Abundance and activity of soil organisms in fields of maize grown with a white clover living mulch

The effects of a white clover (Trifolium repens) living mulch on the soil detritus food-web during maize (Zea mays) culture were studied on Andosols for 2 years. In the first year, the use of white clover (W) and Italian ryegrass (I; Lolium multiflorum) was compared against the control treatment in the absence of fertilization. In the second year, combinations of white clover and inorganic fertilizers were studied. Bacterial and fungal substrate-induced respiration and the population densities of protozoa (flagellates, naked amoebae, ciliates), nematodes, and microarthropods (mites, collembolans) increased with the use of white clover living mulch. In the first year, nematode and microarthropod populations increased throughout the growing season in the living mulch plots. In the second year, the communities of soil organisms under the white clover living mulch had reached a more mature successional stage and were characterized by increased populations of organisms in the fungal pathway of organic matter decomposition and by a high population density of higher trophic groups (e.g., mesostigmatid mites and ciliates). The higher litter decomposition rate in the living mulch plots suggested that the function of the detritus food-web was enhanced under the living mulch system. On the other hand, inorganic fertilization only increased populations of nematodes and mesostigmatid mites in mid-summer, possibly owing to better maize growth, and had no effect on other soil organisms.