Francis Turkelboom

Reassessment of tillage erosion rates by manual tillage on steep slopes in northern Thailand

Abstract Changing land-use practices in northern Thailand have increased tillage intensity. This study re-assesses the rate of tillage erosion by manual hoeing on steep slopes (17–82%) in northern Thailand. Previously collected soil translocation data during an on-farm tillage erosion experiment and additionally collected data during an on-farm tillage erosion survey have been analysed whereby a new calculation method (i.e. trapezoid tillage step) has been used. A comparison with previously collected data indicates that the trapezoid tillage step method and the tracer method are the most reliable methods to assess downslope translocation by manual tillage. Based on newly acquired understanding of the processes involved, soil fluxes by tillage erosion are quantified by linear functions for different slope gradient classes rather than one single diffusion-type equation for the whole slope range. For slope gradients smaller than 3%, soil fluxes are close to zero as farmers do not have a preferred tillage direction. For slope gradients between 3% and 70%, soil is tilled only in the downslope direction and soil fluxes range between 16 and 67xa0kgxa0m −1 tillage pass −1 . On slopes with gradients in excess of 70%, the angle of repose for soil clods is often exceeded resulting in a sliding down of the complete tilled top layer. These data are used to assess the soil flux for complete cropping cycles for the most dominant cropping systems in the highlands of northern Thailand: i.e. upland rice, maize, (soy) beans, cabbage and ginger. The on-site effects of tillage erosion will be very pronounced if parcels are short with respect to their slope length, cultivated for upland rice or cabbage, or when weed pressure is high. Tillage erosion results in a tillage step with low soil fertility and low infiltration capacity. Solutions to reduce tillage erosion intensity depend on the degree that tillage intensity can be reduced. This might happen by an improved weed management or by changing landuse to perrenial cropping. Other strategies are concentrating nutrients on the truncated hillslope sections and retaining soil on the field by vegetative buffers.

Options to Improve Livelihoods and Protect Natural Resources in Dry Environments The Case of the Khanasser Valley in Syria

This article reviews work that had the objective of introducing agricultural technologies in a marginal dryland area, the Khanasser Valley, northwestern Syria. The highly variable rainfall is barely sufficient to support livelihoods in this traditional barley—livestock production system. The valley is representative of other marginal dryland areas in West Asia and North Africa. We used a farmer-participatory approach to evaluate the performance of agricultural technologies for dry marginal areas in terms of their contribution to livelihoods and effect on the environment. The integrated approach allowed comprehensively comparing and evaluating the viability of promising technologies, including novel crops, intercropping, soil management techniques, and livestock rearing. The results show that improved barley varieties, olives, cumin, and lamb fattening can improve livelihoods, particularly for the land-owning households, whereas other households can benefit indirectly in terms of employment spillovers. These options are also environmentally friendly and sustain the natural resource base.

An Integrated Livelihoods-based Approach to Combat Desertification in Marginal Drylands

International Centre for Agricultural Research in the Dry Areas, Aleppo, Syria Abstract Previous interventions to combat desertification have often failed because a piecemeal approach was used that was inadequate to deal with the complexities of marginal dryland areas. This paper describes a more relevant, inclusive approach based on the principles of Integrated Natural Resources Management (INRM). It sets out a framework for INRM implementation, with 11 “cornerstones” to guide project design, identify strong and weak areas, and target efforts accordingly. These cornerstones are broadly grouped under three aspects: multidisciplinary, multiinstitution partnerships, local institutional/organizational capacity, and scaling out (including post-project sustainability). ICARDA and its partners applied this framework to a research project in the Khanasser Valley, a marginal dryland area in Syria. A range of best-bet technological, institutional and policy options was developed with community participation. These options were discussed at multi-stakeholder meetings, and tested jointly by researchers, extension agents and the community. They continue to be implemented and refined through iterative learning cycles. Crucially, this approach is not limited to technical solutions alone but includes economic, environmental, social, institutional and policy aspects, and links research findings into a long-term development plan that addresses priorities identified by the community. The best-bet options have proved feasible, profitable and low-risk, and adoption is growing. Policy-makers have shown a willingness to replicate the INRM approach in other parts of Syria.

Modelling the Effects of Soil Conditions on Olive Productivity in Mediterranean Hilly Areas

The majority of olive (Olea europaea L.) production in Mediterranean environments is characterized by low external inputs and is practiced in hilly areas with shallow soils. This study aimed to study the yield and nutritional status for olive (cv. “Zeiti”) trees in northwestern Syria and establish correlations between yield, on the one hand, and soil/land factors and tree nutrition, on the other hand, to determine the most yield-affecting factors. Land and soil fertility parameters (field slope, soil depth, and soil nutrients) and concentrations of leaf minerals were determined. As olive roots can go deep in the soil profile to extract nutrients, the total available nutrients per tree (over the whole profile) were estimated. Multiple regression analyses were performed to determine the model that best accounts for yield variability. Total available soil potassium amount (), soil total N amount (), and soil depth () had the highest correlations with olive fruit yields. Available soil potassium amount and soil depth explained together 77% of the yield variability observed. In addition to these two factors, adding leaf B and Fe concentrations to the model increased the variability explained to 83%.