Adding biochar to soil in a rainfed wheat farming system can help reduce nitrogen losses and improve nitrogen balance. By applying biochar at rates of 5 to 20 tons per hectare, researchers found that nitrogen losses through emissions and leaching were decreased, leading to higher nitrogen retention in the soil. This resulted in increased nitrogen uptake by crops, particularly at higher biochar application rates. Overall, biochar application at 10 tons per hectare was identified as the optimal dose for sustainable nitrogen management in this type of agricultural system.