Research Report
Drought Resistance Response of Tall Fescue Established in Disturbed Urban Soils Utilizing Biosolids Virginia Tech Researchers: Adam Boyd, Graduate Student; Erik H. Ervin, Ph.D., Professor of Turfgrass Culture & Physiology; Gregory Evanylo, Ph.D., Professor and Extension Specialist, Jonathan Dickerson, Research Specialist Sr., and Xunzhong Zhang, Ph.D., Advanced Research Scientist Research Sponsor: Metropolitan Washington Council of Governments Material Suppliers: D.C. Water Authority, Alexandria Sanitation Authority and Spotsylvania Sanitation Authority
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rban development is a primary cause of soil degradation. As populations continue to swell, development extends further from city centers and encroaches into surrounding rural and forested areas. A result of population growth is increased biosolids production. Increasing regulations on agricultural biosolids land application have resulted in wastewater-treatment plants seeking alternative means of land application. Contractor use of biosolids to improve disturbed urban soils following construction offers a beneficial use and alternative means of disposal for wastewater-treatment plants, while also possibly reducing fertilizer and irrigation requirements. The objective of this experiment is to evaluate different biosolids mixes that are applied at estimated agronomic N and P rates and compare their effects on the persistence of tall fescue (Festuca arundinacea) with a synthetic fertilizer when subjected to drought or non-drought conditions.
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In fall 2013, a research plot measuring
110' x 68' was prepared by stripping the O, E, and A horizons leaving the subsoil (B horizon) exposed. The trial was then divided into 40 plots measuring 12' x 12', with a 2' buffer strip separating each. A subterranean irrigation system was installed to allow for uniform irrigation during establishment. Two biosolids products from the Alexandria Sanitation Authority (ASA) and the Spotsylvania Sanitation Authority (SSA) were used. The ASA product is an exceptional quality (EQ) Class A dewatered biosolids and was used unmixed, as well as mixed with sand and sawdust at a ratio of 50% biosolids/25% sand/25% sawdust. The SSA product is an EQ Class A dewatered biosolids that was composted with wood fines. Rates used were based on an annual agronomic tall fescue N requirement of 4.6 lbs./1,000 ft2 and P rate of 1.3 lbs./ 1,000 ft2. Synthetic fertilizers were used to supplement the P-rate-amended biosolids plots and for the comparison control plots. Following incorporation of the amendments, tall fescue was seeded at a rate of 8 lbs./1,000 ft2 and established over the fall 2013 to spring 2014 season.
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Loading rates for each of the amendments are listed below. 1. Synthetic fertilizer (control) — urea (46-0-0) 4.6 lbs. N/1,000 ft2/year (split applications in August and October 2013) 2. Alexandria dewatered biosolids mix (Alex-N) — agronomic N rate: 4.6 lbs. plant available nitrogen (PAN)/1,000 ft2/year (estimated) 3. Alexandria dewatered biosolids mix (Alex-P) — agronomic P rate: 1.3 lbs. PAN/M/year (estimated), supplemented with synthetic fertilizer to apply the other 3.3 lbs. N/1,000 ft2 4. Alexandria dewatered biosolids (Alex-DW) — 4.6 lbs. PAN/1,000 ft2/year (estimated) 5. Spotsylvania biosolids compost (Spots) — 4.6 lbs. PAN/1,000 ft2/year (estimated) In May 2014, supplemental irrigation during establishment was discontinued. The plots were split into their respective irrigation regimens, and evapotranspiration (ET) replenishment cycles commenced. The two different irrigation regimes are 0% and 80% ET replenishment, respectively. The ET rate was estimated using on-site