OLCA Research

Assessing Nitrogen and Phosphorous Run-off from Turfgrass Lawns Established on Subsoil or Topsoil.

Principal Investigator:  Dr. Parwinder Grewal
                                        The Ohio State University/OARDC
                                        Department of Entomology
                                        1680 Madison Ave.
                                        Wooster OH  44691
                                        330-263-3963                  
                                        E-mail: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

Define the need of the project

Urban lawns are often blamed for polluting the environment even though much research in field plots indicates that nitrogen and phosphorus run-off is minimal from well managed turfgrass. Furthermore, there is disagreement about the need for phosphorus application to lawns in Ohio. One possible reason for these discrepancies is that all the published research on nutrient run-off from turfgrass lawns has been conducted on field plots established on well-prepared topsoil. Unfortunately, too often that is not the case for urban lawns. Urban lawns are usually on subsoil or inferior soils due to the removal of top soil during construction. The urban soils also tend to be more compacted and contain stones and concrete. Whereas the results obtained from experimental plots established on favorable soils do not always apply to the urban lawns. Therefore, there is a clear need to establish phosphorus requirements of urban lawns established on subsoil and top soil and to obtain data on the differences of phosphorus and nitrogen run-off from lawns on subsoil or top soil.

Objectives and Rationale

The main objectives of this study are:

1)To establish the phosphorus requirement of lawns established on subsoil compared to the top soil.

2)To determine differences in phosphorus and nitrogen run-off from lawns established on top or subsoil.

Plot design and data collection:

Plots for this research were established in 2006 using the 2006-funding provided by OLCA. There are four main plot treatments: (i) subsoil, (ii) subsoil + compost, (iii) topsoil, and (iv) topsoil + compost. For subsoil treatments, top 12 inches of soil was removed from all plots and the plots were refilled with subsoil, topsoil or a mixture of each with compost (soil: compost = 4:1). The subsoil was obtained from the same area by digging below 12. The topsoil was obtained from the same area, by scapping to the top 0-6 inches of soil. There are three sub-plot treatments: 0, 2, and 4 lbs N/1000ft2/year. There are 4 replications for each sub-plot treatment bringing the total plot number to 48. These plots are arranged in a randomized block design.

Each plot is 5.5 x 7 ft2, with 10 ft wide alleyway (buffer area) between each plot to minimize plot to plot contamination. All plots were raised a little higher than ground surface and the alleyways are slightly shaped to a “V” to create a channel to divert the rainwater away from the plots. Wood frames were used to define edges of plots and to maintain each plot with a 4-degree (3.8 to 4.2) cross-angle slope to collect the run-off. We will install longitudinally cut pipes (halves) on two sides of each plot thus emptying the run-off water into a large bucket embedded into the ground at the lowest point.

Tall Fescue (TF) seed was used at recommended rate of 7 lbs/1000 ft2 in mid-May, 2006. A mix of Kentucky Bluegrass (KB) and Perennial Ryegrass (PR) seeds (KB: PR=4:1) was used in buffer areas between plots at the same time. After TF seeds were seeded, a germination fabric was used to cover the plots to protect water loss and to prevent contamination with KB and PR seeds. After two weeks when grasses began to germinate, the fabric was removed. Plots were manually watered as needed to help establish turfgrass. Weed control “Bayer Advanced All-in-One Weed Killer” was applied into plots at recommended rate (1.5 fl. Oz./gallon water/500 sq. ft.). Plots and alleyways have been moved weekly at 3.5 inch height.

Soil samples collected so far indicate that sub-soil treatments have very low phosphorus. First, we are studying the effect of nitrogen on turf establishment and soil food webs in these plots for which we are applying Nitrogen in the form of Sulphur Coated Urea (38-0-0) (Tyler Grain & Fertilizer Co., Smithville, OH) 3 times: August 2006, October 2006, and Spring 2007. After the nitrogen study is completed in spring 2007, we will use an NPK fertilizer to determine N, P and K run-off from the plots. Run-off will be collected three times after irrigation events to simulate a typical rainstorm. Two separate experiments will carried out simulating a light and a heavy rainstorm. The N, P & K content in the run-off will be quantified by a nutrient analysis lab here at OARDC. At the same time soil samples will be collected to determine NPK content of the soils and turf quality will noted using a 1-9 scale.

Expected results and outcomes

1) This project will determine whether phosphorus application is necessary for lawns established on subsoil.

2) This project will quantify how much nitrogen and phosphorus comes off from the lawns established on subsoil compared to the top soil.

3) Both of these data will be extremely useful for the lawn care professionals to make judicious decisions about nutrient applications on specific lawns.

4) A scientific peer reviewed article will be prepared

5) A newsletter article will be written for both the OLCA and OTF newsletters.