Browsing by Author "Hiernaux, P."
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Co-evolutionary scenarios of intensification and privatization of resource use in rural communities of south-western NigerRovere, R.; Hiernaux, P.; van Keulen, H.; Schiere, J.; Szonyi, J. (Amsterdam, Netherlands: Elsevier Science B.V., 2005)Agricultural production in the semi-arid agro-ecosystems of the Sahel centres on cereal staple crops and pastoralism with increasing crop-livestock integration. Animals mobilize soil fertility through manure production, graze crop by-products, and transfer nutrients from distant pastures to cropped areas. Yet in these systems various interacting factors, i.e. climate variability, poor soil fertility, poverty, and institutional constraints limit the capacity of agriculture to keep pace with the growing needs of an increasing human population.
- Decomposition of land nutrient release from ruminant manure on acid sandy soils in the Sahelian zone in Niger, West AfricaEsse, P. C.; Buekert, A.; Hiernaux, P.; Assa, A. (2001)In ago-pastoral systems of the semi-arid West African Sahel, targeted applications of ruminant manure to the cropland is a widespread practice to maintain soil productivity. However, studies exploring the decomposition and mineralisation processes of manure under farmers' conditions are scarce. The present research in south-west Niger was undertaken to examine the role of micro-organisms and meso-fauna on in situ release rates of nitrogen (N), phosphorus (P) and potassium (K) from cattle and sheep¯goat manure collected from village corrals during the rainy season. The results show that (1) macro-organisms played a dominant role in the initial phase of manure decomposition; (2) manure decomposition was faster on crusted than on sandy soils; (3) throughout the study N and P release rates closely followed the dry matter decomposition; (4) during the first 6 weeks after application the K concentration in the manure declined much faster than N or P. At the applied dry matter rate of 18.8 Mg ha-1, the quantities of N, P and K released from the manure during the rainy season were up to 10-fold larger than the annual nutrient uptake of pearl millet (Pennisetum glaucum L.), the dominant crop in the traditional agro-pastoral systems. The results indicate considerable nutrient losses with the scarce but heavy rainfalls which could be alleviated by smaller rates of manure application. Those, however, would require a more labour intensive system of corralling or manure distribution.
- The effect of clipping on growth and nutrient uptake of Sahelian annual rangelandsHiernaux, P.; Turner, M. D. (1996)Growth and nutrient-uptake responses of annual rangeland to defoliation were studied at 13 sandy range sites located across the Sahelian zone of Mali between 1977 and 1989. 34 cutting experiments (site-years) were conducted using identical treatment designs with respect to the timing and frequency of cutting. The effect of highly variable growing conditions (rainfall and nutrient availability) on the response to cutting was analysed through a series of regression analyses. The growth response of vegetation to cutting was more related to variables associated with rainfall and growing conditions than to cutting frequency. Total yields were lowered most during periods of rapid growth. N and P yields were not affected by growing conditions while cutting consistently increased N and P yields. Greater sink strength in cut plants better explained the observed stimulation of N and P yields than did the increased nutrient availability that could result from modified soil water status after cutting. The significance of these results for the ecological grazing management of Sahelian rangelands is discussed. (CAB Abstract)
- Grazing Effects of Goat-Sheep Mixes on Vegetation Structure and Productivity of Old Fallow in the SahelHiernaux, P.; Fernández-Rivera, S. (1995)In the short term, grazing of a 40-ha fallow in the Sahel, Niger, by sheep and goats reduced the standing herbage mass in the wet season and increased its disappearance during the dry season. The effects of stocking rate (62.5 or 125 kg liveweight/ha) and the proportion of sheep in the mixture (sheep:goat ratios of 0:6, 2:4, 4:2 and 6:0) varied from year to year. In the longer term, grazing also affected the botanical composition. Grasses were promoted at low grazing intensities and dicotyledons at high grazing intensities. (CAB Abstracts)
- Nutrient cycling on integrated rangeland/cropland systems of the SahelPowell, J. M.; Fernández-Rivera, S.; Hiernaux, P.; Turner, M. D. (1996)In the Sahel of West Africa, the productivities of rangelands, croplands and livestock are inextricably linked. Cattle, sheep and goats graze rangelands and crop residues, and their manure/urine is used to fertilize crops. Rangelands provide important feeds during the manuring period, resulting in a net nutrient transfer from rangelands to croplands. This paper examines the sustainability of nutrient transfers in integrated rangeland/cropland systems of the Sahel by examining the impact of grazing on rangeland vegetation structure and floristic composition, the impact of livestock on nutrient balances of rangelands and croplands, and the role of livestock in offsetting nutrient deficits through manuring. Rangeland nutrient balances are in equilibrium (inputs = offtakes) whereas croplands lack the internal capacity to replenish nutrient offtakes in grain (as food) and crop residues (as feed). Although soil nutrient mining is of general concern for the Sahel, local management practices of some farmers (e.g. corralling animals overnight on fields between cropping seasons, use of fertilizers) offset cropland nutrient deficits. The number of additional livestock, and their feed requirements needed to supply sufficient manure to offset cropland nutrient deficits, depend on rangeland and cropland productivity, livestock production goals, and management strategies of farmers. Livestock must be managed so they do not deplete the nutrient supply of rangelands in order to increase the manure supply for improving cropland productivity. Sustained rangeland productivity in the Sahel will depend largely on producing alternative feeds derived mostly from croplands. Land use and tenure policies that inhibit livestock mobility and, therefore, farmers' access to the manure of pastoralists herds, will greatly undermine the resilience of Sahelian rangelands, and increase the need for other external nutrient inputs such as fertilizers to prevent declines in soil fertility and crop yields. (CAB Abstract)