EARTHWORM CONTRIBUTION TO INFILTRATION AND SURFACE RUNOFF AFTER 15 YEARS OF DIFFERENT SOIL-MANAGEMENT

The contribution of earthworm burrows to infiltration and surface runo ff was investigated in a 15-year-old tillage experiment. The tillage t reatments were autumn mouldboard ploughing, autumn stubble cultivation and spring stubble cultivation, each replicated four times. At the ti me of the study, all treatments had been left untilled following the h arvest. Earthworms were sampled by combined formalin extraction and ha nd-sorting. Undisturbed soil samples taken from formalin-sampled areas were subjected to simulated rainfall treatments in the laboratory, an d percolating water and surface runoff were collected. After the rainf all treatments the saturated hydraulic conductivity (K-SAT) Of each sa mple was measured, and a dye was applied to study the preferential pat hways of soil water. The earthworm fauna consisted of the dominant Apo rrectodea caliginosa and clearly less abundant Lumbricus terrestris an d L. rubellus. The only discernible difference between the tillage tre atments was that L. terrestris was present only in unploughed soils, a lthough in very low numbers. During the rains, there were no significa nt differences between the treatments in volumes of percolated water, but there was significantly less runoff from spring stubble-cultivated soil than from autumn-tilled soils. K-SAT was also significantly high er in the spring stubble-cultivated soil. K-SAT was positively related to the volume of percolation, and negatively to the volume of surface runoff collected during the second rain, Total areas of stained earth worm burrows at the depths of 20 and 30 cm were correlated positively with K-SAT. (C) 1998 Elsevier Science B.V.