Microbial Populations and Suppression of Dollar Spot Disease in Creeping Bentgrass with Inorganic and Organic Amendments

Abstract

and sulphur-coated urea were evaluated from 1991 to 1993 on a creeping bentgrass (Agrostis palustris) green and a Kentucky bluegrass (Poa pratensis) lawn for their effects on soil bacterial and fungal populations and dollar spot disease incidence. Over the 3 yr, fertilizers were applied every 4 wk at recommended rates from early June to September, and once again in November. Application of Ringer fertilizers, ammonium nitrate and sulfur-coated urea gave rise to significantly higher microbial populations on turfgrass leaves and in thatch and soil than most other fertilizers. In most experiments, Ringer fertilizers also improved water retention in thatch compared to other treatments. Ringer Greens Super®, Ringer Turf Restore®, or ammonium nitrate on the creeping bentgrass green significantly suppressed dollar spot disease compared to the other amendments or the untreated control, but for most of the season, they did not control disease as well as the fungicide chlorothalonil. Nitrate leaching from inorganic nitrogen fertilizers has the potential to be a significant source of nitrate contamination of ground water in urban areas where turfgrass is the major living ground cover (17). Frequent application of inorganic fertilizers such as ammonium nitrate can change the soil pH and consequently may alter soil microbial populations and affect plant growth (19, 20, 22). Concerns regarding environmental quality are prompting the development and use of various kinds of organic amendments or fertilizers to reduce or replace inorganic fertilizer and synthetic pesticide use. Organic amendments have been reported to suppress soilborne plant pathogens (6, 15). Recently developed organic turf amendments, such as Ringer Lawn Restore®, Ringer Greens Super® and Ringer Turf Restore® are derived from hydrolysed poultry feather meal, blood meal, wheat germ, potassium sulfate and bone meal. These products contain microorganisms that may be very important in the biological control of diseases caused by species of Phytophthora, Pythium, Rhizoctonia, and Sclerotium (18). They may also directly or indirectly affect the decomposition of thatch and nutrient transformations in soil. Turfgrass thatch is a complex of dead and living roots, stems and organic debris (2). Excessive thatch accumulation can be detrimental to turf quality and is normally controlled through verticutting and top-dressing (2). High microbial activity is important to thatch decomposition and nutrient recycling in turf (3). Cole and Turgeon (5) reported that 1 g of dry soil or thatch from turf of Kentucky bluegrass (Poa pratensis L.) can contain up to 2.8 x 10 8 bacteria and up to 2.8 x 10 6 fungi. Berndt et al. (3) found that application of a range of organic amendments reduced thatch thickness of Kentucky bluegrass, whereas Mancino et al. (11) found that addition of organic amendments increased thatch thickness and soil fungal counts. Soil bacteria and fungi can increase the availability of plant nutrients in soil, form symbiotic associations with turfgrass roots, produc...

Fungal plant pathogens and soil biodiversity

“…Certain soils were later shown to be naturally disease-suppressive and the suppressive action was biological in nature (Cook and Baker 1983). More recent work has confirmed that suppressive activity is often biologically based, but can be regulated by the physical and chemical characteristics of soils (Lumsden et al 1987;Anas and Reeleder 1988;Howell et al 1988;Lewis et al 1992;Liu et al 1995;Gracia-Garza et al 1997). These characteristics, in turn, may be adjusted with the use of various crop cultural practices (Lumsden et al 1987).…”

Sustainable Urban Landscaping: Consumer Preferences and Willingness to Pay for Turfgrass Fertilizers

“…While responsible lawn care includes the selection of the proper grass species and management practices to maintain a healthy lawn, eco-friendly fertilizers are typically defined as fertilizers that contain ingredients that cause less environmental damage than traditional fertilizers (Berndt et al 1990;Liu et al 1995;Duble 1996;McCoy 1998;Cheng et al 2008; Washington State Department of Agriculture 2011). While responsible lawn care includes the selection of the proper grass species and management practices to maintain a healthy lawn, eco-friendly fertilizers are typically defined as fertilizers that contain ingredients that cause less environmental damage than traditional fertilizers (Berndt et al 1990;Liu et al 1995;Duble 1996;McCoy 1998;Cheng et al 2008; Washington State Department of Agriculture 2011).…”

Effect of Organic Soil Amendments on Establishment Vigor, Seedling Emergence, and Top Growth in Kentucky Bluegrass

“…soil amendments (OSA) have beneficial effects on improving the soil physical and chemical property (Landschoot and McNitt, 1997). It also provides suitable environment which leads to increased beneficial microorganisms (Ham et al, 1993;Puustjarvi and Robertson, 1975), disease suppression (Liu et al, 1995), increased turf growth (Kim et al, 1998) and fertilizer and organic matter substitute (Garling and Boehm, 2001;Logan and Harrison, 1995). Organic matter in soil amendments is desirable for soil structure, soil aeration, moisture movement, nutrient availability, and ecosystem sustainability (Bandaranayake et al, 2003;Kim, 2007).…”