Soil is an important resource for production system but its productivity is declining day by day due to increasing degradation. The excessive use of fertilizers including agro-chemicals and water under monotonous cropping system to increase the food production, particularly in Indo-Gangetic Plain, resulted in detrimental effect on soil ecosystem (Jagdish Prasad 2004). To maintain the equilibrium in productivity vis-à-vis soil environment, it is necessary to periodically monitor the soil properties and nutrient availability. Soil testing provides information about nutrients availability in soil which forms the basis for the fertilizer recommendation for sustainable production (Doneriya et al. 2013). Present study was conducted to analyze the physico-chemical properties and nutrients in soils of an agriculturally important Harahua block of Varanasi district, Uttar Pradesh. Seventy five soils samples (0-15) were collected from Bhelkha (V1), Chamaon (V2), Koiran (V3), Bhawanipur (V4), Pissaur (V5), Daniyalpur (V6) and Ganeshpur (V7) villages of Harhua block of Varanasi district. Sorghum, pearl millet, maize, paddy, pigeon pea and green gram are major crops during kharif, while wheat, mustard, field pea, and potato are commonly grown in rabi season. Quartering technique was used for preparation of soil sample. The samples were air-dried and passed through 2 mm sieve for analysis. The soil pH and EC were determined with 1:2.5 soil water ratio. The soil samples were analyzed for sand silt and clay (Chopra and Kanwar 1999); organic carbon (Walkley and Black 1934); available N (Subbiah and Asija1956); available P (Olsen 1954); available K (Jackson 1973); available S (Hariram and Dwivedi 1994), bulk density, particle density and porosity following standard procedures. Porosity and nutrient index value (Ghosh and Hasan 1976, 1979 and 1980) were calculated by using the formulae. Porosity = (100 − BD/PD)×100 Nutrient Index Value = [(% soils high in available estimates of a nutrient × 3) + (% soils medium in available quantities ×2) + (% soils low in available quantities × 1)] ÷ 100 The soil pH varied from 6.1 to 8.5 (Table 1). About 57 % samples were neutral (pH 6.6 to 7.3), 29 % samples were mildly alkaline (pH 7.4 to 7.8) and 13 % samples were moderately alkaline (pH 7.9 to 8.4). The electrical conductivity of the soils varied from 0.22-0.47 dS m-1 and were found to be normal (EC < 1.0 dS m-1). The sand, silt and clay content of the soils varied from 31.1-52.1 %, 18-30 % and 18-35.2 % with mean values of 43.8, 23.6 and 26.1, respectively, with standard deviations of 6.35, 4.53 and 5.58. Bulk density and particle density ranged from 1.21-1.47 Mg m-3 and 2.00 to 2.77 Mg m-3. The porosity of the soils ranged from 27 – 57 % with mean value of 46.8 % and standard deviation of 5.88. According to Muhr et al. (1965) rating, the organic carbon content ranged from 0.30 to 0.75 % with an average of 0.63 % and standard deviation of 0.09. About 9 % samples had organic carbon content below 0.50 % and 90 % samples were between 0.50 - 0.75 %.
Taxonomy and biodiversity of the genus Oscillatoria Vauch. ex Gom. (Cyanoprokaryota: Oscillatoriales) with ecological notes from Hooghly in West Bengal, India