Emissions of ammonia, nitrous oxide and methane from cattle manure heaps: effect of compaction and covering

The effect of compaction and covering during storage of beef cattle (Bos taurus) farmyard manure (FYM) on ammonia (NH3), nitrous oxide (N2O) and methane (CH4) emissions was determined. Gaseous emission measurements were made over three separate storage periods of between 90 and 109 days. The effect of the different storage treatments on manure chemical composition was also determined. Compaction was carried out as the manure was put into store and the compacted manures covered with plastic sheeting. Compaction and covering significantly reduced NH3 emissions from manure by over 90% during the first summer storage period . Over the subsequent storage periods NH3 emissions from the FYM were small and unaffected by storage treatment. However, during the second storage period heavy and persistent rainfall during heap establishment and the following week appeared to reduce NH3 emissions markedly. The low ammonium-N content of the FYM in the third storage period may have reduced the risk of NH3 emission and reduced the relative effect of the compaction/covering treatment. Compaction and covering also significantly reduced N2O emissions from cattle FYM by ca. 30% during the first storage period. Subsequent N2O emissions were unaffected by treatment. Methane emissions from cattle FYM were unaffected by treatment over the first storage period and were decreased by compaction in the second storage period yet was increased by compaction during the third storage period. It would appear that compacting and covering manure heaps does have the potential to reduce emissions of both NH3 and N2O when the manure contains relatively high ammonium-N contents. Additional benefits are that N and K are retained in the manure heap for agronomic benefit.