Effects of lime and phosphate on growth and nutrient uptake of lowland rice (Oryza sativa L.) varieties on an acid sulfate soil / Surjit Singh.

Thesis (Ph.D. - - Agronomy) University of the Philippines, College, Laguna.

Includes bibliographical references.

SINGH, SURJIT, University of the Philippines at Los Banos, September, 1905. effects of Lime and Phosphate on Growth and Nutrient Uptake of Lowland Rice (Oryza sativa L.) Varieties on an Acid Sulfate Soil. Major Professor: Dr. R. U. Quintana

Pot and field experiments were conducted to study the effects of lime and phosphate treatments on growth and nutrient uptake of four rice varieties on an acid sulfate soil from Malinao, Albay. The pot experiment was conducted in the screenhouse at U. P. Los Banos in the 1984 dry season, Treatments included 0 and 2 t lime/ha and 0, 200 and 400 ke P,0,/ha in factorial combination, two low lime rates, Maahas clay soil, and four varicties, namely, IR 26, IR 45, IP 46 and IR 4683-54-2. Nutrient element determinations were made at six weeks after transPlanting and at harvest. The field experiment was conducted at Malinao, Albay during the 1984 wet season using the same four varieties, two lime rates and three phosphate rates in factorial combination as those of the pot experiment.

Liming this acid sulfate soil proved ‘not beneficial in both pot and field experiments and adversely affected the yield components and stain yield of all varieties studied. Phosphate additions resulted in improved plant growth and higher nutrient uptake of P, Ca, Mg and Mn in the pot experiment but only P, Ca and Mn from the field experiment determined at six weeks after transplanting. Phosphate additions depressed the ratio of (K + Mg) to Ca and N and K tissue concentrations from both pot and field studies, Root growth was enhanced with phosphate additions in all varieties. Grain yield increases from 18.4 and 28.2% over that of the control were obtained from additions of 200 kg P,05/ha alone in all varieties from the pot experiment. Variety IR 46 was well adapted to acid sulfate conditions and produced the highest grain yield among the varieties studied in both pot and field experiments, while IR 4683-54-2 produced more straw and the lowest grain yield. The grain yield of IR 26 and IR 45 was 15 to 22% lower from that of IR 46 in all treatments in the field due to a lower percent filled spikelets. Variety IR 46 showed a higher Ca and Mn tissue concentration and a lower ratio of (K + Mg) to Ca than IR 26 and IR 45 at both sampling times from the pot experiment.

Varietal differences in tolerance to acid sulfate conditions could be due to differences in uptake of P, Ca and Mn as well as a balance between (K + Mg) and Ca in the tissues, Phosphate additions improved uptake of these nutrient elements and provided a favourable ratio of (K + Mg) to Ca on this particular acid sulfate soil which resulted in increased yields,

Submitted to the University Library 01/07/1994 T-1418