Author : Bernarte, Alejandre M.

Summary : The agronomic response of rice to various fertilizer levels, seedling ages and seedling rates was investigated during the dry season of 1992 at the lowland rainfed area of the Itawes National Agricultural and Technical School, Tuao, Cagayan, Northern Philippines. The area is clay loam with a pH of 6.0. The soil contains 1.5 percent organic matter, 6 ppm available phosphorus and 60 ppm available potassium. The treatments were composed of five levels of fertilizer (0-0-0, 50-40-40, 100-40-40, 150-40-40, and 200-40-40 kg NPK/ha), three seedling ages (30,40, and 50 days old) and two seedling rates (4 and 6 seedlings per hill). The experiment was laid out in split-split plot arranged in randomized complete block design. Most of the agronomic characteristics of rice were favored by the application of 150-40-40 kg NPK/ha. At this level, plants had the highest grain yield considerably because of heavier grains and fewer unproductive tillers. Plants transplanted at 50 days old had the highest grain yield because of more productive tillers and fewer unfilled grains. The combination of fertilizer level, 150-40-40 kg NPK/ha, seedling age of 50 days old and six seedlings/hill indicated better plant performance in terms of grain yield although most of the yield components were significantly affected by their combined factors. The nitrogen content of the straw increased considerably with the application of 200-40-40 kg NPK/ha, but the level of phosphorus in the soil decreased significantly. Plants planted with 50 day old seedlings had higher concentration of nitrogen but lower concentration of phosphorus.