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Effect of Geotechnical and Environmental Properties of Maryland Compost and Compost Amended Topsoils (CAT) on Vegetation Establishment and Growth

Poor structural properties and nutrient profiles of disturbed soils often require supplemental organic matter for promoting better vegetation establishment. Compost and compost-related products, when added to soils, have proven to enhance plant growth and improve infiltration of rainwater, thereby mitigating soil erosion and excess nutrient release through surface runoff. This study commenced with interviewing 13 SHA qualified soil producers, to gain insights into the type of compost products used in their furnished topsoil to meet the SHA organic matter (OM) requirement of 4 – 8%. From these interviews, it was determined that leaf or yard waste compost was the most sought-after material for raising OM content. However, due to high demand and limited supply, the soil producers find it difficult to procure this product. Aged mulch is second in hierarchy for preference given its high OM content, low cost and wide-spread availability. Although easily assessable, biosolids is not preferred because of its high salts content, potential odor, and regulatory requirements related to its storage and transportation. In addition to the interviews, 10 producer-provided furnished topsoil samples were tested to determine soil characteristics and susceptibility to nitrogen (N) and phosphorus (P) losses via subsurface leaching. Results indicate that predicting such losses will require more extensive testing than currently conducted by SHA. Two sets of 8–9-week greenhouse microcosm studies were conducted testing SHA spec furnished topsoils amended with shredded mulch (MAT), leaf compost (LAT), and biosolids (BAT), to compare and evaluate their performance for vegetation growth and nutrient release over time. A control, unamended soil (CUT), was also included in the studies. Each greenhouse study included sixteen tubs (4 treatments with 4 replicates) which were irrigated weekly with 1 inch of tap water over the entire tub to mimic the intensity of a 4 inch/hr rain event. Across the four soil types, greater coverage of turfgrass was found in the LAT and BAT treatments, compared to MAT and CUT, even though their OM contents were similar and fell within a tight SHA specification range of 4 – 8%. Soil C:N ratio and N content were found to be major drivers for controlling turf growth, more so than OM content itself. Water quality analyses showed that the leachate from BAT treatments contained high total nitrogen (TN) concentrations originating from the biosolids amendment. Total Phosphorus (TP) release from LAT treatments increased over time as phosphate loaded tap water was applied weekly, exceeding plant uptake needs and saturating soil P adsorption sites. MAT and BAT treatments effectively reduced tap water P levels by the end of the study. Among the tub study soils, MAT treatments showed increased hydraulic conductivity compared to other soil mixtures. Finally, all treatments used in the microcosm studies were tested for their geotechnical properties. Based on the findings of the study, the UMD research team provide eight recommendations based on soil testing, amendment types, and nutrient information that may help SHA improve specifications for expanding the use of compost and topsoil products of Maryland businesses.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 77p

Subject/Index Terms

Filing Info

  • Accession Number: 01940637
  • Record Type: Publication
  • Report/Paper Numbers: SHA/UM/5-21
  • Contract Numbers: SHA/UM/5-21
  • Files: NTL, TRIS, STATEDOT
  • Created Date: Dec 23 2024 10:36AM