基于三七连作障碍的土壤理化性状及酶活性研究

Properties of Soil Physical-Chemistry and Activities of Soil Enzymes in Context of Continuous Cropping Obstacles for Panax notoginseng

为评价三七(Panax notoginseng(Burk)F.H.Chen)连作对土壤理化性状及土壤酶活性的影响,分析了三七不同种植年限及连作土不同治理方法的土壤理化性状和酶活性,从而为部分解析三七连作障碍形成机制及为缓解并克服连作障碍提供理论依据。结果表明,随着三七种植年限的增加,土壤p H呈显著下降趋势,土壤酸化现象加重;种植三七1年、2年和3年的土壤与未种植过三七的土壤相比有机质含量分别下降73%、87%和83%,并伴随着土壤的板结。与生土和健康土相比,大量元素氮(N)和磷(P)含量在种植三七的土壤及发病土壤中显著下降。铁(Fe)、硼(B)、铝(Al)等元素在种植三七的土壤中却显著升高,种植三七3年的土壤与生土相比,Fe、B、Al分别上升29%、31%、32%。土壤蛋白酶、过氧化氢酶、蔗糖酶、磷酸酶及脲酶活性随着三七种植年限的增加均显著降低,种植三七3年的土壤中,其土壤蛋白酶、过氧化氢酶、蔗糖酶、脲酶及磷酸酶较未种植过三七的土壤分别下降91%、56%、52%、92%、92%和69%;而发病植株根际土壤的过氧化氢酶、蔗糖酶、磷酸酶活性高于健康植株根际土壤的酶活性,其中发病土壤的蔗糖酶活性较健康土高出42%;连作植株根际土壤与经消毒治理后的植株根际土壤相比,脲酶、蛋白酶、多酚氧化酶及过氧化氢酶活性显著较高。研究结果还显示,土壤酶活性与土壤p H、有机质含量、N、P、K及一些微量元素(如:钼、铜)之间存在显著相关关系。本研究结果暗示,三七连作后导致了土壤酸化和板结现象加重及土壤矿质元素组成失衡和某些元素的富集,这可能是诱导三七连作障碍发生的原因之一;另外,三七种植年限增加明显抑制土壤酶活性,这将阻碍三七对某些营养元素的吸收及间接加剧土壤自毒物质的积累,从而也可能诱导连作障碍的发生。

In order to evaluatethe effect of continuous cropping of Panax notoginseng on soil physical-chemical and activities of soil enzymes, in this paper, physical-chemical properties and enzyme activities were analyzed in rhizosphere soil collected from plots whereP. notoginsenghas been cropped for different years and in soil that has been managed with different remedies. The objectives of the present study were to explain the underlying mechanism of continuous cropping obstacle and to provide a theoretical basis for a method to relieve and overcome the continuous cropping obstacle ofP. notoginseng. The result shows that soil pH decreased and soil acidification increased as the cropping time increased. When compared with the uncultivated soil of organic matter, 1-, 2-, and 3-year-cultivated soil of organic matter were decreased by 73%, 87% and 83% , and the cultivated soil had a tendency for hardening. The content of N and P were significantly decreased in the cultivated soil and diseased soil when compared with the uncultivated soil and healthy soil. While the contents of Fe, B and Al were significantly increased by 29%, 31%, 32% respectively, when compared with the uncultivated soil. Acvitivies of protease, catalase, sucrase, phosphatase, and urase in soil significantly decreased as the cropping time proceeded. Activities of protease, catalase, invertase, urease and phosphatase were decreased by 91%, 56%, 52%, 92%, 92% and 69% in the 3-year-cultivated soil ofP. notoginseng than in the uncultivated soil of ones. Activities of catalase, sucrase and phosphatase in diseased soil were higher than those in healthy soil, and the activity of invertase in the former was higher than in the latter even by 42%. In comparison with the continuous cropping soil, the disinfection-treated soil showed the significantly higher activities of urease, protease, polyphenol oxidase and catalase. In addition, the activities of enzyme in soil were significantly correlated with soil pH and contents of organic matter, N, P, K, and some microelements （e.g. Mo and Cu）. The results obtained here indicated that continuous cropping ofP. notognseng aggravate soil acidification and hardening and result in the imbalance of soil mineral elements and the enrichment of some elements, this may induce the continuous cropping obstacle ofP. notoginseng. On the other hand, the activities of enzymes in soil were inhibited by the continuous cropping, this would hinder the absorption efficiency of P. notoginseng for some elements and increase the accumulation of soil autotoxic compounds, this may also induce the continuous cropping obstacle.