Exceptional Quality Biosolids…

Land Application of Exceptional Quality (EQ) Biosolids for Improved Soil Health and Drought Resistance of Tall Fescue Lawn

By Xunzhong Zhang, Ph.D., Mike Goatley, Ph.D., and Jon Dickerson School of Plant and Environmental Sciences Virginia Tech, Blacksburg, VA

Shortage of fresh water for turfgrass irrigation and frequent drought stress are major limiting factors for home lawns in Virginia. Exceptional quality (EQ) biosolids are engineered to be used safely in urban landscapes due to being rich in organic matter and biostimulants. This research project was to assess the effects of long-term land application of exceptional quality (EQ) biosolids on soil health and drought resistance of tall fescue lawn, and examine the quality and physiological responses of turfgrass to EQ biosolids under drought stress and post drought conditions.

The field plots for this research were initiated at the Virginia Tech Turfgrass Research center in 2013 and EQ biosolids treatments were applied from 2013 through 2015 using Alexandria Renew Enterprises Biosolids, and 2016–2018 by DC Water biosolids. Spotsylvania biosolids compost was from Spotsylvania County compost facility. We continued the research in 2021 using these same plots so that the effects of long-term EQ biosolids treatment responses in turfgrass growth, and quality, and soil health could be assessed. There were two irrigation regimes (0 evapotranspiration (ET) replacement and 80% ET replacement) and 5 biosolids-based treatments including (1) Synthetic fertilizer control, urea applied at 152 lb N/A; (2) ‘Bloom’ Biosolids blended with sand and saw dust (1.5:1:1) to supply 80% of annual plant available nitrogen (PAN) rate of 152 lb/A (BBN), 20% of PAN supplied with urea (BBN); (3) ‘Bloom’ biosolids blended with sand and sawdust to supply an annual P rate (57 lb P/A) plus supplemental urea fertilizer to also provide 152 lb PAN/A annually for the entire treatment (BBP); (4) ‘Bloom’ biosolids to supply 80% of annual PAN at 152 lb/A, and 20% of PAN supplied with urea (BLM); and (5) Spotsylvania compost to supply 80% of an annual PAN rate of 152 lb/A (SCN) and 20% PAN provided with urea (SCN).

A split plot design was used with irrigation as main plots and biosolids as subplots and 4 replications of each treatment. The treatments were applied to the mature tall fescue in June 7, 2021 at ½ loading rate (76 lb N/A) and the other ½ in September 23 (photo 1). The same treatments will be applied in 2022. Irrigation was withheld from June 15 to August 15 to induce drought stress for the grass. Irrigation resumed for grass recovery from 16 August to September 15. Soil samples were collected before the treatments were applied each year for analysis of soil nutrient levels and organic matter. In addition, soil samples were collected at the beginning, during drought stress, and at the end of turf recovery to measure soil hormone auxin levels. Turf quality and photochemical efficiency were determined biweekly from the time of drought initiation through end of recovery period each year. Leaf tissue samples were collected monthly from initiation of drought to the end of recovery period for analysis of leaf chlorophyll content, leaf proline, leaf sugar, leaf antioxidant enzymes and leaf hormone content.

PHOTO 1. Biosolids and compost application on tall fescue.

We observed beneficial effects of the biosolids and compost application on turf visual quality and photochemical efficiency during drought and recovery periods (photo 2). As measured at end of drought treatment (August 10), all four treatments improved turf quality relative to the control under 80% ET irrigation regime. Under drought stress conditions (0 ET), ‘Bloom’ biosolids and Spotsylvania compost increased turf quality ratings relative to the control.

PHOTO 2. Treatments effects as observed on July 13, 2021

We acknowledge the Virginia Agricultural Council, D.C. Water and Sewer Authority, Lovingston Blend Compost Facility in Spotsylvania County, and the Virginia Agriculture Experiment Station for their support of this research.

PHOTO 3. Synthetic fertilizer control

PHOTO 3. Spotsylvania compost under drought stress condition (July 13, 2021)