Study of Soil Erodibility in Its Relationship with Coffee Plant Productivity Based on Agroforestry in Silaen Sub-district, Toba Regency

Coffee plants (Coffea sp.) are currently a plantation crop in great demand among farmers in Silaen Sub-district. However, the soil conditions in Silaen Sub-district are dominated by sandy soil, which can trigger soil sensitivity to high erosion potential. One of the efforts to mitigate the decline in coffee production can be done through estimating the soil erodibility index in Silaen Sub-district. This research aims to estimate the soil erodibility index and obtain its relationship with agroforestry-based coffee production in Silaen Sub-district, Toba Regency. The method for determining land boundaries using land map units (SPL) in the form of land use, soil type, and slope. The parameters used are soil texture (M), organic matter (a), structure (b), and permeability (c), as well as coffee beans. Statistical analysis of data takes the form of correlation tests and data regression tests. The results of data analysis show that the highest wet weight of coffee cherries is found at SPL 8 with plantation land use, Typic Hapludands soil type, and land slope of 8–15%. The wet weight value of coffee fruit at SPL 8 is 2.19 t ha–1 with an erodibility value of 0.39. The lowest wet weight of coffee beans is found at SPL 2 with the use of moorland, Andic Eutrudepts soil type, and land slope of 8–15%. The average value of wet weight of coffee beans at SPL 2 is 0.15 t ha–1with an erodibility value of 0.28 while the results of the regression test R2 value of 0.11. So this shows that soil erodibility affects the wet weight of coffee fruit by 11%. Application of conservation techniques, namely making terraces, so that the effectiveness of terracing, organic mulch, and agroforestry in suppressing erodibility for 5–10 years can increase crop yields.