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Effects of Lime and Phosphate on Growth and Nutrient Uptake of Lowland Rice (Oryza Sativa L.) Varieties on an Acid Sulfate Soil
Dissertation Abstract:
Ppot and field experiments were conducted to study the effects of lime and phophate treatments on growth and nutrient uptake of four rice varieties planted in acid sulfate soil from Malinao, Albay. The pot experiment was conducted in a screenhouse at the University of the Philippines Los Baños during the 1984 dry season. Used in the treatments were 0 and 2 t lime/ha and 0, 200, and 400 kg P2O5/ha factorial combination; two low lime rates; Maahas clay soil; and four rice varieties, namely: IR26, IR45, IR46, and IR4683-54-2. Nutrient elements were determined six weeks after transplanting and at harvest.
The field experiment was conducted at Malinao, Albay during the 1984 wet season using the same rice varieties and lime and phosphate rates in the same factorial combination as those in the pot experiment.
Liming the acid sulfate soil in both pot and field experiments adversely affected the yield components and grain yield of all varieties studied.
Phosphate additions resulted in improved plant growth and higher phosphorus (P), calcium (Ca), magnesium (Mg), and manganese (Mn) uptake in the pot experiment. However, only P, Ca, and Mn in the field experiment was determined six weeks after transplanting. Phosphate additions depressed the ratio (potassium (K) + Mg) to Ca as well as nitrogen (N) and K tissue concentrations in both pot and field experiments. Root growth was enhanced with phosphate additions in all varieties.
Grain yield increases of 18.4 and 28.2 percent over that of the control were obtained when 200 kg P2O5/ha alone was applied to all varieties in the pot experiment. Variety IR46 was well-adapted to acid sulfate conditions and gave the highest yield among the rice varieties used in both experiments, while IR4683-54-2 produced more straw and gave the lowest grain yield. The grain yield of IR26 and IR45 was 15-22 percent lower than that of IR46 in all treatments in the field owing to a lower percentage of filled spikelets.
IR46 showed higher Ca and Mn tissue concentration and lower (K + Mn) to Ca ratio than IR26 and IR45 in both sampling timings in the pot experiment.
Varietal differences in tolerance to acid sulfate conditions could be due to differences in P, Ca, and Mn uptake as well as the balance between (K + Mg) and Ca in the tissues. Phosphate additions improved uptake of these nutrients and provided a favorable (K + Mg) to Ca ratio in the acid sulfate soil which resulted in increased yield.
