Organic wastes as ameliorant for depleted soils and its effect on peanut yield

Inappropriate use of inorganic inputs negatively affects soil condition. This limits the availability of soil nutrients needed by plants. Organic wastes are considered useful in improving the soil quality. As such, Subong et al. (WMSU-TC) evaluated the effects of animal manure and decomposed plant residues on the fertility status of the soils and on peanut yield. The study was conducted in the Western Mindanao State University (WMSU)-Tampilisan Campus Reservation Area from October 2003 to January 2006. Each of the three experiments was laid out in 625 sq m area. Organic wastes were applied on the soil 2 weeks before planting peanut. For the first experiment, the application of 2t/ha each of carabao, cow, and sheep manure was adopted. In the second experiment, mixed animal manure at 5t/ha, 7.5t/ha, and 10t/ha were applied basally on the soils. The third experiment involves basal application of 5t/ha, 7.5t/ha and 10t/ha of decomposed plant residues. All treatments were compared with the no application of organic materials. Findings of the study revealed the following: In Experiment 1, plots applied with 2t/ha of sheep manure had the highest projected peanut yield of 594kg/ha. In Experiment 2, plots applied with 10t/ha of mixed manure gave the highest projected yield of 2,173.44 kg/ha. In Experiment 3, plots applied with 10t/ha of decomposed plant residues also had the highest projected yield of 1,881.60kg/ha. In Experiment 1, the potential hydrogen (pH) values of the soil as affected by animal manure slightly increased at reproductive and after harvest stages. However, the pH values in Experiments 2 and 3 decreased compared with the initial reading but the decrease was still within the range (5.5-7.0) tolerable for most crops. Soil organic matter (OM) increased at plants' reproductive stage compared with the initial value, but after harvest, OM slightly decreased. The same trend was observed in phosphorus and potassium contents. In plots applied with decomposed plant residues, phosphorus content remained constant at reproductive stage while potassium slightly increased after harvest. These results show the variability in the effects of organic fertilizer on the soil nutrient contents. Plants treated with 2t/ha of sheep manure obtained the highest ROI of 81.80% followed by plants treated with 10t/ha mixed manure, 78.25%, then plants treated with decomposed plant residues, 54.74%.