Loss of soil organic carbon (SOC)

Loss of soil organic carbon (SOC)

In India SOC content is most of the soils range from 0.2 to 0.5% (2-5 g/kg soil) which works out to 21 and 156 billion tons up to 30 and 150 cm soil depth, respectively while total soil inorganic C pool (SIC) is about 196 billion tons (Pal et al 2000). Loss of SOC is alarming due increasing atmospheric temperature and changing rainfall pattern. Extensive mining of soil fertility, removal or burning of crop residues, soil degradation, inappropriate soil tillage and poor crop management, besides accelerated soil erosion (34 – 50 Tg C/yr) are the major reasons for loss of SOC and decline in crop productivity. Technological options for soil C sequestrations in India include INM, green manuring, mulch farming, conservation tillage, residue recycling, and choice of cropping systems, balanced nutrient use with high nutrient use efficiency etc. (Lal, 2004).

Available information on loss of productivity due to soil degradation indicates that it is higher in red soils compared black and alluvial soils (Velayutham and Bhattacharya, 2000). This warrants a knowledge based alleviation of soil problems, and management of soils and inputs keeping in view the resource quality, cropping system, and nutrient flows in the system for the overall sustainability.

Loss of Soil Organic Carbon (SOC)

Loss of soil organic carbon is an important factor for the fatigue in agricultural production especially in intensive rice crop systems. Loss of soil organic carbon also leads to increased atmospheric CO2. The total soil carbon content includes organic carbon and inorganic carbon, out of which the former has greater influence on soil quality. The SOC status in India has declined owing to losses from erosion, deforestation, vegetation removal, excessive grazing, burning of crop residues, use of cow dung as fuel, over-ploughing, leaching, other soil disturbances, and less addition of organic carbon sources warranting judicious management practices to restore and upgrade SOC pool is essential. These include conservation tillage, precision farming, regulated grazing, increased aforestation, continuous manuring and fertilizer application, suitable cropping sequences, crop residue utilization, scientific water use, amelioration of degraded lands etc. The long-term fertilizer experiments in India have shown that balanced fertilization results in increases status of SOC in the upper 42 cm soil by 8 t ha-1 at the rate of 0.25 t/ha/year

The quantity of residue from the principal grain producing crops in India is estimated at about 340 Mt per year, of which wheat residue constitutes about 27% and that of rice about 51% Approximately 200 Mt of crop residue can be returned to the soil annually. Multiple cropping with optimum fertilization and manuring, adoption of shallow tillage, increased SOC and available nutrients at faster rate. Carbon sequestration due to various soil and crop management practice not only offset rise in atmospheric carbon dioxide, but also improves the overall soil quality essential for sustainable crop productivity. Soil management practices that improve soil organic matter include: (i) more complex crop rotation, especially those with high-residue crops, (ii) intensive use of cover crops, (iii) use of organic amendments, (iv) Balanced fertilization, and (v) reduced tillage

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