Effects Of Different Allelopathic Wheat Root Exudates On Cucumber Growth And Soil Quality

As one of the most popular greenhouse plants, cucumber accounts for 60% of facility cultivated area. Not only because of the contradiction between the increasing market demand and limited arable land, but also driving by cultivation habits and economic benefits, soil sickness of cucumber is common, which leads to the severe continuous cropping obstacle. The new study suggests that the rotation and intercropping of the cucumber and wheat help to improve the soil environment of cucumber and enhance the quality and quantity of cucumber.This experiment attempts to analysis the allelopathy effect of different cultivars of wheat root exudates on cucumber, screen out two different cultivars of wheat which made great allelopathy effect on the growth of cucumber, explore the influence of wheat root exudates on the growth of cucumber and the soil environment. Through explaining the allelopathy effect of wheat root exudates on cucumber and soil environment, the author tries to provide theory basis for the establishing and popularizing of the rational cultivation system. Main results of this paper were as flowing:1. According to the synthesize effect value of allelopathy index on cucumber which collected from 40 wheat cultivars, 70.25 % of root exudates of wheat cultivars play a positive role in synthesized allelopathy effects of cucumber seedlings. In the 40 wheat cultivars, Longfu 04-0348(L11) had the most significant stimulatory effect, and Longfu 17 had the most significant inhibitory effect.2. The Wheat root exudates which play an active allelopathy show excellent acceleration effect on stem length stem diameter, belowground dry weight of cucumber seedlings. The Wheat root exudates which play inhibitory effect show that during the early stage exudates restrained the growth of stem length, stem diameter, aboveground dry weight of cucumber seedlings, while during the late stage exudates accelerated these index.The main disease and economic yield of cucumber were not obvious changed.3. The Wheat root exudates increase the soil PH value of cucumber seedlings first and then decrease, while decrease the soil EC value of cucumber seedlings first and then increase. The Wheat root exudates which play an active allelopathy increase the content of available Nitrogen, Phosphorus and Potassium in cucumber seedlings soil. The Wheat root exudates which play inhibitory effect decrease the content of available available Nitrogen, Phosphorus first and then increase, but increase the content of Potassium first and then decrease. Wheat root exudates decrease the content of available Nitrogen, Phosphorus and Potassium in cucumber non-seedlings soil first and then increase. The change of soil organic matter is not obvious. 4. The wheat root exudates increased cucumber urease activity in cucumber seedlings and non-seedlings soil, however decreased catalase activity first and then increased. The Wheat root exudates which play an active allelopathy increased neutral phosphatase activity in cucumber seedling and non-seedling soil and then decreased. The Wheat root exudates which play inhibitory effect decreased neutral phosphatase activity in cucumber seedling oil first and then increase. At the same time, it increased neutral phosphatase activity in cucumber non-seedling soil and then decreased. The Wheat root exudates exhibited the significant inhibition on soil dehydrogenase activity in early stage and gradually increased in late stage.5. The Wheat root exudates reduced fungi quantity in cucumber seedlings and non-seedlings soil. The Wheat root exudates which play an active allelopathy effect decreased the number of bacteria in cucumber seedlings soil and then increased, meanwhile, decreased the number of actinomycetes. It increased the number of bacteria in cucumber non-seedlings soil, at the same time increased the number of actinomycetes first and then decreased. It had an unconspicuous effect on biomass of C, N in soil microorganism. The Wheat root exudates which play inhibitory effect increased the number of bacteria in cucumber seedlings soil, increased the number of actinomycetes and then decreased. It increased microorganism biomass of C, N in seedling and non-seedlings soil. Almost all the Wheat root exudates decreased DGGE profile bands and diversity index in cucumber seedlings soil at the beginning and then decreased. Besides, exudates increased DGGE profile bands and diversity index in cucumber non-seedlings soil.6. With wheat intercropping treatments, alkali-hydrolyzable nitrogen, available phosphorus, available K, organic matter, pH value increased and decreased EC value. The activity of urease, neutral phosphatase and dehydrogenase was strengthened. The number of bacteria and microorganism biomass of C, N in soil were grown. By interplanting wheat which play an active allelopathy effect, the number of fungi in cucumber soil was decreased, the number of actinomycetes, catalase activity, DGGE band numbers and diversity indices of the soil bacteria were increased. Meanwhile, Cucumber production rose by 2.9%. By interplanting wheat which plays inhibitory effect, the number of fungi and actinomycetes was increased, but the DGGE band numbers and diversity indices were decreased. As a result, Cucumber production rose by 25.5%.