施加生物炭对黑土区坡耕地改土培肥效应的持续影响

Continual Influences of Applying Biochar on Soil Improvements in Sloping Farmland of Black Soil Region in Northeast China

为探明施加生物炭对黑土坡耕地的持续影响,以东北黑土区1.5°、3°、5°的坡耕地田间径流小区为研究对象,对土壤结构及其养分进行为期4年的观测。于2016年试验开始前,按75 t/hm2一次性施加玉米秸秆生物炭,各坡度均设置不施加生物炭的对照组,共计6个小区,后续年份不再施加生物炭。结果表明,单次施加生物炭能够提高土壤气相、液相比例,提高通气性和持水能力,改善土壤三相比例,较对照组土壤孔隙度提高2.83%~5.56%,土壤容重降低1.89%~3.62%。施炭后土壤中有机质、铵态氮、速效钾含量显著提高,分别提高9.54%~18.21%、21.35%~28.02%、11.99%~22.71%。各项指标均随着时间的推移有所降低。采用随机森林回归模型评估得出综合肥力等级指数,并拟合回归方程预测2020—2022年等级指数,比较肥力变化情况得出单次施用生物炭对培肥土壤作用的有效年限为6~7年。

In order to ascertain the sustained influence of the application of biochar on sloping farmland in black soil region of Northeast China,field runoff plots with 1.5°,3°and 5°of typical slops in the region was chosen,where the 4-years experiments were conducted,and soil structure and soil nutrients were observed.In 2016,before the start of the experiment,biochar derived from corn straw was applied with 75 t/hm 2 in the soil,and a control group was without biochar application on each slope plots,counted up to six plots.Biochar was not applied in subsequent years.The results showed that the application of biochar can increase soil gas phase and liquid phase ratio,improve soil aeration,improve soil three-phase ratio,and then increase porosity by 2.83%~5.56%and decrease bulk density by 1.89%~3.62%.The contents of organic matter,ammonium nitrogen and available potassium in the soil were significantly increased after the application of biochar,increased by 9.54%~18.21%,21.35%~28.02%,and 11.99%~22.71%,respectively.And the effects of above was weakened with time.A random forest regression model was used to evaluate the comprehensive fertility grading indexes and fit the regression equation to predict the indexes of 2020—2022.Comparing fertility changes,it was concluded that the reasonable and effective life for one time application of biochar on soil fertility in the region would be 6~7 years.