Deepanjan Majumdar

Reducing nitrous oxide emission from an irrigated rice field of North India with nitrification inhibitors

Nitrification inhibitors may be potential management strategy to reduce N 2O emissions in irrigated rice (Oryza sativa L.). A field experiment was conducted to evaluate chemically synthesized as well as locally available neem plant products on N2O emissions, from an irrigated rice at New Delhi, India. Emission of nitrous oxide (N2O) was monitored during 70 days by closed chamber method in rice (var. IR-72) grown on a Typic Ustochrept (cambisol) soil. Treatments were control (no nitrogen), urea alone, urea mixed with different nitrification inhibitors, namely, urea plus dicyandiamide (DCD), neem (powdered Azadirachta indicaJuss. seeds) coated urea and nimin (commercial derivative of neem) coated urea. Total N2O‐N emission was highest with urea (59.9 g N2O‐N ha 1 ) and lowest in the control (34.3 g N2O‐N ha 1 ). Total N2O emission from both nimin coated urea and neem coated urea were not significantly different from urea alone. Urea treated with DCD significantly reduced N 2O emissions from urea alone (48.9 g N2O‐N ha 1 ). Nitrogen lost through N2O emission were 0.018, 0.010, 0.016 and 0.013% of total nitrogen applied through urea, urea plus DCD, nimin coated urea and neem coated urea, respectively. Fluxes of N2O were low during flooding but increased markedly during drainage of standing water. After 70 days of transplanting of rice, N2O flux was hardly detectable in any of the treatments. The study indicated that some plant products, such as neem seeds and nimin which are more readily available with farmers in India, might be useful in mitigating N2O emissions from rice in addition to DCD, which is a widely used nitrification inhibitor.

Nitrous oxide emission from different fertilizers and its mitigation by nitrification inhibitors in irrigated rice

Abstract N2O emissions from a transplanted irrigated rice grown on a Typic Ustochrept soil at New Delhi, India, were studied to evaluate the effect of N fertilizers, i.e. urea and (NH4)2SO4, alone and in combination with the nitrification inhibitors dicyandiamide (DCD) and thiosulphate. The addition of urea and (NH4)2SO4 increased N2O emissions considerably when compared to no fertilizer N application (control). N2O measurement in the field was done by a closed-chamber method for a period of 98 days. The application of urea with DCD and thiosulphate reduced N2O fluxes considerably. The highest total N2O-N emission (235 g N2O-N ha–1) was from the (NH4)2SO4 treatment, which was significantly higher than the total N2O-N emission from the urea treatment (160 g N2O-N ha–1). DCD reduced N2O-N emissions by 11% and 26% when applied with urea and(NH4)2SO4, respectively, whereas thiosulphate in combination with urea reduced N2O-N emissions by 9%. Total N2O-N emissions were found to range from 0.08% to 0.14% of applied N. N2O emissions were low during submergence and increased substantially during drainage of standing water.

The Blue Baby Syndrome

Blue Baby Syndrome or Methemoglobinemia is caused by decreased ability of blood to carry oxygen, resulting in oxygen deficiency in different body parts. Infants are more susceptible than adults. The disease can be caused by intake of water and vegetables high in nitrate, exposure to chemicals containing nitrate, or can even be hereditary. Groundwater gets contaminated by leaching of nitrate generated from fertilizer used in agricultural lands and waste dumps in rural and urban areas. Prevention of water contamination, abstention from drinking contaminated water and controlling nitrate levels in drinking water by water treatment are effective preventive measures against nitrate poisoning.

Radon: Not so noble

Radon is a radioactive noble gas that occurs naturally but becomes an environmental hazard when it remains concentrated in enclosed places such as houses, caves and mines. Rocks and soils containing uranium produce radon during radioactive decay process. Being a gas, radon diffuses through soils and rocks and enters the atmosphere. Radon is water soluble and may contaminate drinking built on uranium bearing rocks or soils are exposed to high concentrations of radon. Continuous exposure to radon causes lung cancer in human beings.

Global warming: A myth?

Increase in the concentration of several greenhouse gases in the atmosphere during the last few decades has warmed up the atmosphere, a phenomena popularly known as ‘global warming’. There are people who believe that ‘global warming’ does not exist, or will have negligible consequences on the earth and its biosphere, if at all it exists. Satellite record over the past few decades have shown a slight cooling trend in the lower troposphere, casting a doubt on the existence of ‘global warming’. During the same time, atmosphere near earth’s surface has shown a warming trend. Efforts are on to explain this temperature anomaly and it may take time to say conclusively whether ‘global warming’ exists or not.

Global warming: A myth?: 2. Credibility of climate scenarios predicted by systems simulations

ConclusionEarth’s atmosphere is a dynamic system and is driven by numerous interacting factors, which are yet to be studied with precision. Computer models, which are generally run under CO2 doubling scenario, may have uncertainties for several reasons. At the present CO2 emission rate, doubling may be attained only after 70–95 years (at 1% increase yr-1). Global efforts to cut back on CO2 emission, underway for quite sometime, and the stress on the use of alternative non-conventional and renewable energies may increase the doubling time considerably. Nevertheless, the considerable improvements in the capability of ocean-atmosphere models in simulating present climates show that the intricate interplay of several factors in climatic change are now better understood and there is hope for further improvement in the model performance.