EVALUATING THE SOIL BUILDING CHARACTERISTICS AND GROWTH BENEFITS OF FOUR-COMPOSTED ORGANIC WASTE PRODUCTS ON FIELD GROWN WOODY NURSERY STOCK

Open Access
Author:
Harpster, Tracey Lynn
Graduate Program:
Horticulture
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 08, 2011
Committee Members:
  • James C Sellmer, Thesis Advisor
Keywords:
  • soils
  • red maple
  • red oak
  • Fraser fir
  • dogwood
  • crabapple
  • SMS
  • foliar analysis
  • compost
Abstract:
High quality soils are essential for the production and marketability of high quality field-grown nursery stock. Loss of topsoil and depletion of organic matter (OM) are often consequences of field production. As an alternative to removing fields from production and rebuilding soils by growing several seasons of green manure crops, many nurseries are investigating composted organic waste as a means of rebuilding soil OM and soil structure. A side-by-side comparison was conducted to determine the effects of readily available composted OM on soil characteristics and growth of tree liners. Plots amended with spent mushroom substrate (SMS), mixed waste (PSU), yard waste (SCLB), or sewage sludge (UAJA) and a set of unamended control plots were established in Spring 2000 as a randomized complete block design. In the experiment plot five plants of five ornamental tree species including crabapple (Malus ‘Candymint’), Kousa dogwood (Cornus kousa Hance ‘Stellar Pink’), Fraser fir (Abies fraseri (Pursh) Poir), red maple (Acer rubrum L. ‘October Glory’ and ‘Red Sunset’) and red oak (Quercus rubrum L.) were planted. Over the four-year study, total soil OM content increased by 47-52 % and soil porosity increased in the amended soils as compared to the unamended soils. Conversely, bulk density was reduced in the amended plots. The amendments also changed the chemical properties of the soils. The SMS, PSU and SCLB amendments each increased the soil pH, whereas the UAJA amendment decreased pH. All of the amended plots showed an increase of nitrogen, phosphorus, potassium, cation exchange capacity and soluble salts, and a decrease in calcium and magnesium. Plant response varied among the different amended soils. There was no significant difference in height, caliper, survival and quality among the crabapple across all treatments including the control. The Fraser fir and dogwood suffered high losses in all the treatments. The red maple grown in the UAJA amended plots grew significantly larger in caliper and were observed to be of higher quality (e.g., larger darker leaves, more branching, and uniform canopies) compared to the other treatments. Furthermore, all amended plots produced an increase in weed biomass which suggests the need for a more structured weed control program. These observations could be a result of the addition of amendments, the soil’s response to the amendments, or a combination of both. In general the organic supplements did enhance soil characteristics and affected growth. Observations indicate the species do not respond the same to the addition of organic amendments. Owing to the number of variables within nursery fields, plant families and compost qualities, further research on different species, by application rates and with additional supplements such as fertilizer are warranted.