Managing reactive nitrogen in spring wheat cropping systems: insights from Kabul, Afghanistan

Ammonia (NH₃) volatilization and nitrate leaching contribute to major losses of reactive nitrogen (Nr) in agriculture, leading to global environmental concerns. Effective measures are needed to mitigate Nr losses and improve nitrogen (N)-use efficiency in agricultural practices. This study, conducted in farmers' fields in Shewaki near Kabul City, Afghanistan, during the 2021 spring season, sought to address Nr-losses in agriculture. Nine treatments were organized into three categories: (A) animal manure + chemical fertilizer, (B) night soil + chemical fertilizer, and (C) chemical fertilizer alone, along with an unamended control. Chemical fertilizer and manure were applied at varying rates (±25% and a recommended rate) using both surface and sub-surface application methods. Sub-surface application reduced NH₃ emissions by 55% compared to surface application. Treatment group 'A' had a 32% NH₃ loss, while the unamended control (receiving N from irrigation water and dust only) showed a 13% loss. For nitrate leaching, group 'B' showed the highest loss, followed by group 'C'. Overall, agronomic practices reduced N-losses significantly, resulting in a net positive N-balance. Nuse efficiency was highest in group 'C' at 130%, followed by groups 'B' and 'A'. The findings suggest that sub-surface application techniques are effective in reducing N-losses and enhancing N-use efficiency, and highlight the potential to improve nutrient use efficiency by adjusting fertilizer and manure inputs in similar agricultural systems.