Biosolids are rich in plant nutrients and are a byproduct of municipal wastewater treatment and those that meet strict government safety standards can be land applied in most agricultural settings except for the U.S. Department of Agriculture (USDA) certified organic production. Across the United States, about 60% of biosolids are land applied, but in Mississippi almost no biosolids are land applied. Our research goal was to compare plant size in southeastern U.S. soils amended with biosolids at rates of 2, 8, 14, and 20 tons/acre in contrast to soils amended with synthetic fertilizers using ‘Floral Lace Cherry’ dianthus (Dianthus chinensis ×barbatus), ‘Dreams Coral Morn’ petunia (Petunia ×hybrida), ‘Pidgeon White’ kale (Brassica oleraceae var. acephala), and ‘Bright Lights’ swiss chard (Beta vulgaris ssp. cicla). To accomplish this, fertilizers and biosolids were applied to prebedded fields in a randomized complete block design with a split-plot arrangement of nutrient treatments. Plant performance data and soil data were taken 43 and 56 days after transplant. Soil pH was reduced and organic matter increased at the highest application rates (14 and 20 tons/acre) of biosolids, and higher levels of phosphorus, zinc, and sulfur were found in these soils. In plant shoots, higher levels of copper, manganese, magnesium, and zinc were found when grown in soils amended with biosolids at a rate of 20 tons/acre compared with plants grown with synthetic fertilizers. Except for swiss chard, no crops fertilized with biosolids exhibited a difference in dry weights (DW) compared with conventional fertilizers. These data demonstrate that soil properties can be improved and similar plant sizes can be achieved through biosolid applications. We conclude that Grade A biosolids produced in Mississippi can be used to supplement synthetic fertilizers for ornamental and vegetable production.
Shaun R. Broderick and Williams B. Evans
Guihong Bi, Williams B. Evans, and Glenn B. Fain
Pulp mill ash was evaluated as a substrate component in the production of greenhouse-grown French marigold (Tagetes patula L. ‘Janie Deep Orange’). Peat-based substrates (75:10:15 by volume blend of peatmoss, vermiculite, and perlite) amended with 0% to 50% (by volume) pulp mill ash were compared with a standard commercially available substrate. With the exception of an unfertilized control, each substrate blend contained 5.93 kg·m−3 14N–6.2P–11.6K (3- to 4-month release) and 0.89 kg·m−3 Micromax. Substrates containing higher volumes of ash had finer particles, less air space, and more waterholding capacity than the commercial substrate. Bulk density increased with increasing ash volume, and substrate containing 50% ash had 120% greater bulk density than the commercial substrate. Substrates containing ash generally had higher pH and electrical conductivity (EC) than the commercial substrate with substrate pH and EC increasing with increasing ash volume. In general, marigold plants grown in peat-based substrates with the addition of 0% to 50% ash had similar growth indices, flower dry weights, numbers of flowers, and SPAD values as plants grown in commercial substrate; however, plants grown in substrates containing 30% to 50% ash had lower shoot dry weights or root quality ratings than plants grown in commercial substrate. Plant growth index, shoot dry weight, and root quality rating decreased with increasing ash volume.