Evaluation of nutrient management and mulching strategies for vegetable production on an extensive green roof

Substrate nutrient and moisture management are two major concerns in green roof agriculture, especially when using extensive systems, but there are currently no recommendations or best management practices. The purpose of this study was to explore three mulching strategies (pine bark, living sedum, and no mulch) and three fertilization regimens (25, 50, and 100g center dot m(-2) of 14-14-14N-P-K slow release fertilizer applied twice each growing season) over two growing seasons to determine their benefits to rooftop agriculture. Tomatoes (Solanum lycopersicum), beans (Phaseolus vulgaris), cucumbers (Cucumis sativus), peppers (Capsicum annuum), basil (Ocimum basilicum), and chives (Allium schoenoprasum) were grown. The 2010 crops outperformed those grown in 2011, likely because of the more extreme temperature and precipitation variations during 2011. When there were differences among mulch treatments, pine bark usually resulted in higher productivity than live sedum mulch. The effects of live sedum mulch on crop production were mixed, consistent with previous literature on the use of live mulches in agriculture. With the exception of whole plot, tomato, and cucumber grades, there was a positive dose response to fertilizer. Further research into more types of mulch, their effects on the green roof microclimate, and fertilizer composition and release rates is required.