Cultivation impacts soil microbial dynamics in dry tropical forest ecosystem in India |
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Authors: | Nimisha Tripathi Raj S Singh |
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Institution: | Bio-Environment Division, Central Institute of Mining and Fuel Research, Barwa Road, Dhanbad 826 001, Jharkhand, India |
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Abstract: | We studied for two years the seasonal changes in plant available nitrate and ammonium nitrogen (N), nitrification, N-mineralization, microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) in two forest and three cropland sites, derived from a tropical forest ecosystem of India. Results indicated that seasonal values of nitrate N, ammonium N and phosphate P ranged from 7.33–12.99, 5.1–10.22 and 4.0–7.8 μg g?1 in forest and 4.13–9.26, 9.35–14.46 and 2.8–5.8 μg g?1 in cropland ecosystems, respectively, with maximum values in summer and minimum in rainy seasons. Nitrification and N-mineralization values varied from 6–28 and 4–26 μg g?1 mo?1 in forest and 3–14 μg g?1 mo?1 and 4–17 μg g?1 mo?1 in cropland, with maximum values in rainy season and minimum in summer season.MBC, MBN MBP ranged from 393–753, 34–80 and 16–36 μg g?1 in forests and 186–414, 21–41 and 11–22 μg g?1 in croplands, being maximum in summer and minimum in rainy seasons. There was gradual increase in the values of inorganic N, nitrification, N-mineralization and MBC, MBN and MBP along the age of cropland. Analysis of variance indicated significant difference in the concentration of inorganic N, nitrification and N-mineralization and MBC, MBN and MBP due to sites and seasons.Cultivation caused decline in the mean annual organic C, N and P by 42%, 29% and 13%. The values of nitrate N were decreased by 23–38%, while ammonium N was increased by 39–74%. Nitrification and N-mineralization values were reduced by 39–63% and 40–60%, respectively. Microbial C, N and P were reduced by 44–54%, 41–50% and 28–44%, respectively. Nonetheless, the contribution of soil microbial biomass reflected in total N was enhanced from 4.76% in forest to 5.03% in cropland ecosystem. Enhancement of plant available ammonium-N and microbial contribution in total N are an indicator of natural conserving mechanism to check the nitrogen loss from the nutrient poor agro-ecosystem. |
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Keywords: | Soil microbial biomass Inorganic nutrients N-mineralization Tropical forest soil Cropland |
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