生物质炭对黄瓜连作土壤理化性状、酶活性及土壤质量的持续效应

【目的】 探讨不同生物质炭施用量对连作黄瓜根区土壤环境的作用效果，为用生物质炭修复黄瓜连作土壤以及在农业中的推广应用提供科学依据。 【方法】 以如皋市农业科学研究所大棚示范区为试验基地，一次性向设施农田土壤中添加0 (CK)、5 (C1)、10 (C2)、20 (C3)、30 (C4)、40 (C5) t/hm2的生物质炭，通过连续两年温室定位试验，测定生物质炭施用后黄瓜连作根区土壤的物理性状、养分含量及酶活性的变化状况，采用土壤质量指数 (SQI) 评价不同生物质炭施用量对黄瓜连作两季后土壤质量的影响。 【结果】 随着生物质炭施用量的增加，第一季与第二季黄瓜根区土壤的理化性状变化趋势一致，具体表现为容重不断降低，土壤孔隙度、饱和含水量、田间持水量、饱和导水率、有效磷及有机质含量不断升高，且当生物质炭施用量为30 t/hm2(C4处理) 时，土壤中全氮、硝态氮和铵态氮含量最高。与CK相比，生物质炭的施用可以减少黄瓜根区土壤 < 0.25 mm粒径的微团聚体含量，而增加 > 0.25 mm粒径的大团聚体含量，土壤中0.25～0.5 mm和0.5～1 mm粒径的团聚体含量都在高施用量 (40 t/hm 2) 处理中达到最大值。生物质炭施用后的连续两季，黄瓜根区土壤中脲酶与过氧化氢酶活性均随生物质炭施用量的增加呈先增加后降低的趋势，其活性分别在生物质炭施用量为30 t/hm2和20 t/hm2时最大。当生物质炭施用量为30 t/hm2时，两季黄瓜产量都达到最高，分别为3.24 × 104 kg/hm2和6.18 × 104 kg/hm2。通过土壤质量指数 (SQI) 对生物质炭施用后两季黄瓜土壤质量进行评价可知，不同生物质炭施用水平下土壤质量指数依次为C4 > C5 > C3 > C2 > C1 > CK，相应的土壤质量指数分别为0.774、0.740、0.728、0.650、0.635、0.583。 【结论】 施用生物质炭对黄瓜连作田土壤的理化性状和酶活性均有显著影响，高施用量 (40 t/hm2) 条件下对土壤物理性状改善效果最好，当生物质炭施用量为30 t/hm2 (C4处理) 时对黄瓜连作根区土壤的养分含量提升效果最佳。SQI可以客观定量地评价生物质炭施用对连作黄瓜根区土壤质量的影响，其分析结果表明改善黄瓜连作土壤环境的最佳生物质炭施用量为30 t/hm2。

Sustained effects of biochar application on physico-chemical properties,enzyme activities and quality of soil with continuous planting of cucumber

【Objectives】 This study investigated the sustained effects of biochar application on properties of root zone soil continuously planted with cucumber, providing scientific evidences for biochar remediation of continuous cucumber planting soil and widely use in agriculture. 【Methods】 A greenhouse experiment was conducted at Rugao Institute of Agricultural Science, Jiangsu province. Biochar was applied only once at rates of 0, 5, 10, 20, 30, and 40 t/hm2, denoted as CK, C1, C2, C3, C4 and C5, respectively, and physical properties, nutrient contents and enzyme activities of root zone soils continuously planted with cucumber were analyzed in two consecutive years. The soil quality index (SQI) was used to evaluate the impact of different rates of biochar on quality of soil continuously planted with cucumber. 【Results】 The changes of soil physico-chemical properties with different rates of biochar in the first season were consistent with that in the second season. Biochar application reduced the soil bulk density, while increased the soil porosity, saturated water content, field moisture capacity, saturated hydraulic conductivity, available phosphorus and organic matter content, compared with the control without biochar application. The contents of total nitrogen, nitrate nitrogen and ammonium nitrogen were greatest when biochar was applied at 30 t/hm2. Compared with the control, biochar application reduced the mass content of < 0.25 mm soil aggregates, while increased the content of > 0.25 mm soil aggregates. The contents of 0.25–0.5 mm and 0.5–1 mm soil aggregates were greatest when biochar was applied at 40 t/hm 2. soil urease and catalase activity was greatest at biochar rates of 30 t/hm2 and 20 t/hm2, respectively, and showed the same trend of increasing at first and then decreased with increase rate of biochar in consecutive two cropping seasons. Cucumber yield in first and second seasons was 3.24 × 104 kg/hm2 and 6.18 × 104 kg/hm2, respectively, and was highest when biochar was applied at 30 t/hm2. The analysis of SQI indicated that soil quality change in the order of C4 > C5 > C3 > C2 > C1 > CK. 【Conclusions】 The physico-chemical properties and enzymatic activities of the continuous cucumber cropping soil were significantly affected by biochar application. The optimal application rate of biochar was 40 t/hm2 and 30 t/hm2, respectively for soil physico-chemical properties and nutrient contents. The SQI can be used to clearly evaluate the effect of biochar application on continuous cucumber cropping soil. Biochar at 30 t/hm2 was optimal in improving the properties of continuous cucumber cropping soil.