Soil Quality and Its Management in Humid Subtropical and Tropical Environments

The subtropical and tropical ecoregions of the world cover an extensive area of about 4900 million ha, and are characterised by deeply weathered soils derived from geologically old materials, In humid regions, the combination of high temperature and moisture has enhanced the rate and depth of weathering, accelerated leaching and led to the formation of acidic soils with low activity clays. The seasonally dry tropics extend over about 2475 million ha, characterised by savanna vegetation including a mixture of trees and grasses, In comparison with humid ecoregions, the grazing potential is high for soils and climate of the seasonally dry tropics and subtropics, Pastoral land use covers about 3680 million ha in the world, including about 793 million ha in Africa, 478 million ha in South America and 678 million ha in Asia, Soil quality refers to inherent attributes of soil and to characteristics and processes that determine the soil's capacity to produce economic goods and services (e.g., bioremediation) and regulate (e.g., buffer) the environment, It also refers to soil's response to science-based inputs and management, with a positive response to judicious inputs and improved management systems. Principal attributes of soil quality are economic productivity, environmental regulation, biodiversity, and aesthetic and cultural values. Important characteristics related to soil quality are soil structure, water retention and transmission properties, effective rooting depth, intensity and capacity factors for plant-available water and nutrients, soil reaction, dynamics of soil organic matter and biodiversity, Relevant processes that determine soil quality are: (i) physical processes including crusling, compaction and accelerated soil erosion, (ii) chemical processes involving nutrient cycling and transformations, and (iii) biological processes.encompassing species diversily and activity of soil flora and fauna, and soil. carbon including sequestration and transformations, Soil qualily is also related to soil resilience and sustainability, Pastoral land management problems in the tropics are characterised by high stocking rate, uncontrolled grazing, disrupted carbon and nutrient cycling, low inputs and low productivity. Consequently, soil quality and productivity are rapidly deteriorating under poor management regimes. Enhancing soil quality and carrying capacity are the principal objectives of improved management systems through controlled grazing, low stocking rate, ley farming and soil nutrient management.