Increasing land occupancy for farming without conservation principles, particularly in the Indonesian island of Java, is resulting in a severe erosion problem. This study investigated the characteristics of soil erosion and the spatial contribution of land use and land slope on erosion under the tropical climate in a watershed scale. The Revised Universal Soil Loss Equation model with locally source parameters assessment in a Geographic Information Systems was used for soil erosion calculation. Erosion (in unit t ha −1 yr −1 ) and land slope were classified into five classes. Meanwhile, the types of land use were classified into six types. The results showed critical erosions largely occurred in steeply sloping areas, where the main source of erosion was farmland. We found that land cultivation practices have more potential to increase soil erosion in slopes steeper than 15%, and the large amount of erosions were generated from some small areas of the watershed. This study also demonstrated the land slope and erosion correlation equations for five land slope classes, which detected that the largest effect of land slope on erosion was recognized in the low sloping areas. These findings indicated erosion studies in various land slope zones were necessary to understand the uniqueness of erosion in specific land slope areas. The present study provides a fundamental knowledge of land slope zonations for erosion control planning particularly in high-risk erosion areas.

Watershed assessment methods have been developed in many types of approaches and purposes. However, the assessment concepts which are explicitly considering spatial aspects of a watershed remain unclear. The present study performed a spatial modeling for watershed health assessment in a Geographic Information System (GIS). Five indicators presented in GIS raster maps such as annual rainfall, land slope, land use/land cover (LULC) types, soil types and population density were used for the assessment and applied in Progo watershed, Central Java Province, Indonesia. A quantitative scoring was applied to classify indicator value and to categorize the watershed health level in five zones (very poor, poor, moderate, good and very good). The result shows that the study site is covered by three health level zones (poor, moderate and good). About 47.85% of the watershed area has a moderate health level. While, 39.04% and 13.11% of the watershed area are covered by areas with poor and good health level, respectively. Spatially, the area with poor health level is dominated by farmland and steep sloping area. Spatial modeling enables a watershed health assessment with a more specific and understandable result for watershed problems control.

Large-scale land cultivation practices for agriculture which disregard conservation principles are resulting in land degradation problems in tropical regions. The differences of environmental condition become the main concern for determining proper strategies to overcome this problem. The present study aimed to evaluate the application of land and water conservation (LWC) practices in tropical agricultural watersheds. The conservation practices (in the form of regreening bare areas and construction of LWC structures i.e. small-scale dam, terrace and stone weir) were performed in a partnership scheme involving government, higher education institution, local inhabitant and private party. The result showed that the partnership approach made conservation activities possible in a shorter time and a lower risk of failure. Economically, it reduced the unit cost of the conservation structures construction up to 70%. We also assessed the dam performance for LWC purpose. The assessment indicated the dam could effectively increase soil water storage and control the river sedimentation. The use of local resources (community and materials for conservation structures) enabled the sustainable of LWC practices on a watershed scale.

Soil erosion remains a strenuous problem for agricultural practices, particularly in tropical regions as happened in Indonesia. This study aimed to investigate the distribution of soil erosion in agricultural areas of a tropical watershed. The Revised Universal Soil Loss Equation (RUSLE) model in a Geographic Information System (GIS) was used for soil erosion assessment. RUSLE model parameters were collected from various sources. Soil erosion was classified into five classes such as very low (0-15 t ha−1 yr−1), low (15-60 t ha−1 yr−1), moderate (60-180 t ha−1 yr−1), heavy (180-480 t ha−1 yr−1), and very heavy (>480 t ha−1 yr−1). The result showed that the average soil erosion in the study site was 71.1 t ha−1 yr−1. More than 50% of the study site was occupied by very low class soil erosion, while heavy and very heavy class soil erosion occupied more than 20% of the study site. The finding of this study provides a useful reference for soil erosion control and studies.

Deforestation in the Serayu watershed, Central Java province, Indonesia for agriculture and other uses leaves only 0.73% of vegetation. It has triggered a number of problems such as soil loss (erosion), landslides, floods and sedimentation downstream. Environmental damage control needs to be applied through appropriate conservation programs. This study aims to understand the distribution of soil erosion and the effectiveness of soil erosion control by using vegetation cover. Soil erosion modeling and its correlation to vegetation cover was performed by using an Arc GIS based model of the Revised Universal Soil Loss Equation (RUSLE) through five scenarios of vegetation landscape cover such as 10%, 15%, 20%, 25%, and 30% of the total area of the study site. Five parameters namely rain erosivity (R), soil erodibility (K), slope-length (LS) and crop management (C) and conservation practices (P) factor were used to calculate soil erosion. The results indicated 82.25 tons/ha/year soil erosion reduction due to enhancement of vegetation cover from the actual condition 0.73% to the 30% vegetation cover condition. The increase of 5% vegetation landscape cover (forest) detracted the soil erosion rate by 10,20 tons /ha/year. Very high and high soil erosion hazard levels were found in the northern, east, and west watershed areasKeywords:   Soil erosion, RUSLE model, GIS, Serayu watershed, Vegetation cover

Vegetation has an important role in surface runoff and soil erosion control. Deforestation, especially in the upstream watersheds, has increased land degradation problems, mainly in the form of soil erosion. This study aims to investigate the effectiveness of vegetation cover for soil erosion control in an agricultural watershed. Soil erosion calculation was performed using Revised Universal Soil Loss Equation (RUSLE) model. While spatial analysis tools of Arc GIS 10.3 were used for soil erosion-vegetation correlation modelling. Five parameters such as rainfall erosivity (R), soil erodibility (K), length-slope factor (LS), crop management factor (C) and conservation practices factor (P) used to assess soil erosion in the existing condition. Those parameters were presented in grids cell of land units with 30 meters resolution. Five scenarios of vegetation cover such as 10%, 15%, 20%, 25% and 30% were used for the modelling. The result showed the increase of vegetation cover from the existing condition from 4.8% to 30% can significantly reduce about 76% of soil erosion. Preservation of about 30% vegetation cover in the upstream area of the watershed, enables farming practices with a low risk of soil erosion. The findings of this study provide a fundamental base for conservative farming concept development.

Tujuan utama penelitian ini adalah menerapkan dua metode untuk menetapkan kelas kesesuaian lahan Kakao di Desa Nglanggeran. Metode yang digunakan adalah Spatial Multi-Criteria Evaluation (SMCE) dan Weighted Linear Combination (WLC) dengan menggunakan parameter evaluasi lahan: curah hujan, kelerengan, temperatur, pH tanah, tekstur tanah, kandungan bahan organik tanah, dan parameter ekonomi (jarak dari jalan dan pasar). Alat yang digunakan untuk penelitian yaitu seperangkat komputer, ArcGIS 10.3, kamera drone (DJI Phantom 4 Pro V2), peralatan laboratorium untuk menganalisis jenis tanah, dan sekop & ring sampler untuk pengambilan sampel tanah. Bahan yang diperlukan dalam penelitian yaitu sampel tanah dari 10 titik kebun kakao yang ada di Desa Nglanggeran untuk menentukan tekstur, kandungan bahan organik dan pH tanah. Selain itu, penelitian ini menggunakan shapefile peta Desa Nglanggeran, data DEMNAS, dan data iklim. Terdapat tiga penggunaan lahan yang dijadikan target evaluasi lahan yaitu agroforestri, semak, dan lahan tadah hujan seluas 518,66 Ha (64,6% dari total luas wilayah desa). Penelitian ini memodifikasi pembagian kelas, pembobotan, dan skoring dari setiap parameter yang digunakan. Validasi metode SMCE dan WLC dilakukan dengan ratio pixel kebun kakao dan kelas kesesuaian lahan. Penelitian ini menetapkan bahwa sebagian besar wilayah di Desa Nglanggeran merupakan daerah dengan kelas kesesuaian kurang baik untuk budidaya kakao. Lahan dengan kelas sangat sesuai (S1) seluas 14,9% dari total target area. Lahan dengan kategori marginal (S2 dan S3) 49,3% dari total luas wilayah desa. Sedangkan lahan dengan kelas kesesuaian tidak sesuai (N)  0,4% dari total luas wilayah desa. Faktor yang menjadi pembatas kesesuaian lahan Kakao di Nglanggeran (N) adalah kelerengan lahan yang curam, nilai pH tanah yang rendah, dan tekstur tanah yang kurang sesuai di daerah tersebut. Oleh karena itu, penelitian ini mendorong untuk melakukan rekayasa/modifikasi kelerangan lahan dan sifat tanah dengan bahan pengkondisi tanah. Penelitian ini membuktikan bahwa metode SMCE dan WLC dapat diterima untuk menilai kesesuaian lahan kakao di Nglanggeran.

Bata merah merupakan material umum yang dipakai pada bangunan. Bata merah dalam penelitian ini di tujukan untuk pemanfaatan limbah. Limbah batu bata merah dalampenelitian pembuatan beton untuk menghasilkan beton bermutu tinggi.Metode penelitian yang dipakai adalah metode percobaan yang dilakukan di laboratorium STT-Garut, yaitu denganmelakukan pemeriksaan atau percoban secara fisik pada uji beton, yang menggunakan bahan tambahan limbah batu bata merahsebanyak 27 benda uji (10%, 25%, 50%) dankuat tekan beton normal K-200 sebanyak 9 benda uji (200kg/cm 2). Tujuannya untuk mengetahui kuat tekan beton dengan menggunakan bahan tambahan limbah batu bata merah sebanyak 27 benda uji (10%, 25%, 50%) dan kuat tekanbeton normal K-200 sebanyak 9 benda uji (200kg/cm 2 ) sebagai acuan pembanding.Dari hasil penelitian, diketahui beton dengan menggunakan campuran 10%, 25% dan 50% hasil rata-rata sesuai dengan acuan beton pembanding (K-200). Hasil uji kuat tekan limbah batu bata merah 50% campurannya tidak lebih dari 10% dan 25%. Sehingga beton untuk campuran 10% dan 25% menjadi acuan kedepannya sebagai campuran limbah tambahan yang baik untuk pembuatan beton.