Extensive areas in Sudano-Sahelian West Africa are experiencing increasing population densities and cultivation pressure, insecure land tenure, low annual rainfall amounts (500-800 mm/yr), and soil infertility, all of which affect local cropping decisions. This detrimental trend has resulted from an expansion of population growth rates since the 1950s and migration from the dryer north to the moister south that began with the droughts of the early 1970s. Before the 1960s, increasing cultivation pressure was dealt with in the Sudano-Sahelian region by expanding cultivation efforts to adjacent uncropped parcels. Though the productivity of each parcel was less than desirable, cultivation demands could still be met by including a greater number of low-yielding parcels. Today, however, such expansion practices are virtually impossible since there are fewer suitable areas left uncropped than ever before. Lands that are less fertile or more sensitive to erosion are still frequently cultivated despite their poor condition because the demand for food in the region is so high.
[...] The two gradients are combined and this empirical ranking is used to group the soil types into five categories of soil aptitude to crop: - The loamy sands and clayed loams in colluvial and alluvial depression constitute the ‘rich' soil group. These soils offer the highest potential for cropping; however, they are susceptible to flooding which can ruin the crop. Furthermore, the relatively fine texture of the soils makes them more difficult to till. - Thick sandy soils that are moderately leached constitute the ‘fair' soil group. [...]
[...] The purpose of this project is to better understand the relationships between different factors affecting land-use decisions in this specific area, namely soil type, parcel proximity to village, and manuring practices. (See Appendix If the role of these factors in land-use change is better understood, the results can be applied toward the development of land-use policy for planning purposes. The research questions for this project are: 1. Do local farmers favour cultivating one soil type over another? 2. Is the land-use dynamic influenced by proximity to village or soil type? [...]
[...] CONCLUSION The results of this project show that there are significant interrelationships between land-use dynamic, soil type, parcel proximity to village, and manuring practices. There are many more environmental, social, political, and economic factors involved in the land-use dynamic of southwest Niger than were considered in this project but are valid subjects for future research; these include livestock ownership and land tenure, among others. Because our analyses can only suggest statistically significant relationships between the land-use dynamic, soil type, proximity to village, and manuring practices, there is still much work to be done in terms of quantifying the relationship between these different variables in order to understand how much a given soil type affects the land-use dynamic, for example. [...]
[...] Soil Type In preparing data layers for determining if a relationship exists between land-use dynamic and soil type, the cultivated parcels data layer created for Question 2.1 was intersected with the soil type distribution data layer so that the soil type(s) of each cultivated parcel polygon would be known. (Appendix The frequency counts for each soil type land-use dynamic pair were determined from this map and used in a Chi-Square analysis. This map was re-used in subsequent analyses since it contained soil type, change count, and manure count parcel attribute data. [...]
[...] Manuring Practices The research question concerning the relationship between the land-use dynamic in the study area and soil type was divided into three parts: investigating the relationship between manuring practices and soil type, investigating the relationship between manuring practices and parcel proximity to the nearest village, and investigating the relationship between manuring practices and land-use dynamic. Manuring practices are defined here as how many years a parcel was observed to be manured over the four year study period and are reflected in the “manure count” value in the codification scheme. [...]
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