秸秆直接还田和炭化还田对红壤酸度、养分和交换性能的动态影响

Dynamic Effects of Direct Returning of Straw and Corresponding Biochar on Acidity,Nutrients,and Exchangeable Properties of Red Soil

为比较秸秆直接还田和炭化还田对亚热带典型红壤酸度、养分及交换性能的动态影响,试验以水稻和油菜秸秆为材料,设置7个盆栽处理:空白(CK)、水稻秸秆直接还田(R1B0)、水稻秸秆350℃炭化还田(R1B1)、水稻秸秆550℃炭化还田(R1B2)、油菜秸秆直接还田(R2B0)、油菜秸秆350℃炭化还田(R2B1)和油菜秸秆550℃炭化还田(R2B2),秸秆按1%和相应的生物质炭施入土壤,进行水稻培育试验.在水稻秧苗期、分蘖期、灌浆期和成熟期这4个时期采集土壤,分析土壤酸度、养分和交换性能的动态变化.结果表明,红壤pH、NH+4^-N和NO-3^-N含量随生长期呈现减小的趋势,而有机质、CEC和各交换性盐基离子呈现增加的趋势.秸秆直接还田和炭化还田均提高土壤pH,降低交换性酸总量,同时提高有机质含量及交换性能,且作用效果随生长期增大.成熟期时秸秆炭化还田对各项指标的作用效果均好于秸秆直接还田,秸秆原料和炭化温度对各项土壤性质的影响不同,油菜秸秆生物质炭在提高土壤pH、有机质和CEC含量方面略好于水稻秸秆生物质炭.土壤酸度、养分含量和交换性能等因子的相关分析表明,土壤交换性酸与有机质呈极显著负相关关系(R=-0.912,P<0.01),与CEC呈显著负相关关系(R=-0.866,P<0.05),CEC和有机质呈显著正相关关系(R=0.833,P<0.05),说明三者之间密切相关.研究表明,秸秆直接还田和炭化还田均可以达到改良土壤酸性和提高养分含量的效果,在等量秸秆情况下,秸秆炭化还田对阻控土壤酸化、提高有机质含量和CEC的效果比秸秆直接还田较为明显.

To compare the dynamic effects of straw and corresponding biochar on soil acidity,nutrients,and exchangeable capacity in red soil,a pot experiment was performed.The treatments included control(CK),rice straw(R1 B0),rice straw biochar prepared at 350℃(R1 B1)and 550℃(R1 B2),rape stalk(R2 B0),and rape stalk biochar prepared at 350℃(R2 B1)and 550℃(R2 B2).Straw at 1%and corresponding biochar were added to a strongly acidic red soil.The rice was planted as the experimental crop.Soils were collected at the seedling,tillering,filling and mature stages of rice growth,respectively.The changes in soil pH,exchangeable acidity,organic matter,nutrients(NH+4^-N and NO-3^-N),and exchangeable cations in soils were measured.The results showed that soil pH,NH+4^-N,and NO-3^-N concentrations decreased with the growth period of rice,while the organic matter content and cation exchange capacity(CEC)increased.Direct returning of straw and biochar could increase soil pH,organic matter content,and exchangeable cations content,and reduce the total amount of exchangeable acids.In the mature stage of rice,rice straw and rape stalk biochar at 350℃increased the soil pH by 0.29 and 0.42,respectively,compared to the control treatment.Similarly,biochar decreased the exchangeable acidity and exchangeable Al3+content significantly compared to the direct returning treatments of straw.The exchangeable acidity and exchangeable Al3+contents of soils in R1 B2 and R2 B1 treatments decreased by 54.8%and 58.9%,respectively,compared to the control treatment.The soil organic matter(SOM)content and CEC in biochar treatments were significantly higher than those in direct returning treatments of straw.Overall,the effects of rape stalk biochar on soil properties were slightly stronger than those of rice straw.The correlation analysis showed that soil exchangeable acids had a significantly negative correlation with organic matter(R=-0.912,P<0.01),and CEC(R=-0.866,P<0.05).The CEC in soils was positively related to organic matter(R=0.833,P<0.05).Direct returning of straw and biochar applications can effectively improve soil acidity and increase nutrient contents.The effects of straw biochar on soils were stronger than the direct returning of straw in decreasing soil acidity,and increasing soil organic matter content and exchangeable capacity in acidic soils.