EFFECTS OF LAND RECLAMATION MANAGEMENT PRACTICES ON CROP PRODUCTION AND PHYSICAL AND CHEMICAL PROPERTIES ON A TROPICAL SOIL (ACID INFERTILE, HUMID)

Large areas of soils in tropical rainforests have been damaged by poor mechanical land clearing practices. The objectives of this study were to evaluate the effects on crop performance and on soil physical and chemical properties, of various management practices to reclaim acid infertile soils in West Sumatra, Indonesia. Land reclamation treatments evaluated included all combinations of four lime and fertilizer levels (none, low, medium, and high) and six tillage practices (hoeing(H), H + mulching (Hm), H + green manure (Hg), deep forking (F), deep forking in strips (SF), and rototilling (R)). Crop performance (yield, yield components, and growth parameters), soil physical properties (bulk density (Db), mechanical impedance (MI), infiltration rate, soil water characteristic, and moisture content), and soil chemical properties (soil pH, exchangeable Al + H, K, Ca + Mg, effective cation exchange capacity (ECEC), extractable P and Mn), were monitored periodically for five crops over a 19 month period.;Deep forking and strip forking decreased Db and MI and increased macroporosity and infiltration rate as compared to hoeing. Increasing fertility level increased root activity which in turn increased MI and infiltration rate.;The high rate of chemical inputs increased nutrient levels in the soil to near optimum. Periodic K applications were needed to maintain the K level whereas P and lime were applied only once. For the low chemical input level, the application of fertilizer was needed for almost every crop to maintain critical levels. The concentration of basic cations increased linearly with soil pH. Increasing soil pH by liming up to 5.2 resulted in a decrease in exchangeable Al + H to near 0 but had no effect on ECEC; a further increase in pH effected a linear increase in ECEC. Soybean was more sensitive than rice to Al saturation percentage. Mulching decreased the percentage Al saturation, while green manure incorporation increased available Mn.;No crop yield was obtained without lime and fertilizers. Plant growth and grain yield increased dramatically with increasing input. Rice (Oryza sativa L.) responded to chemical inputs up to the low level, whereas soybean (Glycine max L. (Merr.)) and mungbean (Vigna radiata L.) responded up to the high chemical input level. Green manure further increased plant growth and yield, while mulching increased crop yields during the second year. Deep forking did not affect rice but slightly improved soybean production. Strip forking tended to decrease and rototilling tended to increase rice yield.