| Lowland padi (rice) yields have been poor on the acid sulfate soils within the double-cropped, padi-growing area of the Kedah-Perlis coastal alluvial plain in West Malaysia, mainly because of the initial effects of soil acidity, and subsequently iron toxicity, often with other accompanying nutritional disorders.;The second trial was conducted in the 1979-80 main season to study the residual and cumulative effects of liming and crop residue incorporation on the performance of the same two padi varieties. Using the field layout of the first trial, the experimental design was changed to partial confounding of factorial effects in randomized, incomplete blocks. The same lime and crop residue rates were used as in the first trial. Half the number of plots received repeated treatments corresponding to the treatment combinations of the previous trial, while the other half did not.;Crop performance studies conducted in both trials included iron toxicity evaluation, plant height measurement, tiller count, shoot dry weight and elemental content determinations during active tillering and at panicle initiation. The grain and straw yields and grain yield components were also determined. Chemical determinations were done on post-harvest soil samples, and also on soil solution samples collected from the 15-20 cm depth at frequent intervals in the first season.;Lime application at 2.5 ton/ha at the start of the off-season gave a 54% increase in padi yield, mainly by increasing the spikelet number. There was a general improvement in crop growth and nutrient status, as shown by increased shoot dry weight, calcium and phosphorus contents, and reduced iron content, thereby alleviating the iron toxicity symptom. There was no outstanding advantage of the higher lime rate of 5 ton/ha on further improving the grain yield. There was a clear residual lime effect on the succeeding main season padi crop, as was reflected in the crop growth and nutrient status and also in the grain yield. Additional lime application in the main season did not further improve the grain yield.;Field trials were conducted in two successive seasons on the Guar series acid sulfate solid to evaluate padi performance under different management practices. The first trial was conducted in the 1979 off-season, with irrigation, to evaluate the effects of surface drainage, liming and crop residue incorporation on the performance of two padi varieties, Setanjung and Seribu Gantang, and on the soil chemical factors. A split-plot design was employed, with the whole-plot treatment of water control at two levels; one being the normal irrigation practice, while the other was restricted drainage of the plots before transplanting and again before panicle initiation. The subplots comprised 3 x 2('2) factorial combination of the two varieties, crop residue at 0 and 5 ton/ha of chopped padi straw and lime at 0, 2.5 and 5 ton/ha.;Crop residue incorporation at 5 ton/ha at least two weeks before planting the off season crop did not adversely affect crop performance at the later growth stages. It had, in fact, favorable effects on crop growth and on increasing the grain yield by 24%. The main season grain yield was not affected by crop residue treatment at both the residual and cumulative levels, although the cumulative crop residue treatment effects did influence crop growth and nutrient status.;The main benefits of liming had been to increase the soil pH and exchangeable calcium content, improving the plant calcium status, and generally improving the root-zone soil environment for increased nutrient uptake and plant growth. Crop residue incorporation enhanced the plant potassium status and increased the soil exchangeable potassium content.;In the main season when soil conditions were more favorable, crop performance was generally improved, especially for the more susceptible variety Setanjung. |
