Nitrogen loss depends on spreading methods

Nitrogen losses during agricultural spreading vary depending on the product used, the equipment deployed, weather conditions, and the speed of incorporation. The EQ'Air project supports farmers in understanding these mechanisms and identifying ways to reduce volatilization.

Proportion of nitrogen used by crops matters

Spreading operations are typically planned based on equipment availability, field conditions, and weather forecasts. However, the proportion of nitrogen actually used by crops is a critical factor. Part of the supplied nitrogen is lost through volatilization as ammonia, presenting agronomic, economic, and environmental challenges.

Volatilization affects specific nitrogen forms

Volatilization primarily affects ammoniacal nitrogen found in livestock effluents and specific mineral fertilizers. For example, this form of nitrogen constitutes 15% of total nitrogen in cattle manure, 42% in cattle slurry, 70% in pig slurry, and up to 78% in some pig slurry digestates, according to the Regional Agricultural Chamber of Brittany and the Abaa project. Managing these losses requires considering the product's nature and intervention methods.

Equipment type influences nitrogen loss

The type of spreading equipment significantly impacts nitrogen losses. A simulation using the AgrivisioN'air tool for an input of 35 m³/ha of pig slurry showed notable differences. With conventional nozzles without incorporation, losses could reach 38 kg of ammoniacal nitrogen per hectare. These losses decrease to between 27 and 32 kg/ha with a pendulum bar and only 11 kg/ha with a toothed injector.

Quick incorporation reduces nitrogen loss

Incorporating the spread material quickly helps retain nitrogen. The same simulation showed that spreading with nozzles and incorporating within four hours limits losses to about 11 kg/ha. However, if incorporation occurs more than twenty-four hours after spreading, losses exceed 36 kg/ha. Acting quickly after spreading, when conditions permit, is an effective method to retain more nitrogen in the soil-plant system.

Weather affects nitrogen volatilization

Weather conditions such as temperature, wind, and air humidity directly influence volatilization. A reliable weather forecast allows for anticipating favorable conditions and comparing multiple scenarios before beginning the operation. Managing spreading offers triple benefits: improved agronomic efficiency by retaining more nitrogen for crops, environmental benefits by reducing ammonia emissions and limiting fine particle formation in the air, and economic benefits by optimizing fertilizer use.

EQ'Air project combines multiple factors

Better mastery of nitrogen losses requires combining agronomic knowledge, field practices, and air quality considerations. In Normandy, this approach is part of the EQ'Air project, funded by Ademe and led by the Regional Federation of Cuma of the West, Atmo Normandie, and the Normandy Agricultural Chambers.