Soil extract from an alfalfa (Medicago sativa L.) field improves potato rhizosphere enzyme activity and microbial quantity in a pot experiment

摘要

The yield increase and nitrogen use efficiency improvement often recorded in crops following legumes have been a major attribute of crop rotation. However, the impact of crop rotation on soil enzyme activities and microbial community has rarely been reported particularly under potato-legume rotation system. A pot experiment was conducted in 2015 using soil extracts from legume (alfalfa) and potato fields under continuous cropping for years each. Potato cultivar 'Xindaping' and alfalfa (Medicago sativa L. 'Qingshui'), which is a legume, were used in this study. Soil extracts were prepared from these two separate fields and used as treatments in the pot experiment. The treatments were CK (soil extract from sole potato field) while T1-T5 were a mixture of extracts from the potato field and the legume field at ratios of 1:1, 1:2, 1:3, 1:4 and 1:5, respectively. The results indicated that T4 significantly improved catalase and alkaline phosphatase activity within the root zone of the potato in the pots. In addition, it also enhanced the activities of invertase, urease and increased the quantity of actinomycetes at the tuber formation stage. The application of T4 also improved urease activity at the tuber maturity stage. At the tuber growth stage, however, T3 greatly increased urease and invertase activity and enhanced bacteria and actinomycetes quantities but inhibited fungi quantity throughout the growth of the potato plants. Application of T3 maintained a high number of aerobic azotobacter, whereas the quantity of anaerobic azotobacter, nitrifying and denitrifying bacteria were highest in T4. Thus, our experiment has demonstrated that a potato-legume (alfalfa) rotation system could improve soil quality through the enhancement of enzyme activities and increase in the quantities of beneficial soil microbes.