Effects Of Crop Rotation And Fallowing On Soil Characteristics And Growth Of Cucumber In Continuous Cropping In Solar Greenhouse

Continuous cropping barrier has increasingly become an important factor to limit sustainable development of vegetable production in greenhouse. Cucumber is a main type of vegetable in Northern China greenhouse, and also is one of the types in which continuous cropping barrier is severe. By pot experiments, effects of crop rotation of welsh onion, cowpea, tomato and waxy maize with cucumber and fallowing on soil characteristics and growth of cucumber in solar greenhouse were studied, and improving efficiency of continuous cropping soil were compared. It aimed to provide theoretical foundation for establishing reasonable systems of cultivation, reducing or conquering soil obstacle, and achieving sustainable production. The main results were as follows:1. Compared with continuous cropping, crop rotation could reduce the bulk density and increase the porosity of soil at different degree, but fallowing could increase the bulk density and reduce the porosity of soil. Crop rotation and fallowing could increase soil pH, decrease EC, therefore reduced soil secondary salinization and acidifying. Crop rotation of welsh onion, cowpea and tomato with cucumber promoted soil organic matter content. Crop rotation reduced available nitrogen. Crop rotation of welsh onion,cowpea with cucumber increased soil available phosphorus content. Crop rotation of cowpea with cucumber and fallowing increased soil available potassium content, while crop rotation of tomato with cucumber decreased soil available potassium content. Those indicated that crop rotation and fallowing could play a role of balancing nutrient and regulating soil fertility.2. Crop rotation and fallowing were beneficial to improving soil microbial flora. Compared with continuous cropping, the amounts of bacterium and actinomyces increased and the amount of fungi decreased. Soil changed from bacteria type to fungi type significantly. Crop rotation and fallowing enhanced soil invertase, urease, catalase and polypheno oxidase activity to a certain extent. 3. In comparison with cucumber continuous cropping, except crop rotation of tomato with cucumber, the plant height and leaf number of the rest were obvious higher. The stem diameter and the largest leaf area of cucumber increased. Crop rotation of welsh onion, waxy maize with cucumber chlorophyll in cucumber leaf and net photosynthetic rate were significantly higher than those of cucumber continuous cropping. The root activity increased to varying degrees and NR activity was significantly higher than that of cucumber continuous cropping. Those indicated that reasonable crop rotation and fallowing could promote cucumber growth.4. Except crop rotation of tomato with cucumber, crop rotation and fallowing increased yield of cucumber significantly, elevated soluble sugar, soluble protein and reduced nitrate content in cucumber fruit significantly, but influenced vitamin C content little. Crop rotation and fallowing improved the quality of cucumber fruit to a certain extent.5. Under the experimental conditions, considering improvement of soil and growth of cucumber, crop rotation of welsh onion, waxy maize with cucumber had better efficiency. Crop rotation of cowpea with cucumber and fallowing also played a role in overcoming of soil continuous cropping barrier. But crop rotation of tomatoes with cucumber was not conducive to soil improvement and the growth of cucumber. Crop rotation of welsh onion, waxy maize with cucumber was proposed to be applied in production.