Effect of Tobacco Stem Based Composts as Soil Amendments on Nitrogen Mineralization and Other Properties of Soil

A study on tobacco stembased composts was conducted at Zonal Agricultural and Horticultural Research Station, Navile, Shimoga in order to evaluate tobacco stem based composts as soil amendments on nitrogen mineralization and other properties of soil. The two composts viz., poultry manure based tobacco compost (PMC), green leaves (Pongamia) based compost (GLMC) and undecomposed tobacco stem (UTS) as control were applied to soil with and without calcium ammonium nitrate (CAN) application. The application of composts to soil increased the maximum water holding capacity of soil from 20.13 per cent in no compost to 23.16 and 22.47 per cent in PMC and UTS @ 25 t ha⁻¹ with CAN respectively. At 90 days of incubation the soil organic carbon increase was higher in PMC (50.30 per cent) compared to 47.09 per cent in GLMC and 44.21 per cent in UTS. The NH₄-N levels increased up to 15 days and then after it decreased. At initial stage (on day 3) 179.66 mg kg⁻¹ in PMC @ 12.5 t ha⁻¹ with CAN and 203 mg kg⁻¹ of NH-₄-N in GLMC @ 25 t ha⁻¹ with CAN were recorded when compared to no compost with CAN (176.16 mg kg⁻¹). As seen in case of NH-₄-N, release of (NO₃+NO₂)-N also seems to be influenced by rate of decomposition of composts. Direct application of undecomposed tobacco stem (UTS) which has a C: N ratio of 84.8: 1, reducedavailability of appliednitrogen up to 15 days and reduced microbial activity in soil.