In this paper, we developed a new geospatial database of paddy rice agriculture for 13 countries in South and Southeast Asia. These countries have ∼
30% of the world population and ∼
2/3 of the total ...rice land area in the world. We used 8-day composite images (500-m spatial resolution) in 2002 from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the NASA EOS Terra satellite. Paddy rice fields are characterized by an initial period of flooding and transplanting, during which period a mixture of surface water and rice seedlings exists. We applied a paddy rice mapping algorithm that uses a time series of MODIS-derived vegetation indices to identify the initial period of flooding and transplanting in paddy rice fields, based on the increased surface moisture. The resultant MODIS-derived paddy rice map was compared to national agricultural statistical data at national and subnational levels. Area estimates of paddy rice were highly correlated at the national level and positively correlated at the subnational levels, although the agreement at the national level was much stronger. Discrepancies in rice area between the MODIS-derived and statistical datasets in some countries can be largely attributed to: (1) the statistical dataset is a sown area estimate (includes multiple cropping practices); (2) failure of the 500-m resolution MODIS-based algorithm in identifying small patches of paddy rice fields, primarily in areas where topography restricts field sizes; and (3) contamination by cloud. While further testing is needed, these results demonstrate the potential of the MODIS-based algorithm to generate updated datasets of paddy rice agriculture on a timely basis. The resultant geospatial database on the area and spatial distribution of paddy rice is useful for irrigation, food security, and trace gas emission estimates in those countries.
In a field study, long-term application of compost to a tropical Aeric Endoaquept under continuous rice growing in a rice–rice–fallow sequence resulted in the stimulation of microbial biomass and ...select soil enzyme activities. Mean seasonal soil microbial biomass-C (C
mic) increased by 42%, 39% and 89% in inorganic fertilizer, compost and compost+inorganic fertilizer treatments, respectively, over the unamended control. C
mic content was also influenced by the rice crop growth stage and was highest at maximum tillering stage irrespective of treatments and declined thereafter. Soil organic C (C
org) content showed highly significant positive correlation with dehydrogenase, urease, cellulase,
β-glucosidase and fluorescein di-acetate (FDA) hydrolysis activity, and a positive but not significant correlation with invertase and amidase activity. C/N ratio which was lowest in unamended control plots showed a significant positive relationship with only the enzymes involved in C cycle. Stepwise regression analysis revealed that for prediction of both total organic C and total N, FDA hydrolysis activity contributed significantly for the variance and explained up to 85–96% variability. Results demonstrated that microbial biomass and soil enzyme activity is sensitive in discriminating between long-term organic residue amendment practices.
In a field study, potassium (K) applied as muriate of potash (MOP) significantly reduced methane (CH4) emission from a flooded alluvial soil planted to rice. Cumulative emission was highest in ...control plots (125.34 kg CH4 ha-1), while the lowest emission was recorded in field plots receiving 30 kg K ha-1 (63.81 kg CH4 ha-1), with a 49% reduction in CH4 emission. Potassium application prevented a drop in the redox potential and reduced the contents of active reducing substances and Fe2+ content in the rhizosphere soil. Potassium amendment also inhibited methanogenic bacteria and stimulated methanotrophic bacterial population. Results suggest that, apart form producing higher plant biomass (both above- and underground) and grain yield, K amendment can effectively reduce CH4 emission from flooded soil and could be developed into an effective mitigation option, especially in K-deficient soils.
The DNDC (DeNitrification and DeComposition) model was tested against experimental data on CH₄ and N₂O emissions from rice fields at different geographical locations in India. There was a good ...agreement between the simulated and observed values of CH₄ and N₂O emissions. The difference between observed and simulated CH₄ emissions in all sites ranged from −11.6 to 62.5 kg C ha⁻¹ season⁻¹. Most discrepancies between simulated and observed seasonal fluxes were less than 20% of the field estimate of the seasonal flux. The relative deviation between observed and simulated cumulative N₂O emissions ranged from −237.8 to 28.6%. However, some discrepancies existed between observed and simulated seasonal patterns of CH₄ and N₂O emissions. The model simulated zero N₂O emissions from continuously flooded rice fields and poorly simulated CH₄ emissions from Allahabad site. For all other simulated cases, the model satisfactorily simulated the seasonal variations in greenhouse gas emission from paddy fields with different land management. The model also simulated the C and N balances in all the sites, including other gas fluxes, viz. CO₂, NO, NO₂, N₂ and NH₃ emissions. Sensitivity tests for CH₄ indicate that soil texture and pH significantly influenced the CH₄ emission. Changes in organic C content had a moderate influence on CH₄ emission on these sites. Introducing the mid-season drainage reduced CH₄ emissions significantly. Process-based biogeochemical modeling, as with DNDC, can help in identifying strategies for optimizing resource use, increasing productivity, closing yield gaps and reducing adverse environmental impacts.
Methane (CH4) oxidation is the only known biological sink process for mitigating atmospheric and terrestrial emissions of CH4, a major greenhouse gas. Methane oxidation in an alluvial soil planted to ...rice (Oryza sativa L.) under long‐term application of organic (compost with a C/N ratio of 21.71), and mineral fertilizers was measured in a field‐cum‐laboratory incubation study. Oxidation rates were quantified in terms of decrease in the concentration of CH4 in the headspace of incubation vessels and expressed as half‐life (t½) values. Methane oxidation rates significantly differed among the treatments and growth stages of the rice crop. Methane oxidation rates were high at the maximum tillering and maturity stages, whereas they were low at grain‐filling stage. Methane oxidation was low (t½ = 15.76 d) when provided with low concentration of CH4 On the contrary, high concentration of CH4 resulted in faster oxidation (t½ = 6.67 d), suggesting the predominance of “low affinity oxidation” in rice fields. Methane oxidation was stimulated following the application of mineral fertilizers or compost implicating nutrient limitation as one of the factors affecting the process. Combined application of compost and mineral fertilizer, however, inhibited CH4 oxidation probably due to N immobilization by the added compost. The positive effect of mineral fertilizer on CH4 oxidation rate was evident only at high CH4 concentration (t½ = 4.80 d), while at low CH4 concentration their was considerable suppression (t½ = 17.60 d). Further research may reveal that long‐term application of fertilizers, organic or inorganic, may not inhibit CH4 oxidation.
The DNDC (DeNitrification and DeComposition) model was calibrated and tested against experimental data on CH4 emission from rice fields of Central Rice Research Institute, Cuttack, India. There was ...good agreement between the simulated and observed values of grain yield, total biomass, N uptake and seasonal CH4 emission. Overall, the model satisfactorily simulated the seasonal variations of CH4 emission from flooded rice paddy. However, some discrepancies existed between observed and simulated seasonal patterns of CH4 emission. Large discrepancies between simulated and observed seasonal fluxes occurred at sites that used manual chamber flux measurements. Sensitivity test results indicate that soil texture and pH significantly influenced CH4 emission. Changes in organic C content had a moderate influence on CH4 emission at this site. Variation in the quantity of aboveground biomass returning to the soil was predicated to have little effect on short-term seasonal simulations. Increasing the length of mid-season aeration reduced CH4 emissions significantly, while addition of sulphate fertilizer reduced CH4 emissions. With continuous modifications and calibration, DNDC can become a powerful tool for estimation of greenhouse gas emissions, forecasting yield trends and studying the impact of climate change and policy formulations.
In this paper, we developed a new geospatial database of paddy rice agriculture for 13 countries in South and Southeast Asia. These countries have 30% of the world population and 2/3 of the total ...rice land area in the world. We used 8-day composite images (500-m spatial resolution) in 2002 from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the NASA EOS Terra satellite. Paddy rice fields are characterized by an initial period of flooding and transplanting, during which period a mixture of surface water and rice seedlings exists. We applied a paddy rice mapping algorithm that uses a time series of MODIS-derived vegetation indices to identify the initial period of flooding and transplanting in paddy rice fields, based on the increased surface moisture. The resultant MODIS-derived paddy rice map was compared to national agricultural statistical data at national and subnational levels. Area estimates of paddy rice were highly correlated at the national level and positively correlated at the subnational levels, although the agreement at the national level was much stronger. Discrepancies in rice area between the MODIS-derived and statistical datasets in some countries can be largely attributed to: (1) the statistical dataset is a sown area estimate (includes multiple cropping practices); (2) failure of the 500-m resolution MODIS-based algorithm in identifying small patches of paddy rice fields, primarily in areas where topography restricts field sizes; and (3) contamination by cloud. While further testing is needed, these results demonstrate the potential of the MODIS-based algorithm to generate updated datasets of paddy rice agriculture on a timely basis. The resultant geospatial database on the area and spatial distribution of paddy rice is useful for irrigation, food security, and trace gas emission estimates in those countries.
Cooling is one of the most important challenges facing engines performance. Due to limited space at the front of the engine, the size of the radiator is restricted and cannot be essentially ...increased. Therefore, it is necessary to increase the heat transfer capabilities of working fluids. With the advancement of nanotechnology, the new generation of heat transfer fluids called, nanofluids have been developed and these fluids offer higher heat transfer properties compared to that of conventional automotive engine coolants. Nanofluids seem to be potential replacement of conventional coolants in engine cooling system. Recently there have been considerable research findings highlighting superior heat transfer performances of nanofluids about 15-40% of heat transfer enhancement can be achieved by using various types of nanofluids. With these superior characteristics, the size and weight of an automotive car radiator can be reduced without affecting its heat transfer performance.
A very compact dual band notched fractal structured antenna is proposed for UWB applications. A novel fractal patch with defected ground structure is utilized to achieve −10 dB bandwidth of 7.87 GHz ...from 3.77 GHz to 11.64 GHz. To notch upper WLAN band of 5.52–5.90 GHz, an S- shaped slot is introduced in the 50 Ω microstrip feed line. The X- band notch for down link of satellite communication applications from 7.22–8.16 GHz is achieved by two symmetrical L- structured parasitics on both sides of fractal patch. The proposed antenna having a compact size of 16 × 21 mm
2
(
0.2
λ
0
×
0.26
λ
0
) and is fabricated on a low cost FR- 4 substrate. A maximum gain of 4.32 dBi in UWB band with gain drops to −2.53 dBi in WLAN at 5.75 GHz and −4.25 dBi in X-band at 7.35 GHz are noticed. The proposed antenna shows good similarity between simulated and measured electrical parameters such as S
11
, nearly omnidirectional patterns, constant gain and time domain characteristics makes it suitable for portable wireless applications.
A series of 5-nitrofuran–triazole conjugates were synthesized and evaluated for their antimicrobial activity against both Gram-positive and Gram-negative bacterial strains. All the compounds ...exhibited promising inhibition towards Gram-positive pathogenic strains, while mild inhibitory effects were observed towards Gram-negative bacterial strains. Some of the compounds 8a, 8b, 8e, 8f, 8h are most active among the series exhibiting MIC value of 1.17μg/ml against different bacterial strains. The bactericidal activity is found to be in accordance with the bacterial growth inhibition data. Compound 8e was found to be equipotent to the standard drug Ciprofloxacin displaying MBC value of 1.17μg/ml against the bacterial strain Bacillus subtilis. The compounds have also demonstrated promising antibacterial activity against the resistant strain MRSA and were found to be effective inhibitors of biofilm formation. The compound 8b exhibited excellent anti-biofilm activity with IC50 value as low as 0.8μg/ml. These conjugates were also screened for antitubercular activity against Mycobacterium tuberculosis H37Rv strain. Compound 8e showed promising antitubercular activity with MIC value of 0.25μg/ml. Most of these compounds are less toxic to normal mammalian cells than the widely used antibacterial drug Ciprofloxacin.
