Integrated management practices to minimise losses and maximise the crop nitrogen value of broiler litter

This study quantified the effects of contrasting storage methods on ammonia (NH3) emissions from broiler litter and the effects of NH3 abatement strategies during storage and following land spreading on nitrate leaching losses and crop nitrogen availability. There were five storage treatments: conventional, sheeted, turned, ‘A-shaped’ and roofed. Ammonia emissions were highest, (P<0.001) from the roofed heaps (19% of N into store) and lowest from the sheeted heaps (1% of N into store), with intermediate emissions from the other heap treatments (13–16% of N into store). Storage and soil incorporation methods both had significant effects on NH3 emissions following land spreading (P<0.001). Land spreading emissions from the surface-spread sheeted broiler litter were equivalent to 26% of the total N into store and were higher (P<0.05) than those from the surface-spread conventionally-stored broiler litter at 11% of total N into store. To conserve the N retained during sheeted storage, rapid soil incorporation was required, which reduced emissions by 15–87% compared with surface spreading. Ploughing the sheeted broiler litter into the soil within 4 h of land application increased (P<0.05) nitrate leaching losses (14% of total N into store) compared with the surface-spread broiler litter (4% of total N into store). The soil incorporation method had a significant effect on grass N offtake, with ploughing within 4 and 24 h of land spreading increasing (P<0.05) grass N offtakes compared with surface application of broiler litter. The results of this project highlight the need to develop integrated manure management strategies that consider all N loss forms and routes, and that strategies to reduce N losses via one pathway should, ideally, not increase losses via another route (so-called ‘N pollution swapping’).