Peningkatan Produktivitas Tanah Melalui Sistem Agroforestri

. The low soil fertility and high toxic elements caused by high rainfall (>2,500 mm/year) is the main factor responsible for the low soil productivity in the humid tropical zone, like Indonesia. In this condition, agroforestry system is expected to be solution. There are three components of agroforestry: silviculture, agriculture and livestock. Agroforestry in Indonesian is called Wanatani that means planting trees in agricultural land. Trees have deep rooting and spread intensively in subsoil may reduce leaching nutrient both vertically and horizontally. Cover crop protected soil from erosion. This role makes agroforestry as one form of soil and water conservation practices, produced some products that have a high economic value. This situation allowed agroforestry as a system of sustainable land management

Potensi Sumberdaya Lahan Pulau Sulawesi Mendukung Peningkatan Produksi Padi, Jagung, Dan Kedele

. The reconnaissance soil survey and mapping programme at scale of 1: 250,000 in Indonesia has been successfully completed, marked by publication of the soil maps in 2012 for each province in Kalimantan, Sulawesi, Maluku, Nusa Tenggara, Java, and West Papua. From the soil map legends, it can be obtained the information of climate condition, landform, relief an slopes, type and properties of soils that affect land resource potential for agricultural development purpose. The island of Sulawesi (18.7 million ha) has variation of climate condition from wet to dry, which is reflected by udic, ustic and aquic soil moisture regimes. The main landform groups, from the most extensive respectively consists of Tectonic (37.63%), Volcanic (37.39%), Alluvial (11.82%), Karst (8.31%), Marine (2.65%), Fluvio-Marine (0.41%), and Peatland (0.13%). The relief varies from flat to mountainous, with composition of flat to nearly flat (15.85%), undulating (4.86%), rolling (6.50%), hillocks (11.96%), hilly (19.30%), and mountainous (39.85%). The soil parent materials are vary, which composed of organic and alluvium deposits, acid to basic sedimentary rocks, young and old volcanic rocks, acid to basic intrusive rocks, and metamorphic rocks. Nine soil orders were formed from these parent materials, namely from the most extensive respectively Inceptisols (58.15%), Alfisols (10.44%), Ultisols (10.25%), Mollisols (6.21%), Entisols (5.54%), Oxisols (4.87%), Andisols (2.18%), Histosols (0.41%) and Vertisols (0.28%). Based on the biophysical data, there are large potential lands in Sulawesi, consisting of wetland soils with slope of <3% covers about 2.30 million ha for ricefield (sawah), and dryland soils with slopes of 3-15% covers about 1.98 million ha for maize and soybean development. Actually, the most of land potential have been cultivated for various agricultural crops. Therefore, the increasing production of paddy rice, maize and soybean have more opportunity to optimalize or intensify the use of existing agricultural land rather than to land extensification. By assumption, if 50% of the potential wetland is cultivated with paddy twice a year with mean productivity of 4,71 t ha-1, then it would get about 10.82 Mt GKG (dry unhulled rice). And also, if 50% of the potential dryland soils is cultivated with maize and soybean at least one time a year with mean productivity of 4,05 t ha-1 and 1,34 t ha-1 respectively, then it would get about 4.02 Mt dry grain corn, and 1.33 Mt dry grain soybean. Compared to the existing production of the three food crops according to BPS in 2012 (paddy 7.82, maize 2.94, and soybean 0.05 Mt), there are very significant increasing production for paddy, maize and soybean as much as 38.4%, 36.7%, and 2461.5% respectively

Preservation of Organic Matter as Affected by Various Clay Contents in an Acid Soil:Beneficial Impact on Groundnut Yield

Systematic study on the effect of various clay contents on organic C dynamic and groundnut yield (Arachis hypogea) in upland acid soils has not received any attention. The objectives of the study were: (i) to assess the capability of various soil clay contents to preserve organic C, (ii) and to relate the effects of soil clay fraction and organic C on groundnut yield of an acid soil (Ultisol). The soil clay content was artificially adjusted to 15, 30, 45, 60 and 75%. Each soil clay percentage was thoroughly mixed with finely ground rice straw at the rate equals to 0.5, 1, 2, 3, 4, and 5% of organic C. The soil was then transferred into a pot and planted with corn (Zea mays)for the first 6 months and followed by groundnut for further 6 months. The experiment was arranged in a split plot design with three replications under glasshouse conditions. Results for the first 6 months have been published elsewhere. Hence, results for the last 6 months were presented here. Soil clay was the major factor responsible for the preservation of organic C as indicated by (i) the increased soil organic C with increasing clay fraction, and (ii) the low mineralization rate as shown by CO2-C: total C ratio from low to high 75<60<45<30<15% soil clay. It is observed that every 15% clay increment could preserve another 0.3% organic C for the period of 12 months. The increased soil organic C could linearly increase groundnut yield for 15 and 30% clay and quadratic yield for 45 and 60% clay. The maximum grain yield was 25.7-27.6 g pot-1 (equals to 2.9-3.1 t ha-1), which was obtained at 30-45 % clay containing 1.8-1.9% soil organic C