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

摘要

This study quantified the effects of contrasting storage methods on ammonia (NH{sub}3) emissions from broiler litter and the effects of NH{sub}3 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 NH{sub}3 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 4h 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').