Soil degradation and related production constraints

Soil degradation and related production constraints

The country accounts for >2 % of world soil resources with ample diversity in agro climatic condition for producing wide range of crops and vegetation. Several soil and management related constraints, however, hinder sustainable production of food and fodder. Physical degradation like soil erosion, soil crusting and compaction, chemical degradation like loss of organic matter, soil fertility, multi nutrient depletion and deficiencies, salt accumulation, pollution, etc., are some of the major soil and management-related problems reported which account for nearly 60% (188 M.ha) of the total land area (Table).

Soil acidification is a natural soil-forming process accelerated by high rainfall, low evaporation, leaching of bases, and high oxidative biological activity that produces acid. The soil acidity plays major role in determining the nutrient availability to plants and in many instances by specific mineral stress problems. Production constraints are more intense on acid soils, which cover 30% of the world’s land area (UexKull and Mutert, 1995). Acid soil infertility is a syndrome of problems that affect plant growth in soils with low pH. This complex of problems arises from toxicities and deficiencies in acid soils are related to:

1 Presence of the toxic concentration of Al and to a lesser extent Mn toxicity in many     species, 2 Deficiency of bases (Ca, Mg, K) and their poor retention power, 3 High P fixation capacity of soil caused by highly active Al and Fe surfaces, rendering it    unavailable to plants, 4 Deficiency of Mo, especially for the growth of legumes, 5 Reduction of soil biological activities, 6 Impairment of N2-fixation by legumes caused by poor survival of microsymbiont and     inhibition of nodulation, and 7 Fe and Mn toxicities in submerged rice.

Soil acidity is the primary factor limiting crop productivity on acid soils, which comprise large areas of the world land, particularly in the tropics and subtropics (Table 1).

• About 149 M.ha is affected due to water erosion, 13.5 M.ha by wind erosion, 14.0 M.ha   by chemical degradation and about 12 M.ha by physical degradation (Yadav, 2007). • Loss of fertile top soil by water erosion is about 5000 M.tons per year of which about    29% is lost into sea, 10% deposited in reservoirs, 59% is deposited as alluvium. • About 3.5% of the total land area is affected by water logging and 18.2 M.ha are    wastelands not suitable for agricultural production • Chemical degradation of the soil due to human intervention is around 13.6 M. ha of    which salinization accounts for 10.1 M.ha, and nutrient and organic carbon loss in 3.7    m.ha. • Salinity and alkalinity are soil problems associated with low rainfall and high   evaporative demand, improper drainage and excessive flooding causing significant loss    to crop and soil productivity • More than 90% of NEH region is acidic of varying degrees which restrict the crop    choice. Fertilizer use in the region and its efficiency are poor. • Poor structural stability of the fine textured clay soils (Vertisols) renders agricultural    practices very difficult. • Unscientific crop intensification with imbalanced use of fertilizers has led to much    management related nutrient problems like decline in productivity and sustainability, • Extensive use of ground water through tube wells has resulted in significant lowering of    water table which could result in serious productivity declines during low rainfall years.