Structural adjustment and soil degradation in Tanzania. A CGE-model [computable general equilibrium] approach with endogenous soil productivity

agriculteur agricultores cambio estructural changement structurel cropping systems cycle de l'azote deterioro del suelo economic growth environmental impact erosion farmers fertilidad del suelo ganancias impact sur l'environnement impacto ambiental modele modelos models nitrogen cycle petite exploitation agricole profit sistemas de cultivo small farms soil deterioration soil fertility structural change subsidies subsidios subvention tanzania tanzanie