C/N比对好氧堆肥中NH3挥发损失和含氮有机物转化的影响

利用牛粪和不同比例玉米秸秆的混合,设置5个不同C/N比处理(T1=15、T2=20、T3=25、T4=30、T5=35),研究其对条垛式好氧堆肥过程中的NH_3挥发损失和含氮有机物转化的影响。结果表明:在肥堆前24 d有11.1%～23.1%的总氮损失,堆体C/N比越低,总氮损失率越高。堆肥结束时,T1～T5处理的总氮损失率为10.1%～24.1%,其中由NH_3挥发造成的氮损失占总氮损失的30.9%～40.5%。堆肥过程的NH_3挥发主要发生在升温期和高温期,此期的NH_3挥发量占总挥发量的95%以上,是总氮损失的主要途径。堆肥前6 d各处理堆体铵态氮积累并达到最高值,导致pH值迅速升高,是造成堆肥NH_3挥发的直接原因。堆体C/N比越低,pH值越高,NH_3挥发量越大,由此造成的氮损失占总氮损失的比例越大。堆肥材料总氮的90%以上为有机氮,其降解主要发生在堆肥前24 d,堆体初始C/N比越低,有机氮矿化越快。不同有机氮组分的降解速率不同,以氨基酸态氮和酰胺态氮的降解为主。当堆体初始C/N比低于25时,堆肥材料中氨基酸态氮和酰胺态氮等有机态氮快速降解产生大量的铵态氮,由此导致堆体pH值的迅速升高,是导致堆肥过程中大量NH_3挥发和氮素损失的主要原因。

Effects of C/N ratio on NH3 volatilization loss and nitrogen\|containing organic compounds conversion in aerobic composting

Using the mixture of cattle manure and maize straw with different proportion, an aerobic composting experiment was conducted with five different treatments of C/N ratios (T1=15, T2=20, T3=25, T4=30, and T5=35) under the pile composting conditions. The results showed that loss of total nitrogen(TN) in the composting mainly occurred in the first 24 days of composting, and the rate of TN loss in T1 to T5 treatments were statistically recorded as 10.1%~24.1%. Among them, the proportion of nitrogen loss caused by NH₃ volatilization in TN loss reached 30.9%~40.5%. More than 95% of the total NH₃ volatilization occurred during the heating stage and the high temperature period in composting,which was the main mean of total nitrogen loss. Ammonium content of each treatment accumulated and reached its maximumon in the first 6 days of composting, leading to a rapid increase in pH, which was the direct cause of the NH₃ volatilization during the composting. The lower C/N ratio resulted in the higher pH value, which increased loss as NH₃, and the proportion of NH₃-N loss to total nitrogen loss. More than 90% of TN in composting materials was the organic nitrogen, and degradation of them occurred in the first 24 days. Lower C/N ratios however promoted faster degradation rate of organic nitrogen. Different components of organic nitrogen showed the different degradation rate, and the amino acid and amide nitrogen contributed much more to accumulation of ammonium. Therefore, when the initial C/N ratio of the heap was lower than 25, a large amount of ammonium nitrogen being produced due to the rapid mineralization of the organic nitrogen, and the resulting rapid increase in pH value of the heap may be the main cause of NH₃ volatilization and nitrogen loss in composting.