible to low light or high temperature conditions during the reproductive and maturity stages. Two rice cultivars, Fedearroz 50 ('F50') and Fedearroz 733 ('F733'), were planted on three planting dates, January 1st (PD1), February 15th (PD2) and April 1st (PD3), to expose them to different climatic conditions during the different stages of rice development. The experiment was a factorial arrangement. Of the various weather parameters, solar radiation fluctuated the most among the three different planting dates, with PD1 having the highest number of days with values ≥ 450 cal·cm-2·d-1. The yield components were influenced by the planting time. PD3 showed the lowest number of tillers per unit of area and the highest percentage of sterility spikelets. With respect to grain yield, PD1 and PD3 performed the best for both 'F50' and 'F733.' On the other hand, the optimum leaf area index (7) was reached at approximately 85-90 days for both cultivars for all three different planting dates. Similarly, solar radiation had a high correlation with the biomass production (dry matter) and leaf area index. In conclusion, the rice planting date should be adjusted so that the reproductive stage and grain filling do not coincide mainly with periods of low solar radiation (≤ 430 cal·cm-2·d-1) in tropical conditions.