Late-spring Turfgrass Establishment without Herbicides

Abstract

Spring establishment of turfgrass that is managed without herbicides is subject to weed competition, resulting in reduced turfgrass cover. The objective of this experiment was to find an acceptable method for spring turfgrass establishment without the use of pesticides. Thirty-six treatments consisting of three soil amendments combined with three turfgrass species or mixes, and four topdressings or fertilizers in a randomized complete block design were tested. Nutrient-deficient fill soil, fill soil blended with topsoil, and fill soil blended with leaf compost were used as growing media. ‘Firenza’ tall fescue (Schedonorus arundinaceus), an 80/20 mix of ‘Nu Destiny’ kentucky bluegrass (Poa pratensis) and ‘Nexus XD’ perennial ryegrass (Lolium perenne), respectively, and ‘Firefly’ hard fescue (Festuca trachyphylla) were grown with topdressings consisting of biosolids, ash-amended biosolids, 16N–12.2P–3.3K starter fertilizer, and an unfertilized control. The treatments were mowed at 3 inches about once per week. Irrigation was supplied by an overhead sprinkler system (1 inch/week). During the 2010 field study, treatments of tall fescue established in a leaf compost–amended root zone were significantly denser and had a greater percentage of cover (P ≤ 0.05) compared with all other treatments. In 2011, treatments of tall fescue established in fill soil– and leaf compost–amended soils were significantly denser and had a greater percentage of cover (P ≤ 0.05) compared with all other treatments. Kentucky bluegrass/perennial ryegrass and hard fescue treatments had significantly lower (P ≤ 0.05) levels of establishment compared with tall fescue. Topdressing treatments resulted in no significant difference (P ≤ 0.05) in turfgrass establishment.

Abstract

Spring establishment of turfgrass that is managed without herbicides is subject to weed competition, resulting in reduced turfgrass cover. The objective of this experiment was to find an acceptable method for spring turfgrass establishment without the use of pesticides. Thirty-six treatments consisting of three soil amendments combined with three turfgrass species or mixes, and four topdressings or fertilizers in a randomized complete block design were tested. Nutrient-deficient fill soil, fill soil blended with topsoil, and fill soil blended with leaf compost were used as growing media. ‘Firenza’ tall fescue (Schedonorus arundinaceus), an 80/20 mix of ‘Nu Destiny’ kentucky bluegrass (Poa pratensis) and ‘Nexus XD’ perennial ryegrass (Lolium perenne), respectively, and ‘Firefly’ hard fescue (Festuca trachyphylla) were grown with topdressings consisting of biosolids, ash-amended biosolids, 16N–12.2P–3.3K starter fertilizer, and an unfertilized control. The treatments were mowed at 3 inches about once per week. Irrigation was supplied by an overhead sprinkler system (1 inch/week). During the 2010 field study, treatments of tall fescue established in a leaf compost–amended root zone were significantly denser and had a greater percentage of cover (P ≤ 0.05) compared with all other treatments. In 2011, treatments of tall fescue established in fill soil– and leaf compost–amended soils were significantly denser and had a greater percentage of cover (P ≤ 0.05) compared with all other treatments. Kentucky bluegrass/perennial ryegrass and hard fescue treatments had significantly lower (P ≤ 0.05) levels of establishment compared with tall fescue. Topdressing treatments resulted in no significant difference (P ≤ 0.05) in turfgrass establishment.

Traditional turfgrass management techniques require cultural inputs such as fertilizer, pesticides, irrigation, and mowing (Williamson 2006). The recent green movement has caused concern over the fate of synthetic inputs in the world’s ecosystems (Thompson and Sorvig 2008). Management of low-input lawns is possible using proper species selection, cultural practices, and proper fertility programs (Beard 1973; Williamson 2006). Successful establishment of low-input lawns by seeding cool-season turfgrasses in autumn has been documented (Beard 1973; Reicher et al. 2000).

Many factors are important for good turfgrass development, including soil quality, nutrient availability, and turfgrass species (Darmody et al. 1983; Loschinkohl and Boehm 2001; O’Keefe et al. 1986; Thompson and Sorvig 2008). A common practice in new housing developments is to remove topsoil at the beginning of construction that has good structure and is nutrient rich (Christians et al. 2017; Loschinkohl and Boehm 2001). When turfgrass establishment is attempted, the available subsoil is often nutrient deficient, compacted, and not ideal for plant growth. Incorporation of materials such as leaf compost with a low soil-bulk density can add more air space, increase water infiltration, and relieve compaction (Loschinkohl and Boehm 2001). Amending soil with compost has been studied at great lengths to investigate disease suppression and improvement of soil physical and chemical properties, and for turfgrass establishment (Cheng et al. 2007; Darmody et al. 1983; Garling et al. 2001; Loschinkohl and Boehm 2001; O’Keefe et al. 1986; Ros et al. 2006; Schroder et al. 2008).

Sand, compost, and topsoil are common materials used for topdressing established lawns (Beard 1973; Fry and Huang 2004; Munoz 2011). Topdressings such as paper fiber, straw, and other materials have been used to retain moisture (Christians et al. 2017). Composts are biologically active materials created from a variety of materials, including biosolids, manures, and yard wastes (Cheng et al. 2007). Compost products can also increase nutrient availability for established lawns. Com-Til^® (Department of Public Utilities, City of Columbus Waste Treatment Center, Columbus, OH, USA) is composted municipal biosolids (hereafter referred to as biosolids) and Com-Til Plus^® (Department of Public Utilities, City of Columbus Waste Treatment Center) is composted municipal biosolids with an added ash component (hereafter referred to as ash-amended biosolids). The use of topdressings of compost and compost tea has been studied on established lawns (Bero and Soldat 2022). However, little research has been conducted on the use of topdressings during establishment.

Cool-season turfgrass establishment is more successful when seeding occurs during autumn months or with selective preemergence herbicide applications in the spring (Pound and Street 1991). Autumn seeding is recommended because of increased soil moisture, adequate soil temperature, and reduced competition from summer annual weeds (Christians et al. 2017; Dawson and Evans 1931). Turfgrass establishment during the late spring months is often less successful because of weed competition and increased irrigation requirements during the hot, dry periods of the following summer months. Spring establishment is possible; however, for best results, additional synthetic inputs of fertilizers and agrichemicals are often required (Willis et al. 2007). Newer herbicides have been approved for use on seedlings of certain species of cool-season turfgrasses that suppress warm-season weeds and give the desired turfgrasses a competitive advantage. However, use of these products is not desired on organic lawns.

The objective of this research was to determine whether incorporating soil amendments or topdressing with compost would improve spring establishment as measured by vegetative cover and density of either a mix of kentucky bluegrass (Poa pratensis) and perennial ryegrass (Lolium perenne) (KBPR), hard fescue (Festuca trachyphylla) (HF), or tall fescue (Schedonorus arundinaceus) (TF) in the absence of a preemergence herbicide application.

Materials and methods

Field experiments were conducted in 2010 and 2011 at the Ohio Turfgrass Foundation Research Center at The Ohio State University in Columbus, OH, USA. The experiment was repeated on a different, adjacent site in 2011. In each year, the experiment was a 3 × 3 × 4 factorial arranged in a randomized complete block design with three replications. Each block consisted of three rows of 4- × 6-ft plots, separated by a 6-inch alleyway. Three modified root zones were developed, with three turfgrass cultivars, and four topdressing or fertilizer applications.

Root zones consisting of fill soil (FS) (Jones Topsoil, Columbus, OH, USA), fill soil amended with topsoil (TS) (Brookston silty clay loam topsoil on site), and fill soil amended with leaf compost (LC) (Kurtz Bros., Columbus, OH, USA) were installed (Tables 1 and 2). The existing topsoil was removed to an average depth of 6 inches during the construction phase. Four inches of FS was added to the blocks. Two inches of amendment was then added and incorporated to a depth of 4 inches.

The following three turfgrass species or mixes were planted: ‘Firenza’ TF, ‘Firefly’ HF, and an 80/20 mix of ‘Nu Destiny’ kentucky bluegrass and ‘Nexus XD’ perennial ryegrass, respectively (Seed from the Seed Center, Ostrander, OH, USA). These were chosen because of the popularity of bluegrass/ryegrass and the continued development of tall- and fine-fescue cultivars as low-intensity alternatives (Watkins et al. 2014). Seed was applied with hand shakers on 7 Jun of both years and raked into the soil to provide seed-to-soil contact.

Topdressings consisted of biosolids and ash-amended biosolids, and were compared with an untreated control and starter fertilizer (16N–12.2P–3.3K). The starter fertilizer was applied to the designated treatments at 6.25 lb/1000 ft². The biosolids and ash-amended biosolid treated plots received 0.25 inch of product on the surface of each plot. The analysis of the LC, biosolids, and ash-amended biosolids products are listed in Table 3. The control treatments received no supplemental fertilizer or compost.

Plots were mowed at a 3-inch height (Super Recycler^®/Super Bagger lawn mower; The Toro Company, Minneapolis, MN, USA) once per week, with clippings returned to the plots. The irrigation system was designed by Century Equipment (Hilliard, OH, USA) and consisted of 1-inch polyvinylchloride (PVC) piping aboveground with 12 sprinkler heads (Super 800, The Toro Company). Irrigation was supplied at a rate of 1 inch of water per week. A rain sensor (RSD series; Rain Bird Inc., Azusa, CA, USA) rain gauge was installed to shut down the irrigation system during periods of natural rainfall.

The percentage of turfgrass cover of each plot was estimated by visual ratings recorded by two independent observers on 1 Oct 2010 and 2011 (Morris and Shearman 1998). The mean of the two ratings was analyzed by using the general linear models procedure of SAS (ver. 9.4; SAS Institute Inc., Cary, NC, USA).

Turfgrass establishment density was determined with a grid. The grid was a 20- × 20-inch PVC square, strung with fishing line at 4-inch intervals, providing 16 intersection points. The grid square was dropped randomly on each plot three times. Intersections on the grid that fell on the desired turfgrass species were counted after each random drop and analyzed with SAS (ver. 9.4, SAS Institute Inc.). Grid counts were taken on 1 Oct 2010 and 2011.

Soil tests were conducted by CLC laboratories (Westerville, OH, USA) to determine chemical properties of treatments based on root-zone and topdressing applications. Before construction of the treatment plots, the FS and the TS were analyzed. Extraction of soil was done with a 1-inch-diameter soil probe to a depth of 6 inches. Each soil sample analyzed consisted of 15 cores taken from the desired soil type. On 15 Oct 2010 and 2011, soil samples were taken from each combination of soil amendment and topdressing. Soil pH was measured using a 1:1 soil-to-deionized water suspension (Thomas 1996). Phosphorus (P) levels were determined using the Bray-P 1 method by measuring extractable P using a 1:10 extraction volume and colorimetric procedures described by Frank et al. (1998). Base cations—potassium (K), calcium (Ca), and magnesium (Mg)—were measured by extraction with 1 N neutral (pH 7.0) ammonium acetate (Brown 1998). The extract was subjected to atomic emission spectrophotometry for K, and atomic absorption spectrophotometry for Ca and Mg according to Doll and Lucas (1973). The cation exchange capacity was estimated by the summation of measured exchangeable bases: K, Ca, and Mg (Brown 1998). Organic matter was determined by combustion at 440 °C according to Ball (1964).

Data collected on turfgrass cover and density were analyzed separately by year using the general linear models procedure in SAS (ver. 9.4, SAS Institute Inc.). Fisher’s protected least significant difference test was used to compare main effect means.

Results

The analysis of variance is summarized in Table 4. Differences were observed between root zones and species, but not topdressings. The only interaction that was significant was that there was a difference in species establishment in the different root zones. The interaction between root zone and species varied over years, thus the 2 years were analyzed separately.

Differences in visual ratings between turfgrass species as affected by soil amendment were observed in 2010 and 2011. In 2010, TF amended with LC averaged 61% cover, compared with 39% and 33% for TS-amended and FS plots, respectively. In 2010, KBPR and HF amended with LC did not yield any significant differences in percent cover compared with LS or FS (P ≤ 0.05) (Fig. 1). In 2011, FS and LC treatments resulted in greater turfgrass cover than the TS treatment in TF and KBPR. Tall fescue grown in FS resulted in 77% cover, TF grown in LC-amended soils resulted in 76% cover, whereas TF grown in TS-amended soils resulted in 34% cover. The KBPR grown in FS resulted in 50% coverage, KBPR grown in LC-amended soils resulted in 40% coverage, whereas KBPR grown in TS-amended soils resulted in 14% coverage (Fig. 2). Hard fescue establishment was unaffected by soil amendments. No significant differences (P ≤ 0.05) were detected among topdressing applications.

Interactions were also observed when measuring plot density with the grid system. In 2010, TF grown in LC-amended soils averaged 44 grid hits compared with 31 grid hits in TS-amended soils and 29 hits in FS (Fig. 3). In 2011 there was an interaction between TF and both LC-amended soils and FS. There were 35 and 36 grid hits in TF in LC-amended soils and TF in FS, respectively, whereas TF in TS-amended soils had 15 grid hits. Interactions were also observed among KBPR grown in FS and LC-amended soils. The KBPR grown in FS averaged 21 hits. The KBPR grown in LC-amended soils averaged 16 hits, but the KBPR grown in TS-amended soils only averaged five hits (Fig. 4). Hard fescue establishment was unaffected by soil amendments. No significant differences (P ≤ 0.05) were observed among topdressing applications.

Soil analyses were conducted after the experiment to determine chemical properties of all combinations of soil amendments and treatment topdressings. Treatments receiving biosolids and ash-amended biosolid topdressings yielded the greatest levels of P (Tables 1 and 2). However, this did not result in any significant differences in establishment, or any significant interaction between the topdressings and the other treatments.

Central Ohio’s weather patterns from 7 Jun to 30 Sep are generally warm and humid, with historical average temperatures of 22.2 °C. During both trial years, temperatures were higher than average, 23.5 °C in 2010 and 22.9 °C in 2011 (The Ohio State University 2023). Cool-season turfgrass prefers soil and air temperatures between 15 and 24 °C for optimum shoot and tillering growth (Beard 1973). The average soil temperature for 2010 and 2011 was 25.7 and 25 °C, respectively. Neither growing season was ideal for turfgrass establishment because soil temperatures and air temperatures were warmer than optimal conditions. The average precipitation from 7 Jun to 30 Sep in Columbus, OH, USA, was 14.6 inches. In 2010, total precipitation during the growing period amounted to 10.5 inches, with 14.7 inches in 2011. The additional 4.2 inches of precipitation in 2011 may have alleviated some of the seedling stress, thus improving growing conditions for seedling establishment, which may explain some of the increases in turfgrass cover in 2011.

Discussion

Tall fescue is ideally suited as a turfgrass for the transition zone because of its ability to tolerate drought and heat stress (Christians et al. 2017). In our study, TF was able to germinate quickly, out-compete some weed infestation, and become better established during the trial period compared with KBPR and HF. The KBPR plots did not establish as well as TF, primarily because of the inability of kentucky bluegrass to germinate quickly and become established (Fry and Huang 2004). Kentucky bluegrass establishes more efficiently during autumn months with cooler soil temperatures and less weed competition (Reicher et al. 2000). Perennial ryegrass germinated quickly, but was unable to tolerate the extensive periods of heat. Hard fescue was unable to become established in this field experiment, primarily as a result of competition from summer annual weeds such as crabgrass (Digitaria sp.). In our study, we measured establishment at the end of the season and did not measure initial establishment because previous research showed that initial establishment may not always predict the long-term success of a cultivar or species (Gardner and Taylor 2002).

Field soil treatments varied between the two trials. Replication of a study such as this can be difficult because of material availability. Although the FS was purchased from the same supplier each year, it is difficult to ensure uniform soils from year to year. The FS had similar chemical properties in each year; however, there were textural differences from 2010 to 2011, and the weed seed bank of these two soils could have varied.

Weed competition is an important part of turfgrass establishment, and reduced weed competition is one reason that autumn establishment is recommended (Reicher et al. 2000).

During 2011, there were noticeable differences in weed competition and root-zone type. Weed infestation numbers were not measured; however, in general, the topsoil-amended plots had much greater weed pressure, thus the native topsoil may have had a large amount of weed seeds. The FS source for this experiment generally comes from basement foundation excavation. There is reason to believe that soil from > 2.5 m belowground has a smaller weed seed bank than topsoil in the top 10 cm of soil. Cardina et al. (1991) found that 70% to 78% of the total seed bank of a TF sod was in the top 5 cm of soil; 14% to 20%, from a depth of 5 to 10 cm; and 5% to 10%, from a depth of 10 to 15 cm. If FS has reduced levels of weed seeds, then amending with a product such as LC, which should be weed seed free, should result in a decreased weed seed bank. This would give the desired turfgrass a competitive advantage and increase the coverage.

No significant differences were seen in turfgrass coverage with the different topdressing treatments. There were observed increases in soil and plant P and K from the biosolid products. Phosphorus is important in turfgrass establishment; however, in our trials there was no added benefit. It is reasonable to believe that turfgrass establishment was neither improved nor discouraged by the addition of topdressings or starter fertilizer.

Compost products can have many valuable purposes in turfgrass management. Positive effects have been seen when compost is used both as a soil amendment and topdressing on established turfgrass (Munoz 2011). One hypothesis was that improving the soil would aid in germination and improve turfgrass establishment. Leaf compost–amended soils benefited TF plots in 2010, and TF and KBPR plots in 2011. However, LC analysis from 2010 and 2011 showed variability in compost quality. The carbon-to-nitrogen ratios for LC in 2010 and 2011 were 7:1 and 26:1, respectively. The increase in available nitrogen may have aided in LC-amended soils during the 2010 growing season. Determination of an exact protocol for compost utilization, as a soil amendment or topdressing, is difficult because of inconsistencies in the product. Another hypothesis was that the topdressing might act to suppress weed germination and favor the growth of the turfgrass. In our study, topdressing with either the biosolid or ash-amended biosolid product did not result in significant increases in the establishment of any of the turfgrasses tested. Our results show that turfgrass species selection may be more important in determining success with springtime establishment from seed.

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