Release of Carbon Dioxide and Water-Soluble Carbon Amended with Rice and Wheat Residues in an Inceptisols of Varanasi

Crop residues are the main organic source of nutrients in agricultural soils. The active pool of soil organic carbon plays a dominant role in crop production and soil health. Rice and wheat residues were used in 90 days incubation study under controlled conditions (25 degrees C temperature and maximum water-holding capacity) to estimate the release of carbon dioxide and water-soluble carbon in an Indo-Gangetic alluvial soil (Inceptisols) of Varanasi. The experiment was laid out in a factorial completely randomized design with three replications. The rice and wheat residues showed a wide variation in the content of their total carbon (TC), total nitrogen (TN), total phosphorus (TP) and total sulfur (TS). Out of the two crop residues added to the soil, rice residue had higher carbon dioxide-carbon (CO2-C) release than that of the wheat residue over control. Results revealed that conjunctive application of rice residue along with urea (20 kg N ha-1) and Trichoderma viride (10 kg ha-1) had resulted in a higher content of CO2-C (7.44 mg per 100 g per day) at 90 days of the incubation period. The amount of CO2 (mg) released, increases with a combination of crop residues with urea (20 kg N ha-1) and Trichoderma viride (10 kg ha-1) up to 90 days over control. The highest release of CO2 (204.70 mg) was recorded with rice residue treated with urea (20 kg N ha-1) and Trichoderma viride (10 kg ha-1). The study also revealed that the release of water-soluble carbon decreases with an increase in the incubation period irrespective of treatment. At 90 days of the incubation period, the control without any crop residue addition has the highest water-soluble carbon content (459.75 mu g/g). The present study indicates that the incorporation of rice and wheat residues along with urea and supplemental decomposers (Trichoderma viride) has the potential to release adequately active organic carbon pool parameters such as CO2 and water-soluble carbon in an Inceptisols of Varanasi region of India.