Mukesh Sehgal

Impacts of Climate Change on Agriculture

Climate change has emerged as the most prominent of the global environment issues and there is a need to evaluate its impact on agriculture. Crop simulation models help greatly in this regard. Crop models such as WTGROWS, INFOCROP, ORYZA and DSSAT have been widely used for land use planning, agri-production estimates, impact of climate change and environmental impact analysis. Vulnerable regions under future scenarios of climate change and adaptation strategies (agronomic and input management) have been evolved for many important crops by using simulation techniques. One of the simple empirical techniques for evaluating the impact of future climate change is through historic analysis of the response of crops to inter-seasonal climatic variability. The impact of temperature rise is different for crops grown under variable production environments. Interactions exist for changes in temperature, carbon dioxide concentration, solar radiation and rainfall on growth and yield of crops. Adaptation strategies through the adoption of agronomic management options (such as altered date of sowing, scheduling of water and nutrients) can sustain agricultural productivity under climate change. The rapid changes in land use and land cover have to be included for impact analysis. Linking of the socioeconomic aspects needs to be strengthened.

Pedotransfer functions for predicting the hydraulic properties of Indian soils

Most of the data pertaining to Indian soils are limited to the major soil separates, sand, silt, and clay. We examined the possibilities of using these parameters to describe the hydraulic characteristics of the soils of India. The final or steady-state infiltration rate, which is mainly profile-controlled, showed a power function relationship with the maximum and the average clay content in the soil profile. The saturated hydraulic conductivity also showed a similar relationship with the silt + clay content. The soil water content at a given suction could be satisfactorily predicted using the percentage of major soil separates, sand, silt, and clay. The coefficients in the soil water function ψ(θ) were linearly related to the sand content. Non-linear regression equations were developed to predict these coefficients using the percentages of sand and clay in soils. The equations proved to be quite satisfactory for a wide range of textures and provided reasonably accurate estimates of the soil water characteristic curve from a minimum of readily available data.

Calculation of ESR Spin- Spin Relaxation Times (1/T_2) Transition Metal Ion Complexes: A DFT Application

Only a limited experimental ESR research had been carried out in this field because high values of spin orbit constants of transition metal ions which provide an important energy transfer mechanism would affect the values of ESR parameters (especially Aten) of their complexes. Therefore, theoretical predictions were useful. DFT implemented in ADF: 2012.01 was applied by giving a set of commands like Single Point, LDA, Default, Spin Orbit, ZORA, Unrestricted, None, Collinear, Nosym using TZP or TZ2P Basis sets in its ESR/EPR/EFG/ZFS Program after optimization of each one of 141 complexes to obtain their ESR parameters: g11, g22, g33, giso, a11, a22, a33, Aten. ESR SpinSpin Relaxation Times (1/T_2) whose values, to the best of our knowledge, were never reported before were, then, calculated from the giso values of the complexes.