Chemical and biological changes in compost of wood shavings, sawdust and peat moss

Abstract

A comparative composting trial with wood shavings (WS), sawdust (SD) and peat moss (PM) was carried out under field conditions. In each, fresh material was mixed with cattle manure in a 2:1 ratio by volume. The initial pH of the WS, SD and PM composts (CST) were 6.2, 5.1 and 5.3, respectively. The chemical and biological changes in CST related to maturity were determined. Samples taken at 0, 12 and 24 mo of composting were also mixed with soil and increasing rates of N and tested as growing media for faba beans (Vicia faba L.) and corn (Zea mays L.) under greenhouse conditions. During composting, the C/N and E 4 /E 6 values decreased in all cases but much more rapidly in WS pile. Thus, after 36 mo of composting, the C/N value decreased from 43 to 17 in WS pile and from 48 to only 35 in PM pile. As indicated by a low C/N ratio (17) and lower humic absorbance values (E 4 /E 6 = 6.4), WS material was practically mature after 24 mo, more rapidly than SD and PM composts which presented initial lowest pH values. The microbial respiration rate (CO 2 ), the pH and N–NO 3 values increased during composting in all materials but much more in WS than in SD or PM pile. All composts were not harmful to plant growth even after a short time of composting (12 mo), but yields increased with the duration of composting. These data showed that it was possible to obtain, in field conditions, a compost from ligneous materials in 24 mo. Key words: Compost, composting, corn (Zea mays L.), faba beans (Vicia faba L.), microflora, peat moss, sawdust, wood shavings