Effects of intercropping cucumber with onion or garlic on soil enzyme activities, microbial communities and cucumber yield

Soil enzyme activities, soil bacterial and fungal community structures and cucumber yield as affected by different cropping systems were evaluated in a three-successive-growing-season experiment under greenhouse conditions. Intercropping systems, in which onion or garlic were planted on the side of cucumber in the first growing season, were compared to cucumber monoculture. Only cucumber was planted in the second and third growing seasons in order to see if the impacts of intercropping in the first growing season still exist in later growing seasons. Results showed that cucumber yield increased under both intercropping systems in these three growing seasons, compared with monoculture. Increases of soil urease activities under intercropping systems were detected in these three growing seasons. Soil polyphenol oxidase activities under intercropping systems also increased in the first two growing seasons. Soil catalase activity was higher under garlic-cucumber intercropping systems than under monoculture in the last two growing seasons. PCR-DGGE analysis showed that soil bacterial community band numbers and diversity indices decreased with growing seasons under monoculture. These indices were relatively stable under intercropping systems throughout these three growing seasons, and were higher than under monoculture. Garlic-cucumber system had a more obvious effect on soil fungal community structure than onion-cucumber system. This study demonstrated that intercropping cucumber with onion or garlic increased cucumber productivity and improved soil environment at different levels. These impacts of intercropping still existed in the second and third growing seasons. (C) 2011 Elsevier Masson SAS. All rights reserved.