Browsing by Author "Mahesh Kumar Singh"

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Impact of land use change on soil aggregate dynamics in the dry tropics
(Blackwell Publishing Inc., 2017) Mahesh Kumar Singh; Sunil Singh; Nandita Ghoshal
A 2-year study was conducted to elucidate land use change (LUC) impact on the distribution of aggregate size fractions and associated carbon (C) concentration involving natural forest (NF), degraded forest (DF), cropland (CL), and biofuel plantation (JP, Jatropha plantation) in the dry tropical region of India across the soil profile (0–10, 10–20, and 20–30 cm). Across the seasons and the land uses, the proportion of macro- and microaggregates was maximum at upper and minimum at lower layer whereas mesoaggregates increase with depth. The trend of macro- and microaggregate fractions through the soil profile was NF > JP > DF > CL whereas that of mesoaggregates was CL > DF < JP > NF. Dry mean weight diameter was highest at upper layer and decreased down the depth in all the land uses and followed the trend NF > JP > DF > CL. Aggregate associated organic carbon (OC) concentration in all the fractions decreased from NF to DF, CL, or JP indicates that macroaggregate associated OC concentration was more susceptible to loss than that of meso- and microaggregate associated OC concentration. LUC induced decline in macroaggregate associated OC stock and increase in meso- and microaggregate associated OC stock; indicated redistribution of OC stock among aggregate fractions. It may be concluded that JP in dry tropics can be an efficient strategy for rehabilitation of degraded land as it improves aggregate structure and stability in the whole profile and aggregate associated OC stock in upper layer of soil. © 2017 Society for Ecological Restoration
Impact of Land use change on soil organic carbon content in dry tropics
(2011) Mahesh Kumar Singh; Nandita Ghoshal
Land use change leading to loss of soil carbon content is of major global concern. In the present study, the effect of land use change involving forest, degraded forest, Jatropha plantation and agroecosystem in dry tropics was analyzed on the potential of soil carbon sequestration in terms of the concentration of soil organic carbon. Soil organic carbon concentration was found to be highest in forest (0.84%) followed in decreasing order by Jatropha plantation (0.78%), degraded forest (0.36%) and lowest in agroecosystem (0.21%). This study reflected that plantation of Jatropha for about 10 years on degraded soil have large potential of carbon sequestration compared to agroecosystem.
Impact of tree plantations on the dynamics of soil aggregates in urban degraded lands in the dry tropics
(John Wiley and Sons Ltd, 2021) Sunil Singh; Mahesh Kumar Singh; Chandra Mohan Kumar; Priyanka Soni; Nandita Ghoshal
The impact of land-use change in an urban ecosystem on soil aggregate dynamics and soil carbon storage was studied through two annual cycles under five land uses. All the land uses namely: (1) natural mixed vegetation (NV) growing in a protected area; (2) grass fallow (GF); and tree plantations of (3) Cassia siamea (CP); (4) Jatropha curcas (JP); and (5) Tectona grandis (TP) were grown on urban degraded waste lands in a dry tropical region of India. Proportions of soil aggregate fractions, their stability, and soil carbon storage were analyzed at upper (00–15 cm), and lower (15–30 cm) soil depths during the rainy, winter, and summer seasons. Across all the land uses and at both the soil depths, the proportion of macroaggregate was highest during summer and lowest during the rainy season, whereas the reverse trend was observed for mesoaggregate. The annual mean proportion of macroaggregate decreased while meso- and microaggregates increased, with increasing soil depth across all the land uses. At the upper layer, the trends of macroaggregate, aggregate stability, and soil C storage were NV > CP > JP > TP > GF whereas at lower depth, the trend was NV > TP > CP > JP > GF. Across all the land uses in both the depths, soil C storage was strongly and positively correlated with annual mean fraction of soil macroaggregate. All tree plantations improved soil properties considerably as compared to GF at upper soil layer, yet TP reached near NV in these soil properties at lower depth. Soil aggregate fractions may be used as an index of carbon storage capacity in the urban ecosystems. © 2021 John Wiley & Sons, Ltd.
Microbial Biomass Dynamics in a Tropical Agroecosystem: Influence of Herbicide and Soil Amendments
(Institute of Soil Science, 2016) Alka Singh; Mahesh Kumar Singh; Nandita Ghoshal
The influences of herbicide alone and in combination with the soil amendments with contrasting resource qualities on dynamics of soil microbial biomass C (MBC), N (MBN), and P (MBP) were studied through two annual cycles in rice-wheat-summer fallow crop sequence in a tropical dryland agroecosystem. The experiment included application of herbicide (butachlor) alone or in combination with various soil amendments having equivalent amount of N in the forms of chemical fertilizer, wheat straw, Sesbania aculeata, and farm yard manure (FYM). Soil microbial biomass showed distinct temporal variations in both crop cycles, decreased from vegetative to grain-forming stage, and then increased to maximum at crop maturity stage. Soil MBC was the highest in herbicide + Sesbania aculeata treatment followed by herbicide + FYM, herbicide + wheat straw, herbicide + chemical fertilizer, and herbicide alone treatments in decreasing order during the rice-growing period. During wheat-growing period and summer fallow, soil MBC attained maximum for herbicide + wheat straw treatment whereas herbicide + FYM, herbicide + Sesbania, and herbicide + chemical fertilizer treatments showed similar levels. The overall trend of soil MBN was similar to those of soil MBC and MBP except that soil MBN was higher in herbicide + chemical fertilizer treatment over the herbicide + wheat straw treatment during rice-growing period. In spite of the addition of equivalent amount of N through exogenous soil amendments in combination with the herbicide, soil microbial biomass responded differentially to the treatments. The resource quality of the amendments had more pronounced impact on the dynamics of soil microbial biomass, which may have implications for long-term sustainability of rainfed agroecosystems in dry tropics. © 2016 Soil Science Society of China.
Soil CO2-C flux and carbon storage in the dry tropics: Impact of land-use change involving bioenergy crop plantation
(Elsevier Ltd, 2015) Mahesh Kumar Singh; Hastings Astley; Pete Smith; Nandita Ghoshal
The study was conducted to evaluate the impact of land-use change in the dry tropics on soil CO2-C flux and soil organic carbon (SOC) storage, along with the major factors controlling them i.e. soil microbial biomass (SMB), belowground net productivity (BNP), and soil aggregate size fractions. Land-use change, in this study, involved conversion of natural forest, to degraded forest and then to an agroecosystem or a bioenergy crop plantation of Jatropha curcas. The soil CO2-C flux was highest in the agroecosystem followed in decreasing order by degraded forest, bioenergy crop plantation and smallest in the natural forest. The inverse trend was found in case of SOC storage, SMB and BNP. The proportion of macroaggregate in the soil follows the trend of SOC storage, whereas mesoaggregate follows the trend of CO2-C flux across all land-use types. The CO2-C flux showed significant negative correlation with BNP, SMB, macroaggregate size fraction, and SOC. Our study suggests that the flux of soil CO2-C was regulated directly by the soil aggregate fraction and not by SMB or BNP. However, soil aggregate formation was, in turn, related to the SMB and/or below BNP. Macroaggregates appear to protect the SOC, which results in lower CO2-C flux and higher SOC storage. It can be concluded that the bioenergy crops plantation on degraded forest lands in the dry tropics, may increase C storage in soil and reduce soil CO2-C flux, thereby helping in the mitigation of global climate change in addition to providing feed stocks for fossil fuel substitution. © 2015 .
Sustainability in agroecosystems: Management strategies involving herbicides and organic inputs
(Nova Science Publishers, Inc., 2018) Mahesh Kumar Singh; Biswadip Mukherjee; Chandra Mohan Kumar; Alka Singh; Nandita Ghoshal
Long-term sustainable management of agroecosystems has now become a global challenge, along with the major objective of maximizing the crop yield. This has led to the switching of research focus, from ‘high input and maximum yields’ to ‘low input and high efficiency sustainable agriculture’. Such approaches have generated renewed and wide interest in ecological aspects of crop production and sustainable agriculture. Organic inputs, rather than the chemical fertilizers are now considered to have the potential to conserve the soil fertility, in terms of a greater soil C storage, the soil microbial biomass, and the crop productivity in the tropical dryland rainfed agroecosystems, especially in the dry tropics of the Indian subcontinent. Weed infestation is a severe problem in agroecosystems, especially in rainfed croplands, as compared to the irrigated systems. The application of herbicide is a common method to control the weeds. Since the continuous and extensive use of herbicides may differently affect the soil organic matter dynamics, therefore, concerns are raised for the long-term sustainability of agroecosystems. The application of high-quality organic resources along with herbicide, not only negates the harmful side effects of these farm-chemicals, but also benefitted the first crop, in terms of improving the soil microbial biomass, the soil carbon sequestration potential, the soil N balance, and the total crop productivity, whereas these benefits were observed in the subsequent crop, when low quality inputs were added along with the herbicides. The combined application of herbicides with the organic inputs of contrasting resource qualities may thus help in, not only sustaining the long-term soil fertility and productivity, but also, in mitigating the increased atmospheric carbon dioxide concentration through its sequestration in agroecosystem soils. © 2018 Nova Science Publishers, Inc.
Variation in soil microbial biomass in the dry tropics: Impact of land-use change
(CSIRO, 2014) Mahesh Kumar Singh; Nandita Ghoshal
The impact of land-use change on soil microbial biomass carbon (C) and nitrogen (N) was studied through two annual cycles involving natural forest, degraded forest, agroecosystem and Jatropha curcas plantation. Soil microbial biomass C and N, soil moisture content and soil temperature were analysed at upper (0-10cm), middle (10-20cm) and lower (20-30cm) soil depths during the rainy, winter and summer seasons. The levels of microbial biomass C and N were highest in the natural forest, followed in decreasing order by Jatropha curcas plantation, degraded forest and the agroecosystem. The highest level of soil microbial biomass C and N was observed during summer, decreasing through winter to the minimum during the rainy season. Soil microbial biomass C and N decreased with increasing soil depth for all land-use types, and for all seasons. Seasonal variation in soil microbial biomass was better correlated with the soil moisture content than with soil temperature. The microbial biomass C/N ratio increased with the soil depth for all land-use types, indicating changes in the microbial community with soil depth. It is concluded that the change in land-use pattern, from natural forest to other ecosystems, results in a considerable decrease in soil microbial biomass C and N. Jatropha plantation may be an alternative for the restoration of degraded lands in the dry tropics. © CSIRO 2014.