Economic values of erosion in upland farms in Rizal and Batangas, Philippines 1989-1994

The estimated average economic values of erosion impacts per hectare per year range from P2,568 to P11,640 in Rizal and P4,612 to P10,889 in Batangas [Philippines]. In Rizal, the soil was low in fertility, but the crops responded well to the application of the recommended fertilizer rates. The highest value of erosion impacts was estimated from the change in productivity approach while the lowest was estimated from the nutrient replacement cost approach. In Batangas, where the soil contained relatively medium phosphorus and high exchangeable bases, the highest value was estimated from the nutrient replacement cost approach while the lowest was estimated from the soil replacement cost approach. The initial condition of the soil affected the estimates such that more nutrients were washed away in fertile lands. The environmental BCA [benefit cost analysis] in Rizal showed that the marginal net return of adopting alley cropping + hedgerows with the application of the recommended fertilizer rates (T3) for six years of cropping was P36,210 per hectare. In Batangas, the marginal net return was P9,810 per hectare. The values implied high potential gains in adopting soil conservation measures. Investment analysis for alley cropping + hedgerows with the application of half the fertilizer rates (T2) in Batangas showed an IRR of 77 percent. For T3 the IRR was 82 percent in Rizal and 101 percent in Batangas. The net present value of the net benefits at different discount rates of T3 was always higher than that of T2. Soil erosion control costs P38,411 per hectare and with the application of the recommended fertilizer rates, this increases to P39,659. The difference in costs is only P1,248, but the difference in returns over six years of cropping is P8,892. This means that the use of T3 is advantageous over T2. Moreover, the investment cost can be paid back, discounted at 20 percent in three years