Integrated soil fertility management strategies for enhanced and sustained rice productivity in Ifugao rice terraces [Philippines]

In 2004, the impact of wild sunflower (Tithonia diversiflora), occasional drainage, and zinc sulfate treatment on rice yield were demonstrated in 16 rice terraces, Ifugao [Philippines]. In DS [dry season], soil samples were collected for analysis and on-field MOET evaluation. Each paddy was given 300 g fresh sunflower per sq m 3 weeks before transplanting, or the seedling root was treated with 2% zinc sulfate; the paddies were drained 30 and 50 DATP for three and five days, respectively. Rice yield and yields components and the planting distance were measured. The obtained yield was then adjusted based on the actual number of hills per unit area. In wet season, the paddies were planted to PSBRc92, with only one portion receiving sunflower. Rice yield was then estimated in the two portions and compared. Soil analysis revealed: the soils were highly acidic (pH averaged 4.6); contained high OM (6.6%) and medium N (0.25%); CEC averaged 18 cmol/kg soil, with light medium texture; 62.5% were P and 16.3% S deficient. By MOET, the soils were identified mostly deficient in N, P, K, Zn, and Cu. The average grain yield of harvested hills was slightly higher (3687 kg/ha) than the adjusted yield (3374 kg/ha) and yield estimate three yield components (3627 kg/ha). Traditional varieties had few panicles per hill (3.0-7.0) but relatively high number (133) of high density (25-27 mg/grain) grains per panicles. In wet season, yield in sunflower treated paddies was significantly more (2106 kg/ha) than untreated paddies (1896 kg/ha). The increase was mainly due to increased number of panicles per hill (50%). Number of filled grains per panicle reduced by 11%, however the total grains per hill increased in treated paddies. With sunflower and proper management, the yield was more than 3 tons/ha. Further increases would depend largely on the extent of increasing number of panicles with high number of high density grains. These are achieved by correcting soil fertility limitations, proper management, use of cold and lodging tolerant varieties with heavy root system for effective plant anchorage and nutrient uptakes.