Nitrous oxide emission from a transplanted rice field in alluvial soil as influenced by management of nitrogen fertiliser

We investigated nitrous oxide (N₂O) emission from an irrigated rice field over two years to evaluate the management of nitrogenous fertiliser and its effect on reducing emissions. Four forms of nitrogenous fertilisers: NPK at the recommended application rate, starch–urea matrix (SUM) + PK, neem‐coated urea + PK and urea alone (urea without coating) were used. Gas samples were collected from the field at weekly intervals with the static chamber technique. N₂O emissions from different treatments ranged from 11.58 to 215.81 N₂O‐N μg/m²/h, and seasonal N₂O emissions from 2.83 to 3.89 kg N₂O‐N/ha. Compared with other fertilisers, N₂O emissions were greatest after the application of the conventional NPK fertiliser. Moreover, SUM + PK reduced total N₂O emissions by 22.33% (P < 0.05) compared with NPK during the rice‐growing period (P < 0.05). The results indicate a strong correlation between N₂O emissions and soil organic carbon, nitrate, ammonium, above‐ and below‐ground plant biomass and photosynthesis (P < 0.05). The application of SUM + PK in rice fields is suitable as a means of reducing N₂O emissions without affecting grain production.     

Dissipation of the herbicide dithiopyr in soil and residues in wheat (Triticum aestivum L) grain under Indian tropical conditions

Dissipation of dithiopyr in soil was monitored after application to wheat crop as pre- or post-emergence applications at two rates, viz 100 and 200 g AI ha(-1). The level of dithiopyr in the soil was assessed by gas chromatography, and its disappearence was found to follow a first-order decay curve irrespective of rate or method of application. The half-life in soil ranged between 17.3 and 25.0 days and residues at harvest (150 days after application) ranged between 4.0 and 8.8% of amounts applied. Investigation of microbial degradation of dithiopyr was conducted in minimal salt and Czapek Dox media in which 80% of the compound degraded within 15 days. Residues were not detected in wheat grain at harvest.     

Potential of a novel antibiotic, 2-methylheptyl isonicotinate, as a biocontrol agent against fusarial wilt of crucifers

Screening for newer bioactive compounds from microbial metabolites resulted in the isolation of a novel antibiotic from the culture filtrate, Streptomyces sp 201, of a soil. The bioactive compound, with antifungal and antibacterial activity, was identified as 2-methylheptyl isonicotinate. The antifungal activity of live culture, culture broth and the isolated bioactive compound showed marked inhibition against dominant soil-borne phytopathogens such as Fusarium oxysporum Schlect, F moniliforme Sheldon, F semitectum Berkeley & Ravenel, F solani (Martius) Sacc and Rhizoctonia solani Kuehn. The compound had no effect on seed germination and seedling development as displayed by root and stem growth of the test plant species. In pot experiments with seedlings of cruciferous plants such as Raphanus sativus L (radish), Brassica campestris L (yellow mustard), Brassica oleracea var botrytis L (cauliflower), the antibiotic compound showed promising protective activity of 92% when seeds of the test plants were treated at a dose of 50 micrograms ml-1 prior to sowing. Seed treatment with a spore suspension (3 x 10(8) spores ml-1) of the Streptomyces sp 201 displayed protective activity in the range of 56-60%. Seeds coated with 2.5% methyl cellulose-amended spores of the antagonist showed protective activity in the range of 64-72%. Further, seed treatment with the culture filtrate of the antagonist also showed promising protective activity in the range of 64-84%.     

Influence of in-house produced biochars on cracks and retained water during drying-wetting cycles: comparison between conventional plant,animal, and nano-biochars

Purpose

Biochars produced from different feedstocks (such as wood, pig manure) possess varying physical and chemical properties, which have influence on crack and evaporation rate of biochar-amended soil (BAS). Furthermore, influence of compaction state and drying-wetting cycles on evaporation rate and cracking of BAS has not been investigated comprehensively. The objective of this study was to investigate the effects of biochar types, compaction state of BAS, and drying-wetting cycles on crack propagation and retained water (or evaporation rate).

Material and methods

An animal and plant feedstock-based biochars were produced in-house from pig manure (PM) and wood (W), respectively. In addition, nano structured chalk and wheat biochar (CWB) were also produced. Soil amended with individual biochars was compacted in petri-glass discs at two densities. Disc specimens were subjected to multiple drying-wetting cycles, and evaporation rate of specimens and crack area were monitored throughout the experimental period (70 days). Images were captured after every 24 h and processed using image processing technique to obtain the crack intensity factor (CIF).

Results and discussion

The results show that plant-based W BAS showed the high water retention, i.e., low evaporation rate and low CIF. Furthermore, the crack potential of CW BAS was seen to be higher. In dense compacted soil, maximum CIF% can be reduced from 3.9 to 0.4% for W BAS, from 3.9 to 1.7% for PM BAS, and from 3.9 to 1.6% for CW BAS.

Conclusion

WB was able to resist cracking more efficiently than other types of biochar. Evaporation was found to be minimal for plant-based W BAS at 10% biochar percentage. Higher biochar content in soil was seen to increase the water retention of BAS significantly. Dense state of BAS at high biochar content (i.e., 10%) was effective in reducing evaporation rate and crack progression.

     

Methane emission from irrigated rice ecosystem: relationship with carbon fixation,partitioning and soil carbon storage

Rice is a major agricultural crop and accounts for 40 % of the total food grain production of India. A field experiment was conducted for two successive seasons (December–June, 2012–13 and December–June, 2013–14) to assess the efficiency of rice varieties for methane (CH₄) emission in relation to atmospheric carbon fixation, partitioning of carbon, and storage in the soil. Six high yielding rice varieties, Bahadur, Cauvery, Dinanath, Joymoti, Kanaklata, and Swarnabh were grown under irrigated condition. Results of the present investigation depicted differences in photosynthetic rate among the varieties accompanied by differential ability for plant biomass partitioning between the shoots and the roots. Stomatal frequency of flag leaf at panicle initiation stage was found to have strong influence on photosynthesis. Low CH₄-emitting rice varieties, Bahadur and Dinanath, were found to have lower size of the xylem vessels than the high CH₄-emitting rice varieties, Joymoti and Kanaklata, and found to influence the CH₄ flux. Soil organic carbon storage of 0.505 Mg C ha^?1 y^?1 in the plough layer of soil (0–15 cm) confirmed that irrigated rice ecosystem is an effective sink of carbon. These findings suggest that selection of suitable rice varieties with higher photosynthetic efficiency and lower emission of CH₄ can be a suitable biological mitigation of this greenhouse gas. Although an inverse relationship of CH₄ with carbon dioxide (CO₂) efflux was observed, irrigated rice ecosystem has a good potential to store substantial amount of carbon in the soil.     

Identification of optimal level of nitrogen fertilizer and tillage practice to reduce nitrous oxide emissions and maximize the nitrogen use efficiency and productivity from tropical rice paddy

Paddy and Water Environment - Agricultural tillage practices and fertilizer play an important role in production and consumption of greenhouse gases (GHGs), which contribute to global climate...     

Crude Oil-Contaminated Soil Phytoremediation by Using Cyperus brevifolius (Rottb.) Hassk

The degradation of total oil and grease (TOG) in crude oil-contaminated soil in the presence of Cyperus brevifolius (Rottb.) Hassk was investigated in a net house study. C. brevifolius plants were transplanted in to spiked soil containing 8% (w/w) crude oil. The capability of plant for enhancing the biodegradation process was tested in pots containing fertilized and unfertilized soil over a 360-day period. Analysis of the degradation of hydrocarbon contaminants, plant growth, and biomass was conducted at 60-day interval. In the presence of contaminants, plant biomass and height were significantly reduced. The specific root surface area was reduced under the effects of crude oil. Concerning TOG content in soil, C. brevifolius could decrease up to 86.2% in TA (crude oil-contaminated soil with fertilizer) and 61.2% in TC (crude oil-contaminated soil without fertilizer). In the unvegetated pots, the reduction of TOG was 13.7% in TB (crude oil-contaminated soil with fertilizer) and 12.5% in TD (crude oil-contaminated soil without fertilizer). However, biodegradation was significantly more in vegetated pots than in unvegetated pots (p?=?0.05). The addition of fertilizer had positive effect on TOG degradation in the presence of C. brevifolius compared to the unfertilized treatments. Thus, there was evidence of C. brevifolius enhancing the biodegradation of crude oil in soil under the conditions of this experiment.     

Sarcoptic mange infestation in pigs in a hilly region of Meghalaya

Skin lesions were collected from 15 adult crossbred pigs maintained at the pig farm of ICAR Research Complex for the North-Eastern Hill Region, Umiam, a hilly region of the state of Meghalaya, India. Skin scrapings of these 15 animals were examined by KOH digestion method. Presence of mites were detected in five animals which were indistinguishable from Sarcoptes scabiei var. suis. Infected pigs were treated with a single dose of Ivermectin at 200 ug/kg body weight, subcutaneously. No mites were recovered from treated pigs after a period of 10 days of post-treatment. The presence of S. scabiei var. suis in pigs from this part of the country has never been reported. This infestation has great significance because it affects the growth rate and feed conversion significantly, specially to the grower and weaned pigs. It can be concluded that S. scabiei var. suis infestation is prevalent in hilly region of Meghalaya. The pig producers are generally unaware about the severity of the problem of mite infestation, so precaution should be taken to prevent their valuable pigs from S. scabiei var. suis infestation.     

Impact of nitrogen fertilization and tillage practices on nitrous oxide emission from a summer rice ecosystem

ABSTRACT

Identification of the combination of tillage and N fertilization practices that reduce agricultural Nitrous oxide (N₂O) emissions while maintaining productivity is strongly required in the Indian subcontinent. This study investigated the effects of tillage in combination with different levels of nitrogen fertilizer on N₂O emissions from a rice paddy for two consecutive seasons (2013–2014 and 2014–2015). The experiment consisted of two tillage practices, i.e., conventional (CT) and reduced tillage (RT), and four levels of nitrogen fertilizer, i.e., 0 kg N ha^–1 (F1), 45 kg N ha^–1 (F2), 60 kg N ha^–1 (F3) and 75 kg N ha^–1 (F4). Both tillage and fertilizer rate significantly affected cumulative N₂O emissions (p < 0.05). Fertilizer at 45 and 60 kg N ha^–1 in RT resulted in higher N₂O emissions over than did the CT. Compared with the recommended level of 60 kg N ha^?1, a 25% reduction in the fertilizer to 45 kg N ha^?1 in both CT and RT increased nitrogen use efficiency (NUE) and maintained grain yield, resulting in the lowest yield-scaled N₂O-N emission. The application of 45 kg N ha^?1 reduced the cumulative emission by 6.08% and 6% in CT and RT practices, respectively, without compromising productivity.     

Biodegradation of beta-cyfluthrin by fungi

Five fungal species, namely, Trichoderma viride strain 5-2, T. viride strain 2211, Aspergillus niger, A. terricola, and Phanerochaete chrysoporium were screened for degradation study of beta-cyfluthrin. Each fungal species was allowed to grow in Czapek dox medium containing beta-cyfluthrin (5 mg/mL) as the major carbon source of the medium. The highest degradation of beta-cyfluthrin was observed by T. viride 5-2 (T(1/2) = 7.07 days), followed by T.viride 2211 (T(1/2) = 10.66 days). The degradation of beta-cyfluthrin followed first-order kinetics with a fast degradation rate during first 7 days of growth of the fungi. In the case of T. viride strain 5-2, five degradation products were isolated after 20 days of growth of the fungi, out of which three products were identified as alpha-cyano-4-fluorobenzyl-3- (2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylate, alpha-cyano-4-fluoro-3-phenoxy benzyl alcohol, and 3(2,2-dichlorovinyl)-2,2-dimethyl cyclopropanoic acid.