Banashree Sarma

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.

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.%.

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.

Responses of Soil Enzymes and Carbon Mineralization to Applied Organic Amendments: A Short-term Study in Acidic Sandy Loam Soil

Predicting carbon (C) mineralization due to fertilizer application is important for predicting carbon dioxide (CO2) emissions into the atmosphere. This study was conducted to evaluate the effects of different organic amendments and inorganic fertilizers on C mineralization and soil enzyme activities along with the changes in soil pH, available nitrogen (N) and phosphorus (P). Eight treatments were applied using inorganic fertilizer and organic amendments (FYM, vermicompost and biochar) at different rates. Higher activities of soil enzymes (urease, phosphatase and dehydrogenase) were recorded till 60 days of incubation with addition of organic amendments. Among the applied organic amendments, vermicompost showed greater availability of N and P. Both vermicompost and FYM application recorded enhanced activities of soil enzymes and C mineralization rate while biochar application noted higher C half-life and soil pH. Thus, addition of biochar in acid soil would be a sustainable option to reduce the C mineralization which also maintains nutrient status of sandy loam soil of north-east India.

FIELD EVALUATION OF SOIL AND WHEAT RESPONSES TO COMBINED APPLICATION OF HARDWOOD BIOCHAR AND INORGANIC FERTILIZERS IN ACIDIC SANDY LOAM SOIL

Biochar application appears to be a promising method to improve soil physicochemical and biological properties by increasing soil carbon. Along with the influence of hardwood biochar on wheat growth, yield and soil quality for a period of two years, this study also evaluates the major soil parameters to be taken as minimum data set while assessing the impact of hardwood biochar in an acidic sandy loam soil. Five fertilizer treatments combining inorganic fertilizers and biochar were applied: unfertilized control (T1); 100% NPK (T2); 5 Mg ha −1 biochar (T3); 100% NPK + 5 Mg ha −1 biochar (T4); and 50% N + 100% PK + 5 Mg ha −1 biochar (T5). Biochar application (T3 vs. T1; T4 and T5 vs. T2) significantly increased leaf chlorophyll content, net photosynthesis rate, leaf N concentration and above and below-ground biomass, with improved wheat yield and grain quality (total grain protein and carbohydrate). Soil pH, water-holding capacity, available nutrients (N, P and K), organic carbon and its fractions also enhanced in biochar applied plots with reduced bulk density. Increased activities of soil enzymes urease, phosphatase, dehydrogenase, fluorescein di-acetate and arylsulphatase were recorded in biochar treatment along with significant increase in N recovery index (22%) and agronomic efficiency (40%). Multivariate analysis identified activity of phosphatase, pH and humic acid to fulvic acid ratio as the indicators to explain the total variance from biochar addition in acidic sandy loam soil under wheat cultivation. Soil quality index showed a significant improvement when biochar was added with reduced N doses (T5). This study confirms the efficacy of biochar as a soil conditioner when applied with reduced N fertilizer and would be a sustainable option to improve wheat production and soil quality in acidic sandy loam soils of northeast India.

Nitrogen Management for Sustainable Soil Organic Carbon Increase in Inceptisols Under Wheat Cultivation

ABSTRACT Application of nitrogen (N) fertilizers to increase crop yield is a worldwide practice, which also has a positive influence on the soil organic carbon (SOC) increase. This study was carried out to investigate the dynamics of SOC and its fractions under different levels of N fertilization in wheat grown inceptisols of Northeast India over a period of 2 years. For the purpose of this study, fertilizer treatments with five N levels (40, 60, 72, 80, and 100 kg N ha−1) were applied in randomized block design. Increased SOC particulate organic carbon (POC), humic acid carbon, and fulvic acid carbon were recorded under application of higher N. Stability of SOC as indicated by E4/E6 ratio and microbial biomass carbon (MBC) was higher on application of 72 kg N ha−1. Among the SOC fractions, POC and MBC respond rapidly to different N fertilization rates. Available N and phosphatase activity increased while pH and urease activity (UA) decreased as a function of applied N fertilizer levels. Nitrogen fertilization increased wheat yield and biomass with insignificant differences among 100, 80, and 72 kg N ha−1. Thus, under the present experimental conditions, application of 72 kg N ha−1 can sustain SOC and soil health without compromising wheat yield in the inceptisols of Northeast India.