Fish-Wood Compost for Road Rehabilitation
Department of Forest Sciences, University of British Columbia
British Columbia, Canada
This study evaluated the use of fish-wood compost as an amendment to facilitate rehabilitation of logging roads in British Columbia. Screened hog fuel fines and dry-land sort debris were piled in a windrow 3 m high and liquid fish waste was applied through a perforated soaker hose that ran 30 cm from the top of the pile. Temperatures in the pile reached 55°C within 18 days, and the compost was removed after 21 days. The compost was applied to disused logging roads at six sites. The effects of compost application, both surface and blended, as well as scarification and fertilization at planting were assessed two years after treatments were applied.
The effects of the compost on survival and growth of the seedlings were obvious and striking. Seedlings in compost-treated plots were usually healthy looking, with lush green foliage, while those in untreated plots often had necrotic foliage and multiple leaders. Surface application of compost consistently improved survival and growth of seedlings relative to unamended control plots. Scarification improved seedling survival and growth; compost amendment provided a further increase in growth in one trial. The effect of compost on seedling growth and survival was slightly better than that provided by fertilizer teabags at planting. The cover of ground vegetation was consistently between 80 to 90% in all compost-treated plots and less than 20% in all control plots.
Rates of decomposition and carbon and nitrogen mineralization from fish-wood compost and other organic amendments were compared during 391-day incubations in the greenhouse and at two field sites. These incubations provide information on the nutritional value and potential for nitrate leaching of compost relative to other organic materials for which loading guidelines exist. Relative to the other materials, fish-wood compost lost organic matter and nitrogen very rapidly during the first two weeks of the incubation. Thereafter, the compost lost little weight or N, while the other materials continued to decompose and release N. Fish compost released a greater proportion of its initial organic N content during the incubation, compared to the other materials. The results of the incubation experiments indicate that the fish-wood compost has a very high capacity for providing nitrogen, relative to other organic residuals and natural forest litter. Thus compost should be applied at times when the vegetation is actively growing (early summer), to maximize uptake of the released N. The very slow decay and N release from compost after the first two weeks indicated that about 80% of the original organic matter added in compost would remain in for several years. Although this compost will not serve as a significant source of N during subsequent years, it will continue to provide organic matter that will provide an improved rooting medium for plants and improved soil moisture retention for many years.
The results of this incubation test indicates that the fish-wood compost has a very high capacity for providing nitrogen, relative to other organic residuals and natural forest litter. In conclusion, the experiments confirmed the ability of fish-wood compost to supply nitrogen and improve the survival and growth of seedlings on disused logging roads in British Columbia.