In situ nitrogen fixation by white clover in mixed swards in Nova Scotia.
J.K. Vessey and D.G. Patriquin. 1984. Canadian Journal of Plant Science 64: 625-636.
ABSTRACT At three sites, cloveR cover increased from less than llVo in April to 5O-70% during anthesis in July. It began to decline in September, reaching 20-30% in December. Acetylene-reduction activity (ARA), measured by an in situ technique, commenced in April when soil temperature was 5-7’C. “Clover-specific ARA” (ARA measured in clover patches where cover of clover was 100%) was generally high through most of May, June and July, and then declined, reaching low levels by November. Clover-specific ARA was correlated with total rainfall during the period between 7 and 28 days before the assay (r=0.729, P<0.01 ). The amount of N2 fixed by white clover over a 1-yr period was estimated at 66 and 81 kg N/ha for two pasture sites and 100 kg N/ha at a lawn site. Clover cover and thermal regime appeared to be the two main factors influencing the amount of N. fixed by white clover at a site. Eight sites of widely varying clover cover (2-53%) were compared in July with regard to cover, clover-specific ARA, edaphic characteristics and fertilizer and grazing management. Management strategy appeared to have the greatest influence on clover abundance in pasture.
The Oaks Experiments on Organic Management of Turf: Final Industry Report The Oaks Experiments on Organic Management of Turf: Final Industry Report
D.G. Patriquin., D.A.Reid. & M.D. Walsh. 1996. Edmonds Landscape and Construction Services Limited, Halifax, Nova Scotia, Canada. (Posted on Dalspace, the Dalhousie University electronic archives). The link is to the abstract and a downloading link; the document is 380 pages, 161MB. View an Extended Summary (28 pages).
The Oaks experiments were designed to address practical questions about organic management of turfs (lawns, sports fields etc.), notably: (i) How do we use organic fertilizers and soil-building amendments on turf for maximum aesthetic benefit without overusing them?; (ii) What turf species and mixtures are most suitable for organically managed turfs? The experiments were conducted at an urban site (“The Oaks”) in Halifax, Nova Scotia over three full growing seasons (1992-1994), with some observations continued over a fourth season.
Turf quality response to municipal solid waste compost and Dutch white clover (Trifolium repens L.) under organic management
J.D. Atkinson Van Dommelen. 2003. MSc thesis, Dalhousie University ABSTRACT
The use of “manufactured topsoil” by developers is common in urban areas. These soils typically have a sandy texture and a low content and/or low quality of organic matter. Such soils have proven to be poor substrates for organically managed turf, requiring large fertilizer amendments to maintain commercially acceptable quality.
A field experiment was conducted from 1998-2001 at Halifax, Nova Scotia, Canada to examine potential benefits for organically managed turf from amending manufactured topsoil with mature municipal solid waste (MSW) compost. The design was a split plot with three replicates (blocks). Test plots, 3 x 4 m by 12.5 cm depth, were filled with manufactured topsoil. Main plot treatments were 0, 2.5, and 5 cm of mature MSW compost which was mixed into the topsoil. Plots were seeded with Canada #1 turfgrass on 18 September 1998. Subplot treatments were 0 and 147 kg N ha-1 year-1 supplied in three topdressings with an organofertilizer (9-2-5). The no-compost plus fertilizer treatment corresponds to typical commercial practice. Sward biomass and greenness ratings were used as measures of turf quality. Biomass was determined 3 times each year, and greenness monthly through the field season. Soil samples, collected annually, were analyzed for organic matter, pH, and nutrients.
In June 1999, there was an outbreak of red thread (Laetisaria fuciformis [MacAlpine] Burdsall) on the lower fertility plots. Compost and fertilizer had negative effects on red thread, but did not completely suppress it. In the late summer, the site was overseeded with Dutch white clover (Trifolium repens L.) to help, along with other measures, to suppress the disease. There was no recurrence in 2000 and 2001. Clover is considered a desirable component of organic turfs. Clover was abundant through 2000 and early 2001, but declined to low levels by the fall of 2001. Clover biomass was consistently highest in plots with no amendments and lowest in plots with some combination of compost and fertilizer.
Composted plots without fertilizer had higher greenness ratings and biomass than nocompost, no-fertilizer plots in 1999. When clover abundance was high, total biomass and greenness ratings were similar across all treatments. In 2001, clover declined to low levels, and again compost had positive effects on greenness and biomass. Overall, greenness and biomass values on the composted plots without fertilizer were equivalent to those for no-compost plots receiving fertilizer, indicating that the compost effectively substituted for fertilizer. There was little or no difference in turf biomass and greenness between 2.5 and 5 cm compost treatments. However, the soil organic matter at the end of 2001 in the 5 cm compost treatment (4.6%) was still substantially higher than in the 2.5 cm compost treatment (3.0%) and the control (2.1%), so longer persistence of benefits could be expected in the 5 cm treatment.
The results demonstrate that compost effectively substituted for fertilizer over 3 years; soil organic matter data suggest that such benefits could be expected to extend beyond 3 years. When clover was abundant, it masked differences in turf quality associated with fertilizer and compost treatments.
Forbs in Lawns ofThree University Campuses in Halifax Regional Municipality
V.B. Kavanagh. 2004. Honours thesis, Dalhousie University.
ABSTRACT: A ban on the cosmetic use of herbicides and pesticides on turf and gardens in Halifax Regional Municipality (HRM), except on commercial properties, was implemented in 2003. There has been little formal research on forbs (non graminoid, non~woody angiosperms) in the temperate zone turfs ofNorth America, other than on certain problematical weeds, so how the forb composition will change is largely unknown. It is expected that an increase in overall abundance and number of species on turfs previously treated with herbicide will occur. This study, conducted on 3 university campuses in HRM addresses two questions: (i) are there distinct groupings offorb species in lawns of the three campuses? and (ii) can differences in species composition and distribution of individual species be related to environmental andlor management variables? Three campuses (Mount Saint Vincent University, Saint Mary’s University, and Dalhousie Univeristy) were chosen for study because each presents a range of site conditions (e.g. shadedlunshaded, shallow/deep soils, disturbed/undisturbed) under a single management regime but the regimes and history ofherbicide use differ between campuses. Seventeen sites (discrete turf areas), selected for different degrees of shading, disturbance, and position (edge or contiguous turf) were examined on each campus. Primer E, non-metric multivariate statistical procedures were used to examine the data for species groupings and for the relationship of species composition at different sites to environmental factors. Sites at edges ofturls were characterized by 3 species at which occurred exclusively or predominantly at these sites. Differences between other (contiguous) sites were associated mainly with differences in abundance ofglobally common species. Multidimensional scaling analysis (MDS) revealed different patterns in the distribution of individual species across sites, but these were not strongly related to the environmental factors examined. The data permitted a test ofthe proposal ofTilman et al. (1999) that dandelion (Taraxacum officinale) abundance is determined by resource supply rates, in particular by potassium (K) and calcium (Ca). However, there was no correlation between dandelion and soil K or soil Ca.