不同耕作措施对甘肃引黄灌区耕地土壤有机碳的影响

为了探明不同耕作措施对甘肃引黄灌区耕地土壤有机碳的影响,2014-2017年在连续翻耕8a的玉米地上设置翻耕(CT)、旋耕(RT)、深松(ST)、免耕(NT)4个单一耕作处理和翻耕-免耕(CT-NT)、深松-免耕(ST-NT)2个轮耕处理开展了研究。结果表明,连续免耕(NT)显著增加了0～40cm土层有机碳含量和有机碳储量(P0.05),平均比CT增加4.45%和5.27%,比RT增加7.23%和8.50%;连续深松(ST)也有较好的固碳效果,在4个单一耕作措施中仅次于NT;连续翻耕(CT)和旋耕(RT)显著降低了土壤有机碳含量和有机碳储量(P0.05),RT的降低幅度大于CT。CT-NT和ST-NT2个轮耕处理既有较好的固碳效果,又符合当地农民操作习惯,有机碳含量分别比CT增加2.44%和4.82%,比RT增加5.12%和7.55%;有机碳储量比CT增加2.50%和5.47%,比RT增加5.64%和8.70%。不同耕作制度会使土壤有机碳发生层化,但有机碳含量的层化更多表现在不同土层之间,相同层次各处理之间变化不大;而有机碳储量只在耕层以下发生了层化,相同土层各处理之间也表现出比较明显的层化特征。因此,综合分析认为,任何一个单一耕作措施都有其局限性,CT-NT和ST-NT是比较理想的耕作模式,在该区域农业可持续发展中具有一定的应用价值。

Effects of different tillage practices on soil organic carbon of cultivated land in Gansu Yellow River irrigation district

It is necessary to improve plough layer for solving the problems of shallow and compacted plough layer and plough layer lack, which are caused by a long-term single rotation and shallow tillage. In order to examine the effects of different tillage practices on soil organic carbon contents and storages, soil organic carbon stratification ratio of cultivated land, four single tillage treatments and two rotational tillage treatments were conducted including conventional tillage (CT), rotary tillage (RT), subsoiling tillage (ST), no tillage (NT) treatment and conventional tillage -no tillage (CT-NT), subsoiling-no tillage (ST-NT) in Gansu Yellow River irrigation district on continuous 8-year-tillage cornfields from 2014 to 2017. The results showed that the 0-40 cm layers organic carbon contents and storages of continuous no-tillage (NT) were significantly increased by 4.45% and 5.27% compared with CT, 7.23% and 8.50% compared with RT. Continuous subsoiling tillage (ST) also had a good carbon sequestration effect, second only to NT in four single tillage practice, the organic carbon contents and storages were significantly increased by 2.28% and 4.03% compared with CT, 3.52% and 7.22% compared with RT. Continuous conventional tillage (CT) and rotary tillage (RT) both significantly reduced soil organic carbon contents and storages, the decreases of soil organic carbon contents and storages were 2.79%, 2.32% and 1.18% , 0.62% respectively, and the reduction of RT were greater than CT. The two rotational treatments of CT-NT and ST-NT both had good carbon sequestration effect, and also accorded with the local farmers operating habits, the organic carbon contents were significantly increased by 2.44% and 4.82% compared with CT, and 5.12% and 7.55% compared with RT respectively, and the organic carbon storages increased by 2.50% and 5.47% compared with CT, and 5.64% and 8.70% compared with RT. The soil organic carbon were stratified by different tillage practices, the stratification of SR·Cc(stratification ratio of organic carbon content )showed significant difference from the first year, but the stratification of SR·esm (stratification ratio of organic carbon storage)came to this until the third year. The stratification of organic carbon contents were more manifested in different soil layers, the mean values of SR3 and SR2 were respectively higher 29.12% and 9.32% than those of SR1(The ratio of organic carbon content in soil layer of 0-10 cm to 10-20 cm), but there were little change between treatments at the same level. However, the organic carbon storages were stratified only below the topsoil, the mean value of SR2 (The ratio of organic carbon storage in soil layer of 0-10 cm to 20-30 cm)same as SR1, but SR3 (The ratio of organic carbon reserves in soil layer of 0-10 cm to 30-40 cm) was higher 17.82% than SR1. Moreover, the stratified characteristics were obvious among the same layers, RT was significantly lower and NT was significantly higher than other treatments at the same level. We consider the most typical reason for this situation was the soil bulk density between different tillage treatments in calculating the SR·esm. As for which calculation method can better represent the stratification characteristics of soil organic carbon, more in-depth research is needed. Therefore, any single tillage measure has its limitations, and the two rotational tillage treatments of CT-NT and ST-NT are ideal tillage practices, which had certain application value in this regional agricultural development.