保护性措施对中低肥力黑土区有机质变化的影响

为探索农户采用保护性措施对东北黑土区土壤有机质(SOM)变化的影响,通过跟踪2008年至2015年间梨树县19个乡镇341块农田SOM的变化,分析了免耕、秸秆还田和有机肥施用三项保护性措施采用情况对SOM变化的影响。2015年梨树县SOM平均为18.8 g·kg^-1,较8年前下降了10.5%(P<0.05)。土壤初始SOM含量越高,其SOM下降越明显。在初始SOM>20 g·kg^-1的区域,SOM显著降低,但在初始SOM≤20 g·kg^-1的区域,SOM含量较2008年提升了4.5%(15.3 g·kg^-1)。主要是因为SOM≤20 g·kg^-1区域采用过保护性措施的农户比例高达63.2%,而SOM>20 g·kg^-1区域农户采用比例为49.3%。同时发现在初始SOM较低的土壤,采用单项保护性措施可以维持甚至提高SOM,同时采用三项措施显著提升了SOM。但在初始SOM较高的土壤,两项措施结合才可维持SOM不下降。目前梨树黑土区保护性措施的采用可以维持甚至提高SOM,但在应用时需要加强应用时间的连续和技术间的集成。

Effect of conservation practices on soil organic matter in medium or low fertility black soil

In order to explore the effect of conservation practices on soil organic matter in the black soil area of northeast China,the soil or ganic matter(SOM)from 341 sites across 19 townships of Lishu County were tracked in 2008 and 2015,and the SOM change was analyzed which was affected by three conservation practices,including no-tillage,straw return and manure application.Compared to the initial in 2008,the average SOM content decreased by 10.5%with an average of 18.8 g·kg^-1 in 2015.The higher the initial organic matter content was,the more obvious the decrease was.Significant decrease were found in the groups of initial SOM>20 g·kg^-1.However,in groups of ini tial SOM≤20 g·kg^-1,the SOM increased by 4.5%compared with that in 2008(15.3 g·kg^-1).The main reason is that the proportion of con servation practices adopted by farmers in the groups of SOM≤20 g·kg^-1 was as high as 63.2%,which was much higher than that in the groups of SOM>20 g·kg^-1(49.3%).Furthermore,the soil fertility could be improved by the combination of two practices in areas with low initial SOM,and SOM was significantly enhanced by three measures using together.But in areas with high initial SOM,these two practices contributed only to maintaining soil fertility.Now,SOM of black soil area of Lishu could keep up and even increase by using conservation practices,but we need to strengthen technological integration and continuous adoption.