秸秆直接还田及炭化还田对土壤酸度和交换性能的影响

Direct returning of maize straw or as biochar to the field triggers change in acidity and exchangeable capacity in soil

【目的】本研究旨在通过连续4年田间微区定位试验,比较等氮磷钾养分条件下秸秆炭化还田与等量秸秆直接还田对土壤酸度及交换性能的影响,以期为土壤酸化改良及秸秆、生物炭资源合理利用提供理论依据。【方法】试验以沈阳农业大学植物营养与肥料研究所玉米渗滤池微区定位试验为基础,共设6个处理,分别为不施肥(CK)、氮磷钾配施(NPK)、单施生物炭(C)、生物炭+NPK(CNPK)、单施秸秆(S)、秸秆+NPK(SNPK)。其中NPK、CNPK和SNPK处理养分投入总量相等,均为N 225 kg/hm^2、P2O5 112.5 kg/hm^2和K2O 112.5kg/hm^2,S处理秸秆施用量为4500 kg/hm^2,单施生物炭处理生物炭施用量为1500 kg/hm^2。应用化学分析法对土壤活性酸、交换性酸、阳离子交换量及交换性盐基离子进行分析和测定。【结果】经过连续4年的不同施肥处理,施用生物炭及秸秆均显著提高了土壤pH,降低了土壤交换性酸总量和交换性铝含量,但各处理间交换性H+含量差异不显著。相较于试验前土壤(pH 6.05),单施生物炭和单施秸秆处理分别使土壤pH提高了0.55和0.45个单位。在等氮磷钾养分条件下,CNPK和SNPK处理较试验前分别使土壤pH提高了0.31和0.13个单位,且CNPK处理显著高于SNPK,但二者之间对土壤交换性酸含量的影响无显著差异。同时各处理交换性盐基离子总量均显著高于CK,单独施用生物炭对提高土壤盐基总量、交换性Ca2+和交换性Mg2+的效果显著优于单独施用秸秆。在等秸秆量与等氮磷钾养分条件下,秸秆炭化还田及秸秆直接还田较不施肥对照分别使交换性盐基总量提高了17.6%和15.1%,且秸秆炭化还田对提高土壤有效阳离子交换量的效果显著优于秸秆直接还田。与CK处理相比,C、CNPK、S和SNPK处理分别使土壤阳离子交换量提高了1.68、2.52、1.53、2.30cmol/kg,其中以CNPK处理效果最佳。【结论】在等秸秆量和等氮磷钾养分条件下,施用生物炭和秸秆能有效降低土壤酸度和交换性酸中交换性铝含量,提高土壤盐基离子含量及交换性能,且秸秆炭化还田的效果更为明显。

【Objectives】The study compared the effects of straw return or biochar of maize on the changes of soil acidity and exchangeable capacity at the same application rate of NPK in the field micro-plots,thus providing a theoretical reference in rational utilization of straw and biochar for the alleviation of soil acidification.【Methods】A located micro-plot experiment was conducted for four consecutive years in the Experimental Station of Institute of Plant Nutrition and Fertilizer,Shenyang Agricultural University.Six treatments were setup,including no fertilizer(CK),nitrogen,phosphorus and potassium(NPK),biochar(C),NPK with biochar(CNPK),straw(S),and NPK with straw(SNPK).The nutrient inputs in treatments of NPK,CNPK and SNPK were all N 225 kg/hm2,P2O5 112.5 kg/hm2 and K2O 112.5 kg/hm2,the straw input in S treatment was 4500 kg/hm2 and the biochar input in C treatment was 1500 kg/hm2.Changes in active acid,exchangeable acid,CEC and baseexchangeable ions in soils were evaluated.【Results】The application of biochar or straw enhanced soil pH,and decreased the contents of exchangeable acid and exchangeable aluminum in soil,but did not affect the contents of exchangeable H+in all the treatments after continuous experiment of four years.The C and the S treatments increased soil pH by 0.55 and 0.45 units,respectively;but the CNPK and SNPK treatments only increased soil pH by 0.31 and 0.13 units relative to the pH before the experiment(6.05),respectively.Soil pH value in the CNPK was significantly higher than that in the SNPK,but no significant difference in soil exchangeable acid contents was observed between the two treatments.The total base-exchangeable ions in all treatments were significantly higher than those in the control.The C treatment significantly increased the amounts of base-exchangeable ions,exchangeable Ca2+and Mg2+compared to the S treatment.Under equal amounts of straw and NPK nutrients,the amounts of base-exchangeable ions in the CNPK and SNPK treatments were increased by 17.6%and 15.1%compared with CK,respectively,suggesting that straw carbonization returning was greatly beneficial to increasing the soil CEC,which were increased by 1.68 cmol/kg in the C treatment,2.52 cmol/kg in the CNPK treatment,1.53 cmol/kg in the S treatment and 2.30 cmol/kg in the SNPK treatment compared with the CK,respectively,and the CNPK exhibited the highest soil CEC.【Conclusions】When equal amounts of straw and NPK nutrients were applied,both the biochar and straw returning could reduce soil acidity and the contents of exchangeable aluminum in exchangeable acid,and increase the accumulation of base-exchangeable ions and exchangeable capacity in soil,indicating the improvement effects of biochar in alleviating soil acidity were very remarkable.