生物炭对旱作农田土壤有机碳及氮素在团聚体中分布的影响

Biochar Effects on Organic Carbon and Nitrogen in Soil Aggregates in Semiarid Farmland

为研究生物炭输入对旱作农田土壤团聚体及其团聚体碳氮分布的影响,通过分层(0~10、10~20 cm和20~30 cm)采集设置0 t·hm-2(CK)、10 t·hm-2(C1)、20 t·hm-2(C2)和30 t·hm-2(C3)4个生物炭水平的田间定位试验的土样,利用湿筛法获得不同粒径(>2mm、2~0.25 mm、0.25~0.053 mm和<0.053 mm)的团聚体,测定各级团聚体中有机碳及全氮含量,分析添加生物炭后旱作农田土壤团聚体及团聚体中有机碳和全氮的分布特征。结果表明:与未施生物炭对照相比,施用生物炭两年后,0~10 cm和10~20 cm土层>0.25 mm粒级水稳性大团聚体的含量均呈增加趋势;且高添加量(30 t·hm-2)显著增加了10~20 cm和20~30 cm土层0.25~0.053 mm粒级微团聚体的含量。生物炭显著增加了各土层不同粒级团聚体中有机碳和全氮的含量,随施用量的增加0~10 cm和10~20 cm土层增加规律一致,均表现为C3>C2>C1>CK。0~10 cm土层不同粒级水稳性团聚体中有机碳和全氮的贡献率表现为2~0.25 mm粒级最高,且随土层加深,<0.053 mm粒级团聚体有机碳和全氮的贡献率增加。从0~30 cm土层团聚体有机碳和全氮的平均贡献率来看,随生物炭施用量的增加,2~0.25 mm和0.25~0.053 mm粒级贡献率均增加。

Biochars have many benefits to soil,including increasing soil carbon,enhancing soil water and nutrient retention,and improving soil aggregates.In the present study,the effects of biochar amendments on the distribution of soil organic carbon(SOC)and total nitrogen(TN)in soil aggregates in semiarid farmland were investigated.Soil samples from different depths(0~10 cm、10~20 cm and 20~30 cm)in a field experiment with four biochar application rates:0 t·hm-2(CK),10 t·hm-2(C1),20 t·hm-2(C2)and 30 t·hm-2(C3)were collected.The soil samples were fractionated into different sized aggregates(>2 mm,2~0.25 mm,0.25~0.053 mm and <0.053 mm)using wet sieving method,and then SOC and TN in each aggregate fraction were measured.Compared with the control,two-year amendments of biochar trended to increase the content of >0.25 mm water-stable macro-aggregates in the 0~10 cm and 10~20 cm soil layers.At the rate of 30 t·hm-2,the percentages of 0.25 ~0.053 mm micro-aggregates in the 10 ~20 cm and 20 ~30 cm soil layers were also significantly increased.Biochar additions significantly increased the SOC and TN content in different aggregates both in the 0~10 cm and 10~20 cm soil layers with C3 >C2 >C1 >CK.In the 0 ~10 cm soil layer,the contribution rates of SOC and TN in the 2 ~0.25 mm aggregate to the whole soil were the greatest among all the water-stable aggregates.The contribution rates of SOC and TN in the <0.053 mm aggregates increased with soil depth.In 0 ~30 cm soil,the average contribution rates of SOC and TN in the 2 ~0.25 mm and 0.25 ~0.053 mm aggregates increased with biochar amounts.