Growth Response of Annual Transplants and Physical and Chemical Properties of Growing Media as Influenced by Composted Sewage Sludge Amended with Organic and Inorganic Materials

Abstract

Composted sewage sludge was combined with several other organic and inorganic components to form 19 growing media. Increasing the proportion of sludge compost in media from 25 to 50% increased media pH, electrical conductivity (EC), airfilled pore space (AS), and nutrient levels, and usually increased growth of pansy, snapdragon, and cabbage plants. Of the other organic components, sawdust-based media had the highest pH, EC, and AS; sphagnum peat-based media the highest water holding capacity. Plant fresh weights were highest with bark, which produced media with highest retention of K, Ca, Mg, and Na. Of the inorganic components, pumice produced media with lower AS and lower yields of each crop than did perlite or vermiculite. Inorganic components had no effect on media pH or EC. Yields of all crops were usually higher in media containing compost than in 5 commercial potting mixes but less than in a fertilizer-amended bark medium. High yields appeared to be associated with higher medium AS and higher initial levels of major and minor plant nutrients.