Browsing by Author "Dharmendra K. Singh"

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Changes in species composition, diversity and biomass of herbaceous plant traits due to N amendment in a dry tropical environment of India
(Oxford University Press, 2014) Punita Verma; R. Sagar; Hariom Verma; Preeti Verma; Dharmendra K. Singh
Aim: European and North American studies have suggested that nitrogen (N) depositions reduce plant diversity and increase primary productivity due to changes in plant traits. To predict the vegetation response to future global change, experimental validations from other regions are widely needed. We assessed the effects of N treatment by urea fertilization on the diversity and biomass of the herbaceous plant traits (HPTs) in a dry tropical environment of India. Methods: Diversity and biomass of different HPTs were determined on the basis of data collected in year 2010, from 135, 1 m x 1 m plots distributed over 15 locations. The plots were treated with urea fertilizer in different doses (Control, 60kgNha-1 yr-1 and 120kg N ha-1yr-1) since 1st January 2007. The plots were ordinated and data were subjected to appropriate statistical analyses. Important Findings: Correspondence analysis (CA) suggested uniqueness of species composition due to N amendment. Species number and biomass of the trait categories varied due to N fertilization and traits. All studied trait categories (except N-fixers) yielded maximum mean species number at moderate level of N fertilization. Different levels of N fertilization exhibited different species diversity-primary productivity (D-P) relationships. Further, study showed reduction in plant diversity due to increase in biomass at high rates of N addition. Conclusions: Tall, erect, non N-fixers, annuals, grasses HPTs were favoured by N enrichment. N dose above 60kg enhanced the biomass of fast growing, erect, annuals, non N-fixers, nitrophilic HPTs. The changes in traits with N addition, especially the increase in annuals and grasses and decrease in typically N-rich N-fixers, have implications for sustainable cattle production. © The Author 2014. Published by Oxford University Press on behalf of the Institute of Botany, Chinese Academy of Sciences and the Botanical Society of China. All rights reserved.
Spatiotemporal variations in 50 microbial mediated nitrogen (N) release under N-fertilization experiment from Banaras Hindu university, India
(Springer India, 2014) Punita Verma; R. Sagar; K. Kuldip; Dharmendra K. Singh
Globally, atmospheric nitrogen depositions due to fossil fuel combustion, industrial, and agricultural activities have been identified as serious threats to soil, water, and vegetation. In soil, N-deposition affects the respiration, microbial activities, enzymes actions, litter decomposition, and Nmineralization. The process of N-mineralization involves ammonification and nitrification. Ammonification is mediated by Clostridium sp., Micrococcus sp., Proteus sp., etc. Nitrification is mediated by the activities of diverse group of microorganisms (Nitrosomonas europaea, Nitrosococcus nitrosus, Nitrosospira briensis, Nitrosovibrio, Nitrocystis, Nitrobacter winogradski, Nitrospira gracilis, Nitrosococcus mobilis, Penicillium, Aspergillus, Streptomyces, Nocardia, etc.). In the present study, spatiality, rates of ammonification, nitrification, and net N-mineralization were governed by the soil properties (pH, moisture, C, N, and litter quality) and temporally these processes are determined by the rainfall pattern. Further, the study suggested th t the rates of ammonification, nitrification, and net N-mineralization were greater at moderate level of N application. This affinity can be speculated as: at low levels of N resource, soil-C and -N are not enough for the activities of nitrifiers to release them in available form. As N increases more, actively participating microorganisms are enabled to release the nutrients in available form through the process of ammonification, nitrification and thus net N-mineralization, at sufficiently high N level, nitrifier population as well as their activities could be limited and thus the process of N-mineralization is limited. On the other hand, excessive N-application may damage the natural flora and fauna of soil which depletes the soil fertility. It could be also speculated that the N-limited ecosystems keep the deposited N by using it for the growth and developments of plants and microbes, in addition to accumulation in biomass and soil organic matter. At a certain point, the deposited N commences to go beyond the biotic and abiotic needs for N within the system and the ecosystem is predicted to fail its N-retention ability. As the capability to keep N exceeds, surplus N is offered to be vanished from the ecosystem through solution losses and gas flux. Thus, in this study moderate level of N accelerated the process of N-mineralization. © Springer India 2014 This work is subject. All rights reserved.
Species diversity-primary productivity relationships in a nitrogen amendment experiment in grasslands at Varanasi, India
(Indian Academy of Sciences, 2015) R. Sagar; Punita Verma; Hariom Verma; Dharmendra K. Singh; Preeti Verma
[No abstract available]