Short-Term Contribution of Mineral N from Soil Organic Matter during the Rainy Season in a Vertisol of the Semi-Arid Tropics of Sudan

Abstract

This study was conducted to monitor the effect of tillage on potentially mineralizable nitrogen during the growing season of rain-fed sorghum (Sorghum bicolor). Two sites (with conventional tillage & traditional tillage) located southern central clay plain were selected. Auger soil samples were taken from the 0-30 and 30-60 cm soil depths every two weeks during the rainy season. Results showed that content of total mineral nitrogen (NH+ 4-N+NO- 3-N) in traditional tillage was significantly higher than that obtained under conventional tillage. Accordingly, mineral nitrogen under traditional tillage determined after 2, 4, 6, 8 and 10 weeks were 366.2, 217.78, 206.12, 202.86, 189.8 kg ha-1, respectively. Respective values for conventional tillage were 139.01, 160.34, 166.13, 177.18, 212.08 kg ha-1. This possibly reflects the effects of accumulation of undisturbed crop residues in traditional tillage, thereby, securing more N. Therefore, traditional tillage system is characterized by fewer chances of leashing of NO- 3-N. It could be concluded that less soil disturbance with traditional tillage provides the subsequent crop with substantial amounts of mineral N during the growing season, unlike conventional tillage where NO- 3-N was leached down beyond the rooting zone. This should also be taken into consideration during establishment of N fertilization budget.