SPLIT APPLICATIONS OF SUPPLEMENTARY N FER TILIZER FOLLOWING INCORPORATION OF CHIPPED RAMIAL WOOD - CHANGES IN SELECTED BIOLOGICAL AND CHEMICAL-PROPERTIES OF A SOIL CROPPED TO POTATOES

A field experiment was conducted in 1992 and 1993 in a potato crop (So lanum tuberosum L.). Biological and chemical soil properties were inve stigated following incorporation of chipped ramial wood (chipped fine branchwood) combined with split applications of supplementary N fertil izer. Fungal populations showed a a temporary increase following incor poration of low CM chipped wood, whereas bacteria and actinomycete pop ulations remained unchanged. Chipped ramial wood did not induce develo pment of common scab or rhizoctonia on tubers. Soil total carbon (C) a nd water-holding capacity increased with inputs of chipped wood but C/ N ratio and pH were not affected. Only available P content decreased f ollowing incorporation of chipped wood, likely due to immobilization b y microorganisms. Splitting supplementary N fertilizer showed little e ffect on soil chemical properties, but it reduced the incidence of com mon scab on tubers in 1992. Soil amendment with chipped ramial wood in combination with split N applications improved biological activity an d caused a short-term increase of total C.