Soil erosion assessment in the agroforestry area :: A case study in hilly area of Gesing subwatershed Purworejo Regency-Central Java

ROHMAWATI, Wulan, Dr. M. Pramono Hadi, M.Sc

2008 | Tesis | S2 Geo-Informasi untuk Manajemen Bencana

Land degradation due to soil erosion by water is a widely recognized problem. It is a serious environmental problem affecting areas of different landscapes and land uses. The aims of this research were: to assess the soil erosion rate in agroforestry area in the hilly area of Gesing subwatershed during the end of 2005 – 2006 and to assess the effects of different crop types in agroforestry on soil erosion. There are 33 state forest blocks in the study area which consist of pine trees and agricultural crops. The revised MMF model were used to estimate soil loss in those 33 forest blocks. The model was run in ILWIS 3.3 a raster based GIS software packages, using map calculation after all the input parameters of rainfall, soil, topography and land use/cover were generated. The reliability of the model’s result was validated with the actual erosion of the study area. The actual erosion was derived from the soil loss indicator evidence in the field. Result showed that the soil erosion in this agroforestry area was 11.71 ton/Ha during the period. Soil erosion in this area was low which undermined the need for conservation practices, but the combination of the crops which were planted in the certain slope steepness influenced the soil loss. The greenpea and groundpeanut planted with the young pine in the moderately steep area and steep area were not good for the conservation. The best plants to be planted with the pines were Calliandras. The highest soil loss was occurring on April 2006 due to the highest rainfall. The validation was carried out by comparing the model’s result with the actual soil loss. On the basis of the t test it was safe to assume at the 0.05 and 0.01 significance level that there was no difference between the mean value of the MMF results and the actual erosion. The RMMF had a good reliability of result.

Kata Kunci : Erosi tanah,Agroforestry,Penaksiran, soil erosion, assessment, agroforestry