Soil boron status: impact of lime and fertilizers in an Indian long-term field experiment on a Typic Paleustalf

In Indian agriculture, nitrogen (N) and phosphorus (P) fertilizers are predominantly used by the farmers, often ignoring secondary and micronutrients. Significance of boron (B) in nutrient management studies has been increasingly underlined under intensive cropping systems particularly in acid soils. In order to understand the distribution of soil native B in different fractions and their contribution to plant B uptake as influenced by nutrient management, soil samples collected after wheat (2009–2010) from a long-term experiment (LTE) continuing since 1972–1973 on Typic Paleustalf of Ranchi were subjected to sequential fractionation of soil B. Treatments included N alone, NP, NPK, 150% of recommended NPK, NPK + farmyard manure (FYM), NPK + lime, and an unfertilized-control. Five soil B fractions were determined along with hot CaCl₂-extractable (available) B. Averaged across the treatments, the soil had low organic carbon (C), pH and cation exchange capacity (CEC), and high free sesquioxides. Total B content was 21.7 mg kg^?1. Among different B fractions, residual B was the major contributor to total B and other fractions collectively shared 7% of total B only. Application of N alone depleted readily soluble, specifically adsorbed and organically bound B bringing the contents even below unfertilized-control. Conjoint use of lime or FYM with NPK increased significantly these fractions, whereas a decrease in oxide bound B was noticed under these treatments. Available B was positively correlated with these fractions indicating their significance in controlling B availability in the soil. The study revealed that use of lime or FYM helped modifying the distribution of soil B in different fractions by way of changing soil pH and organic C content, resulting in enrichment of plant available pool. A drastically low available B content in different treatments receiving fertilizers alone, however, suggested the necessity of B fertilization at prescribed rates for maintaining soil B fertility as also high crop yields.     

Impact of Subsurface Drainage on Improvement of Crop Production and Farm Income in North-West India

The Indian Council of Agricultural research has given priority to control and manage salinity problems that have developed in north-west India. Multi-disciplinary taskforces have recommended installation of subsurface drainage for salinity control, based on design and management techniques developed by the Central Soil Salinity Research Institute (CSSRI), to rehabilitate lands with excess soil salinity. After small-scale studies, large-scale pilot projects were launched to install subsurface drainage in problem areas. One such attempt in was initiated in the north-west region of India where a large-scale drainage project was carried out with Dutch collaboration. We assessed the impact of investments in subsurface drainage in order to validate past funding on research of drainage in India. The important methods used for assessing the efficiency benefits of drainage investment were: to determine the impact of subsurface drainage in terms of net present value, internal rate of returns, consumers' surplus and producers' surplus; to assess the social welfare in terms of social equality and sustainability of the drainage system; and to examine the factors affecting the sustainability of the technology. The internal rate of return was computed to assess the efficiency parameter of subsurface drainage for salinity management. In order to measure the changes in inequality distribution of income, Gini concentration ratios were computed with and without installing sub surface drainage. The Radar Approach, a method based on a graphical display of differences between actual ideal performance, was used to quantify drainage sustainability in terms of optimizing gains and conserving, or improving the quality of soil and water resources. There were several farm-level benefits as a result of installing subsurface drainage: these included: (i) a substantial increase in farm income; (ii) cropping intensification and diversification toward high value crops; and (iii) generation employment. A high internal rate of return justified investment in subsurface drainage. Income inequalities across farms were reduced. The radar approach showed improvement in sustainability in terms of economic gains and resource conservation. Despite of these economic, social, and environmental benefits, the sustainability of subsurface drainage technology is questionable. The specific reasons include: (i) the nature of the technology; (ii) lukewarm collective action by the beneficiaries; (iii) conflicting objectives among beneficiaries; and (iv) growing numbers of free riders. To a large extent these were addressed in the study area by forming village committees. Without appropriate institutional arrangements, subsurface drainage may not yield the desired results, and in the long run may result in neglect of operation and maintenance needs and ultimately the abandonment of the technology.     

Long-term irrigation with zinc smelter effluent affects important soil properties and heavy metal content in food crops and soil in Rajasthan,India

Use of wastewater for irrigating agricultural crops is on the rise, particularly in the developing countries. The present study was undertaken to assess the long-term effect of irrigation with zinc smelter effluent on important soil properties including heavy metal status. Metal concentration in the edible parts of the crops grown on smelter effluent-irrigated soils was also measured. For this purpose, the agricultural lands which have been receiving the zinc smelter effluent irrigation for about five decades at Debari, Udaipur, India were selected. The adjacent tubewell water-irrigated fields were selected as reference. Long-term irrigation with smelter effluent resulted into significant buildup of ethylenediaminetetraacetic acid extractable Zn (57.7 fold), Cu (4.51 fold), Fe (3.35 fold), Mn (1.77 fold), Ni (1.20 fold), Pb (45.1 fold), and Cd (79.2 fold) in soils over tubewell water-irrigated fields. Total Zn, Cu, Mn, Ni, Pb, and Cd content in effluent-irrigated soils was also increased by 27.0, 1.60, 1.40, 1.30, 26.2, and 167 fold, respectively. Risk assessment indicated a very high to moderate potential ecological risk due to Cd, Pb, and Zn in soils close to the immediate vicinity of the smelter plant. Cadmium and Pb concentrations in edible parts of almost all the crops grown on effluent-irrigated soils were above the safe limit of CODEX commission. On an average, soil pH dropped by 0.31 units due to smelter effluent irrigation. Smelter effluent irrigation resulted into significant increase in soil organic carbon, electrical conductivity, and CaCO₃ content. On an average, there was decrease in available N (21.0%) and P (20.8%) content in effluent-irrigated soils over the tubewell water-irrigated ones. An increase in available K (102%) and S (26.0 fold) was recorded in effluent-irrigated soils. Long-term irrigation with zinc smelter effluent resulted into reduced microbial activities in soil as evidenced from the level of microbial biomass carbon and dehydrogenase activity. In view of the buildup of heavy metals and subsequent imbalance in essential plant nutrients in smelter effluent-irrigated soils, appropriate remediation-cum-fertilization strategy needs to be adopted for better soil health and plant nutrition.     

Threonine deaminase: a novel activity stain on polyacrylamide gels

With phenazine methosulfate and nitro blue tetrazolium, an activity stain for threonine deaminase has been developed. Because the deamination reaction does not involve any overall oxidation or reduction, it is proposed that one of the intermediates of the reaction, alpha-aminocrotonate or alpha-iminobutyrate, is the reducing agent. Studies with ferricyanide as the artificial electron acceptor indicate that a decarboxylation of the intermediate occurs during the dye reduction.     

Effect of electrolyte solution on saturated hydraulic conductivity of soils varying in clay type and content,and iron oxides

Changes of hydraulic conductivity (HC) at electrolyte solutions having different combinations of sodium adsorption ratio (SAR)¹ and electrolyte concentration (EC), were monitored in soil columns packed with samples from Rhodustalf, Chromustert, Andic Eutropept and Oxic Rhodustult, four subtropical soils varying in clay type and content, and iron oxides. In general, it was observed that the HC dropped with the decrease of EC and with the increase in SAR of solutions, or, with the increase in exchangeable sodium percentage (ESP) of the soil. In montmorillonitic soils the reduction of HC had been most pronounced, while the kaolinite-rich soils showed only an insignificant drop in HC even at the highest SAR coupled with the lowest EC. The improvement or revival of HC from its final drop was examined upon leaching the soil columns finally with the initial high concentration solution. Montmorillonitic soils showed moderate to high revival of HC, while for montmorillonite-illite-kaolinite mixed clayey soils and kaolinitic soils the improvement of HC was low and practically nil respectively. The percentage revival of HC from its final drop was employed as a criterion to assess the major cause of HC reduction and it was found that irrespective of clay mineralogy “dispersion and subsequent pore plugging” played a major role in reducing the HC of soils, though in montmorillonitic soils swelling had been found to be an almost equivalent additional cause of HC drop. Simple correlations (r) between the saturated HC at varying SAR & EC and different physico-chemical and mineralogical properties have been calculated and its role and implications have been discussed.     

Predicting Metal Uptake and Risk to the Human Food Chain from Leaf Vegetables Grown on Soils Amended by Long-Term Application of Sewage Sludge

The success of risk assessment of metal contaminated soils depends on how precisely one can predict the bio-availability of metals in soil and transfer to the human food chain. In the present investigation, we tested several formulations of the ‘free-ion activity model (FIAM)’ to predict uptake of Cd, Zn and Cu by perpetual spinach (Beta vulgaris, Cicla) grown on a range of soils amended with sewage sludge. The model was parameterised using data measured on samples of pore water extracted by centrifugation and with porous Rhizon samplers installed within the rhizosphere of the growing plants. Free ion activities (M²⁺) were estimated following speciation of solution data using version 6 of the ‘Windermere Humic Aqueous Model (WHAM-VI). For all three metals, the best formulation of the FIAM appeared to require only one hypothetical root sorption site without competition from protons. Values of (M²⁺) could also be predicted satisfactorily from a pH-dependent Freundlich relation. Thus, from a combined FIAM–Freundlich relation and population dietary information, it was possible to estimate risk (hazard quotients) to consumers from very simple soil measurements: extractable metal content (0.05 M EDTA (Zn and Cu) or 1 M CaCl₂ (Cd)), soil humus content and pH. The role of increased soil organic matter content and soil pH, in reducing risk to consumers, is illustrated for Cd in a hypothetical soil at the current UK statutory Cd limit for sludge application to agricultural land.     

Carbon Stock, Afforestation and Acidic Deposition: An Analysis of Inter-Relation with Reference to Arid Areas

Recent advances in desert afforestation underlines its viability and importance in combating global warming and acidification. In this paper, the inter-relation between afforestation, global warming and acid rain has been analyzed. Numerical simulations indicate that afforestation of deserts has distinct advantage as carbon sink and as an important factor for changing microclimate of the region rather than a source of energy. Acidic deposition may well be utilised as fertiliser in nutrient deficit soil of tropical arid areas. However, past trends and projections of acidic deposition in arid areas adjacent to Thar deserts indicate an early efforts are required to cap the opportunity. Delays may contribute towards more incidences of failures.     

Genotype and hormonal effects on callus formation and regeneration in mulberry

Summary Twenty-five mulberry genotypes were studied for callus induction, to evaluate the effectiveness of hormones in promoting callus growth and to identify genotypes capable of regenerating plants. Fifteen genotypes showed callus initiation. Genotypic variation was also noted for longevity and rate of growth of callus cultures. Calli of different genotypes were maintained for more than one year. Frequency of callus initiation was high on Murashige & Skoog's modified medium incorporated with 2.0 mg/l 2,4-D, 100 mg/l casein acid hydrolysate and 150 ml/l coconut water. Regeneration through organogenesis was achieved in six genotypes indicating genotypic specificity.