Analysis of the on-site cost of soil erosion
1989
Lasmarias, N.C.
The rate of soil loss with the "gen-gen" [an indigenous compost-terracing technique of the Ikalahans] was estimated to be 1.76 cm/ha per year or approximately 137.28 tons/ha per year. Without the structure, the rate of soil loss was 2.50 cm/ha per year or 195 tons/ha per year. With these estimates, the corresponding average tuber yield losses of sweet potato without the "gen-gen" were 513.75 cans/ha per year or 2.63 cans/ton of soil lost. With the "gen-gen", tuber yield losses were about 319.28 cans/ha per year or 2.32 cans/ton soil. For gabi (Colocasia esculenta), without "gen-gen", 71.10 cans/ha were lost annually which was roughly equal to 0.36 cans/ton of soil lost. With the simple conservation technique, the loss was 78.26 cans/ha or 0.57 cans/ton of soil. Inputing monetary values on these losses, with the use of the "gen-gen", an incremental gross revenue of P15,134.33/ha was estimated from a one-hectare swidden planted to sweet potato and gabi. Because of very high labor expenditures, however, the long run advantage of the "gen-gen" was in the form of lower net income losses. Simulation analysis showed that a more effective soil conservation technique must be employed if the farmer intends to plant a parcel of land continuously for ten years. Technical innovation is one of the answers to the problems of the Ikalahan. Any innovation introduced in the area must satisfy these concerns: resource protection, adaptability to the socio-economic and cultural characteristics of the areas, and improvement in the income status of the farmers. This can take the form of yield-increasing technical innovations combined with an intensive agro-forestry scheme. Ways to improve and maintain soil fertility in the cultivated and fallowed areas are also important in light of the shortening swidden cycle.
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