Topsoil Carbon and Nitrogen Storage under Different Tillage Systems in the Arid - Tropics of Sudan

摘要

Loss of soil organic matter (SOM) has been associated with increased tillage intensity. Two sites were selected for this study to determine and give a model of the effect of long-term tillage (more than 30 years) on topsoil C and N storage. One site was cultivated conventionally by sub- soiler, smoothing by disc harrow, levelling and ridging and was compared with grassland as control. The second site was traditionally cultivated by "wasoge" drawn by animal. Soil samples were taken from profiles at an interval of 7.5 cm to a depth of 30 cm. The results showed that in all soil depths, values of organic carbon (OC) reported in traditional tillage (TT) were significantly (p≤0.004) higher than that of conventional tillage (CT). Organic carbon determined in TT (14.82 gkg{sup}(-1)) was significantly (P≤0.01) higher than that of CT (9.26 gkg{sup}(-1)). In the 7.5 - 15.0 cm depth, OC in TT (14.56 gkg{sup}(-1)) was significantly (P≤0.05) higher than that of CT (8.58 gkg{sup}(-1)). In the third depth (15 - 22.5 cm), OC in TT (15.08 gkg{sup}(-1)) was significantly (P≤0.01) higher than that of CT (7.28 gkg{sup}(-1)) and in the same depth, total nitrogen (TN) in native vegetation (NV) (0.37 gkg{sup}(-1)) was significantly (P≤0.05) higher than that of CT. In the lower soil depth (22.5-30 cm) OC in TT (14.82 gkg{sup}(-1)) was significantly (P≤0.004) higher than that of CT (7.89 gkg{sup}(-1)), in the same depth, OC in NV (16.9 gkg{sup}(-1)) was significantly (P≤0.05) higher than that of TT (14.82 gkg{sup}(-1)). Modeling the effect of tillage on soil C and N showed that OC was more affected by tillage (R2 89%) than TN (R2 40%).