Fall Applications Research Articles

Dissipation of Antimicrobials in a Seasonally Frozen Soil after Beef Cattle Manure Application.

Land application of manure containing antimicrobials results in the dispersion of the antimicrobials in agro-ecosystems. Dissipation of excreted antimicrobials in seasonally frozen agricultural soils has not been fully characterized under field conditions. This study investigated the field dissipation kinetics of chlortetracycline, sulfamethazine, and tylosin over a 10-mo period after fall application of manure from cattle () administered 44 mg chlortetracycline (chlortetracycline treatment [CTC]), 44 mg each of chlortetracycline and sulfamethazine (CTCSMZ), or 11 mg tylosin per kg feed daily. Antimicrobial concentrations in manured soil reflected the same relative concentrations in manure: chlortetracycline > sulfamethazine > tylosin. The first-order dissipation half-life (DT) for chlortetracycline from the CTCSMZ treatment was 77 d during the growing season and 648 d during the nongrowing season when the soil was frozen for an extended period. By comparison, dissipation of chlortetracycline added alone (treatment CTC) did not differ significantly between the two seasons (mean DT, 121 d). During the nongrowing season, chlortetracycline from CTC dissipated faster ( = 0.004) than that from the CTCSMZ treatment, indicating that the presence of sulfamethazine may have altered the dissipation of chlortetracycline. Dissipation kinetics for sulfamethazine and tylosin were not determined due to low detection in the manure-amended soil. Sulfamethazine was detected (up to 16 ± 10 µg kg) throughout the 10-mo monitoring period. Tylosin concentration was ≤11 ± 6.6 µg kg and gradually dissipated. Chlortetracycline was detectable 10 mo after application in the seasonally frozen soil, indicating a risk for residue build-up in the soil and subsequent offsite contamination.

What motivates farmers to apply phosphorus at the “right” time? Survey evidence from the Western Lake Erie Basin

Abstract Phosphorus loadings from the Maumee River watershed have significantly compromised the Lake Erie ecosystem, as evidenced by the most severe harmful algal bloom in Lake Erie in 2015 and the shut-down of Toledo drinking water supply in 2014. Despite government payments for adoption of voluntary conservation practices, excess nutrient runoff from agricultural production remains a substantial challenge. The right timing of nutrient application is a critical best management practice (BMP). Using a unique survey of 2540 farmer respondents in the Maumee River watershed, this paper analyzes how socio-psychological, socio-demographic, and field-based spatial characteristics impact farmers' adoption of timing-related best practices for nutrient management, including delaying broadcast application before a storm event, avoiding winter application of nutrients, and avoiding fall application of nutrients. Results reveal three unique classes of farmers for each of the timing-related management decisions. While the significance of most farmer and field characteristics varies across the three BMP adoption decisions, perceived efficacy—the belief that the particular practice will actually reduce dissolved phosphorus runoff from farm fields—is positively correlated with a higher likelihood of adopting each of the BMPs across almost all classes of farmers. For example, results from the ordered logit model suggest that a 20% increase in perceived efficacy would result in the likelihood of actual adoption of delaying broadcast from 35% to 48%. An implication is that policies and outreach efforts aimed at increasing farmers' perceived efficacy of practices could lead to higher adoption levels, but the effectiveness may vary across different classes of farmers.

Application of Nitrapyrin with Banded Urea, Urea Ammonium Nitrate, and Ammonia Delays Nitrification and Reduces Nitrogen Loss in Canadian Soils

Core Ideas Nitrapyrin has been tested in fallow field trials in cereal and oilseed growing regions of Canada. Nitrapyrin maintained N in the ammonium form through critical loss periods. Nitrapyrin preserved more mineral N in the soil relative to non‐stabilized fertilizer. Soil N loss is a significant impediment to maximizing yield and profitability for farmers in Canada. Maintaining N in the stable and plant‐available NH4+ form via use of nitrification inhibitors limits the potential for soil N losses from denitrification or leaching. Between 2013 and 2015, twenty‐one research trials were established across the major cereal and oilseed growing regions of Canada to evaluate the efficacy of two commercially available formulated nitrapyrin products, eNtrenchTM and N‐Serve, at stabilizing soil N in the NH4+ form and protecting against N loss. Urea, urea ammonium nitrate (UAN) or NH3 fertilizer treatments were banded in the fall or spring on fallow land, and the soil was sampled to a depth of 60 cm at multiple time intervals after application. Fall applications of nitrapyrin resulted in 21–63% more NH4N, and 10–19% more total mineral N, at spring sampling after soil thaw relative to non‐stabilized fertilizer. Spring applications of nitrapyrin resulted in larger pools of NH4–N for at least 8 weeks after treatment, and they increased total mineral N by up to 25%, compared with non‐stabilized treatments. Results suggest that eNtrench and N‐Serve are useful tools for growers looking to protect their N investment, optimize crop yield potential, and enhance flexibility of their N application timing.

Lower Nitrous Oxide Emissions from Anhydrous Ammonia Application Prior to Soil Freezing in Late Fall Than Spring Pre-Plant Application.

Fall application of anhydrous ammonia in Manitoba is common but its impact on nitrous oxide (NO) emissions is not well known. A 2-yr study compared application before freeze-up in late fall to spring pre-plant application of anhydrous ammonia on nitrous oxide (NO) emissions from a clay soil in the Red River Valley, Manitoba. Spring wheat ( L.) and corn ( L.) were grown on two 4-ha fields in 2011 and 2012, respectively. Field-scale flux of NO was measured using a flux-gradient micrometeorological approach. Late fall treatment did not induce NO emissions soon after application or in winter likely because soil was frozen. Application time did alter the temporal pattern of emissions with late fall and spring pre-plant applications significantly increasing median daily NO flux at spring thaw and early crop growing season, respectively. The majority of emissions occurred in early growing season resulting in cumulative emissions for the crop year being numerically 33% less for late fall than spring pre-plant application. Poor yield in the first year with late fall treatment occurred because of weed and volunteer growth with delayed planting. Results show late fall application of anhydrous ammonia before freeze-up increased NO emissions at thaw and decreased emissions for the early growing season compared to spring pre-plant application. However, improved nitrogen availability of late fall application to crops the following year is required when planting is delayed because of excessive moisture in spring.

Averages and Seasonality of Prices for Nitrogen Fertilizers

From 2009 through 2015, anhydrous ammonia had an average price equal to $.45 per pound of actual nitrogen (N). This $.45 price was lower than the prices for urea ($.54 per pound) and liquid N ($.61 per pound). From 2009 through 2015, nitrogen prices averaged less in the fall than in the spring. Often, applying anhydrous ammonia in the fall is one of the lowest cost methods of placing nitrogen on fields. Benefits from a combination of higher yields or lower application rates need to be obtained to cause spring and early summer applications to be competitive with fall applications.

Annual and seasonal phosphorus export in surface runoff and tile drainage from agricultural fields with cold temperate climates

Abstract Phosphorus (P) export from agriculture fields is contributing to algal blooms within Lake Erie. Field data quantifying the magnitude, timing and pathways of P loss are required to develop and test solutions. This study quantifies annual and seasonal losses of dissolved (DRP) and total (TP) phosphorus in surface runoff and tile drainage from three reduced tillage fields (October 2011 to April 2013). The non-growing season (NGS, October to April) was a critical period, with 83 to 97% of annual combined [surface + tile] runoff; 84 to 100% of DRP loss; 67 to 98% of TP loss occurring in this time. Annual export (May 2012 to April 2013) ranged from 0.332 to 0.419 kg TP/ha/yr and 0.034 to 0.096 kg DRP/ha/yr. Tile drainage contributed the majority of annual water export from fields (78 to 90%) whereas surface runoff contributed little (10 to 22%). Tiles exported 0.169 to 0.255 kg TP/ha/yr (40 to 77% of total TP load) and 0.017 to 0.023 kg DRP/ha/yr (19 to 67% of total DRP load). Thus, surface runoff, which primarily occurred during winter thaws, exported disproportionately more P relative to its contribution to flow. Phosphorus losses in tile drain effluent monitored over an additional NGS (October 2011 to April 2012) were elevated at two sites following the fall application of P. This study provides an improved understanding of edge-of-field P losses in humid, cold temperate regions that experience significant winter periods, and provides estimates of P loads from fields in which P conservation strategies are employed.

Winter and growing season nitrogen mineralization from fall-applied composted or stockpiled solid dairy manure

Adequate characterization of nitrogen (N) mineralization with time from manure and other organic sources is needed to maximize manure N use efficiency, decrease producer costs, and protect groundwater quality. The objective of our 2-year field study at Parma, ID, was to quantify in situ N mineralization with time as affected by a one-time fall application of solid dairy manure, either composted or stockpiled. The experiment included five treatments: a non-N fertilized control, two first-year rates of stockpiled solid dairy manure (21.9 and 43.8 Mg ha−1, dry wt.) and two rates (53.1 and 106.1 Mg ha−1, dry wt.) of composted dairy manure (hereafter termed compost). Net N mineralized (mineralization less immobilization) was determined to a depth of 0.3 m by repeatedly measuring soil inorganic N (NH4-N + NO3-N) concentrations in buried polyethylene bags. Overwinter mineralization was measured between amendment incorporation in fall and sugarbeet (Beta vulgaris L.) planting the following spring. In-season mineralization was measured in situ for seven consecutive incubation periods during the c. 220-day growing season for furrow-irrigated sugarbeet. Net N mineralized often varied among amendments and from year to year through mid-season, likely due to seasonal variation in soil temperature, annual differences in amendment properties, and other factors. In early spring 2003 after a warmer-than-normal winter, immobilization exceeded mineralization, regardless of treatment. In-season net N mineralized peaked between mid-August and early September (DOYs 230–251) each year, regardless of treatment. Annual (c. 11-month) net N mineralized in 2003 averaged 52 kg N ha−1, similar among treatments. In 2004, annual net N mineralized was similar between rates within amendments and averaged 250 kg N ha−1 where manure treated, 150 kg N ha−1 where compost treated, and 106 kg N ha−1 where untreated. On average in 2004, 31 % of compost’s annual net N mineralized occurred before the growing season and 69 % during the season while essentially all of manure’s net N mineralized occurred during the season. None of the amendments’ total N was, in net, mineralized in 2003 but in 2004 on average, 2 % of compost’s and 16 % of manure’s total N was mineralized, similar between rates within amendments. When estimating annual net N mineralized from fall-applied organic amendments, one must account for abnormal temperatures, including those overwinter.

Timing of Soil-Residual Herbicide Applications for Control of Giant Ragweed (Ambrosia trifida)

Fall-applied residual and spring preplant burn-down herbicide applications are typically used to control winter annual weeds and may also provide early-season residual control of summer annual weed species such as giant ragweed. Field experiments were conducted from 2006 to 2008 in southern Illinois to (1) assess the emergence pattern of giant ragweed, (2) evaluate the efficacy of several herbicides commonly used for soil-residual control of giant ragweed, and (3) investigate the optimal application timing of soil-residual herbicides for control of giant ragweed. Six herbicide treatments were applied at four application timings: early fall, late fall, early spring, and late spring. Giant ragweed first emerged in mid- and late-March in 2007 and 2008, respectively. The duration of emergence varied by year, with 95% of emergence complete in late May of 2008, but not until early July in 2007. Giant ragweed emergence occurred more quickly in plots that received a fall application of glyphosate + 2,4-D compared with the nontreated. Fall-applied residual herbicides did not reduce giant ragweed emergence in 2007 when compared with the nontreated, with the exception of chlorimuron + tribenuron applied in late fall. Giant ragweed control from early- and late-spring herbicide applications was variable by year. In 2007, saflufenacil (50 and 100 g ai ha−1) and simazine applied in early spring reduced giant ragweed densities by 95% or greater through mid-May; however, in 2008, early-spring applications failed to reduce giant ragweed emergence in mid-April. The only treatments that reduced giant ragweed densities by > 80% through early July were late-spring applications of chlorimuron + tribenuron or saflufenacil at 100 g ha−1. Thus, the emergence patterns of giant ragweed in southern Illinois dictates that best management with herbicides would include late-spring applications of soil-residual herbicides just before crop planting and most likely requires subsequent control with foliar or soil-residual herbicides after crop emergence.

Herbicide and winter flood treatments for controlling volunteer rice off-season

Field experiments were conducted to study the efficacy of 12 herbicide treatments for volunteer rice control with, or without, winter-flooding in Stuttgart and Rohwer, Arkansas, USA over two years (2012–13 and 2013–14). Herbicides were applied either in the fall or at 35 d prior to planting rice in the spring. Commercially harvested Clearfield™ long-grain inbred rice 'CL152' was used as volunteer rice seed, broadcasted and lightly incorporated in October, 2012 and 2013. 'Jupiter' (medium-grain inbred, conventional rice) was planted in May as the rice crop. Winter-flood was initiated soon after the fall herbicide treatments were applied and terminated in February. Winter-flood reduced volunteer rice germination by 34% in 2013 and by 40% in 2014. Some fall herbicide treatments, without winter flood, generally caused more injury to the rice crop planted in the spring than the winter-flooded treatments. Fall application of pyroxasulfone (0.12 kg ha−1), flumioxazin (0.14 kg ha−1), and sulfentrazone (0.34 kg ha−1) as well as pre-plant application of pyroxasulfone (0.12 kg ha−1) and 2,4-D (2.24 kg ha−1), resulted in lower volunteer rice infestation, averaged over flood treatments. Pre-plant application of 2,4-D (2.24 kg ha−1), sulfentrazone in the fall (0.34 kg ha−1) and pyroxasulfone pre-plant (0.12 kg ha−1) injured the rice crop by 20%, 23%, and 47%, respectively. Fall application of pyroxasulfone (0.12 kg ha−1) followed by a lower rate of 2,4-D (1.12 kg ha−1) 35 d pre-plant caused minimal (6%) crop injury and did not reduce yield. This treatment provided better volunteer rice control (73%) than pyroxasulfone alone at 0.12 kg ha−1 applied in the fall (64%). To evaluate the overwintering potential of hybrid and non-hybrid volunteer seeds, these seed types were planted at three depths (0, 7.5, 15 cm) in flooded and non-flooded conditions in a buried-pot experiment at Stuttgart and Rohwer over 2 years. Winter-flood reduced rice germination by 50% in 2013–14 and 40% in 2014–15 (averaged over seed type and burial depth), after 160 d and 130 d of burial, respectively. After the winter, the viability of hybrid seed (germinable + dormant) was higher (13 and 53%) than that of non-hybrid seed (8 and 27%) in both years.

Low-Dose Glyphosate Does Not Control Annual Bromes in the Northern Great Plains

AbstractAnnual bromes (downy brome and Japanese brome) have been shown to decrease perennial grass forage production and alter ecosystem functions in northern Great Plains rangelands. Large-scale chemical control might be a method for increasing rangeland forage production. Although fall application has been shown to be the most effective and least likely to impact co-occurring native species, spring germination of downy brome may reduce the efficacy of fall-only herbicide application. We assessed the impact of a low glyphosate dose rate (210 g ha−1) applied to rangelands in fall or in fall and spring on nontarget species and on annual brome abundance at two sites in eastern Montana over 2 yr. We tested the following hypotheses: (1) nontarget effects are greater with spring herbicide application, (2) fall and spring herbicide application are necessary for effective downy brome control, and (3) fall herbicide application is sufficient to control Japanese brome. Few nontarget effects occurred; two dicotyledonous species exhibited small increases in response to herbicide. We found that that a single fall application reduced downy brome cover and seed bank density, but after the second fall application in the following year, downy brome did not continue to show a response to herbicide. After 2 yr of fall herbicide application, Japanese brome had denser seed banks in plots where herbicide had been applied. Blanket glyphosate application on rangelands is an unreliable method for controlling annual brome invasions in the northern Great Plains.

Evaluating Annual Bluegrass Herbicide Resistance Evolution in Golf Course Fairways

Annual bluegrass is one of the most diverse plant species in the world and is the most problematic winter annual weed in commercial turfgrass. Continuous application of the same herbicide mechanism of action for annual bluegrass control on golf courses has increased herbicide-resistant populations. The purpose of this research was to simulate six herbicide-use strategies to evaluate the risk of annual bluegrass resistance evolution to glyphosate. In a worst-case scenario of yearly glyphosate applications at dormancy, resistance evolved within 10 yr and was predicted to evolve in > 90% of populations by yr 20. When glyphosate was rotated on alternate years with a unique mechanism of action, resistance was delayed for 12 to 15 yr. Season-long control of annual bluegrass often requires multiple herbicide applications. Therefore, additional strategies were simulated in which glyphosate was applied at dormancy with combinations of PRE and/or POST herbicides at various timings. Resistance was most effectively delayed with a PRE application in late summer, a POST application in fall, and alternating glyphosate with a different POST option at dormancy. This delayed resistance by 25 yr and a 35% risk was predicted after 50 yr. Strategies utilizing three annual herbicide applications with unique mechanisms of action were more effective for controlling population growth compared to other strategies. Resistance was predicted to evolve within 35 yr for each of the strategies simulated. However, these results indicate annual bluegrass herbicide resistance can be managed by using an integrated herbicide program, rotating unique mechanisms of action as frequently as possible.

Effectiveness of Herbicides for Control of Hairy Vetch (Vicia villosa) in Winter Wheat

A field experiment was conducted in 2009–2010 at Pennsylvania and Maryland locations, and repeated it in 2010–2011 to test the effectiveness of POST-applied herbicides at fall and spring timings on seeded hairy vetch in winter wheat. A total of 16 herbicide treatment combinations was tested that included synthetic auxins, acetolactate synthase (ALS) inhibitors, and a protoporphyrinogen oxidase inhibitor. Spring applications tended to be more effective than fall applications. Among synthetic auxins, clopyralid (105 g ae ha−1) and treatments containing dicamba (140 g ae ha−1) were effective at both timings, resulting in greater than 90% hairy vetch control at wheat harvest. Pyroxsulam and prosulfuron applied at 18 g ai ha−1provided the most effective hairy vetch control (> 90%) at both application timings among ALS inhibitors. Spring applications of several herbicides provided moderate (> 80%) to high (> 90%) levels of hairy vetch control, including: 2,4-D amine (140 g ae ha−1), mesosulfuron-methyl (15 g ai ha−1), tribenuron-methyl (13 g ai ha−1), and thifensulfuron/tribenuron-methyl treatments (16 and 32 g ai ha−1). Winter wheat injury was evaluated, but symptoms were negligible for most treatments. Winter wheat yields declined with increasing hairy vetch biomass. Fall herbicides may be prioritized to reduce hairy vetch competition during the fall and early spring growing season. Our research has established that several synthetic auxin and ALS-inhibiting herbicides, applied POST in fall or spring, can be safely used in winter wheat to control hairy vetch in an integrated weed management program.

Efficacy of Soil-Applied Neonicotinoid Insecticides for Long-term Protection Against Emerald Ash Borer (Coleoptera: Buprestidae).

Protection of green ash trees (Fraxinus pennsylvanica Marshall) from the emerald ash borer (EAB), Agrilus planipennis Fairmaire, by soil applications of neonicotinoids (imidacloprid, clothianidin, and dinotefuran) was tested at five locations between 2005 and 2013. Application rate and spring versus fall application dates were evaluated in tests with neighborhood street trees and in one plantation of 65 ash trees. Insecticide treatments of ash trees at all five sites were initiated as the leading edge of the EAB invasion began to kill the first ash trees at each location. Trees were treated and evaluated at each site for 4 to 7 yr. Spring applications of imidacloprid were more efficacious than fall applications. Application rates of 0.8 g a.i./cm dbh or greater per year gave a higher level of protection and were more consistent than rates of 0.56 g a.i./cm dbh per year or less. The number of years between the first observation of canopy loss due to EAB and death of most of the control trees varied from three to seven years among test sites, depending on how many non-treated ash trees were nearby.

Evaluation of Metarhizium brunneum F52 (Hypocreales: Clavicipitaceae) for Control of Japanese Beetle Larvae in Turfgrass.

Experimental and commercial preparations of Metarhizium brunneum (Petch) strain F52 were evaluated for control of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarbaeidae), larvae (white grubs) in the laboratory and under field conditions. Experimental preparations consisted of granule and liquid formulations made using in vitro produced microsclerotia, which are intended to produce infective conidial spores after application. These formulations were compared against commercial insecticides (imidacloprid and trichlorfon), and commercial formulations of M. brunneum F52 (Met 52) containing only conidia. Field-collected grubs were susceptible to infection in a dosage-dependent relationship when exposed to potting soil treated with experimental microsclerotia granules in the laboratory. The LC(50) for field-collected larvae was 14.2 mg of granules per cup (∼15 g granules/m(2)). Field plots treated with experimental and commercial formulations of M. brunneum F52 after 10 September (targeting second and third instar grubs) had significantly lower grub densities compared with untreated plots, providing 38.6-69.2% control, which sometimes equaled levels of control with chemical insecticides. Fungal treatments made prior to 21 August provided 14.3-69.3% control, although grub densities resulting from these treatments were often not significantly lower than those in untreated control plots. By comparison, chemical insecticide treatments provide 68-100% grub control, often providing better control when applied earlier in the season. In conclusion, P. japonica larvae are susceptible to infection by M. brunneum, and grub densities were reduced most consistently by fall applications targeting later instars.

Safety of Sequential Fall Methiozolin Applications on Creeping Bentgrass Putting Greens

Methiozolin is an herbicide with preemergence (PRE) and postemergence (POST) activities for control of annual bluegrass (AB; Poa annua L.). Previous research reported that fall applications provide better control than spring applications when methiozolin is applied as a POST, and PRE application appears to show a higher degree of efficacy than POST applications. Preemergence application for AB control on creeping bentgrass (CB; Agrostis stolonifera L.) putting greens requires treatment starting in late summer to early fall, when CB greens are likely under summer stress. Three field studies were conducted to evaluate the safety of fall sequential methiozolin applications on CB greens. Treatments consisted of methiozolin at 0.22, 0.45, 0.67, or 0.89 lb a.i./acre applied 1, 2, or 4 weeks apart, totaling 1.78 to 2.01 lb a.i./acre per season. Phytotoxicity was consistently observed in one out of three studies but was at an acceptable level (≥6 on a scale of 1–9) in all evaluations. Methiozolin applications, regardless of rate or application interval, resulted in a consistent AB control up to 95% over the season, compared with the nontreated control. Results suggest that sequential applications of methiozolin in fall with the initial treatment starting in late summer to early fall may provide effective AB control with acceptable safety to CB putting greens.

Nitrogen Applications for Wheat Production across Tillage Systems in Alabama

Alabama wheat (Triticum aestivum L.) farmers are changing management practices, which include using higher N fertilizer rates and planting wheat with no‐tillage or other conservation tillage systems to maximize yields. Experiments were conducted to (i) determine the level of tillage necessary to optimize wheat yields across different regions of Alabama and (ii) determine if N requirements change across tillage systems and regions in Alabama at four locations resulting in 9 site‐year comparisons. Each experiment consisted of a split‐plot design with tillage as the main plot and 12 N fertilizer treatments as subplots, replicated four times to compare Zadoks’ Growth Stage (GS)‐30 tiller densities, tiller N concentrations, tiller biomass, GS‐31 wheat biomass, biomass N concentration, wheat yields, and grain crude protein. Nitrogen treatments consisted of different rates across fall, GS‐30, and GS‐31 application times. Tillage systems had no effect on tiller density, tiller N concentration, or tiller biomass, but fall N increased tiller density 15% and tiller biomass 34% across Coastal Plain locations. Non‐inversion tillage increased wheat yields 13% on Coastal Plain soils compared to conventional tillage. Fall N increased wheat yields 10%, and N applied at GS‐30 improved yields 18% compared to delaying application until GS‐31, indicating application of fall N and applying total N by GS‐30 was imperative for successful wheat production on Coastal Plain soils. Neither tillage system nor N applications affected wheat production extensively across the Limestone Valley. Non‐inversion tillage or no‐tillage with current recommended N practices can be successfully used in Alabama wheat production.

Winter wheat straw management on subsequent processing tomato yield, quality, economics and nitrogen dynamics

Van Eerd, L. L., Loewen, S. A. and Vyn, R. J. 2015. Winter wheat straw management on subsequent processing tomato yield, quality, economics and nitrogen dynamics. Can. J. Plant Sci. 95: 273–283. The removal of crop residues to meet the anticipated demand for the bioeconomy sector may impact subsequent crop productivity. A field experiment was designed to evaluate the response of processing tomato (Solanum lycopersicum L.) on winter wheat (Triticum aestivum L.) straw management practices of: (1) retaining straw, (2) removing straw, or (3) retaining straw with a fall application of calcium ammonium nitrate at 34 kg N ha−1 to enhance straw decomposition. At two locations in 2006–2009, a split-plot design within a randomized complete block experiment, with wheat straw management as main-plot factor and nitrogen fertilizer (0 and 145 or 224 kg N ha−1) to the tomato crop as split-plot factor. At Ridgetown, marketable and total yield and profit margins were significantly higher with straw retained compared with straw removed treatments (total yield of 74.4 vs. 66.3 Mg ha−1 yr−1, respectively) but the straw retained plus fall N treatment (total yield 72.8 Mg ha−1 yr−1) was not different. However, at Leamington, straw management had no effect on yield or profit margins likely due to the rye (Secale cereale L.) cover crop used in the production system. At both locations, tomato quality (color, pH, soluble solids) was not influenced by straw or N management. Nitrogen fertilizer application to tomato had a significant effect on total processing yield, soil mineral N, and plant N, but wheat straw management had no effect on these parameters and there were no N fertilizer by straw management interactions. Winter wheat straw management did not impact soil N fertility for subsequent crop production. Thus, there may be significant undesired effects of removing crop residues on a subsequent crop yield; however, planting a cover crop may mitigate subsequent yield losses associated with biomass removal.

The efficacy of winter cover crops to stabilize soil inorganic nitrogen after fall-applied anhydrous ammonia.

There is a dearth of knowledge on the ability of cover crops to increase the effectiveness of fall-applied nitrogen (N). The objective of this study was to investigate the efficacy of two cover crop species to stabilize inorganic soil N after a fall application of N. Fall N was applied at a rate of 200 kg N ha into living stands of cereal rye, tillage radish, and a control (no cover crop) at the Illinois State University Research and Teaching Farm in Lexington, Illinois. Cover crops were sampled to determine N uptake, and soil samples were collected in the spring at four depths to 80 cm to determine the distribution of inorganic N within the soil profile. Tillage radish (131.9-226.8 kg ha) and cereal rye (188.1-249.9 kg ha N) demonstrated the capacity to absorb a minimum of 60 to 80% of the equivalent rate of fall-applied N, respectively. Fall applying N without cover crops resulted in a greater percentage of soil NO-N (40%) in the 50- to 80-cm depth, compared with only 31 and 27% when tillage radish and cereal rye were present at N application. At planting, tillage radish stabilized an average of 91% of the equivalent rate of fall-applied N within the 0- to 20-cm, depth compared with 66 and 57% for the cereal rye and control treatments, respectively. This study has demonstrated that fall applying N into a living cover crop stand has the potential to reduce the vulnerability of soil nitrate and to stabilize a greater concentration of inorganic N within the agronomic depths of soil.

Glyphosate Tolerance of Two Perennial Ryegrass Cultivars from Fall Applications and at Seedling Growth Stages

The use of glyphosate-tolerant perennial ryegrass (Lolium perenne L.) (PRG) cultivars JS501 and Replay provides turfgrass managers a unique option for annual bluegrass (Poa annua L.) (ABG) control. Both cultivars can tolerate a maximum glyphosate rate of 0.81 kg·ha−1 acid equivalent (a.e.) after establishment under optimal growing temperatures (16 to 24 °C). However, tolerance to applications made immediately after germination and during low air temperatures has received limited investigation. Therefore, objectives of this research were to determine the seedling tolerance and low-temperature response after a fall season glyphosate application to both cultivars. Field trials were conducted in Idaho and Oregon. For the fall application response trial in Idaho, glyphosate was applied at 0, 0.15, 0.29, 0.58, 1.16, 1.74, 2.32, and 3.48 kg·ha−1 a.e. In Oregon, glyphosate was applied at 0, 0.15, 0.29, 0.44, 0.58, 1.16, and 3.48 kg·ha−1 a.e. At both sites, applications were made between late September and early October. To determine seedling tolerance, both cultivars were sprayed with glyphosate at the one-leaf stage (LS), two LS, three LS, or four LS at rates of 0, 0.15, 0.29, and 0.58 kg·ha−1 a.e. Across all trials, ratings included PRG color, cover, and injury. At both trial locations, regression analysis revealed a rate of ≈0.27 kg·ha−1 a.e. was required to cause 20% leaf firing in the fall application response trial. In the seedling tolerance trial, glyphosate applied at 0.58 kg·ha−1 a.e. at the one LS, two LS, and three LS had color ratings 8.0 or greater; however, color ratings dropped to 4.6 when an application was made at the four LS. Based on the environmental conditions of each trial, results suggest glyphosate applications greater than 0.27 kg·ha−1 a.e. as minimum air temperatures approach 0 °C should be avoided. Also, applications should be avoided at the three to four LS if the application rate is greater than 0.29 kg·ha−1 a.e.

Alternative timing of carbaryl treatments for protecting lodgepole pine from mortality attributed to mountain pine beetle

Carbaryl is regarded among the most effective, economically viable, and ecologically-compatible insecticides available for protecting conifers from bark beetle attack in the western United States. Treatments are typically applied in spring prior to initiation of bark beetle flight for that year. We evaluated the efficacy of spring and fall applications for protecting individual lodgepole pine, Pinus contorta Dougl. ex Loud, from mortality attributed to mountain pine beetle, Dendroctonus ponderosae Hopkins, the most notable forest insect pest in western North America. Both spring and fall treatments of 2.0% a.i. carbaryl (Sevin® SL) were efficacious for two field seasons, while results from a third field season were inconclusive due to insufficient beetle pressure. We discuss the implications of these and other results to the management of D. ponderosae.