Effect of Compost-Fertilizer Blends on Crop Growth

Abstract

Two growth chamber studies were conducted to determine whether compost-fertilizer combinations or blends were equal to or better than nitrogen (N) fertilizer alone for tall fescue (Festuca arundinacea) growth and N uptake. A sewage sludge compost(SC) or a compost made from both sewage sludge and municipal refuse (MC) was added on the basis of total N to Sassafras soil at rates equal to 17, 33 and 50% of the N requirement of fescue. The remaining N was supplied by NH₄NO₃ or urea. All combinations were compared to 50 to 100% fertilizer application rates and to each other. After approximately 150 days, fescue N uptake from the 83% NH₄NO₃:17% compost N blend equalled that from 100% NH₄NO₃ treatment which was not different from 83% NH₄NO₃. The 67% NH₄NO₃:33% MC blend equalled the 83 and 100% NH₄NO₃ alone treatments. The 67% urea:33% sewage sludge compost N blend equalled the 83 and 100% urea alone treatments. Because compost N is only partially mineralizable during the first year, the equality of compost:fertilizer blends to fertilizer alone suggests that ingredients other than N are benefitting the fescue. The studies presented herein suggest that the ability of compost in blends to substitute for a fraction of the fertilizer requirement is both compost and fertilizer dependent. The data suggest that blends with urea would be successful in substituting for one-third of the N fertilizer required by fescue.