Abstract. Steeply sloping lands are widespread in the tropics. An estimated 500 million people practice subsistence agriculture in these marginal areas. Continued population growth has led to the intensified cultivation of large areas of the sloping lands, exacerbating the problem of soil erosion. Although research shows that alley cropping and other contour agroforestry systems can stabilize the sloping lands, these systems have not been widely adopted by farmers.The Framework for Evaluating Sustainable Land Management (FESLM) has been tested in sloping land areas in the Philippines. Sustainable land management must be productive, stable, viable, and acceptable to farmers, while protecting soil and water resources. Farms on which contour hedgerow intercropping has been adopted meet the multifaceted requirements of FESLM, whereas the farmers' current practice does not. Appropriate land management measures for particular locations depend on a complex suite of social, economic, and biophysical factors, and need to be developed in participation with farmers.The role of agroforestry in sustainable management of sloping lands is the subject of networks coordinated by the International Board for Soil Research and Management (IBSRAM) in seven countries in Asia (ASIALAND) and four countries in the Pacific (PACIFICLAND). We review selected outcomes from a wealth of network data. From these results the following conclusions about the sustainability of various agroforestry systems for sloping lands can be drawn:In the Pacific, soil loss from sloping lands due to water erosion under farmers' current practices is episodic, unpredictable, and possibly not severe; Agroforestry systems that utilize legume shrubs, fruit trees, coffee (Cojfea spp.) or rubber (Hevea brasiliensis) provide useful economic returns, but are not an essential component in terms of soil protection because grass or pineapple (Ananas comosus) planted on the contour are equally effective in reducing erosion; Agricultural intensification will lead to nutrient mining, reduction of aboveground biomass, declining yields, and less soil protection unless external sources of nutrients are used; nitrogen can be effectively supplied using legumes; Cash derived from hedgerow trees and/or shrubs may provide an incentive for their adoption by farmers, as well as funds to purchase external inputs such as fertilizers; Labor may be a major constraint to the adoption of complex agroforestry systems.We also discuss the information management systems required to effectively manage and utilize the extensive sets of experimental and indigenous data being accumulated. We believe such information systems can facilitate technology transfer across and between regions, and improve the efficiency of research into agroforestry and other land-management approaches. 122

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Runoff rates were estimated from rainfall rates and runoff amounts for 4 experimental sites in China, Malaysia, and Thailand before a physically based erosion model GUEST was used to determine the soil erodibility parameter and evaluate the potential to use the erosion model to predict the amount of soil loss on an event basis. We also examined 3 different ways of determining the soil erodibility parameter for the same storm event using: (i) hydrographs estimated from rainfall intensities and runoff amounts; (ii) an effective runoff rate calculated from the hydrograph; (iii) an estimate of the effective runoff rate based on a scaling technique involving the peak rainfall intensity and the gross runoff coefficient. All 3 methods can produce consistent soil erodibility parameters for a given runoff event. The calculated soil erodibility for individual storm events for all sites shows considerable temporal variation and for most sites a decreasing trend over time, as observed elsewhere in the same region. Among the 4 soils examined, the average soil erodibility tends to decrease as the ratio of coarse to fine materials decreases. When the erosion model GUEST is used to predict event soil loss using estimated soil erodibility parameters, an average model efficiency of 0·68 is achieved for the sites tested.

This study was designed to investigate the impact of three land‐use practices in Thailand on soil organic matter (SOM) composition. The land uses were continuous farming (till), alley‐cropping, and secondary forest. Samples, taken from the top 10 cm soil surface, were fractionated into clay‐ (< 2 μm), silt‐ (2–20 μm), and sand‐sized particles (20–2000 μm) prior to analyses of C, N, lignin‐derived phenols and individual carbohydrates. As particle size increased, the C/N ratio and the concentration of lignin‐derived phenols increased, whereas the degree of lignin oxidation as well as ratios of microbially derived hexoses to plant‐derived pentoses decreased. Thus, the coarser the particle size, the less the SOM was altered by microbes. Seven years of alley‐cropping increased SOM levels only little but considerably affected SOM composition by affecting the SOM of the sand fraction. The SOM concentration in the sand fraction increased in the order continuous farming < alley‐cropping < secondary forest. In the same order, microbial alteration of lignin and carbohydrates of sand‐sized SOM decreased. Both the different concentrations of SOM in the sand fractions as well as its different composition contributed, therefore, to different SOM among the sites. Increasing lignin‐to‐carbohydrate ratios for bulk soils and fractions in the order continuous farming < alley‐cropping < secondary forest reflected such changes in SOM composition sensitively.

Powdered ZnSO4 · 7H2O was plowed down for corn (Zea mays L.) in a Zn‐deficient Fieldon silty clay loam at five rates, row banded, or banded at four rates after mixing with NH4NO3. The effect of dusting corn seed with Na2Zn‐EDTA was also compared, using leaf Zn and grain yields for 5 years as criteria. Soil analyses and greenhouse studies with 65Zn, eight years after Zn fertilization, were conducted to determine possible cause(s) of extreme variations in field availability of indigenous soil Zn for corn, and the residual effect remaining where Zn fertilizer was used eight years previously.Plowing down ZnSO4 · 7H2O at higher rates resulted in higher leaf Zn in all 5 years, whereas initially effective lower treatment rates decreased with time. Banded Zn and/or N had little or no effect on leaf Zn. Grain yields were increased by both plow down and band ZnSO4 · 7H2O treatments until the fifth year. Dusting corn seed with Na2Zn‐EDTA had no effect on leaf Zn or on annual grain yield, but increased the 5‐year yield.Soil analyses 8 years after Zn fertilization showed that vegetative Zn‐deficiency symptoms of corn in the field and subsequent low grain yields were significantly related to high extractable P/extractable Zn ratios in the surface 30.5‐cm soil depth. There was no observed effect of temperature, moisture, pH, conductivity, calcium carbonate equivalent, or exchangeable K. More Zn was extracted from the surface soils where Zn had been applied nearly 8 years previously, but “A values” were larger only in soils receiving the heaviest 1962 Zn treatment of 44.8 kg/ha.