Effects of Platycodon grandiflorum and Allium fistulosum intercropping on soil nutrients, microorganism and enzyme activity

Objectives Effects of Platycodon grandiflorum and Allium fistulosum intercropping on soil properties under different intercropping patterns were studied. The aim was to supply academic base for solving continuous cropping obstacle of P. grandiflorum.

Methods Field experiments were conducted in a field where P. grandiflorum had been continually cultured for 3 years. The intercropping trial included three modes of P. grandiflorum and A. fistulosum as 2∶1, 3∶1 and 4∶1, and the monoculture of P. grandiflorum was set as control. Soil samples of 0–20 cm depth were collected since the 15th day after transplanting, and with a sampling interval of 30 days. The nutrient status, microorganism and main enzymatic activities of soils were determined.

Results Compared with monoculture, P. grandiflorum & A. fistulosum intercropping enhanced the contents of soil available nitrogen, which were increased by 22.3% to 50.0%, and the increment was decreased with the increase of the row ratio between P. grandiflorum and A. fistulosum. The soil available phosphorus content in the intercropping was higher than that in monoculture from May to August (within 105 days after transplanting), whereas the tendency was reverse after August. No significant difference was detected in readily available potassium content among all planting patterns. The P. grandiflorum & A. fistulosum intercropping improved activities of soil phosphatase and polyphenol oxidase but did not affect both the activities and tendency of urease and invertase. The P. grandiflorum and A. fistulosum intercropping increased microorganism quantities mainly through increasing bacteria quantities, consequently increasing soil fertility. The fungi quantities in the P. grandiflorum monoculture were greater than those in P. grandiflorum & A. fistulosum intercropping, but the ratio of bacteria to fungi showed an opposite tendency.

Conclusions P. grandiflorum & A. fistulosum intercropping could modify soil microorganism and enhance soil fertility, which could act as an innovative strategy to reduce successive cropping obstacle of P. grandiflourm.