Effect of dolomite and biochar addition on N2O and CO2 emissions from acidic tea field soil

A laboratory study was conducted to study the effects of liming and different biochar amendments on N2O and CO2 emissions from acidic tea field soil. The first experiment was done with three different rates of N treatment; N 300 (300 kg N ha-1), N 600 (600 kg N ha-1) and N 900 (900 kg N ha-1) and four different rates of bamboo biochar amendment; 0%, 0.5%, 1% and 2% biochar. The second experiment was done with three different biochars at a rate of 2% (rice husk, sawdust, and bamboo) and a control and lime treatment (dolomite) and control at two moisture levels (50% and 90% water filled pore space (WFPS)). The results showed that dolomite and biochar amendment significantly increased soil pH. However, only biochar amendment showed a significant increase in total carbon (C), C/N (the ratio of total carbon and total nitrogen), and C/IN ratio (the ratio of total carbon and inorganic nitrogen) at the end of incubation. Reduction in soil NO3--N concentration was observed under different biochar amendments. Bamboo biochar with the rates of 0.5, 1 and 2% reduced cumulative N2O emission by 38%, 48% and 61%, respectively, compare to the control soil in experiment 1. Dolomite and biochar, either alone or combined significantly reduced cumulative N2O emission by 4.6% to 32.7% in experiment 2. Reduction in N2O production under biochar amendment was due to increases in soil pH and decreases in the magnitude of mineral-N in soil. Although, both dolomite and biochar increased cumulative CO2 emission, only biochar amendment had a significant effect. The present study suggests that application of dolomite and biochar to acidic tea field soil can mitigate N2O emissions.本研究开展了室内培养试验，旨在探究施石灰与不同生物炭改良剂对酸性茶园土壤N₂O与CO₂排放的影响。第一组试验设置3个氮肥施用量梯度：N 300（300 kg N ha⁻¹）、N 600（600 kg N ha⁻¹）与N 900（900 kg N ha⁻¹），以及4个竹炭施用量梯度：0%、0.5%、1%与2%。第二组试验采用2%施用量的3种不同生物炭（稻壳炭、锯末炭与竹炭），设置空白对照与石灰（白云石）处理，并在两个土壤含水量水平（50%与90%田间持水孔隙度（water filled pore space, WFPS））下开展。研究结果显示，白云石与生物炭改良均可显著提升土壤pH值。仅生物炭改良可在培养试验结束时显著提升土壤总碳（C）含量、碳氮比（总碳与总氮的比值，C/N）以及总碳与无机氮比值（C/IN）。不同生物炭改良处理均降低了土壤硝态氮（NO₃⁻-N）浓度。相较于第一组试验的对照土壤，施用量为0.5%、1%与2%的竹炭可分别使累积N₂O排放量降低38%、48%与61%。在第二组试验中，白云石与生物炭单独或配施均可使累积N₂O排放量显著降低4.6%至32.7%。生物炭改良下N₂O产生量降低的原因在于土壤pH提升与土壤矿质氮含量下降。尽管白云石与生物炭均提升了累积CO₂排放量，但仅生物炭改良产生了显著效应。本研究表明，向酸性茶园土壤施用白云石与生物炭可有效缓解N₂O排放。