Soil science: Management and conservation

Abstract

Conversion of natural to agricultural ecosystems, involving 1070 million hectare (Mha) of forests and woodland/shrubland and 660 Mha of grassland, and subsequent soil cultivation caused depletion of the soil organic carbon pool, disruption in elemental cycling, and increase in susceptibility to degradation by erosion, salinization, and fertility depletion. The severe problem of soil degradation, caused by extractive farming practices and fragile soils, is likely to be exacerbated by the projected climate change. Despite the severe problem of soil degradation, cereal yields in developing countries must be increased by 35 to 63% by 2025 and 58 to 121% by 2050 without and with any dietary change, respectively. The global fertilizer use is projected to increase from 136 million nutrient tons in 2000 to 165 million tons in 2015 and 188 million tons by 2030, and most of the projected increase is to occur in India, China, and other Asian and Latin American countries. Similarly, global irrigated land area is projected to increase, with most expansion in South and East Asia, but not in sub-Saharan Africa. Strategies of improving soil quality include increasing soil organic matter pool, improving soil structure, and strengthening elemental cycling. Conservation and sustainable management of soil resources involve adaptation of no-till farming, using crop residue mulch, growing cover crops, creating positive nutrient balance, using soil-specific or precision farming, conserving and recycling water, and using drip or subirrigation. Biofuel must be produced from lingocellulosic biomass grown on energy plantations of short-rotation woody perennials or warm-season grasses.