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- Author or Editor: Jeffrey Beasley x
Controlled-release fertilizers (CRFs) provide an extended period of nutrient availability for turfgrass growth and may limit offsite nutrient losses compared with water-soluble fertilizers (WSFs). However, increasing temperatures and soil moisture accelerate nutrient release from many CRFs. As a result, turfgrass managers growing turfgrass in warm, humid climates with high rainfall question how effective CRFs are in reducing nutrient runoff losses while maintaining aesthetic quality. A study was conducted to examine the effect of three fertilizer treatments—an unfertilized control, a CRF applied at 87 lb/acre nitrogen (N), and a WSF applied at 87 lb/acre N as a split application (43.5 lb/acre N) at 0 and 45 d after initial fertilization (DAIF)—on nutrient losses from ‘Tifway’ hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) during surface runoff events. Rainfall simulations were conducted 3, 28, 56, and 84 DAIF at an intensity of 3 inches per hour to induce 30 minutes of runoff. Water samples were analyzed for inorganic N and dissolved total phosphorus (DTP). Hybrid bermudagrass quality was similar among fertilizer treatments with CRF application, resulting in slightly higher quality. Across all fertilizer treatments, hybrid bermudagrass exhibited similar runoff initiation time and volumes within each rainfall simulation event. Nutrient losses from fertilized hybrid bermudagrass were greatest at the first runoff event at 3 DAIF, with WSF having the greatest losses. The subsequent application of WSF 45 DAIF did not result in greater N and DTP losses compared with CRF application, most likely a result of water incorporation applied to prevent wilting. Hybrid bermudagrass fertilized with a single application of CRF resulted in 23.6% and 55.6% reductions in cumulative inorganic N and DTP losses, respectively, compared with hybrid bermudagrass fertilized with the a split application of WSF.
Trinexapac-ethyl (TE) [4-(cyclopropyl-a-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] effects on turfgrass root architecture are not known. It has been postulated that PGR application could cause photoassimilate that is normally used for shoot growth to be funneled to root growth. This study evaluated the effects of a single TE application on kentucky bluegrass (KBG) root and shoot growth for seven weeks. Individual KBG plants were grown in a hydroponic system and harvested weekly. At each harvest, tiller height, tiller number, and color ratings were recorded. Estimates of total root length (TRL), root surface area (SA), and average root diameter were measured using the WinRhizo system. Trinexapac-ethyl reduced plant height for 4 weeks followed by a period of postinhibition growth enhancement. Trinexapac-ethyl increased tiller number over the course of the study and slightly enhanced plant color. Trinexapac-ethyl reduced TRL and SA 48% and 46% at 1 week after treatment (WAT) followed by an accelerated growth rate 1 to 4 WAT. Trinexapac-ethyl had no effect on root diameter. On a tiller basis, TE initially reduced TRL and SA 30% and 31%, respectively. Total root length per tiller and root surface area per tiller were reduced by TE treatment, but by 7 WAT, those differences were no longer significant. Initial reductions in TRL and SA per tiller may reduce tiller competitiveness for water and nutrients. Based on data for TRL and SA per tiller, shoot and root growth must be considered in total to fully understand TE effects on plant growth. Field research is needed to corroborate results from hydroponic-studies and examine the effect of various TE rates and multiple applications on turfgrass root and shoot growth.
Industrial insect rearing is expected to increase as a feedstock to meet growing global food demand. This will lead to greater production of insect excreta known as frass, a nutrient-dense organic material that has shown promise as a natural fertilizer source with potential environmental benefits. In this study, black soldier fly (Hermetia illucens) frass (BSFF) was compared with a synthetic fertilizer (SF) during production of containerized ornamentals grown under greenhouse conditions. Fertilizers were incorporated into a bark-based substrate at 0, 0.1, 0.2, or 0.3 kg⋅m–3 nitrogen (N) planted with coleus (Plectranthus scutellarioides) plugs. Growth index, shoot dry weight, and leaf quality were assessed for a period of 6 weeks. In addition, coleus fertilized at 0.3 kg⋅m–3 N and a control had leachate collected and analyzed weekly for volume, pH, electrical conductivity, and nutrient losses. Black soldier fly frass was found to produce marketable coleus plants at 0.3 kg⋅m–3 N and reduce cumulative N leaching by 87% compared with coleus fertilized with SF at the same rate. Therefore, BSFF can be a suitable fertilizer source for coleus production without compromising growth and leaf quality while potentially decreasing nutrient leaching losses.
Managed turfgrass species require frequent inputs to maintain an acceptable level of density and appearance. Among these inputs, the N supply is often the most limiting input in terms of growth and development of the turfgrass stand. However, N fertilization has been linked to nonpoint source (NPS) pollution of groundwater and natural water bodies. White clover (WC), which would provide N in mixed turfgrass swards, could help reduce NPS pollution from N fertilization of turf. To test the feasibility of introducing WC into existing turf, a field study was designed to determine the best method of incorporating WC in mature stands of two cool-season grasses. Two varieties of WC, ‘Dutch White’ (DW), and ‘Microclover’ (MC), were sown (24.4 kg·ha−1) into existing stands of kentucky bluegrass (KBG) (Poa pratensis L.) and tall fescue (TF) (Festuca arundinacea Schreb.). Establishment techniques tested included core aeration (CA), scalping (SC), and vertical mowing (VM) compared with direct sowing into the turfgrass stand. Establishment treatments were performed in April, July, and October of 2012–13 to examine for any seasonal timing effect on establishment. No significant difference in plant numbers (individual clover plants per square meter) was found between WC varieties among planting dates and techniques. The SC treatment resulted in the highest individual clover plant numbers. However, turfgrass recovery was significantly slower from the SC treatment than all other treatments. The summer planting date yielded the highest WC plant numbers. Recovery of the turfgrass from all preplanting treatments was also highest at the spring and summer planting dates.
Phosphorus (P) fertilizers with high water-solubility are often applied in excessive amounts to porous horticultural substrates to produce high-quality plants. As a result, high P losses during containerized plant production have presented an environmental challenge to responsible growers. Poultry litter ash (PLA), a byproduct of bioenergy production, contains P concentrations comparable to conventional P fertilizers but is characterized as having lower water-solubility. Therefore, a series of experiments were conducted to characterize effects of PLA on container-plant growth and P leaching. PLA was compared with superphosphate (SP), a highly water-soluble P source, in ratios of 0:100, 25:75, 50:50, 75:25, and 100:0 (SP:PLA) in the production of Lantana camara L. ‘New Gold’. In 2011, lantana fertilized with higher ratios of PLA exhibited slower growth with lower shoot and root biomasses compared with 100% SP-fertilized lantana. However, in 2012, differences in fertilizer treatments lessened, with 100% PLA-fertilized lantana exhibiting 14% less shoot biomass and no differences in root biomass compared with 100% SP-fertilized lantana. Measurement of shoot:root biomass, a common indicator of P deficiency, was not different between any P treatments in 2011 or 2012. This indicates root growth was most likely the driving factor in P-treatment effects on shoot biomass in each year of the experiment. During a postproduction field trial, no differences in growth or biomass were observed between lantana previously fertilized with P, regardless of source. However, application of PLA as the single P source reduced dissolved reactive P (DRP) concentrations in leachate >90% and total P (TP) mass losses 69% compared with 100% SP-fertilized lantana during container production, with P treatments reducing DRP and TP losses as PLA ratios increased. Therefore, the benefit of P-loss reduction during container production achieved through PLA application may warrant the acceptance of slightly smaller plants or extending production cycles.
As turfgrass quality of seeded bermudagrass (SB) [Cynodon dactylon (L.) Pers.] cultivars has increased over the past 20 years, so has their use. Improved SB cultivars offer ease of establishment and convenience of storage while providing an economic advantage over vegetative propagation. Currently, most improved seeded cultivars are marketed with a seedcoating unique to each seed company. However, germination of some of the new cultivars is not ideal. The objectives of this study were to determine commercial coating effects on germination, compare germination among cultivars, and evaluate the effect of temperature on germination of five bermudagrass cultivars. ‘Princess-77’, ‘Riviera’, ‘Transcontinental’, and ‘Yukon’ were selected for a series of 21-day germination studies with ‘Arizona Common’ included as a standard cultivar. The study compared two seed lots of coated and uncoated samples of the five cultivars for germination response to six temperature regimes. Cumulative count intervals occurred on Day 7, Day 14, and Day 21. Overall, commercial seedcoating did not significantly affect SB germination. However, both temperature regime and cultivar were significant factors. Germination percentage was greatest with either the 35/25 °C or the 30/20 °C temperature regimes. ‘Riviera’ exhibited the lowest overall germination, whereas ‘Transcontinental’ and ‘Arizona Common’ exhibited the highest.