连续14年保护性耕作对土壤总有机碳和轻组有机碳的影响

依托于2001年布设在陇中黄土高原半干旱雨养农业区的保护性耕作定位试验,于2014年测定了5种保护性耕作(免耕+秸秆覆盖NTS、免耕NT、传统耕作+秸秆翻埋TS、传统耕作+地膜覆盖TP和免耕+地膜覆盖NTP)和传统耕作T处理下小麦-豌豆双序列轮作中表层土壤(0~5、5~10、10~30 cm)总有机碳(SOC)和轻组有机碳(LFOC)在作物生育期前后的变化。结果表明:土壤总有机碳和轻组有机碳在土壤剖面上均随着土层深度的增加而降低;相比传统耕作T,NTS和TS处理能显著提高0~30 cm土层中SOC、LFOC的含量,在作物播种前较T分别提高了19.51%、64.58%和13.36%、42.08%,在收获后分别提高了28.00%、85.37%和18.61%、77.82%,而SOC、LFOC含量NT和TP处理与T处理间差异不显著;从作物播种前至收获后,各处理下0~30 cm土层SOC含量均有减小趋势,其中NTS和TS处理变化量最小,NT和TP处理加大了作物生育期间SOC和LFOC的消耗;LFOC可以灵敏地反应出土壤有机碳的变化。因此,在该区推行以免耕、秸秆覆盖为主的保护性耕作措施更有利于碳的积累和土壤质量的改善,促进该区农业的可持续发展。

Soil total organic carbon and its light fractions in response to 14 years of conservation tillage

The study was carried out on a long-term field experiment set up in 2001 in Dingxi,which is a typical semiarid rainfed agriculture area on the western Loess Plateau .The objective of the experiment was to determine the effect of conventional and conservation tillage practices on soil organic carbon (SOC)and light fraction organic carbon (LFOC) in surface soil of wheat-pea double sequence rotation system .The experiment was laid out in a randomized complete block design with four replications .Treatments included six types of tillage practices;conventional tillage with no straw (T),no-tillage with no straw mulching (NT),conventional tillage with straw incorporation (TS),no-tillage with straw mulching (NTS),conventional tillage with plastic film mulch (TP),no-tillage with plastic mulching (NTP).The main results were as follows:(1)the soil SOC and LFOC content decreased with increasing soil depth;(2)compared with the conservation tillage,no tillage with stubble incorporated (NTS)and tillage with straw incorporation improved soil SOC and LFOC,it has increased by 19.51%,13.36%and 64.58%,42.08%before sowing,increased by 28.00%,18. 61%and 85.37%,77.82%after harvest.However,no-till without straw incorporated (NT)and conventional tillage with plastic film mulch (TP)did not show obvious effect;(3)the SOC content from sowing to harvest exhibited a down-ward tendency,with the minimum change occurring in NTS and TS;but NT and TP expanded the consumption of SOC during crop growth stage .(4)LFOC was sensitive as an indicator of soil organic carbon .