Balanced fertilization for sustainable development of agriculture in the savannas of South America:towards a geographical approach
South American countries still own considerable land reserves for agricultural development. Huge areas of virgin lands and natural pastures were recently occupied by commercial crops and suffer increasing pressure of agriculture. Growing demand for food in the world and attractiveness for capital investment drive colonization all further deep into the regions, which cannot be converted to commercial agriculture without serious negative consequences for the environment. Agricultural development in these areas neither can be considered sustainable economically, as high production costs sometimes surpass revenues from the harvest. Most of the regions of recent colonization in South America are those under savanna landscapes, where lack of nutrients in the soil restricts agricultural use. Understanding the problem of sustainability of agricultural development in savannas is impossible without geographical analysis. Spatial approach at different scales enables precise vision of weak points of recently established agricultural systems and helps to draw solutions for diminish their instability. The paper is based on research, realized during 2004–2010 in Brazilian savannas (cerrado) with the purpose of improve efficiency of mineral fertilizers use.