(301) Bioavailability of Dairy Manure Compost Nutrients to Urban Landscape Plants

Abstract

Dairy manure compost (DMC) may be an effective soil amendment when establishing new urban landscapes. The objective of this study was to evaluate the bioavailability of DMC nutrients to typical urban landscape plants. In March 2003, DMC rates of 0, 9, 18, and 27 kg/m2 (0, 1.25, 2.5, 5 cm) were incorporated into the top 10 to 15 cm of Austin silty clay soil. Half of each 6 x 6-m plot was established with bermudagrass sod and the other half with six types of ornamental plants consisting of annual, perennial, and woody species. During the third 2005 growing season, plant tissue was harvested from selected landscape plants to measure biomass production and nutrient uptake. Plant growth and nutrient contents were compared to plant available soil nutrients that were measured during fall 2004 and 2005. Plant available P in the upper 7.5 cm of soil ranged from 89 to 170 mg/kg in September 2004 and from 31.3 to 105.5 mg/kg in August 2004. Potassium and trace elements (Fe, Cu, and Zn) were also increased in the upper 7.5 cm by DMC applications. Increased concentrations of plant available soil nutrients in DMC-amended plots were correlated to overall increases in plant growth and nutrient uptake. Bermuda grass exhibited increased growth and increased tissue concentrations of N, P, K, and Zn. Penta biomass and nutrient uptake were also increased by DMC applications. Lantana stem weights significantly increased with DMC application rate up to 18 kg/m2, but no additional increases were obtained with the 27 kg/m2 rate. Results of this study show that, after three growing seasons with no additional fertilization, a 1- to 2-cm application of dairy manure compost is sufficient to provide continued fertility to landscape plants.