Utilization of MSW compost in nursery stock production

This three year study was conducted to evaluate the suitability of municipal solid waste (MSW) compost as a soil amendment or a mulch to suppress weeds in the production of field grown nursery stock. In the soil amendment experiment, compost was applied at the rates of 0, 56, and 112 t/ha and incorporated into the soil prior to planting. In the mulch/weed control experiment, 224 t/ha of compost was applied to one set of plots as a mulch after planting and compared to plots treated with herbicide and untreated controls. Each plot in both experiments contained four rows with one each of red maple (Acer rubrum L.), sugar maple (Acer saccharum Marsh.), white pine (Pinus strobus L.), and pin oak (Quercus palustris Muenchh.). Mortality and weed counts were determined during the first growing season. Annual measurements of crown height, crown width, and caliper (at the 1 foot level) were made the following three winters. Two inches of compost mulch (224 t/ha) provided adequate weed control only in the first year. Mowing suppressed the weeds that invaded the plots beyond the first year. For maples, first year mortality in pints mulched with 224 t/ha compost or amended with 112 t/ha compost was significantly less than unamended controls. In subsequent years, the mulched maples grew more than trees in the unamended controls. In the plots amended with 56 or 112 t/ha compost, sugar maples had increased height, canopy, and caliper growth compared to the unamended controls. The hearty pin oak saplings survived transplanting and there was a significant increase in caliper growth in plots amended with 112 t/ha (1 inch) of compost. Mortality of white pine increased when mulched with 224 t/ha compost. Increased mortality was most likely due to high concentrations of ammonium and soluble salts in the immature compost. Beyond the first year, there were no negative impacts on the growth of white pine from any of the compost treatments.