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Aim: The investigation was undertaken to identify the Minimum Data Set (MDS) for Soil Quality Index (SQI) assessment in continuouslong-term tea cultivation systems. Methodology: In the study under very deep, fine loamy, well-drained soil, five age groups of tea plantations viz. less than 15 years, 15-30 years, 30-45 years, 45-60 years and more than 60 years were selected and identified minimum data set and soil quality index. Results: In very deep, fine loamy, well-drained soil under continuous tea cultivation, SQI, 14.74 was obtained for less than 15 years, 14.06 for 15-30 years, 11.12 for 30-45 years, 12.94 for 45-60 years and 11.37 for more than 60 years of plantation, respectively. Interpretation: The most sensitive soil quality indicators identified in very deep, fine loamy, well-drained soil were pH for less than 15 years, total nitrogen for 15-30 years, available nitrogen for 30-45 years, organic carbon for 45-60 years and exchangeable aluminium for more than 60 years of continuous tea cultivation.

The effect of forest litter biochar on seed germination and early growth of two tree species (Trewia nudiflora and Lagerstroemia speciosa) was examined in a selected forest area of Nameri National ...

Mineralization of soil organic carbon has a significant impact on the atmospheric CO2 concentration. Application of organic amendments can affect the dynamics of carbon present in soil through the process of mineralization and immobilization. This study assessed the efficiency of biochar on soil carbon mineralization through respiration and the priming effect (positive or negative) after addition of the external carbon biomass in a controlled incubation experiment (90 days) at two different temperature regimes viz. 15 °C and 30 °C. A decrease in total CO2 respired was found with the addition of biochar in the soil where 6 t ha−1 of biochar treatment (T7) produced the lowest amount of CO2 for both the temperature regimes. The calculated half-life (t1/2) and rate constant (k) showed resistivity towards mineralization with increasing doses of biochar. Significantly negative priming effects were observed with addition of biochar in comparison to the control treatment at the end of the incubation period.

Biochar, a co-product of the pyrolytic conversion of biomass and biowastes to biofuel is a carbon rich recalcitrant material. It has received much attention in the recent times for its prospective application in various fields viz. as a soil amendment for improving the physical, chemical, and biological qualities of agricultural soils, as an adsorbent for removal of various organic and inorganic contaminants in water, for removal of pesticides residues in soil, for correcting soil acidity, as a precursor for chemical synthesis, for industrial applications such as supercapacitor application, as a support material for fuel cells, for enhancement in biogas generation to name a few. In addition to all these, biochar’s green-house gas mitigation potential, and C-sequestration potential are two most significant attributes that has made biochar a suitable component for SDGs. Further, these applications have made biochar as one of the most researched topics in recent times. The ease of biochar production is also another advantage which can be beneficial for farmers even with a marginal land holding. In this chapter, an attempt has been made to discuss the role of biochar in management of agricultural soils, as well as its vast environmental application possibilities.

A 2-year field study was conducted with wheat (Triticum aestivum L.) - green gram (Vigna radiata L.) crop rotation in an inceptisol to compare the effect of vermicompost and biochar on soil organic carbon (SOC), its fractions and carbon mineralization when applied with inorganic fertilizers. Experimental treatments used were only inorganic nitrogen, phosphorus and potassium (NPK) at recommended dose as control, 50% N + PK, NPK + vermicompost (2.5 t ha−1), NPK + biochar (2.5 t ha−1), 50% N + PK + vermicompost (5 t ha−1) and 50% N + PK + biochar (5 t ha−1). Compared to lone application of inorganic fertilizers, application of organic amendments significantly increased the total organic carbon (4–10%), particulate organic carbon (POC) (5–21%), microbial biomass carbon (MBC) (40–55%), recalcitrant carbon (F4) (16–67%), humic acid carbon (HAC) (2–12%) and fulvic acid carbon (FAC) (8–37%). Higher concentration of labile carbon fractions (F1 and F2), POC and MBC were noted with vermicompost application while addition of biochar produced more stable carbon fractions (FAC, HAC and F4). Vermicompost application increased (5–15%) the C mineralization rate with higher (29–55%) soil respiration, and lower (35–58%) C half-life compared to biochar. Principal component analysis confirmed a close association among the stable C fractions (FAC, HAC and F4) and degree of humification. Labile carbon fractions (F1, F2 and MBC) indicated higher sensitivity to the applied fertilizers. Biochar application promoted higher leaf and root biomass in the tested crops whereas the grain yields were not significantly (P ≤ 0.038) different suggesting equal potentiality of both the amendments towards productivity. The benefit cost ratio was higher (1.89 and 2.89) for application of vermicompost but greater agronomic efficiency (0.10 and 0.12 kg kg−1) and lower (10–22%) soil available nitrogen content were noted with biochar application, which indicates environmental sustainability. Thus, biochar introduction into the fertility program of wheat-green gram crop rotation along with inorganic fertilizers would be a better option which not only uphold crop productivity but also sequester higher SOC compared to vermicompost.

Addition of organic amendment with inorganic fertilizers is a suitable strategy to achieve sustainable agricultural production. But this practice is associated with increased carbon mineralization leading to release of carbon dioxide, a potential greenhouse gas for global warming. In this perspective, the present experiment was conducted in acidic sandy loam soils of north-east India to characterize the carbon mineralization, soil enzyme activities and okra (Abelmoschus esculentus L.) productivity under three (farmyard manure, vermicompost and biochar) commonly used organic amendments when added with inorganic fertilizers. Eight treatments were laid in a randomized block design with three replications. Vermicompost application increased the activities of soil enzymes with greater availability of soil nitrogen, phosphorous and potassium while biochar (hardwood) addition decreased the enzyme activities. Addition of biochar recorded the lowest rate of carbon mineralization (9%), the highest half -life of carbon (64%), higher soil organic carbon (12%) and stable organic carbon fractions (F3 fraction-12% and F4 fraction- 9%) with the highest okra yield compared to vermicompost and farmyard manure. Plant morphological attributes (plant height, leaf number, leaf area and photosynthesis of okra) were significantly enhanced due to addition of organics especially vermicompost and biochar with inorganic fertilizers. The addition of biochar recorded lower benefit cost ratio (3.5 and 3.8) but its application with inorganic fertilizers recorded the highest agronomic efficiency signifying potentiality to uphold efficient nitrogen use and environmental sustainability. Thus, addition of biochar in acidic soil would be a sustainable option to reduce carbon mineralization and uphold crop productivity.

An experiment was conducted to evaluate the efficacy of a consortia formulation of Pseudomonas fluorescens and Trichoderma harzianum for management of bacterial wilt disease of ginger in Assam. Inhibitory effect of the biocontrol agents was evaluated in vitro following dual culture assay method for their efficacy against Ralstonia solanacearum , the ginger wilt pathogen. Quantitative assay of population dynamics of the two antagonists, mass cultured in organic substrates viz., vermicompost (VC) and mustard oil cake (MOC) revealed that the antagonists maintained a high population count up to 120 days of storage at room temperature. Pseudomonas fluorescens recorded highest average population (45.47 x 10 7 cfu/g) when mass cultured in the mixture of VC and MOC, while T. harzianum recorded maximum average population (34.14 x 10 7 cfu/g) when mass cultured in MOC. Bioformulations were further evaluated for their efficacy in ginger wilt management under field condition. Efficacy of one fungicide (Copper oxychloride) and an antibiotic (Streptocycline) was also tested for comparison. Lowest disease incidence (15.63%) was recorded in the treatment of seed treatment (ST) and soil application (SA) of P. fluorescens and T. harzianum consortia mass cultured in the mixture of VC and MOC. It was followed by ST and SA of T. harzianum mass cultured in MOC (21.88%), which was statistically at par with the application of copper oxychloride (26.25%).

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.%.

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.