Response of lowland rice to S in the Philippines.
1988
Gonzales P.B. | Mamaril C.P.
Based on the preliminary balance sheet on the S requirement of Philippine agriculture reported earlier, there is a net accretion of S. However, results of soil analyses and some experiments show that S deficiency occurs in some of the country's major rice growing areas. In a recent survey of S status of 153 sites in the Philippines, available S content in the surface layer of 40 sites were less than 10 ppm -- the critical level for rice. Five S-containing materials at different rates were evaluated in the greenhouse and in farmers' field on apparently S-deficient lowland soils. Significant increases in yield over the control were recorded in pots or plots applied with ammonium sulfate, urea sulfur, elemental sulfur and calcium sulfate. At the Batangas site, the effective sources increased grain yield on the average of 97.2% over the NPK treatment while S bentonite increased yield by only 26%, indicating that the latter source did not provide sufficient available S for the plants. S uptake in rice was apparently correlated with yield. Residual effect of applied S was observed only on the subsequent rice crop. Proper timing of S application for an early and medium maturing rice was investigated. Higher yields of rice can be obtained when S is applied at transplanting time for early-maturing cultivars (100-110 days) and not later than 15 days after transplanting (DT) for medium-maturing cultivars (111-120 days).
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