Organic matter management of acid soils in Bukidnon [Philippines] and its effects on some soil properties and yield of corn (Zea mays L.) and peanut (Arachis hypogaea L.)

Field experiments were conducted at three sites, namely Malaybalay (Hapluhumults) from 1991-1994, Upper Poblacion (Dystropipts) and Alanib (Hapluhumult) Lantapan, Bukidnon from 1995-1996. The highest yields for corn and peanut were obtained with high fertilizer rate with lime and compost in the seven croppings. However, a lower fertilizer rate with compost proved to be a good alternative. A corn-peanut rotation is better than corn monocrop in terms of higher net income and improved soil properties. The corn cob compost can substitute for lime up to 1.0 Mg/ha. Increasing rates of compost tended to decrease the yield of corn and peanut. Lower fertilizer and organic materials such as green manure, cattle manure and corn cobs can substitute for the conventional fertilizer and lime as sources of nutrients, notably N, P, and K and to correct Al toxicity. A corn-corn-green manure or corn-peanut-green manure system can be feasible especially in areas where there is enough residual moisture for the green manure to germinate. Organic matter tended to decrease bulk density, increase infiltration rate but had no measured effect on soil penetration resistance. Organic matter tended to delay pH depression, slightly increased pH, available P, exchangeable K, Ca, and Mg, and to a certain extent decreased exchangeable Al and percent Al saturation. Microbial biomass C and N in acid soils was decreased by fertilizer application and increased by organic matter addition, crop rotation and green manuring. Among the organic materials evaluated, chicken manure was found to be the most effective in increasing pH, decreasing exchangeable Al concentration and increasing availability of phosphorus. In a laboratory set-up malic and oxalic acid, humic and fulvic acid were equally effective in suppressing toxic effect of high Al concentration