Agronomic Response of Lowland Rice PSB Rc 18 (Oryza sativa L.) to Different Water, Spacing and Nutrient Management

A field experiment was conducted for PSB Rc 18 in two cropping seasons at the experimental area of the Department of Agronomy and Soil Science, Visayas State University, Visca, Baybay, Leyte to examine the agronomic responses of lowland rice grown under different water, spacing and nutrient management. The wet season cropping was from 8 November 2007 to 29 February 2008 while the dry season cropping was from 14 April to 17 August 2008. Different sources of fertilizers were designated as the mainplot and plant spacing as the subplot nested within 2 water regimes i.e. continuous flooding (conventional) and no flooding (soil was saturated but not flooded). Lowland rice may not need continuous flooding in order to produce high grain yield. Yield of PSB Rc 18 under non flooded condition was significantly higher than under continuous flooding water management system by 12-15% with water saving of 52-53%. This is applicable in high rainfall areas such as in the Visayas State University. Reduced plant height was recorded under no flooding condition, a characteristic that imparts resistance to lodging even at high grain yield. Composted goat manure and compost mixture (G. sepium + goat manure + rice straw + carbonized rice hull) as organic fertilizers gave similar. grain yield as inorganic fertilizer, implying that these materials are viable alternatives to expensive inorganic fertilizers. Plant spacing of 20 x 20 cm and 40 x 10 cm did not differ significantly in most agronomic characteristics as well as grain yield. However, in 20 x 20 cm spacing, transplanting and weeding were managed with less difficulty. Hence, 20 x 20 cm spacing is the appropriate distance of planting for optimum grain yield of PSB Rc 18 under organic production system. The treatment combination of no flooding, application of goat manure and closer spacing of 20 x 20 cm was the best combination that gave similar yield to PSB Rc 18 plants applied with inorganic fertilizer at 90-30-30 kg ha(-1) NPK.