【作者】 李敏；

【导师】 李长田；

【作者基本信息】 吉林农业大学 ， 生态学， 2012， 硕士

【摘要】 连作是目前影响农业生产,造成农田生态环境破坏的主要原因之一,连作障碍是土壤-病原菌-植物三个系统内部诸多因素综合作用的结果。本试验通过对土壤微生物区系、理化性状、土壤有机化合物组成以及根系分泌物的化感作用等内容进行研究,探索连作对土壤环境改变而引发连作障碍的机理,主要研究结果如下：1.对五个主产区的土样中微生物数量的统计结果都显示出连作引起土壤真菌数量增加、细菌数量减少的趋势。连作对土壤放线菌数量的影响在不同地区显示出不同的结果,山东金乡有的样地显示出连作使放线菌数量减少,有的样地则无显著差异。江苏邳州也显示出连作使放线菌数量减少,而河南中牟、河北永年、江苏射阳的试验结果则显示连作使放线菌数量增加。这说明连作对土壤放线菌数量的影响较为复杂,可能是土壤环境、微生物区系等多方面因素共同作用的结果。2.五个主产区中只有邳州连作样地pH略高于非连作样地,其他四个地区连作样地pH均低于非连作样地。说明大蒜多年连作会导致土壤pH下降,但不是必然规律,土壤pH显然还受其他因素影响。金乡、中牟、永年、射阳四个大蒜主产区的非连作样地中速效N、P、K的含量高于连作样地。邳州连作样地中速效N少于非连作样地,速效P、速效K含量无明显规律。结合五个大蒜主产区的整体情况,大蒜连作会导致土壤中速效N、P、K的含量降低,土壤养分亏缺,影响大蒜的正常生长。3.大蒜种植的土壤中有机化合物主要有十二烷、十三烷、十四烷等烷烃类；十二醇等醇类、邻苯二甲酸二异丁酯、软脂酸甲酯、硬脂酸甲酯等酯类；2,6-二叔丁基苯酚等酚类、1-甲氧基-4-(1-丙烯基)苯等苯类,非连作土样和连作土样有一定的成分差异,但无明显规律性。金乡所取的四个样地土样中均含有2,6-二叔丁基苯酚和邻苯二甲酸二异丁酯,这两种物质都被报道是化感物质,能抑制植物的光合作用。研究表明大蒜根系分泌物中含有这两类物质,这就表明连作土壤中的大蒜根系分泌物的积累,可能影响大蒜正常生长,造成连作障碍。4.大蒜根系分泌物不仅对不同属作物白菜的种子萌发产生抑制作用,而且对同属作物小葱、韭菜的抑制作用更为明显。当大蒜根系分泌物浓度较低时,对小葱的发芽起到了促进作用,但对白菜和韭菜仍是抑制作用。低浓度根系分泌物对种子萌发的促进作用可能与根系分泌物中的一些营养物质为种子提供了有效的能源有关。大蒜根系分泌物对同属作物显示出的化感作用,为研究大蒜连作中根系分泌物的影响作用提供了理论依据。更多还原

【Abstract】 Continuous cropping is one of the main reasons for the destruction of farmland ecological environment; it influences the agricultural production seriously. Continuous cropping obstacle was affected by many factors in the system of soil-pathogens-plant. In this paper, the soil microflora, soil physical and chemical properties, the composition of soil organic compounds and the allelopathy of root exudates were studied to explore the reasons of continuous cropping obstacle. From this paper, some conclusions are acquired as follows:1.In the five main producing areas, the number of soil fungi was lager after continuous cropping, and the number of soil bacterium was reduced. The influence of continuous cropping on the number of soil actinomycetes was different in different areas. This showed that the impact on soil actinomycetes was complicated, may be resulted by the soil environment, microbial flora and other factors.2. In the five main producing ares, only Pizhou’s continuous cropping soil pH slightly higher than the non-continuous cropping soil samples, in the other four ares, the continuous cropping soil pH were lower than the non-continuous cropping soil samples. Continuous cropping of garlic lead to the soil pH decreased. But the soil pH was obviously also affected by other factors.Combined with the conditions of five main producing areas of garlic, continuous cropping caused the contents of available N, P and K decreased, nutrients deficient in soil, affected the normal growth of the garlic.3. In the soil which planted garlic, the main organic compounds are alkenes, alcohols, esters, phenols, benzene and so on. There were some different between the four soil samples, but no regular pattern were found. There were2,6-Di-tert-butylphenol and diisobutyl phthalate in the four soil samples, they are allelochemicals. Studies have shown that garlic root exudates contain these two allelochemicals. It showed that the accumulation of garlic root exudates in soil may affect the normal growth of Garlic, resulted in continuous cropping obstacles.4. Garlic root exudates not only inhibited the germination of Cabbage seed, but also inhibited Shallot and Chinese chive, which belong to the same genera with Garlic. The low concentration of Garlic root exudates played a catalytic role on the germination of onion, may be related to some of the nutrients in the root exudates provide an effective energy to seeds.更多还原