Friday, 14 July 2006
95-11

Air and Soil Pollution Reduction through Conservation Agriculture in Indo Gangetic Plains.

S.S. Singh1, Anisur Rahman Khan2, Raj K. Gupta1, and Alok Kumar Sikka2. (1) RWC-CIMMYT, India, ICAR Research Complex for Eastern Region Floor, Walmi Campus, Patna, 801 505, India, (2) ICAR Research Complex For Eastern Region, Walmi Campus, Phulwari Sharif, Patna, 801505, India

Indo Gangetic plains (IGP) occupy one-sixth of south Asia's geographical area, hold nearly 42 per cent of its population and produce more than 45 per cent of its food. Rice-wheat is grown on more than 12 million ha and provides livelihood for millions. An increase of temperature by 10 C in the IGP would be equivalent to a 150 km Northward shift of isotherms (lines joining places with similar temperature) or about 150 m lower altitude. There is a 5 per cent decrease in rice yield of every 0C rise above 320 C. According to recent estimates by IPCC, by 2100 A.D., the average global surface temperature is projected to increase by 1.4 to 30 C above 1990 levels (which was highest) for low emission scenario of GHG and between 2.5 to 5.80 C for higher emissions. To assess how environmentally efficient the various production systems are with respect to GHG emission, a Carbon to Productivity Ratio (CPR) is an ideal measure. Yield data of a long-term experiment at Pantnagar (India) with NPK fertilizers at 50, 100 and 150 per cent of the recommended dose when analyzed after constructing annual GHG budgets individually for CO2, CH4 and N2O indicated that CPR values of 0.45 to 0.48 were possible with zero tillage (ZT) and retention of crop residues at all three levels of N fertilizer use as against 0.54 for control, (without fertilizer). In conventional tillage practices and burning of crop residue the CPR values were 0.57 to 0.73 showing a higher level of ineffectiveness in the production system. The lower the CPR, the more efficient the system is at producing food with respect to the health of the global environment. Conservation agriculture, which includes Reduced/ ZT practices and crop residue retention, can reduce GHG emission and curb global warming. Positive changes in agronomic practices like tillage, manuring and irrigation can help reduce greatly the release of greenhouse gases. Adoption of ZT and controlled irrigation can drastically reduce the evolution of CO2 and N2O. Reduction in burning of crop residues reduces the generation of CO2, N2O and CH4 to a significant extent. Saving on diesel by reduced tillage and judicious use of water pumps have major role. Each liter diesel burning generates 2.6 kg CO2. About 3.2 Mt CO2/annum (about 0.8 MMTCE) can be reduced by ZT in the 12 million ha under rice wheat systems in the IGPs alone. Intermittent irrigation and drainage will further reduce CH4 emission from rice fields by 28% to 30%. Use of calcium nitrate or urea instead of ammonium sulphate and deep placement of N through ZT machines can increase its efficiency and plant uptake thereby reducing N2O emission. ZT systems on one hectare of land would save up to 100 liters of diesel and approximately 1 million liters of irrigation water. Using a conversion factor of 2.6 kg of CO2 per liter of diesel burned, this represents a quarter ton less emission per hectare of CO2, a principal contributor to global warming. ZT even on 5 million hectares of rice-wheat system area would save 5 billion cubic meters of water each year. About 0.5 billion liters of saving in diesel every year will help reduce carbon dioxide emissions by 1.3 million tons every year. Judicious management of water is imperative in ZT to improve productivity of land and water. Adoption of resource conservation technologies (RCTs)/ZT has assumed greater acceleration in the IGPs. In ZT direct seeded rice 12 15 cm water (30 liter diesel) is reduced for puddling. Due to no cracking of ZT field (which is common in puddled field), there is saving of 7-8 irrigations (210 liter diesel) per hactare in rice cultivation. Total saving of 240-liter diesel reduces CO2 emission by 624 kg/ha. Further, reduction in ground water exploitation reduces the high concentrations of toxic arsenic in drinking water especially in West Bengal and Bihar states of India. In first irrigation under ZT wheat, there is saving of 5-6 hrs/ha (20-21 hrs in conventional and 14-15 hrs in ZT) under 5HP diesel motor pumping. This saves 14.3 kg CO2 emission. In permanent bed planting of rice wheat system the total requirement of water is reduced by 30 per cent (from 155 cm in conventional to 108 cm) which means saving of 47 cm depth of water (220 liter diesel = 572 kg CO2). Better placement of N through ZT helps to increased N use efficiency and reduced NO3 leaching to soil. RCTs improve water use efficiency/ water productivity and overall input use efficiency. Reduction of water use in land preparation (ZT Direct Seeded Rice and wheat, ZT transplanted rice) and adoption of second generation RCTs are worth considering in this regard. These RCTs are cost effective to improve total factor productivity as well as to reduce air and soil pollution.

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