PENGARUH PEMBERIAN BAHAN HUMAT DAN KOMPOS SISA TANAMAN TERHADAP SIFAT FISIK TANAH DAN PRODUKSI UBI KAYU

A study about the effect of humic substance and green manure on soil physical characteristics and cassava production was conducted on a Sandy loam soil in Sukadana-East Lampung. Humic substance was obtained from Proper Humic, whereas green manure was obtained from crop residue and weed surrounding the experimental site. Humic substance applied was 15 liters ha-1 and green manure applied was 2 tons ha-1. The result of the experiment indicated that in general, humic substance and green manure applied had no significant effect on soil physical characteristics. However, there was a tendency that water content at field capacity (pF 2.54) and water available capacity increased as humic substance and green manure were applied. Similar tendency was also observed for water retained in soil where field soil water content at 7 consecutive no-raindays was slightly higher at soil with humic substance and green manure. With the application of humic substance and green manure, soil could hold water in a longer time. The effect of green manure on field soil water content was, however, slightly better than that of humic substance. Nevertheless, application of humic substance 15 l ha-1 increased significantly cassava growth and production and the effect was better than those from green manure with the dosage of 2 ton ha-1. Key words: cassava production, humic substance, water retentio

Application of Fuzzy Sets Function for Land Attributes Mapping

A study was conducted to evaluate the potential use of Geographical Information System (GIS) for mapping thebiophysical resources of watershed PC-based GIS soft-wares were used in the analysis, processing and mapping of spatialdata. The conventional mapping technique that presents land attribute in form of polygon with abrupt change across classboundaries was improved using Fuzzy technique. This technique involves the generation of membership maps for each soiltype based on the relationship between the soil type and it's forming factors like geology, elevation, slope gradient, slopeaspect, slope curvature, and land cover. The fuzzy technique was found to be more appropriate than the conventionaltechnique of mapping in expressing continuous and gradually changing soil or land attributes. Validation with observed soilor land attributes values indicated that root mean square error (RMSE) obtained for Fuzzy method was lower than that fromthe conventional metho

CO2 Flux from Tropical Land Uses on Andisol in West Java, Indonesia

This study measured CO2 flux by segregating effect of root respiration and organic matter decomposition by microbes. The study involved a mineral soil containing high organic matter (Andisols), in the tropic devoted to different land uses i.e. natural forest, tea plantation, and horticultural farm CO2 emission from those land uses were compared to from peatland. Observed CO2 fluxes came out in the following order: bare plot  7.32, tea plantation  10.22, horticultural farm  15.60, and natural forest  15.62 Mg C-CO2 ha-1 yr-1. While, root respiration accounted for substantial proportions: tea plantation  28%, horticultural farm  53%, and natural forest  53%. Soil temperature demonstrated a significant positive correlation with the CO2 flux, except in the natural forest. On the other hand, water-filled pore spaces displayed varying correlation with site CO2 flux: a negative relationship in both bare plot and tea plantation, appreciably positive in the horticultural farm, and weakly related in the natural forest. Soil respiration and C-organic content appeared to be strongly correlated; the rate of soil respiration increased with higher C-organic content. In field, CO2 flux from organic matter decomposition in Andisols, Latosols, and peatland ranged from 5.35-13.22 Mg C-CO2 ha-1 yr-1, with root respiration contributing most of the flux, which was, in turn, influenced by type vegetation, humidity and soil temperature.Keywords: CO2 flux; decomposition; horticultural farm; natural forest; organic matter; tea plantation [How to Cite: Jon H, Suwardi, B Sumawinata and DPT Baskoro. 2014. CO2 Flux from Tropical Land Uses on Andisol in West Java, Indonesia. J Trop Soils 19: 121-130. Doi: 10.5400/jts.2014.19.3.121]    

Peranan Pergerakan Air Dalam-Tanah dalam Menurunkan Aliran Permukaan

The main cause of flooding and erosion that creates critical land in various regions in Indonesia is surface runoff. The surface runoff will occur if rainfall exceeds the capacity of soil water absorption (infiltration capacity). The soil management of each land use could improve the infiltration capacity. The water movement both on the surface and in the soil determines the water infiltration. This study predicts surface runoff based on the infiltration rate of various land uses and rainfall in the Ciliwung Watershed. A series of studies were performed in the upstream and middle areas of the watershed. Observations of soil properties, water movement, and rainfall were carried out in various dry land uses. The results showed that the soil's physical properties mostly determine the constant infiltration rate, which affected the water movement in the soil. The initial water content, the degree of saturation of the initial moisture content, and the soil's physical properties determine the time of constant infiltration rate. The value of constant rate infiltration and the time of its achievement determine the amount of surface runoff that occurs. Keywords: hydraulic conductivity, run off, soil management, time achievement of infiltration capacit

REGRESI LOGISTIK BINER DAN RASIONAL UNTUK ANALISIS BAHAYA TANAH LONGSOR DI KABUPATEN CIANJUR

Sepanjang tahun 2002-2007 Cianjur telah mengalami 33 kali kejadian longsor. Tujuan penelitian ini adalah: (i) mengidentifikasi faktor yang paling berpengaruh terhadap bahaya tanah longsor di Kabupaten Cianjur, dan (ii) menganalisis bahaya tanah longsor di Kabupaten Cianjur. Metode yang digunakan untuk mengidentifikasi faktor yang paling berpengaruh terhadap bahaya longsor di Kabupaten Cianjur adalah analisis regresi logistik biner dan analisis rasional. Berdasarkan hasil analisis regresi logistik biner dan rasional, curah hujan merupakan faktor yang paling berpengaruh terhadap terjadinya longsor di daerah penelitian. Hal ini ditunjukkan oleh nilai koefisien parameter curah hujan yang tertinggi pada ketiga persamaan (0.542 pada hasil menggunakan SPSS, 0.920 pada hasil menggunakan Idrisi, dan 0.29 pada hasil analisis rasional). Kejadian longsor dipengaruhi terutama oleh kelas curah hujan yang tinggi. Ketiga peta bahaya longsor menghasilkan lokasi-lokasi untuk kelas bahaya sedang sampai tinggi. Pada peta bahaya longsor hasil regresi logistik biner menggunakan SPSS, kelas bahaya sedang sampai tinggi terdapat di bagian barat laut dan tenggara Cianjur. Pada peta hasil analisis menggunakan Idrisi, kelas tersebut di bagian tengah dan bagian utara Kabupaten Cianjur. Peta bahaya longsor hasil rasional, kelas bahaya longsor sedang dominan dan menyebar di seluruh kecamatan di Kabupaten Cianjur. Peta bahaya longsor hasil regresi logistik biner menggunakan Idrisi lebih baik dibandingkan dua peta bahaya lainnya, karena mempunyai nilai koefisien determinan terbesar yaitu 0.980.  Kata kunci: Regresi logistik biner, bahaya, tanah longsor, rasionalCianjur had 33 times occurrence landslides during 2002-2007. The objectives of this study were: (i) to identify the main cause of landslide hazard; and (ii) to analyze the landslide hazard areas in Cianjur. Analysis methods to identify the main cause of landslide hazards were based on binary logistic regression and normalization. Based on binary logistic regression and normalization result, rainfall is the main cause of landslide hazard in this study area. This was shown by the highest coefficient value of rainfall at the 3 equation (0.542 by using SPSS, 0.920 by using Idrisi, and 0.29 by using normalization). Positive coefficient value means that the occurrence of landslide mainly influenced by the highest class of rainfall. The three landslide hazard maps resulted from different methods showed different locations with moderate to very high-level hazards. A hazard map of binary logistic regression using SPSS showed that the moderate to very high-level hazard was found in the northwest and southeast part of Cianjur. Hazard map using binary logistic regression on Idrisi showed that the moderate to very high-level hazard was found in middle and north part of Cianjur. Hazard map using the normalization method showed the domination of moderate level hazard which was spread through all subdistricts in Cianjur. The landslide hazard map of binary logistic regression on Idrisi was better than two other maps, indicated by the highest determinant coefficient value which is 0.980. Keywords: Binary logistic regression, hazard, landslide, normalizatio

Alokasi Pemanfaatan Lahan Komoditas Unggulan Tanaman Pangan di Kabupaten Purwakarta

Purwakarta Regency is one of the regencies in West Java Province that plays an essential role in agricultural development. One of the efforts to encourage sustainable agricultural development is by developing potential commodities so that scenarios can be drawn up that are in accordance with the region's potential. Optimum land use scenarios with several constraint targets need to be prepared by considering food needs, ecological sustainability, and farm income. This study aims to identify land available for food commodities and simulate the land use allocation of food commodities in Purwakarta Regency to meet food needs, farm income, and tolerance for erosion. Location quotient index, shift-share analysis, land suitability & capability analysis, and Multiple Goals Programming were used to achieve research objectives. The identified leading commodities are peanuts, cassava, and sweet potato. We suggest 15 classes of land available for optimum land use allocation. Space optimization is organized into four scenarios considering erosion control targets, meeting farmers' minimum incomes, and rice production. The smallest erosion is 13,159 tons/ha/year, while the highest possible income is IDR300,500,000,000. The highest rice production is 202.070 tonsGKP, cassava production is 16,919 tons, sweet potato is 2.014 tons, and peanut production is 531 tons. Achieving production targets can support agricultural development and food security improvement programs through sustainable production improvement.   Keywords: erosion, farming, income, land suitability, MG

Land Use Projection for Spatial Plan Consistency in Jabodetabek

Land use changes in Greater Jakarta area are very dynamic because of the need for settlements and converting agricultural land. It indicates land use inconsistency regard to spatial plan that can cause land damage in the future. Land use which has potential inconsistency in the future are requires for land use control in this region. This study uses spatial analysis to look at the potential inconsistencies by comparing land use projection in the future in two scenarios that is with and without control by policies. Policies in this study are land suitability and forest allocation. The result shows that land use consistency with policies raise until 97,4 % but only 93.9 % without control by policies. Areas that could potentially have inconsistency in the future are Bogor, Bekasi, Tangerang and Jakarta North City for area which is directed as forest and buffer zones of cultivation

Soil Moisture Characteristics on Several Soil Types

Soil water availability is one of the important factors injluencing plant growth. Soil that can store more water in alonger time can support a better plant growth. This study was aimed to evaluate the dynamics of soil water of four differentsoils with different characteristics. Four soils classes are clayey textured soils-Red Yellowish Podsolik Jasinga, Clayeytextured soils-Latosol Darmaga, . Sandy Textured soil-Regosol Sindang Barang, and highly organic mater content soi/sAndosolSukamantri. The result showed that at every-suction analyzed, Andosol Sukamantri had consistently highest watercontent while Regosol Sindang Barang was consistently lowest. Similar tendency wasfoundfor available water capacity. Theresult also showed that moisture content at Regosol decrease more rapidly than those of the other three soils. The time need to reach likely constant moisture content is variable with soil type; lowest at Regosol Sindangbarang (45 hours after completely saturated and drained) followed by Podsolik Jasinga (73 hours), Latosol darmaga (74 hours) and Andosol Sulcamatri (76 hours)

Pendugaan Erosi Tanah dan Perencanaan Tutupan Lahan Hulu DAS Jeneberang, Sulawesi Selatan

Soil erosion is the main cause of land degradation. Jeneberang watershed is one of the priority watersheds in Indonesia. It has a big problem related to erosion in the upstream area. Jeneberang watershed is important area, its function is as water catchment for Bili-bili reservoir.  It is served for flood control, irrigation water sources, water and hydroelectric energy supply. The aims of this study were to analyze the soil erosion prediction based on existing condition; develop an ideal land cover scenario to decrease soil erosion; and suggest land cover planning recommendations based on tolerable soil loss indicators in the upstream of Jeneberang watershed. This study was conducted using map overlay method to determine the value of the erosion factor. Erosion was predicted based on Universal Soil Loss Equation (USLE). Land scenarios and simulations was calculated by estimating the erosion in forest area and spatial planning land cover. The result showed that soil erosion of existing condition was approximately 813.1 tons/ha/year. The tolerable soil loss was only 22.9 tons/ha/year. The landuse scenario that chooses the lowest presumed erosion result is the implementation of spatial planning of Gowa district 2012-2032 with soil conservation technique applied. It can reduce erosion and sediment as 96.6% in upstream Jeneberang watershed.   Keywords: erosion, Jeneberang watershed, scenario, landus

Effect ofMeasurement Method and Wet Sieving Time on Index of Soil Aggregate Stability

Aggregate stability is one of the important factors to be taken into account in controlling soil degradation. It influences soil ability to resist soil erosion. Therefore, it is necessary to have accurate measurement of aggregate stability that able to express well its resistance to dispersion. In this study, aggregate stability of various soil types were measured using different wet sieving time and aggregate size. Latosol Sindangbarang showed the highest aggregate stability index (ASI), followed by Podsolik Jasinga, Andosol Sukamantri, Lalosol Darmaga, and Regosol Sindangbarang Wei sieving time significantly affected AS!. The ASI decreased as wet sieving time increased The result also showed that different methods result in significantly different stability index. The method that used smaller size aggregates (< 2.83 mm) results in about 3 to 4 times higher stability index