Browsing by Author "Jay S. Singh"

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A comparative account of the microbial biomass-N and N-mineralization of soils under natural forest, grassland and crop field from dry tropical region, India
(Institute of Agricultural and Food Information, 2009) Jay S. Singh; D.P. Singh; A.K. Kashyap
This study investigated microbial biomass-N (MB-N) and N-mineralization in soils of four different vegetation systems including forest (sal), mixed forest, savanna and cropland ecosystems in the Vindhyan region, India. A change was noted in the above region due to physiographic differences and anthropogenic disturbances. Annually the soil moisture (SM) content across the different study sites ranged from 7.5 to 24.3% being maximum in forest sites compared to savanna and cropland sites. The NH4+-N, NO 3--N and MB-N concentrations varied from 4.3 to 10.2 μg/g; 1.1 to 5.8 μg/g and 21.3 to 90.2 μg/g dry soil, respectively, with minimum values in the wet and maximum values in the dry season. The trend of seasonal variation in net N-mineralization was similar to that of moisture content but counter to the concentrations of inorganic-N and MB-N. The net N-mineralization rates at different investigated sites ranged from 4.5 to 37.6 μg/g month. Cultivation reduced the N-mineralization and MB-N by 58.5% and 63.5%, respectively. Experiments showed that the percentage contribution of MB-N to total-N was 8.01 to 19.15%. MB-N was positively correlated with the inorganic-N (n=180, r=0.80, P<0.001) but negatively with soil moisture (n=180, r=0.79, P<0.001) and net N-mineralization rates (n=180, r=0.92, P<0.0001). The higher N-mineralization and MB-N in the soil of forest ecosystem was reported compared to savanna and cropland and the order of soil MB-N levels and net N-mineralization followed the sequence: forest (sal) > mixed forest > savanna > cropland.
Antarctic cyanobacteria as a source of phycocyanin: An assessment
(2008) S.P. Shukia; Jay S. Singh; S. Kashyap; D.D. Giri; A.K. Kashyap
The growth characteristics and phycocyanin contents were examined in antarctic and tropical isolates of three cyanobacterial genera Anabaena, Nostoc and Phormidium in batch cultures, and in indoor and outdoor mass-culture units under varying conditions of temperature, light and nutrients. The Antarctic isolates showed 54-62% higher phycocyanin content than the tropical ones. The contents recorded in Antarctic isolates were 1.8 to 3.3 folds higher than the reported values for one of the commercially used strain of Spirulina maxima. The study proves that Antarctic cyanobacteria can yield higher amount of phycocyanin by manipulating growth conditions. The information will serve as a base line data for future biotechnological applications of antarctic cyanobacterial strains within the preview of the Antarctic treaty.
Contrasting pattern of nitrifying bacteria and nitrification in seasonally dry tropical forest soils
(2007) Jay S. Singh; Ajai K. Kashyap
Samples of surface (0-20 cm) soils were collected from six sites (forest and savanna) in seasonally dry tropical Vindhyan regions of India, to evaluate the effects of different sites and seasons on the dynamics of nitrifier population size and nitrification on comparative basis. The sites selected for the present investigation are situated along a gradient of dominant vegetation cover, soil physico-chemical characteristics, soil nutrient status and moisture content of soils. The results showed that forest soils had significantly higher water-holding capacity, organic-C, total-N and total-P, but lower bulk density than the savanna sites. A significant difference in the population size of nitrifying bacteria and nitrification rate was observed across different study sites and seasons. Amongst the different sites investigated, the viable population size of ammoniumand nitrite-oxidizing bacteria (AOB and NOB) and nitrification rate recorded were maximum at Hathinala moist site (forest) and minimum at Telburva (savanna) site. During an annual cycle the soil moisture content, nitrifier population size and nitrification rate observed were highest during rainy season and lowest during summer season in all the sites. The numbers of free-living cells of AOB and NOB were significantly related with each other as well as with soil moisture content and nitrification rates. There was a significant site and season interaction, indicating that the effect of different seasons differed across the studied sites. The combination of low moisture content, organic-C and total-N suppressed the number of freeliving cells of AOB and NOB and nitrification rates at the savanna sites. Our results support earlier findings that vegetation cover, soil characteristics, nutrient status and moisture content of soils govern the population dynamics of nitrifiers (AOB and NOB) and nitrification in seasonally dry tropical forest and savanna ecosystems.