Effect of Forest Conversion into Tea Plantation on the Available Nitrogen in the Soils at Andro, Northeast India

L. Ibechoubi, Pratap S. Yadav


We studied the changes in NH4+-N and NO3-N in the soil after conversion of a sub-tropical forest into tea plantation in Northeast India. The forest is dominated by Lithocarpus fennestrata and Passania pachyphlla and part of the forest was felled for tea (Camellia sinensis) plantation intercepted by Emblica officinalis and Cymbopogon cladestinus. The NH4+-N ranged from 2.19 (December) to 4.84 µg g-1 soil (June) in forest and 2.53(January) to 4.91 µg g-1 soil (June) in tea plantation during the year. NO3-N ranged from 0.66 (April) to 3.88 µg g-1 soil (March) in forest and 0.72 (April) -2.98 µg g-1 soil (March) in tea plantation. NH4+-N was recorded to be highest in rainy followed by summer and winter in both the sites. Seasonal changes in NH4+-N and NO3-N values may be due to the variation in the mineralization rates, uptake by plants and microbes through soil erosion, leaching and denitrification.  Significant positive relationship between NH4+-N and soil temperature, soil organic carbon and total soil nitrogen in both the sites  indicates that these are the controlling factors in the NH4+-N concentration. NH4+-N and NO3-N concentrations were relatively higher under tea plantation than the forest.


Denitrification; Nitrogen; Mineralization; Soil Temperature; Subtropical Forest


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