玉米植株不同部位还田土壤活性碳、氮的动态变化

Labile carbon and nitrogen dynamic changes in soils incorporated with different parts of maize plants

探讨玉米植株不同部位腐解对还田土壤活性碳、氮动态变化的影响。采用室内培养方法,通过动态监测土壤微生物量碳(SMBC)、微生物量氮(SMBN)、可溶性碳(DOC)和矿质氮含量,研究等量玉米根茬、秸秆、茎及叶4个部位在连续7季还田(秸秆+根茬还田)和不还田土壤(仅根茬还田)中的腐解转化特征。结果表明,秸秆腐解的最初7 d是土壤活性碳、氮动态变化的高峰期;腐解期间(62 d)SMBC、SMBN含量表现为添加秸秆始终高于根茬,叶分别在前28 d、14 d内高于茎,后期则低于茎,秸秆介于茎、叶之间;土壤DOC、矿质氮含量为叶>秸秆>茎>根茬;培养结束时,各处理SMBC和矿质氮含量均较起始(0 d)显著提高,DOC含量基本保持不变,SMBN含量显著下降。与不还田土壤相比,还田土壤对新鲜残体的腐解影响不显著,且两者间土壤活性氮组分的差异较碳组分明显。腐解期间土壤活性碳、氮的动态变化主要取决于各器官碳、氮等化学组分的差异性,等量秸秆较根茬更有利于补充土壤活性碳、氮数量,土壤活性氮组分对还田土壤的响应较碳组分灵敏。

An incubation experiment was carried out to investigate the labile carbon and nitrogen dynamic changes in soils added with different parts of maize plants （straw, root, stem and leaf）. The strawamended soils had been incorporated with both straw and root residues, and the control soils with only root residues in consecutive sevenseasons of summer maize and winter wheat rotation system in Guanzhong Plain, Shaanxi province, China. The soil microbial biomass carbon （SMBC）, soil microbial biomass nitrogen （SMBN）, dissolved organic carbon （DOC）, mineral nitrogen are determined regularly over 62 days, incubation. The results show that soil labile carbon and nitrogen change rapidly in the first 7 days. The contents of SMBC and SMBN amended with straw are significantly （P〈0.05） higher than those with root. The SMBC and SMBN contents are greater in soils added with leaves than with stems at the first 28 d and 14 d incubation, and opposite afterwards. The SMBC and SMBN contents in soils added with straws are in between of the leaves and stems additions. The soil DOC and mineral nitrogen contents are in the order： leaf 〉 straw 〉 stem 〉 root. At the end of the incubation, both the SMBC and mineral nitrogen contents increased significantly, soil DOC contents kept unchanged and the SMBN contents declined in all straw parts treatments. Compared to the non-added soils, the straw-added soils had no significant effect on the decomposition of fresh residues, and the differences in soil labile N between the two soils are greater than those in soil labile C. Therefore, soil labile C and N dynamics are influenced primarily by the ratio of C to N in the different straw parts. A same amount of straw is more efficient in replenishing soil C and N than roots after incorporated into soil, and the soil labile N is more sensitive than C to straw addition.