Effect of additives on greenhouse gas emissions and nitrogen losses during storage of pig manure in Vietnam
This study investigated the effects of three different types of additives to stored pig manure on total nitrogen andammonia (NH3) loss and greenhouse gas (GHG) emissions in Vietnam. The experiment consisted of five treatments (T1) farmer’s practices, continuous manure addition, T2 control, all manure added initially, T3 biochar amendment, T4 superphosphate amendment and T5 microbial inoculants) with three replicates of each treatment. Through the 90-day storageexperiment, no significant increase in temperature occurred in any of the treatments, indicating no active compostingtook place, possibly due to only partial aerobic conditions in the reactors. Cumulative analyses for the individual gasesCO2, CH4 and N2O indicate that GHG emissions resulting from the different treatments were not hugely different.Farmers normal practices generally had higher emissions than other practices, with losses that were significantly highestfor CO2, whilst for CH4 they were just as high as the highest emitting treatment (biochar), and for N2O the emission washighest. Overall N losses were not markedly affected by the treatments, and therefore the effects of additives arerelatively marginal, although it was clear that farmers practice of continuously adding manure without proper coverageor other elimination of loss risk will result in a manure of poorer fertilizing quality. We therefore recommend that moreexperimental work needs to be carried out, where larger volumes of manure are treated and other methods oramendments are tested, in order to find ways to efficiently reduce manure N losses and GHG emissions to theenvironment.
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