Valuation of nutrient losses due to soil erosion in a tropical upland agroecosystem
2001
Josue, D.S. (Mindanao State Univ. Maguindanao, Datu Odin Sinsuat, Maguindanao (Philippines) Mendoza T.C.
Soil erosion rates and nutrient losses in four different cropping systems in Batabat Sur, Bondoc Peninsula, Quezon Province in the Philippines, were measured and analyzed with belt transects (BTs) sampling and their monetary equivalents computed with current market valuation. Large differences in soil erosion rates were observed among BTs in the four cropping systems. The highest soil erosion rate was observed in BTs under corn monocrop at 159 t/ha/yr valued at PhP7169 t/ha/yr, and the lowest was 5.0 t under coconut monocrop valued at PhP642 t/ha/yr in the same slope range of 15.1-35%. NPK losses in corn monocrop, coconut monocrop and coconut-corn intercrop were 362, 12 and 200 kg/ha/yr, respectively. Lowest values were observed under coconut monocrop at all slope ranges where soil erosion was lowest. Coconut was able to prevent soil erosion. The presence of this crop is essential in soil-water conservation practices in the uplands of Bondoc Peninsula. While coconut monocropping was still the dominant cropping system (53.3% of the 60 BTs), the practice of intercropping corn (25% at the start of the study) would increase at the end of the study. This could be attributed to the low income derived from growing coconut alone. Intercropping corn under coconut increase the net income, but it also led to a 12-fold increase in the rate of soil erosion (90 tons/ha/yr in the 15.1-35% slopes). The added net benefit from corn (PhP1,024/ha) was lower compared with the value of nutrient losses (PhP3,521.5/ha) in the eroded soil. Based on the findings, it is necessary to promote soil conservation-oriented coconut-based farming systems in the Bondoc Peninsula and similar agroecosystems in the country
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