M. C. Jain

Emission of nitrous oxide from rice-wheat systems of Indo-Gangetic plains of India.

Nitrous oxide (N2O) accounts for 5%of the total enhanced greenhouse effect and responsiblefor the destruction of the stratospheric ozone. The rice-wheat cropping system occupying 26 million ha ofproductive land in Asia could be a major source ofN2O as most of the fertilizer N in this region isconsumed by this system. Emission of N2O asinfluenced by application of urea, urea plus farm yardmanure (FYM), and urea plus dicyandiamide (DCD), anitrification inhibitor, was studied in rice-wheatsystems of Indo-Gangetic plains of India. Total emissionof N2O-N from the rice-wheat systems varied between654 g ha-1 in unfertilized plots and 1570 g ha-1 in urea fertilized plots. Application of FYM and DCDreduced emission of N2O-N in rice. The magnitude ofreduction was higher with DCD. In wheat also N2O-Nemission was reduced by DCD. FYM applied in rice had noresidual effect on N2O-N emission in wheat. In riceintermittent wetting and drying condition of soilresulted in higher N2O-N emission than that ofsaturated soil condition. Treatments with 5 irrigationsgave higher emissions in wheat than those with 3irrigations. In rice-wheat system, typical of a farmersfield in Indo-Gangetic plains, where 240 kg N isgenerally applied through urea, N2O-N emission is1570 g ha-1 (0.38% of applied N) and application ofFYM and DCD reduced it to 1415 and 1096 g ha-1,respectively.

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.

Methane production in rice soil is inhibited by cyanobacteria

The present study was aimed at understanding the role of cyanobacteria and Azolla in methane production and oxidation in laboratory simulation experiments using soil samples from rice fields. All the seven cyanobacterial strains tested effected a significant decrease in the headspace concentration of methane in flooded soil, incubated under light. Synechocystis sp. was the most effective in retarding methane concentration by 10-20 fold over that in controls without cyanobacteria. The decrease in the headspace concentration of methane was negligible in nonsterile soil samples, inoculated with Synechocystis sp. and then incubated under dark. Moist soil cores (0-5 cm depth), collected from rice fields that had been treated with urea in combination with a cyanobacterial mixture, Azolla microphylla, or cyanobacterial mixture plus A. microphylla, effected distinctly more rapid decrease in the headspace concentration of methane added at 200 microl(-1) than did the soil cores from plots treated with urea alone (30, 60, 90 and 120 kg N ha(-1)), irrespective of the rate of chemical nitrogen applied to rice fields. Besides, soil cores from plots treated with urea alone at 60, 90 and 120 kg N ha(-1) oxidised methane more rapidly than did the core samples from plots treated with urea alone at 30kg N ha(-1). Cyanobacteria and A. microphylla, applied to flood water, appear to play a major role in mitigation of methane emission from rice fields-through enhanced methane oxidation.

Methane emission from two Indian soils planted with different rice cultivars

Abstract In a greenhouse study, methane emissions were measured from two diverse Indian rice-growing soils planted to five rice cultivars under similar water regimes, fertilizer applications and environmental conditions. Significant variations were observed in methane emitted from soils growing different cultivars. Total methane emission varied between 8.04 and 20.92gm–2 from IARI soil (Inceptisol) and between 1.47 and 10.91gm–2 from Raipur soil (Vertisol) planted to rice. In all the cultivars, emissions from IARI soil were higher than from Raipur soil. The first methane flux peak was noticed during the reproductive phase and the second peak coincided with the grain-ripening stage of the rice cultivars.

Effect of potassium salts and distillery effluent on carbon mineralization in soil

Distillery effluent, a rich source of potassium, is used for irrigation at many places in the world. A laboratory experiment was conducted to study the influence of potassium salts present in post-methanation distillery effluent (PME) along with two other salts, KCl and K2SO4, on mineralization of carbon in soil. PME oxidized with H2O2, raw PME, KCl and K2SO4 solutions containing K equivalent to 10%, 20%, 40% and 100% of K present in PME were added to the soil separately, maintaining four replications for each treatment and control. Addition of salts up to a certain concentration stimulated C mineralization but a decline was noticed at higher concentrations. All the levels of salts caused higher CO2 evolution than the control suggesting that the presence of K salts enhanced the microbial activity resulting in increased CO2 evolution. The influence of K2SO4 was significantly higher than KCl in stimulating C mineralization in soil. Oxidized effluent had a higher stimulating effect than inorganic salts, showing the influence of other salts accompanying K in the PME. Raw PME, which contained excess organic C, increased CO2 evolution even at the highest salt level (100% PME) signifying the effect of added C on alleviating the salt stress on microbial activity.

Increased biogas production using microbial stimulants

Laboratory studies were undertaken to evaluate the effect of microbial stimulants Aquasan and Teresan, on biogas yields from cattle dung and combined residues of cattle dung and kitchen waste, respectively. The addition of single dose of Aquasan at the rate of 10, 15 and 20 ppm to cattle dung on the first day of incubation resulted in increased gas yields ranging between 45.1 and 62.1 l/kg dry matter. Subsequent addition of Aquasan at 15 and 20 ppm dosage after a period of 15 days increased the gas yields by 15-16%. The gas production was found to be optimum at a dosage level of 15 ppm and was 39% and 55% higher with single and dual additions, respectively, than untreated cattle dung. In another bench scale study (1:1 dry matter) the addition of Teresan at 10 ppm concentration to the mixed residues of cattle dung and kitchen wastes at different solids concentration, produced 34.8% more gas (272.4 l/kg d.m.) than the uninoculated mixture at 15% TS concentration (202.4 l/kg d.m.).

Persistence of α and β isomers of endosulphan and endosulphan sulphate in diverse soils of india as influenced by flooding

Laboratory studies were undertaken to evaluate the persistence of alpha-endosulphan, beta-endosulphan and endosulphan sulphate in four diverse soils under non-flooded and flooded conditions. Significant variations were observed in the extent of persistence of the three chemicals in different non-flooded soils with maximum persistence observed in Alfisol and the least in Mollisol having near neutral pH and higher organic matter. Degradation was more in all the flooded soils than in the non-flooded counterpart but in Vertisol under flooded and non-flooded conditions, the rate of degradation of endosulphan sulphate was found to be nearly same.

Effect of Crown Angulation of Maxillary Incisor on Effective Arch Perimeter

INTRODUCTION It has been postulated that crown angulation and inclination has potential space implication within the arch. With the insight of space implication of the axial relations of teeth, cases of genuine tooth size discrepancies can be dealt with improved stability. AIM This in vitro study was designed to investigate and quantify the influence of angulation and inclination of maxillary incisors on the effective arch perimeter. MATERIALS AND METHODS Acrylic teeth were arranged over typhodont frame with spaced maxillary anterior segment. Known value of tip and torque in increments were incorporated to maxillary incisors through bracket positioning and corresponding consumption of the interdental spaces were measured using coordinate measuring machine. RESULTS Study revealed that increase in maxillary incisor crown angulation by 1o results in consumption of approximately 0.012 mm of arch perimeter. Similarly, there is a consumption of 0.021 mm of arch perimeter with each degree increase in labial crown inclination. CONCLUSION The knowledge of the space implication can be included in the space analysis during the orthodontic treatment planning. Depending upon the amount of space discrepancy, an accurate degree of required alteration in the axial relation of one or more teeth can be planned.