Increasing nitrogen use efficiency by reducing ammonia and nitrate losses from tomato production in Kabul, Afghanistan

Over the past century, the inefficient use of reactive nitrogen (N_r) has raised concerns regarding global food production and planetary sustainability. This study investigates nitrogen (N) losses in tomato production near Kabul, Afghanistan, aiming to improve nitrogen use efficiency (NUE) for enhanced food security and environmental protection. Three fertilizer treatments were tested: (A) animal manure + 1/4 dose of chemical fertilizer, (B) night soil + 1/4 dose of chemical fertilizer, and (C) full dose of chemical fertilizer, with sub-treatments varying in N application (25% less, 25% excess, and farmers' practice). A no-fertilizer control treatment was included. Nitrogen losses through ammonia emissions and nitrate-N leaching were monitored, while nitrogen balances and NUE were calculated. The findings revealed that ammonia emissions decreased by 33% in treatment A₂ and by 30% in treatment B₃ compared to surface application. However, nitrate-N leaching peaked at 145 kg N ha^-1 in A₂ and 128 kg N ha^-1 in B₃, with positive N balances observed across treatments, the highest being 300 kg N ha^-1 in treatment A. NUE ranged from 30% (A and B) to 55% (control), highlighting the widespread overapplication of N in Afghan agriculture. This study demonstrates that efficient N management practices can reduce environmental losses while maintaining tomato yield, offering a novel pathway toward sustainable farming in the region.