Author : Laud, Domingo B.

Summary : The agronomic response to zinc sulfate, zinc oxide, inorganic fertilizer, and indole acetic acid (IAA) applications as well as the nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn) uptake of IR72 rice variety was evaluated in three field experiments during the 1990 wet and 1991 dry seasons. These were conducted in a farmer's field in Tayabo, San Jose City. The soil was silt loam, irrigated lowland, and relatively poorly drained because it was located at the lowest portion of the landscape. It contained 8.12 percent organic matter and 0.41 ppm available Zn. Six treatments were evaluated during the two cropping seasons, namely: 1) control, 2) ZnO + 60-30-30 (CF); 3) ZnSO (subscript 4) (Foliar) + CF; 4) ZnSO (subscript 4) (Basal) + CF; 5) CF alone; and 6) IAA + CF. Across seasons, the basal application of ZnSO (subscript 4) proved superior over the other treatments in terms of number of grains per panicle, number of filled grains per panicle, weight of filled grains per panicle, weight per 1000 grains, and grain yield per hectare. Its grain yield of 8.8 tons/ha was 16 and 31 percent higher than the other treated plants and the control, respectively. On the average, the dry season crops produced 2.02 to 2.34 times more grain yield than the wet season crop. The addition of basal ZnSO (subscript 4) and IAA resulted in the production of the tallest plants, heaviest straw yield, and longest panicles. Tiller production was similar in all treated plants. These variation was not much in soil organic matter, N, P, and K during the trial period, although in general, values were higher during the dry season. he N concentration in grain was least in the control and highest in those which received CF only. Soil treatment did not influence the percentage of P, K, and Zn in both grain and straw. However, in all instances, the concentration of these nutrients in grain was higher than in straw. Total N uptake was highest in basal ZnSO (subscript 4) treatment (191.24 kg/ha) and lowest in the control (121.33 kg/ha).