Improving Management of Natural Resources for Sustainable Rainfed Agriculture in Northeastern Thailand

Lands of northeastern Thailand are sloping and fragile. A large proportion of these soils are degraded due to soil erosion. Degraded soils are one of the major constraints for agricultural production in this region. ICRISAT in collaboration with the Department of Agriculture, Land Development Department, and Khon Kaen University, Thailand started a project in 1999 with the financial support from the Asian Development Bank to improve the management of natural resources for sustainable rainfed agriculture through integrated watershed approach. This paper summarizes all the research work carried out for three years during the project period. This includes selection of benchmark site in the ecoregion, baseline surveys, establishment of monitoring devices and various interventions in cropping systems, land and water management and fertility management areas, and human resource development. The initial results of research indicate a reduction in soil erosion and improvement of crop yields due to various interventions. There is sufficient scope to scale up this work in the ecoregion. The details of various activities undertaken and the outputs are presented in the pape

Role of microorganisms, soluble N and C compounds in fermented bio-extract on microbial biomass C, N and cowpea growth

Previous field and pot experiments showed that the sole application of the bio-extract did not increase plant dry weight and yield. However, application of bio-extract (BE) with organic fertilizers increased plant dry weight (leaf, stem and yield). It has been hypothesized that the bio-extract may act as a direct source of beneficial microorganisms or/and substrates to stimulate soil microbial activities in decomposing organic fertilizer and to release nutrients to plants. The objectives of this pot experiments were to investigate the roles of live microorganisms and/or chemical constituents of bio-extract combined with or without compost on microbial biomass and crop growth. Autoclave treatment on the bio-extract showed that the living microorganisms contained in the bio-extract were not significant source of microorganisms responsible for decomposing organic fertilizer in the soil. There were no significant differences in microbial C and N in the soils treated with either original or autoclaved bio-extracts in the short term (8 days). Bio-extract after autoclaving could still enhance crop growth (top dry weight) when being combined with municipal compost. Moreover, cowpea treated with original, autoclaved or artificial (only soluble C and N) bio-extracts did not show significant difference in top dry weight. Our studies suggest that some substrates, such as soluble organic acids, amino acids, in the bio-extract might play some important roles to stimulate soil microbial activities and enhance crop growth

Multiple sources of water for multiple purposes in northeast Thailand

Many farms in tropical countries suffer from droughts in the dry season and sometimes even in the rainy season. In order to significantly increase the capacity to store water, the grassroots Farmer Wisdom movement in Northeast Thailand innovated pond construction on homesteads. This Working Paper first documents how pond water is mainly used to irrigate crops and fruit trees, and is also used for livestock or fish, and for domestic uses, even if ample piped water is available. Households were also found to harvest rainwater from roofs; take water from canals and streams; lift water manually from shallow wells and with electric pumps from deep wells; channel run-off from roads to paddy fields; use precipitation as green water on fields; and buy bottled water. Most households combine at least six of these nine water sources. The second part describes scenarios and some outcomes of a new simulation model, BoNam. This model provides guidelines for the optimal size and site of such ponds according to biophysical factors (weather, soil and crops), socioeconomic factors (prices, availability of labor and off-farm income) and household aspirations

Role of soil resource data in assessing soil acidification risk: An example from Northeast Thailand

In Eswaran, H.; Vijarnsorn, P.; Vearasilp, T.; Padmanabhan, E. (Eds.). Innovative techniques in soil survey: Developing the foundation for a new generation of soil resource inventories and their utilization. Bangkok, Thailand: Land Development Departmen

Remediation of soil acidification by form of nitrogen fertilizer on grass swards of Australia and Thailand

Acidification of soil profiles from legume and N fertilized crops is a serious sustainability threat. Under tropical conditions of Northeast Thailand and Northern Australia, acidification to >90 cm has been recorded in Stylosanthes and Leucaena based pasture systems. Acidification has also been measured in other Australian cropping systems fertilized with urea or ammonium forms of N. The major processes contributing to what could be termed anthropogenic acidification are removal of base cations in the harvested product and leaching below the root zone of nitrate from ammonium and urea N fertiliser or legumes resulting in an accumulation of protons in surfaces horizons. If prophylactic applications of lime are not undertaken, acid generation in surface horizons will progressively move down the profile inducing subsoil acidification. Subsoil acidity is often difficult to correct using conventional applications of liming products. Field experiments with pastures on Acrisols in Northeast Australia (two sites) and Northeast Thailand (one site) compared the rates of alkalisation or acidification from N applied as nitrate or as urea (Australia) or ammonium sulphate (Thailand). Soil pH increased where N was applied as nitrate and decreased where N was applied as urea or ammonium sulphate. At one of the sites in Australia, regular applications of N as nitrate at 350 kg N ha-1 year-1 were made to irrigated Digitaria melanjiana cv Jarra. This significantly increased soil pH (1:5 0.01 M CaCl2) by up to 0.5 units to a depth of 0.90 m over a period of 4 years when compared to bare soil. The alkalisation of the profile was equivalent to 2.7 t/ha of calcium carbonate distributed evenly down the profile. Urea at the same rate of N decreased soil pH at 20-50 cm by 0.2 units. Similar but smaller changes were measured at the other Australian site (Brachiaria decumbens) and the site in Thailand (Andropogon gayanus cv Carimagua (Gamba grass). Treatment effects at these sites were restricted by time (1 year) or seasonal conditions that limited the number of N applications that could be applied (290 kg N/ha over 3 years) at the Thai site. The research has clearly demonstrated that nitrate N fertilizer can rapidly correct soil acidity down the soil profile to 0.9 m and this is attributed to the release of alkali from roots as nitrate is taken up. Such a strategy may be an effective approach to addressing subsoil acidification where surface applications of lime are ineffective and profile modification is cost prohibitive