Nirmali Gogoi

Hazard remediation and recycling of tea industry and paper mill bottom ash through vermiconversion

Considerable amount of bottom ash (BA) is produced by tea and paper factories in Northeast India. This significantly deteriorates soil and surface water quality through rapid acidification, releasing sulfur compounds and heavy metals. The present investigation endeavoured to convert this waste to organic manure through vermicomposting by Eisenia fetida. Substantial increment in bioavailability of N, P, K, Fe, Mn and Zn along with remarkable decline in toxic metal like Cr due to vermicomposting was noteworthy. Furthermore, vermicomposted mixtures of Tea Factory BA (TFBA) or Paper Mill BA (PMBA) with organic matter (OM) attributed profuse pod yield of French Bean (Phaseolus vulgaris L.). Hence, bioconversion of TFBA and PMBA is highly feasible through vermicomposting and the converted materials can be utilized as potential organic fertilizer.

Efficacy of bioconversion of paper mill bamboo sludge and lime waste by composting and vermiconversion technologies.

Paper mill bamboo sludge (PMBS) and Paper mill lime waste (PMLW) are extensively produced as solid wastes in paper mills. Untreated PMBS and PMLW contain substantial amount of heavy metals (Zn, Pb, Ni, Cd, Cr) in soluble forms. Efficiency of vermiconversion and aerobic composting with these wastes is reported here. Adopted bioconversion systems enhanced the availability of some essential nutrients (N, P, K and Zn) in various combinations of cow dung (CD) with PMBS and PMLW. Colonization of nitrogen fixing bacteria and phosphate solubilizing bacteria considerably intensified under the vermiconversion system. Moreover, significant metal detoxification occurred due to vermiconversion. Various combinations of bioconverted PMBS and PMLW were applied to tissue cultured bamboo (Bambusa tulda) and chilli (Capsicum annum). Accelerated nutrient uptake coupled with improved soil quality resulted in significant production of chilli. Furthermore, vermiconverted PMBS+CD (1:1) and PMLW+CD (1:3) confirmed as potential enriching substrate for tissue cultured bamboo.

Effect of 10 years of biofertiliser use on soil quality and rice yield on an Inceptisol in Assam, India

In the present study, field experiments were performed over 10 consecutive years (2006–15) to assess the effects of biofertiliser and enriched biocompost on soil quality, total organic carbon (TOC) and rice yields in an Inceptisol. Experiments were conducted in a randomised block design with four replicates and five treatments: unfertilised control (T1); recommended doses of inorganic fertiliser (T2); biofertiliser with reduced (50%) inorganic N and P fertilisers (T3); reduced (50%) inorganic N and P fertilisers with 1 t ha–1 enriched biocompost (T4); and reduced (75%) inorganic N and P fertilisers with 2 t ha–1 enriched biocompost (T5). T3 improved soil chemical and biological properties with enhanced soil quality index (40%), total P (23%), total K (42%) and fungal (38%) and bacterial (44%) colony counts. T5 significantly improved the carbon pool index (29%) and available nutrients (N, P and K at rates of 37%, 22% and 10% respectively) and increased soil pH (11%), resulting in a higher sustainable yield index (39%) of rice. Fraction 2 (labile carbon) of TOC, total P, available K, microbial biomass carbon and phosphate-solubilising bacteria were key indicators to assess the suitability of these fertilisers in rice cultivation in north-east India.

Effects, tolerance mechanisms and management of salt stress in grain legumes

Salt stress is an ever-present threat to crop yields, especially in countries with irrigated agriculture. Efforts to improve salt tolerance in crop plants are vital for sustainable crop production on marginal lands to ensure future food supplies. Grain legumes are a fascinating group of plants due to their high grain protein contents and ability to fix biological nitrogen. However, the accumulation of excessive salts in soil and the use of saline groundwater are threatening legume production worldwide. Salt stress disturbs photosynthesis and hormonal regulation and causes nutritional imbalance, specific ion toxicity and osmotic effects in legumes to reduce grain yield and quality. Understanding the responses of grain legumes to salt stress and the associated tolerance mechanisms, as well as assessing management options, may help in the development of strategies to improve the performance of grain legumes under salt stress. In this manuscript, we discuss the effects, tolerance mechanisms and management of salt stress in grain legumes. The principal inferences of the review are: (i) salt stress reduces seed germination (by up to more than 50%) either by inhibiting water uptake and/or the toxic effect of ions in the embryo, (ii) salt stress reduces growth (by more than 70%), mineral uptake, and yield (by 12-100%) due to ion toxicity and reduced photosynthesis, (iii) apoplastic acidification is a good indicator of salt stress tolerance, (iv) tolerance to salt stress in grain legumes may develop through excretion and/or compartmentalization of toxic ions, increased antioxidant capacity, accumulation of compatible osmolytes, and/or hormonal regulation, (v) seed priming and nutrient management may improve salt tolerance in grain legumes, (vi) plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi may help to improve salt tolerance due to better plant nutrient availability, and (vii) the integration of screening, innovative breeding, and the development of transgenics and crop management strategies may enhance salt tolerance and yield in grain legumes on salt-affected soils.

Fabrication of biochars obtained from valorization of biowaste and evaluation of its physicochemical properties

This study investigated the yields and the physicochemical properties of biochar from three different feedstocks viz., i) bioenergy byproducts (deoiled cakes of Jatropha carcus and Pongamia glabra), ii) lignocellulose biomass (Jatropha carcus seed cover), and iii) a noxious weed (Parthenium hysterophorus), obtained through slow pyrolysis at a heating rate of 40°Cmin-1 with a nitrogen flow 100mlmin-1 at a temperature range of 350-650°C. For successful utilization of biochar for C-sequestration, its ability to resist abiotic or biotic degradation was deduced from recalcitrance index R50 by using TG analysis. It was observed that the biochar produced at higher temperature had higher water holding capacity (WHC) and pH, suggesting its suitability as an amendment in soil with low water retention capacity; thus biochar may be designed to selectively improve soil chemical and physical properties by altering feedstocks and pyrolysis conditions. Biochar produced at 650°C had highest yield in the range of 28.52-39.9 wt.%.

Biochemical changes in two Vigna spp. during drought and subsequent recovery

Drought is one of the major environmental factors restricting crop production world over. The present experiment was conducted to evaluate the changes in important biochemical traits and yield of pulses under drought stress imposed during reproductive stage. Black gram (Vigna mungo L.) genotypes: T-9, PU-19 and green gram (Vigna radiata L.) genotypes: Pratap, TMB-37 were taken as test material in a randomized block design with three replications. Leaf chlorophyll content, nitrate reductase activity and total flavonoid were found to be positively correlated with soil moisture content, while negative correlations were obtained with proline and anthocyanin content. Significant differences among genotypes, treatments and interaction between the genotypes and treatment were observed for yield and other biochemical parameters, which demonstrated the existence of differences among the genotypes studied for drought tolerance. Genotypes T-9 of black gram and Pratap of green gram were found to be more tolerant to drought stress. Among the crops, black gram showed better drought tolerance than green gram. Biochemical parameters chlorophyll content, leaf proline content, nitrate reductase activity and anthocyanin content were identified as marker traits for selecting drought resistant pulse genotypes.

Germination and seedling growth of Okra (Abelmoschus esculentus L.) as influenced by organic amendments

Abstract This study was designed to understand the effects of different soil organic amendments on germination and seedling vigour of Okra (Abelmoschus esculentus L.). Five treatments with organic amendments (farmyard manure, vermicompost and biochar) and mineral fertilizers were designed in randomized block design with three replications. Results showed that organic amendments significantly enhanced per cent seed germination and emergence speed index compared to inorganic fertilizer. Highest homogeneity of seed germination (CVgt = 20.74) was observed in vermicompost. Plant height, root length and leaf area were higher in vermicompost and biochar than farmyard manure. Both allocation of biomass to above ground parts and Dickson quality index were highest in seedlings from the plots amended with vermicompost. The study revealed that compared to biochar, vermicompost and farmyard manure significantly enhanced the germination and growth of Okra seedling, but the stimulation was best in vermicompost-amended plots.

Morphological responses of pulse (vigna spp.) crops to soil water deficit.

The present experiment was conducted with two common pulse crops namely black gram (Vigna mungo.L) and green gram (Vigna radiata.L) with the objective to study the morpho-physiological changes that took place in response to low moisture stress. Parameters such as plant height, leaf number, leaf area and pod number were studied under moisture stress condition as well as subsequent recovery stages. At harvest, yields of these two crops were recorded and various yield indexes like drought susceptibility index, drought tolerance index, mean and productivity rate were calculated. The study revealed that moisture stress has a significant impact on all these parameters in both crops. The effect was more significant in green gram compared to black gram. From the findings it is observed that moisture stress during flowering stage is detrimental for yield of the pulse crops and re-watering does not have a significant impact on yield improvement. Black gram variety T9 and green gram variety Pratap were identified as drought-tolerant varieties.

Pyrolysis and kinetic analyses of a perennial grass (Saccharum ravannae L.) from north-east India: Optimization through response surface methodology and product characterization

The objective of the present investigation was to optimize the pyrolysis condition of an abundantly available and low cost perennial grass of north-east India Saccharum ravannae L. (S. ravannae) using response surface methodology based on central composite design. Kinetic study of the biomass was conducted at four different heating rates of 10, 20, 40 and 60 °C min-1 and results were interpreted by Friedman, Kissinger Akira Sunnose and Flynn-Wall-Ozawa methods. Average activation energy 151.45 kJ mol-1 was used for evaluation of reaction mechanism following Criado master plot. Maximum bio-oil yield of 38.1 wt% was obtained at pyrolysis temperature of 550 °C, heating rate of 20 °C min-1 and nitrogen flow rate of 226 mL min-1. Study on bio-oil quality revealed higher content of hydrocarbon, antioxidant property, total phenolic content and metal chelating capacity. These opened up probable applications of S. ravannae bio-oil in different fields including fuel, food industry and biomedical domain.

THE EFFECT OF OSMOTIC STRESS ON ANTI-OXIDATIVE CAPACITY OF BLACK GRAM ( VIGNA MUNGO L.)

In order to assess the response of four popularly grown black gram (Vigna mungo L.) genotypes (T9, PU 19, USJD 113, KU 301) under osmotic stress, the present study was carried out by monitoring the changes in relative leaf water content (RLWC), carotenoid, total soluble protein (TSP), membrane lipid peroxidation (MDA), H2O2 scavenging capacity, and the activities of superoxide dismutase (SOD) and catalase (CAT). Osmotic stress was applied by withholding irrigation for 15 consecutive days at vegetative, flowering and pod filling stages. Under stress condition, several fold increase in the content of MDA, H2O2 scavenging activity and antioxidant enzyme activity was recorded while, RLWC, carotenoid and TSP were found to decrease. Flowering stage was found to be most sensitive in terms of economic yield. The genotype T9 experienced lowest reduction in yield (12.10–33.91%) with maximum value of drought tolerance index (DTI) (7.48) which can be attributed to its higher tolerance capacity to drought. On the other hand, USJD 113 had the highest yield loss (26.48–60.99%) and lowest DTI (6.07) value, indicating its susceptibility towards osmotic stress.