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Of late, intensive farming for higher food production is often associated with many negative implications for soil systems, such as decline of soil organic matter (SOM), increase in risks of soil erosion by wind and/or water, decline in soil biological diversity, increase in degradation of soil physical quality, lower nutrient-use efficiency, high risks of groundwater pollution, falling water tables, increasing salinization and waterlogging, in-field burning of crop residues, pollution of air and emission of greenhouse gases (GHG), leading to global warming, and decline in factor productivity. These negative implications necessitate an objective review of strategies to develop sustainable management practices, which could not only sustain soil health and ensure food security, but also enhance carbon sequestration, decrease GHG emissions, and offer clean and better ecosystem services. Conservation agriculture (CA), that includes reduced or no-till practices along with crop residue retention and mixed crop rotations, offers multiple benefits. Adoption of a system-based CA conserves water, improves and creates more efficient use of natural resources through the integrated management of available soil nutrients, water, and biological resources, and enhances use efficiency of external inputs. Due to apparent benefits of CA, it is increasingly being adopted and now covers about 180 million hectares (Mha) worldwide. However, in South Asia its spread is low (<5 Mha), mostly concentrated in the Indo-Gangetic Plains (IGP). In this region, one of the serious issues is "residue burning" with severe environmental impacts. A huge amount of crop residue left over after the combine harvest of rice has forced farmers to practice widespread residue burning (∼140 M tonnes) to cope with excessive stubble and also for timely planting/sowing of succeeding crops. In rice-wheat cropping systems, which cover more than 10 Mha in the IGP, CA practices are relatively more accepted by farmers. In these systems, any delay in sowing leads to yield penalty of 1–1.5% per day after the optimum sowing date of wheat. The strong adoption of CA practices in IGP is mainly to overcome delayed sowing due to the field preparation and control of weeds, timely planting, and also escape from terminal heat during the grain-filling stage. Major challenges to CA adoption in South Asia are small land holdings (<1 ha), low technological reach to farmers, nonavailability of suitable farm implements for small farm holders, and the staunch conventional farming mind-set. South Asia region consists of many countries of diverse agro-ecologies with contrasting farming systems and management. This region, recently known for rapid economic growth and increasing population, necessitates higher food production and also hot-spots for adoption of CA technologies. Therefore, in this review critically explores the possibility, extent of area, prospects, challenges, and benefits of CA in South Asia. Conservation agriculture (CA), consisting of reduced or no-tillage and crop residue retention, is a self–sustainable system which offers an alternative to crop residue burning. The CA approach improves soil health by increasing soil organic carbon (SOC) and aggregation and also conserves soil, water and energy than conventional farming systems. South Asian countries are suitable for adoption of CA practices but the area under CA remains low (<5 Mha) as compared to the global area (180 Mha). Adoption of CA in South Asia has skewed distribution, mainly in Indo-Gangetic Plains (IGP) in India, Pakistan, Nepal and Bangladesh in South Asia. Development of herbicide-resistant weed species and weed shift by continuous application of herbicides are the major challenges in adoption of CA. The traditional-farming mind-set, socio-economic conditions, small farm-holdings, weed and residue management, and non-availability of suitable machinery are key constraints to the low adoption of CA practices in South Asia. [ABSTRACT FROM AUTHOR]

The presence of high concentration of arsenic in conventional water sources can cause serious health and environmental hazards. An urgent need is to find an efficient adsorbent for the removal of arsenic ions (As3+) from contaminated water. In the present study, molecular dynamics simulation is used to understand the adsorption behaviour of As3+ on hexagonal boron nitride (h-BN) and graphene nanosheets. The adsorption of As3+ follows the Langmuir isotherm and the maximum adsorption capacities are found to be 270.1 and 211.7 mg/g for h-BN and graphene nanosheets, respectively. Further, potential of mean force (PMF) of As3+ revealed that the h-BN nanosheet possesses lower contact minima (-1.35 kcal/mol) for arsenic ion compared to graphene nanosheet (-1.2 kcal/mol). These results indicate strong interaction between arsenic ion and h-BN nanosheet. On the other hand, desorption of As3+ on h-BN nanosheet showed higher energy barriers (2.3 kcal/mol) compared to graphene nanosheet (1.5 kcal/mol). Correspondingly, the residence time of As3+ is approximately threefold higher on h-BN nanosheet compared to graphene nanosheet. We also report that the presence of partial charges on B and N atoms in the h-BN sheet influence the adsorption behaviour As3+ ions and the maximum adsorption capacity of h-BN nanosheet with partial charges is found to be 311.7 mg/g. Thus, our study strongly suggests the potential applicability of h-BN nanosheet as an efficient adsorbent for the removal of arsenic ions. [ABSTRACT FROM AUTHOR]

Urease activity (by buffer and non-buffer method) of soils of different agro-ecosystems in alluvial soil was studied. Urease activity by buffer method records a higher value than the non-buffer method. Both the methods showed significant positive correlation (0.99**) between each other. Urease activity by both methods showed positive correlation with organic matter (0.88** and 0.89**, buffer method) and clay content (0.91** and 0.83*, non-buffer method)) of the soils. Multiple regression analysis showed that the stabilization of urease activity in the soils studied was due to an organic matter-enzyme complex. Among the organic matter humus C plays a dominating role to control the urease activity of the soils. [ABSTRACT FROM AUTHOR]

A method combining an initial search phase to find an admissible starting solution followed by a multidimensional minimization phase is proposed for robust pole placement. [ABSTRACT FROM AUTHOR]