GROWTH-RESPONSE AND NUTRIENT AVAILABILITY IN WESTERN REDCEDAR PLANTATIONS FOLLOWING AMENDMENT WITH FISH-WOOD COMPOST AND STRAW

Fish-wood compost and wheat straw were applied to chlorotic plantation s of western redcedar (Thuja plicata Donn ex D. Don) on northern Vanco uver Island to determine their effectiveness as fertilizers. Two years after application, tree growth was greater in the compost- and straw- amended plots than in control plots. The greatest growth response was in straw-amended plots. The first pear after application, foliar conce ntrations of N, P, I;, and S were higher in trees in the straw and com post plots. Two years after treatment, foliar nutrient concentrations returned to pretreatment levels in the compost plots, but remained ele vated in the straw plots. Concentrations of KCl-extractable N in fores t floors 2 years after treatment were greater in the straw plots than in the control plots prior to and after a 29-day incubation. The rate of CO2 evolution from the forest floor was also greatest in the straw plots 2 years after treatment. These results suggest that addition of a fresh residue such as straw to these sites may promote a long-term i ncrease in N availability and tree growth.