Abstract:

For the problems of soil environment deterioration,yield and quality decline caused by excessive application of chemical fertilizer in current cucumber production,we used‘Jinyou 35’ cucumber（Cucumis sativus L.） as the experimental material,and investigated the effect of organic fertilizer（cow dung∶bean cake = 4∶1）and chemical fertilizer ratio on the soil environment of root zone and root characteristics of cucumber,through six continuous positioning fertilization in three years（2018–2020）. We set up three organic fertilizer/chemical fertilizer treatments which were 30%/70%,40%/60%,50%/50% and a pure chemical fertilizer control. The results showed that the root zone soil of control plants showed a gradually decrease in pH and porosity,increase in electrical conductivity（EC）,and little change in bulk density as planting time increased,and it started acidification and hardening. However,the soil of the three treatments revealed a little change in pH,decrease in bulk density,but increase in porosity and EC. At the same planting time,no significant differences were observed in physical properties of root zone soil among treatments of the three treatments,whereas,the three treatments displayed much higher pH and porosity,but significantly lower bulk density and EC in root zone soil relative to the control. The contents of alkaline nitrogen,available phosphorus,available potassium and organic matter in the three treatments all increased gradually with planting time. There were no significant difference in alkaline nitrogen,available phosphorus,available potassium and organic matter among the three treatments and the control at the first three crops,but the three treatments were much higher than the control in the following three crops,especially in 40%/60% treatment. The quantity of bacteria,fungi and actinomycetes in rhizosphere soil of the three treatments also showed an increasing trend,and the increase in them was the largest in 40%/60% treatment,while that in control was the least. From the high-throughput sequencing results,we found that the three treatments showed a significant increase in the relative abundance of beneficial bacteria,such as Sphingomonas and Bacillus,while an obvious decrease in that of pathogenic fungi such as Fusarium in rhizosphere soil,compared with the control. The three treatments also markedly increased the bacterial diversity,but decreased the fungus diversity,and consequently improved the microbial community structure in rhizosphere soil of cucumber,especially in 40%/60% treatment. Compared with the control,the activities of nitrate reductase（NR）,urease（URE）,acid phosphatase（ACP）,catalase（CAT）and invertase（INV）all distinctly increased in 30%/70%,40%/60%,and 50%/50%-treated rhizosphere soil of cucumber. The root length,root volume,root superficial area and root tip numbers were much more in the three treatments than in the control plants. However,the root diameter was significantly lesser in the three treatments than that in the control. The root activities also showed an obvious increase in the three treatments relative to the control. By comprehensive comparison,40% organic fertilizer + 60% chemical fertilizer treatment revealed the best soil environment,highest root activity,optimum root characteristics and maximum root growth among the four treatments,and it could to be applied in cucumber production under this experiment condition.

Key words: cucumber, organic fertilizer, chemical fertilizer, physical and chemical properties of soil, microbial diversity, root characteristic