Soil degradation: I. Basic processes

Abstract

This paper examines soil and land degradation. It describes basic processes and factors responsible for degradation, illustrates the cause-effect relationships and differentiates between natural and man-induced regressive effects. The 'critical limit' concept is described in terms of properties beyond which the soil will not support an economically-viable agriculture. This paper is not an exhaustive literature review but emphasizes the scientific principles involved and highlights natural against man-induced processes. Important natural processes are: laterization, hard-setting, fragipan and clay pan formation, and geologic erosion. In comparison, man-induced processes consist of: soil compaction, accelerated erosion, desertification, salt accumulation and leaching and acidification. One of the principal constraints is the problem of data reliability. A reliable database and precise criteria are definitely lacking and hinder the assessment of the extent, type and degree of soil degradation and establishing the cause-effect scenario. Improving our database is, therefore, of a high priority if we are to adopt land use policy for sustainable soil management and long-range resource management. Also outlined, are vital research and development strategies. Judicious resource management policy should emphasize managing prime agricultural land to produce to its maximum potential so that there is no need to cultivate marginal and easily-degraded fragile ecosystems. A strict code of conduct is needed for utilizing marginal/fragile lands. Methods of restoring the productivity of degraded lands must be researched so as to minimize the need to clear and develop new lands.

Natural Chemical Degradation of Soils in the Indian Semi-Arid Tropics and Remedial Measures

“…Lal et al 7 defined soil degradation as 'diminution of soil quality (and thereby its current and potential productivity) and/or a reduction in its ability to be a multi-purpose resource due to both natural and human-induced causes'. Processes that lead to soil degradation include accelerated erosion, increasing wetness and poor drainage, laterization, salinization, nutrient imbalance, decline in soil organic matter and reduction in activity and species activity of soil fauna and flora 7 .…”

“…Processes that lead to soil degradation include accelerated erosion, increasing wetness and poor drainage, laterization, salinization, nutrient imbalance, decline in soil organic matter and reduction in activity and species activity of soil fauna and flora 7 . Processes of soil degradation include chemical, physical and biological degradation of soils; and the interactions among these factors affect the capacity of a soil for self-regulation and productivity.…”

“…Factors causing soil degradation are both by natural and human-induced and enhance degradation, leading to changes in properties of soils and the attributes for their life support 7 . Although selected pedogenic processes such as laterization, hard setting, fragipan formation and claypan formation are hitherto considered as natural soil degradation processes as they lead to less desirable physical and chemical conditions, causing degradation of soils 7,8 , the majority of the information on soil degradation at national 9,10 , regional 11 or international level 12,13 has focused only on anthropogenic degradation.…”

“…Soil misuse and extreme climatic conditions can damage such self-regulating capacity and give way to regressive pedogenesis 6 , and thus might lead to the soil to regress from higher to lower usefulness and or drastically diminished productivity. Such an un-favourable endowment of soils is termed 'soil degradation' 7 .…”

Soil moisture retention and mass movement of volcanic soils from the “Sabinas” sector in Caldas, Colombia

“…The mass movement of soils by rainfall are the most frequent. Lal, Hall & Miller (1989), indicates that soil degradation processes usually starts with soil structure deterioration and especially, soil functional attributes, which have allowed to transmit and retain soil moisture and facilitate root development. Given these concerns, the aim of this research was to relate soil physical characteristics with soil moisture storage capacity, and to assess the soil moisture retention capacity and soil cover as detonating factors for mass removal phenomena of volcanic soils in Caldas, Colombia.…”