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Integrated biophysical and socio-economic evaluation of water and soil conservation techniques : a case study from Niger

Book - Dissertation

Subtitle:Geïntegreerde biofysische en socio-economische evaluatie van water- en bodemconserveringstechnieken : een casestudy uit Niger
As a result of growing population pressure and limited fertile land availability, Nigerien farmers increasingly rely on marginal lands (Plinthosols) for crop production. These degraded lands, however, generally provide poor millet yields (<100 kg ha-1 yr-1) due to their low soil nutrient content and imbalanced partitioning of water over the root-zone. This dissertation aims to provide scientific verification of the potential of small-scale water and soil conservation (WSC) techniques to tackle these two major crop growth limitations. The overall objective is to evaluate the biophysicail and socio-economic viability of WSC techniques in the Tillaberí region of Niger. In order to monitor WSC techniques, a field experiment was laid on a Plinthosol nearby Sadoré. The treatments include: zaï + manure (Z), demi-lunes + manure (DL), scarification + manure (SCAR), control + manure (CF) and control (C). Grain yields for the conventional practices (C and CF) were extremely low and soil-water storage in the rootzone remained below the critical value for drought stress, even if there was sufficient rainfall. WSC techniques, on the other hand, successfully mitigated drought stress. WSC increased grain yields to 700 kg ha-1 yr-1 for Z and to 250 kg ha-1 yr-1 for DL and SCAR. By applying WSC, soil-water storage increased above the critical value for drought stress. This was mainly a result of significant run-off reduction under WSC (i.e. from approximately 25% for C to 5-10%). WSC techniques were, on the other hand, found to have only little impact on soil evaporation. A design optimization study with a three-dimensional coupled surface-subsurface soil hydrological model showed that rainwater use efficiency of DL could be improved by increasing the density of DL bunds per surface area while decreasing the number of millet plants per DL bund. Soil quality analysis showed that, SOC content increased significantly for the treatments with manure application (CF,SCAR, DL and Z), from ± 2.5 to ± 5 g kg-1. WSC techniques did not improve physical soil quality, but did significantly improve biological soil quality. A socio-economic survey indicated that the adoption of WSC techniques in the region is limited by manure shortage and a lack of specific erosion knowledge.
ISBN:9789059898110
Publication year:2015
Accessibility:Open