Search

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.

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%).