3, 9.2gkg?1 organic C, 0.01% 0.5molL?1 NaHCO3-extractable P, and 0.003% of 1molL?1 NH4OAc-extractable K and C:N ratio 11.5 (Table 1).Table 1Characteristics of organic residues and soil.Bulk Nilotinib Leukemia density of 0�C15cm layer measured using cores, and it was 1.28g/cc. Rice straw and rice root were collected from rice fields after grain harvest. Then it was washed with distilled water and dried at 70��C in laboratory. Rice straw, rice root, cow dung, and poultry litter C were 48.90, 42.20, 17.43, and 47.41%; and total NPK contents were 0.63, 0.40, 1.04, and 1.00; 0.08, 0.29, 0.82, and 0.69%; and 2.35, 0.34, 0.68, and 0.95%, respectively, (Table 1). C:N ratio was 77.61, 105.5, 16.75 and 47.41 in rice straw, rice root, cow dung, and poultry litter, respectively.

The straw was cut into small pieces (<1cm), ground, and mixed with soil samples for incubation. The experiment was setup using complete randomized design with 10 treatments, replicated five times (each 5th replication as control). Rice straw, rice root, cow dung, and poultry litter including control where no use of organic residues were tested under two water levels, that is, moistened condition:field capacity (MC) and flooding condition ?2cm water level (FC) systems. Organic residues were thoroughly mixed with soil then transferred into air tight PVC pots for an equivalent of 200g soil to 0.25g C per pot. Samples were wetted slowly with calculated amount of deionized water to maintain designed water level. The pots were then incubated at the constant temperature of 25��C.

The pots filled soil with rice straw, rice root, cow dung, and poultry litter and 50mL beaker containing 25mL of 0.05N NaOH solutions were placed on soil surface inside the pot to absorb carbon dioxide. Pots were covered with polyethylene sheets and incubated in the darkness at 25��C for 120 days. Excess NaOH was titrated with 0.05N HCl after precipitating carbonates with BaCl2 using phenolphthalein as indicator and subtracted from the amount titrated in absolute control where no soil and organic residues were used. All the pots were taken out and opened periodically, aerated for a few minutes, and soil water content was checked and adjusted by weighing then adding distilled water to maintain water levels. The CO2-C evolved was measured at 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 105, 112, and 120th day of incubation.

The amount of CO2-C was calculated by using the following formula:mg??evolved??CO2day=(T2?T1)M��22t,(1)where, T1 = amount of HCl used to neutralize NaOH, T2 = T1 + amount of HCl used to dissolve precipited BaCO3, M = molarity of HCl, 22 = 22mg CO2/1mL 1M HCL, and t = time in days. The CO2-C in the control treatment was subtracted from the calculated value for CO2-C Batimastat release. At the end of incubation, soil samples were analyzed for organic carbon (SOC) content in soil.