Growth and yield performance of hybrid rice varieties as influenced by planting distance and rate of nitrogen fertilizer in rainfed lowland

A field experiment was conducted to: 1) determine the yield and yield components of four (4) hybrid rice varieties; 2) determine the influence of planting distance and rate of N on the yield and yield components of four (4) hybrid rice varieties; and 3) determine the interaction effect among hybrid rice varieties, distance of planting and rate of N application. The main treatment was planting distance - 15 x 15 cm., 20 x 20 cm. and 25 x 25 cm.; subtreatment, rate of N application - 90, 120 and 150 kg/ha; and sub-subtreatment, hybrid rice varieties - PSB Rc 72H, NSIC Rc 116H, LP 0330 and LP 0345. PSB Rc 9 was used as check variety Data were analyzed using the analysis of variance for split-split plot design and DMRT for treatment comparison. The yield components of the different hybrid rice varieties such as the number of productive tillers, number of filled grains per panicle, percent fertility and weight of 1,000 grains were significantly affected by the different treatments imposed in this study. there was a significant interaction between two variables studied on some agronomic parameters but not among the three variables evaluated. In terms of grain yield, there was a significant interaction between planting distance and hybrid rice variety and between rate of N application and variety. Regardless of planting distance, NSIC Rc 116H produced high grain yield than any treatment combinations. In general, high grain yield was obtained at closer planting distance of 15 cm x 15 cm than at wider plant spacing. Except for LP 0330 where higher grain yield was obtained at higher N rate, grain yield of other hybrid rice varieties remained unaffected by N application. This indicates the need for higher N rate for this hybrid rice variety to produce higher grain yield. At 120 kg N/ha, LP 0330 yielded 8.16 t/ha. On the average, grain yield was in the order of NSIC Rc 116H (8.47 t/ha) LP 0330 (7.91 t/ha) LP 0345 (6.75 t/ha) PSB Rc 72H (6.13 t/ha). NSIC Rc 116H and LP 0330 had a yield advantage of 1.33 t/ha or 16.33% than the inbred variety PSB Rc 9. NSIC Rc 116H produced more productive tillers per hill and heavier 1,000-grain weight and consequently higher grain yield.