Development of unique soil organic carbon stability index under influence of integrated nutrient management in four major soil orders of India.

Stability of soil organic carbon (SOC) is pre-requisite for stabilization of C leading to long-term C sequestration. However, development of a comprehensive metric of SOC stability is a major challenge. The objectives for the study were to develop novel SOC stability indices by encompassing physical, chemical, and biochemical SOC stability parameters and identifying the most important indicators from a Mollisol, an Inceptisol, a Vertisol, and an Alfisol under long-term manuring and fertilization. The treatments were control, 100%NPK, 50% NPK+ 50% N through either farmyard manure, cereal residue, or green manure. SOC stability indicators were selected, transformed and integrated into unique SOC stability indices via conceptual framework and principal component analysis. Principal component analysis identified Al-macroaggregate, humic acid C-microaggregate, microaggregate-C, particulate organic matter-C-macroaggregate and polyphenol-microaggregate as the important SOC stability indicators. The principal component analysis -based SOC stability index varied from 0.2 to 0.9, 0.1 to 0.5, 0.2 to 0.6, 0.1 to 0.5 for Mollisol, Inceptisol, Vertisol and Alfisol, respectively. The SOC-stability index derived from conceptual framework and principal component analysis significantly lined up well with one another, although NaOCl-Res-C showed a high correlation with both conceptual framework (r = 0.8) and principal component analysis-based (r = 0.7) SOC stability indexes, suggesting that both methods might be used to quickly assess SOC stability in four soil orders. Overall, 50%NPK+50%N by farmyard manure or green manure emerged as the most effective management practices for enhancing stability of SOC in Mollisol, Inceptisol, Vertisol, and Alfisol of India which might act as major C sink in rice-wheat and maize-wheat cropping systems. The other aspect of C sequestration is to enhance agricultural productivity without depending much on expensive chemical fertilizers. The model yardstick thus developed for assessing SOC stability might be useful to other systems as well.

Plant Nutrition: An Effective Way to Alleviate Abiotic Stress in Agricultural Crops.

By the year 2050, the world's population is predicted to have grown to around 9-10 billion people. The food demand in many countries continues to increase with population growth. Various abiotic stresses such as temperature, soil salinity and moisture all have an impact on plant growth and development at all levels of plant growth, including the overall plant, tissue cell, and even sub-cellular level. These abiotic stresses directly harm plants by causing protein denaturation and aggregation as well as increased fluidity of membrane lipids. In addition to direct effects, indirect damage also includes protein synthesis inhibition, protein breakdown, and membranous loss in chloroplasts and mitochondria. Abiotic stress during the reproductive stage results in flower drop, pollen sterility, pollen tube deformation, ovule abortion, and reduced yield. Plant nutrition is one of the most effective ways of reducing abiotic stress in agricultural crops. In this paper, we have discussed the effectiveness of different nutrients for alleviating abiotic stress. The roles of primary nutrients (nitrogen, phosphorous and potassium), secondary nutrients (calcium, magnesium and sulphur), micronutrients (zinc, boron, iron and copper), and beneficial nutrients (cobalt, selenium and silicon) in alleviating abiotic stress in crop plants are discussed.

Effect of ammonia stress on immune variables of Pacific white shrimp Penaeus vannamei under varying levels of pH and susceptibility to white spot syndrome virus.

Of late, Pacific white shrimp Penaeus vannamei culture has intensified globally and is a major contributor to the cultured shrimp produced worldwide. Intensification of its culture has led to elevated ammonia concentration during grow-out. Ammonia toxicity is a function of water pH, temperature, salinity and beyond the optimum range, creates stress to cultured aquatic species which can reduce growth, increase susceptibility to diseases and eventually mortality. The present study was aimed at quantifying the toxic effect of total ammonia nitrogen (TAN) (1, 3, 6 & 9 mg/l) and pH levels (6, 8 & 10) individually and in combination on median survival (50% lethal time) of shrimp (8 g) after exposure for 14 days followed by post-stress challenge with white spot syndrome virus (WSSV) for 9 days. Mortality risk factor and the toxicity effect on the immune variables were evaluated. Individual stressors showed a risk factor of 1-13 times, whereas combined treatments considerably increased the risk of dying compared to control. Low survival (15%) was observed in pH6TAN9 and pH10TAN3 treatments and was substantiated by prominent histological obliteration in gills of shrimp. The cumulative mortality in post-stress WSSV challenged trials was 1-5 times and 1-35 times in individual and combination treatments, respectively compared to control. The study revealed that variations in ammonia and pH beyond the optimal range significantly influence the non-specific immune mechanisms in P.vannamei and increases the susceptibility to WSSV especially in combination treatments.