Abstract
Unsustainable farming practices such as shifting cultivation and slash-and-burn agriculture in the humid tropics threaten the preservation of the rainforest and the health of the local and global environment. In weathered soils prone to cohesion in humid tropic due to low Fe and carbon content and the enormous amounts of P that can be adsorbed, sustainable soil use is heavily dependent on the availability and efficient use of nutrients. This paper reviews the literature in the field and provides some insights about sustainable soil use in the humid tropics, mainly for the Brazilian Amazonia region. Careful management of organic matter and physical and chemical indicators is necessary to enhance root growth and nutrient uptake. To improve the rootability of the arable layer, a combination of gypsum with continuous mulching to increase the labile organic matter fraction responsible for the formation of a short-lived structure important for root growth is recommended, rather than tillage. Unlike mulching, mechanical disturbance via ploughing of Amazonian soils causes very rapid and permanent soil organic matter losses and often results in permanent recompaction and land degradation or anthropic savannization; thus, it should be avoided. Unlike in other regions, like southeast Brazil, saturating the soil solely with inorganic potassium and nitrogen soluble fertilizers is not recommended. Nutrient retention in the root zone can be enhanced if nutrients are added in a slow-release form and if biologically mediated processes are used for nutrient release, as occurs in green manure. Therefore, an alternative that favors using local resources to increase the supply of nutrients and offset processes that impair the efficiency of nutrient use must be pursued.
Highlights
Sustainable agriculture can be defined as “the management and conservation of the natural resource base, and the orientation of technological change in such a manner as to ensure the attainment of continued satisfaction of human needs for present and future generations
It is worth highlighting that the extensive agrosystem and monocultural agriculture established for other tropical regions such as southeastern Brazil is not adequate for humid tropic environments because such an agrosystem does not meet the food and income needs of the region’s family farmers [2]. Keeping these factors in mind, studies undertaken in this region, mainly by researchers from the Agroecological Program of the State University of Maranhão [10], have shown that many practices recommended for the subsavannah soils of southeast Brazil, such as saturating soils with soluble nutrients, do not raise productivity or ensure the sustainability of land use when applied to agroecosystems of the Amazonian periphery [2]
This paper presents a review of present knowledge of the issue and aims at contributing to a better understanding of how soil management practices may affect the sustainability of soil use and the rainforest ecosystem health of the humid tropics, mainly of the Brazilian Amazonia region
Summary
Sustainable agriculture can be defined as “the management and conservation of the natural resource base, and the orientation of technological change in such a manner as to ensure the attainment of continued satisfaction of human needs for present and future generations. It is worth highlighting that the extensive agrosystem and monocultural agriculture established for other tropical regions such as southeastern Brazil is not adequate for humid tropic environments because such an agrosystem does not meet the food and income needs of the region’s family farmers [2] Keeping these factors in mind, studies undertaken in this region, mainly by researchers from the Agroecological Program of the State University of Maranhão [10], have shown that many practices recommended for the subsavannah soils of southeast Brazil, such as saturating soils with soluble nutrients, do not raise productivity or ensure the sustainability of land use when applied to agroecosystems of the Amazonian periphery [2]. In contrast to chemical fertility indicators, few examples of physical indicators with closed relationships to plant production are known, the effects of physical indicators on the growth of some plants have been investigated [13]
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