Steve B. Orloff

Control of Medusahead (Taeniatherum caput-medusae) and other Annual Grasses with Imazapic

Invasive annual grasses, such as medusahead, can reduce forage production capacity and interfere with revegetation projects in California rangelands. Because of the taxonomic similarity to other more desirable grasses, achieving selective control of invasive annual grasses can be difficult. In selectivity trials conducted in Yolo and Siskiyou counties, CA, the herbicide imazapic gave control of many nonnative annual grasses yet provided some level of selectivity to specific perennial grasses used in revegetation projects throughout the western United States. The selectivity difference between newly seeded perennial and annual grasses was greater with PRE applications than with POST treatments. Both perennial and annual grasses within the tribe Hordeae were more tolerant to imazapic than other grass species. In addition, field experiments were conducted at three sites in northern California (Yuba, Yolo, and Lassen counties) and one in southern Oregon (Lake County) to test the response of imazapic to varying management conditions. Imazapic was applied PRE in fall (and also spring in Lake County) at rates from 35 to 210 g/ha on undisturbed rangeland, in comparison with rangeland cleared of standing plant material and thatch by either tillage, mowing and raking, or burning. Imazapic generally showed enhanced weed control when applied following disturbance. Rates as low as 70 g/ha, if combined with thatch removal, provided significant suppression of medusahead. In addition, disturbance alone generally reduced medusahead cover in the following year. Although imazapic showed potential for control of medusahead and other annual grasses, its selectivity window was relatively narrow. Nomenclature: Imazapic, medusahead, Taeniatherum caput-medusae (L.) Nevski, ELYCM

Soil water dynamics differ among rangeland plant communities dominated by yellow starthistle (Centaurea solstitialis), annual grasses, or perennial grasses

Abstract Californias interior grasslands have undergone dramatic changes during the last two centuries. Changes in land-use patterns and plant introductions after European contact and settlement resulted in the conversion of perennial-dominated grasslands to exotic annual grasses. More recently, the annual grasslands have been heavily invaded by the deeply rooted late-maturing forb yellow starthistle. This series of invasions and conversions has changed the community structure and phenology of the grasslands. We hypothesized that these changes have resulted in significant differences in soil water–use patterns in the grasslands. We studied soil water depletion and recharge patterns of three grassland community types dominated by perennial grasses, annual grasses, or yellow starthistle with contrasting phenology and rooting depths for 4 yr. Soil moisture measurements were taken every month from March to December in 1998, 1999, and 2000 and every other month in 2001. Measurements were taken with a neutron probe at depths of 30 to 150 cm at 30-cm intervals. The results indicate that the yellow starthistle community maintained a significantly drier soil profile than the annual grass community. The perennial grass community maintained an intermediate soil water content that was not significantly different from either of the other two communities. Significant time by community and depth by community interactions indicated that the yellow starthistle community continued depleting soil moisture later into the season and at deeper depths than the other grass communities. This study demonstrates the effect of plant invasion on soil water recharge and depletion patterns in California grasslands. Nomenclature: Yellow starthistle, Centaurea solstitialis L. CENSO.

Integrating prescribed burning and clopyralid for the management of yellow starthistle (Centaurea solstitialis)

Abstract Prescribed burning and the herbicide clopyralid are very effective tools for the management of yellow starthistle. However, repeated use of either can be impractical or can present other problems. The potential solution is the development of an effective integrated weed management strategy using a combination of the two approaches. In small plot studies (0.2 ha), we tested one of five possible treatments: (1) untreated control, (2) 2 consecutive yr of clopyralid (0.105 kg ha−1), (3) 2 consecutive yr of prescribed summer burning, (4) first-year clopyralid followed by second-year prescribed burning, and (5) first-year prescribed burning followed by second-year clopyralid. Treatments were made in 1999 and 2000 at three study sites in California (San Benito, Yuba, and Siskiyou counties). In 2001, the year following the final treatment, 2 consecutive yr of clopyralid or first-year burning followed by second-year clopyralid consistently reduced yellow starthistle cover in the following year by 92 to 100%. However, at the Yuba site, clopyralid alone increased medusahead and ripgut brome cover. Although 2 consecutive yr of burning was effective in Yuba, very high levels of starthistle infestation in San Benito were not completely burned in the second year because of the lack of available consumable fuel. Clopyralid treatment the first year followed by prescribed burning in the second year stimulated yellow starthistle germination and did not reduce the infestation. In a large-scale study conducted at two sites (13 and 81 ha) in southern Monterey County, we used a first-year burn followed by either 2 yr of clopyralid (0.158 kg ha−1) or a single year of clopyralid (0.210 kg ha−1) and a subsequent burn. Results were in close agreement with those found in the small-scale studies. In the year following the final treatment, control of yellow starthistle was greater than 99% when the burn was followed by 2 yr of clopyralid. In contrast, when a prescribed burn was used in the last year of the program, the level of control was not as good, probably because of the increased germination of the remaining soil seedbank. These results indicate that a first-year prescribed burn followed by a second-year clopyralid treatment can provide consistently good control of yellow starthistle, as well as reduced levels of noxious annual grasses, including medusahead and ripgut brome. Nomenclature: Medusahead, Taeniatherum caput-medusae (L.) Nevski ELYCM; ripgut brome, Bromus diandrus Roth BRODI; yellow starthistle, Centaurea solstitialis L. CENSO.

Perennial Grass Establishment Integrated with Clopyralid Treatment for Yellow Starthistle Management on Annual Range1

Yellow starthistle is an aggressive annual forb that has invaded millions of hectares of Californias annual range. Control efforts such as burning and herbicides have been effective for short-term management. However, recruitment from the seedbank or reinvasion of the annual grassland system results in a rapid return to yellow starthistle dominance. Establishing perennial grasses would be ideal for suppression of yellow starthistle. However, a lack of effective weed control options in California during a seeding program has limited perennial grass establishment. Clopyralid was used to control yellow starthistle annually for 1, 2, or 3 yr to provide a window of reduced competition for pubescent wheatgrass establishment. Total plant cover, yellow starthistle density, biomass, and seedhead number were quantified for 6 yr. Clopyralid treatment significantly reduced yellow starthistle and allowed pubescent wheatgrass establishment with a single treatment. Both clopyralid treatment and pubescent wheatgrass establishment significantly affected the range plant community composition. Annual grasses and forbs increased in plots only treated with clopyralid for 2 or 3 yr, whereas clopyralid-treated pubescent wheatgrass plots maintained lower annual grass and forb cover. Integrating pubescent wheatgrass seeding with clopyralid treatment provided long-term yellow starthistle suppression, whereas clopyralid treatment alone resulted in a plant community susceptible to repeated invasion. These findings support the establishment of competitive perennial grasses in annual grasslands as an important component of long-term yellow starthistle management. Nomenclature: Clopyralid; yellow starthistle, Centaurea solstitialis (L.) #3 CENSO; pubescent wheatgrass, Thinopyrum intermedium (Host. Barkworth and Dewey) Nevski var. ‘Luna’. Additional index words: Integrated management, revegetation. Abbreviation: MANOVA, multivariate analysis of variance.

Site Characteristics Determine the Success of Prescribed Burning for Medusahead (Taeniatherum caput-medusae) Control

Abstract Medusahead is one of the most problematic rangeland weeds in the western United States. In previous studies, prescribed burning has been used successfully to control medusahead in some situations, but burning has failed in other circumstances. In this study, trials were conducted using the same protocol at four locations in central to northern California to evaluate plant community response to two consecutive years of summer burning and to determine the conditions resulting in successful medusahead control. During 2002 through 2003 large-scale experiments were established at two low-elevation, warm-winter sites (Fresno and Yolo counties) and two higher elevation, cool-winter sites (Siskiyou and Modoc counties). Plant species cover was estimated using point-intercept transects, and biomass samples were taken in each plot. After 2 yr of burning, medusahead cover was reduced by 99, 96, and 93% for Fresno, Yolo, and Siskiyou counties, respectively, compared to unburned control plots. Other annual grasses were also reduced, but less severely, and broadleaf species increased at all three sites. In contrast, 2 yr of burning resulted in a 55% increase in medusahead at the coolest winter site in Modoc County. In the second season after the final burn, medusahead cover remained low in burned plots at Fresno and Yolo counties (1 and 12% of cover in unburned controls, respectively), but at the Siskiyou site medusahead recovered to 45% relative to untreated controls. The success of prescribed burning was correlated with biomass of annual grasses, excluding medusahead, preceding a burn treatment. It is hypothesized that greater production of combustible forage resulted in increased fire intensity and greater seed mortality in exposed inflorescences. These results demonstrate that burning can be an effective control strategy for medusahead in low elevation, warm-winter areas characterized by high annual grass biomass production, but may not be successful in semiarid cool winter areas. Nomenclature: Medusahead, Taeniatherum caput-medusae (L.) Nevski

Control of yellow starthistle (Centaurea solstitialis) and coast fiddleneck (Amsinckia menziesii) with aminopyralid.

Abstract Yellow starthistle is the most widespread broadleaf invasive plant in the western United States, and it is particularly prevalent in California. Prior to the registration of aminopyralid in 2005, the standard for chemical control of yellow starthistle was the herbicide clopyralid. We report on a compilation of several independent trials comparing the efficacy of aminopyralid and clopyralid on yellow starthistle. Treatments were applied at several rates and timings at 11 locations in four states between 2001 and 2007. Treatments were made pre-emergence and postemergence at the seedling and rosette stages of yellow starthistle. Results showed that aminopyralid, even at the low rate of 18 g ae ha−1, provided nearly complete control of yellow starthistle when treatments were made at the seedling stage. However, less consistent control (80 to 100%) resulted with applications made at the pre-emergence and rosette stages. At the seedling stage, aminopyralid is about four times more effective on yellow starthistle compared to clopyralid, based on the rate of acid equivalent. In the Central Valley of California, complete control was obtained at the lowest registered rate (53 g ae ha−1) when applications were made from December through February. At two locations we also evaluated control of the poisonous native plant coast fiddleneck. Although clopyralid does not adequately control coast fiddleneck, aminopyralid provided almost complete control when applied in the winter growing season. Applications of aminopyralid at the rosette stage resulted in a two-fold increase in annual forage grass biomass the following year. These results indicate that aminopyralid is a valuable tool for land managers and can play an important role in integrated management strategies for yellow starthistle and coast fiddleneck. Nomenclature: Aminopyralid; clopyralid; yellow starthistle; Centaurea solstitialis L.; coast fiddleneck; Amsinckia menziesii (Lehm.) A. Nels. & J. F. Macbr. var. intermedia (Fisch. & C. A. Mey.) Ganders. Interpretive Summary: Yellow starthistle is one of the most invasive species of rangelands and natural areas in the western United States. Several control options have been developed including mowing, grazing, burning, biological control, and herbicides. Until 2005, the herbicide clopyralid was considered the most effective chemical option for yellow starthistle control. However, clopyralid does not provide effective control of coast fiddleneck, which often co-occurs with yellow starthistle in rangelands of California. Coast fiddleneck is toxic to livestock and often increases in cover following clopyralid treatment. Aminopyralid was registered for use in noncrop areas in 2005. In this study we compared the efficacy of aminopyralid and clopyralid for yellow starthistle and coast fiddleneck control at several rates and timings at 11 locations in four states during the time period ranging from 2001 to 2007. Our results indicate that aminopyralid requires about one-fourth the active ingredient compared to clopyralid to achieve similar control of yellow starthistle at the seedling stage. Unlike clopyralid, aminopyralid also provides excellent control of coast fiddleneck. Although pre-emergence applications and late-season applications (rosette stage) also control yellow starthistle, those timings were less consistent at lower rates and therefore required higher rates as per label instructions. Late-stage applications were more effective given higher rainfall. We did find that late-season application resulted in increased annual forage grass production the following year. In the Central Valley of California, the optimal timing of application was from December through February. In cooler climatic regions the optimal application timing window might be somewhat later. Our results indicate that aminopyralid is a very effective tool for the management of yellow starthistle and coast fiddleneck and could be incorporated into an integrated management program.

Winter Annual Weed Control with Herbicides in Alfalfa-Orchardgrass Mixtures

Alfalfa–orchardgrass hay is popular in the Western United States because of an expanding horse-hay market. However, weed control in mixed alfalfa–orchardgrass stands is problematic, as herbicides must be safe for both species. Most growers rely solely on the competitiveness of the crop for weed control, which is often insufficient, especially in older stands. Field experiments were established in northern California to determine the efficacy and crop safety of several herbicides for winter annual weed control in established alfalfa–orchardgrass. Metribuzin at 560 or 840 g/ha and hexazinone at 420 g/ha applied in late fall provided at least 95% control of shepherds purse and at least 80% control of downy brome without crop injury. Imazethapyr at 70 g/ha applied shortly after crop green-up provided more than 85% control of emerged mustards without crop injury. Paraquat at 560 g/ha applied shortly after crop green-up gave 50 to 82% weed control and caused significant injury to orchardgrass, which was still noticeable at first cutting. Nomenclature: Hexazinone, imazethapyr, metribuzin, paraquat, downy brome, Bromus tectorum L., shepherds purse Capsella bursa-pastoris L,, alfalfa, Medicago sativa L., orchardgrass, Dactylis glomerata L

Assessing Nitrogen Fertilization Needs for Irrigated Orchardgrass in the Intermountain Region of California

Nitrogen fertilization is a critical component of maximizing yield for grass hay production. However, the steady increase in fertilizer price along with concerns for off-site N movement make prudent use of N important. On-farm studies in northeastern California were conducted in irrigated orchardgrass to examine the influence N fertilizer rates and application times have on forage yield, forage quality, soil nitrate, and economics for retail hay. N rates up to 400 lb/acre increased annual yield and net return in a three-cut system. N fertilizer also increased crude protein. Applying fertilizer in split applications gave higher yield, crude protein, and economic return for second and third cut compared to a single fertilizer application at grass green-up. Apparent N recovery decreased with increasing fertilizer rate and ranged from 80 to 38%. N fertilizer did not influence forage neutral detergent fiber. At the highest N fertilizer rates, forage NO3-N at first and second-cut was above 1500 ppm. Fertilizing with N at 600 lb/acre/season elevated fall soil NO3-N at the 24 to 36-inch soil depth compared to the control at multiple sites. Split applications of N fertilizer are imperative to maximize yield, crude protein, and economic return, but excessive N fertilization can increase the likelihood of high forage nitrate and nitrate accumulation below the root zone. Introduction Orchardgrass (Dactylis glomerata) is a popular irrigated grass species grown in the intermountain region of California. Orchardgrass is desired for hay, and it produces high quality forage with proper irrigation and fertilization. Most intermountain orchardgrass fields are managed with efficient irrigation systems (center-pivot, wheel-line, or laser-leveled flood) and cut for hay three times per season. Grass hay prices are high — hay for horses often brings a price greater than dairy-quality alfalfa (4) — making grass hay more valuable than pasture. With high fuel, fertilizer, and energy costs, producers must maximize yield and production efficiency to be Fig. 1. Unfertilized orchardgrass (right) and orchardgrass fertilized with 100 lb N per acre at grass green-up (left) at first-cut harvest. 18 June 2008 Forage and Grazinglands profitable (2). N fertilization is necessary to obtain high grass yields, but applying too much or too little N has negative economic or environmental consequences. Several studies have examined N fertilization of cool-season perennial grasses (2,3,8,10). These studies showed that forage yield increases with increasing N rate, but apparent N recovery (ANR) decreases with high N rates. They also found split applications of N usually produce higher yields compared to applying all the N in early spring. Discrepancies between published studies emerge with optimal N fertilization rates, application timings, and ANR and are likely the result of differences in climate, soil, and management between experiments (9). Management practices, cutting schedules, economics, and soils in the intermountain region of California differ greatly from previous N fertilization research published in the literature, especially since many of these studies were conducted under rain-fed systems east of the Mississippi. Thus, our objective was to determine the optimum N fertilization rate and timing to maximize yield, N use efficiency (NUE), ANR, and returns for orchardgrass grown for retail hay in the intermountain region of California. N Fertilization Study The study was conducted at four orchardgrass sites (McArthur, Ft. Jones, Doyle, and Lookout) in 2005 and two orchardgrass sites (Montague and Susanville) in 2006. Sites’ soil and climate attributes are shown in Table 1. The experiment at every site was a completely random design with 4 replicates and 8 N fertilization treatments. Plot size was 20 by 20 ft. Soil samples were collected at each site before initiating the experiment, and sites were fertilized with phosphorus, sulfur, or potassium if the pre-treatment soil test suggested a deficiency. Watermark soil moisture sensors (Irrometer Co., Riverside, CA) were buried at an 8-inch depth at all sites before N treatments were applied to measure soil moisture throughout the growing season. Table 1. Site soil and climate attributes. N treatments were applied by hand in the form of urea (46-0-0) at the rates listed in Table 2. Treatments totaled 100, 200, 300, 400, or 600 lb of N per acre for the entire season. N application rates at grass green-up in March were 0, 100, 200, or 300 lb/acre. Split application rates after first and second cutting were 0, 50, 100, or 200 lb/acre and were applied immediately before the first Site Soil type Mean annual temperature (°F) Mean annual precipitation (inches) Elevation (feet) Doyle Calpine sandy loam Aridic Haploxerolls 50.6 11.4 4275 Ft. Jones Stoner gravelly sandy loam coarse-loamy, mixed, active, mesic Typic Haploxerepts 50.5 20.6 2747 Lookout Modoc sandy loammesic Vitritorrandic Durixerolls 48.5 15.8 4144 McArthur Esperanza loam fine, smectitic, mesic Pachic Argixerolls 50.6 19.1 3311 Montague Montague clay fine, montmorillonitic, mesic Typic Chromoxererts 51.7 19.5 2634 Susanville Mottsville gravelly loamy course sand mixed, mesic, Torripsammentic Haploxeroll 49.4 14.3 4258 18 June 2008 Forage and Grazinglands irrigation after first and/or second harvest. All fertilizer applications were incorporated into the soil with rainfall or irrigation ≥ 0.5 inch within one to two days of application. The first harvest occurred when grasses were in the flowering stage, and the second and third harvest occurred 40 to 50 days after the previous cutting. Drought stress occurred in mid-summer at the Doyle, Lookout, and Ft. Jones sites in 2005. Therefore, the crop at these sites was only harvested twice, once at flowering and again in early fall. Yield was measured by harvesting a 3by 20-ft strip at a 3-inch stubble height from each plot with a Carter Harvester (Carter Mfg. Co. Inc., Brookston, IN). Forage samples were oven-dried at 140°F for dry matter (DM) determination and forage quality analysis. Dried forage samples were analyzed for total extractable nitrate N (NO3-N), total N (N), total crude protein (CP) and neutral detergent fiber (NDF) using University of California ANR Analytical Lab preparation and analyses methods (UC ANR Analytical Lab, Davis, CA) (7). In the fall after the last cutting, soil was sampled for NO3-N at three depths: 0 to 12 inches, 12 to 24 inches, and 24 to 36 inches. Soil cores were taken from 10 random locations in each plot for three fertilization treatments (unfertilized, 100-100-100, and 200-200-200). Soil was air-dried and analyzed for NO3-N using University of California ANR Analytical Lab methods (UC ANR Analytical Lab, Davis, CA). Yield, forage quality, and soil nitrate data were analyzed by analysis of variance (ANOVA) followed by a comparison of treatment means using Fischer’s least significant difference (LSD) at P ≤ 0.05. Regression analysis was used to determine the relationship between first-cutting yield and N fertilizer rate applied in early spring (SAS Institute Inc., Cary, NC). Site data were pooled for analysis if a site by treatment interaction was not significant at P ≤ 0.05. Influence on Forage Dry Matter Yield and NUE Both N fertilizer rate and application timing had a significant effect on orchardgrass yield (Table 2). First-cut harvest produced more forage than secondor third-cut harvest (Table 2). First-cut orchardgrass yield increased rapidly from 0 to 100 lb N per acre, however the yield response diminished at rates above 100 lb N per acre (Fig. 1). At the moisture-stressed 2-cut sites, orchardgrass yield almost doubled from 0 to 100 lb N per acre, but the yield increase from fertilization lessened from 100 to 200 lb N per acre, and leveled off at fertilizer rates above 200 lb N per acre (Fig. 1). At 3-cut sites, the relationship between first-cut yield and fertilizer was similar to 2-cut sites, but yield at 3-cut sites increased slightly from 200 to 300 lb N per acre (Fig. 1). Applying N fertilizer in split applications produced higher secondand thirdcut yield compared to applying all N at grass green-up (Table 2). Second-cut yield was 0.26 to 0.66 ton/acre higher if fertilizer was applied at 100 lb N per acre in early spring and 100 lb N per acre after first cutting (100-100) compared to 200 lb N per acre in early spring (200-0) (Table 2). Second-cut yield was 0.15 to 0.78 ton/acre higher if fertilizer was applied at 200-100 compared to 300-0 (Table 2). Split applications of N fertilizer were essential for increasing third-cut yield. Even at the highest single N rate (300 lb/acre), yield did not differ from the unfertilized plots if fertilizer was only applied in early spring (Table 2). In contrast, applying fertilizer in split applications at 100-50-50, 100-100-100, or 200-100-100 increased third-cut yield by at least 190% compared to unfertilized plots (Table 2). 18 June 2008 Forage and Grazinglands Table 2. The effect of nitrogen rate and application time on orchardgrass yield and nitrogen use efficiency. x N use efficiency represents lbs of additional forage for each lb of applied N. It was calculated as [(total yield at Nx – total yield at N0) * 2000 ÷ lb N per acre applied at Nx], where x = N rate > 0. y N fertilizer treatments shown as lb of N per acre applied: at spring green-up – after first cut – after second cut. Orchardgrass sites 100% Dry matter yield (tons/acre) N use efficiencyx (lbs) 1st cut 2nd cut 3rd cut Total 2-cut 0-0y 1.51 0.88 2.39 100-0 2.71 1.11 3.82 29 100-50 2.75 1.68 4.43 27 200-0 3.05 1.50 4.55 22 100-100 2.82 1.96 4.78 24 300-0 3.13 1.66 4.79 16 200-100 3.13 2.15 5.28 20 200-200 3.08 2.27 5.36 15 LSD (P = 0.05) 0.27 0.28 0.42 4 3-cut 0-0-0 1.93 0.91 0.41 3.26 100-0-0 3.22 1.31 0.54 5.08 35 100-50-50 3.29 1.77 1.22 6.28 30 200-0-0 3.42 1.29 0.49 5.20 18 100-100-100 3.25 1.95 1.37 6.58 22 300-0-0 3.86 1.37 0.55 5.78 17 200-100-

Burrow fumigation versus trapping for pocket gopher (Thomomys spp.) management: a comparison of efficacy and cost effectiveness

Abstract Context. Pocket gophers (Geomyidae) cause extensive damage to many crops throughout western North America. A variety of methods are available to manage these populations, but data are often lacking on their efficacy and especially their cost effectiveness. Additionally, little peer-reviewed data are available that compare multiple methods simultaneously. Aims. We tested aluminum phosphide and pressurised exhaust using the Pressurised Exhaust Rodent Controller (PERC) as burrow fumigants, and compared them to trapping to determine which approach was most efficacious and cost effective. Methods. We assessed the efficacy of aluminum phosphide, the PERC machine, and trapping through the use of the open-hole monitoring method after single and multiple treatments over multiple years. We determined material and labour costs for each treatment type and amortised this cost over 1250 days of application to determine which treatment type was most cost effective. Key results. Aluminum phosphide had the shortest time for application, but we were able to make far more applications per day using the PERC machine, given our ability to treat multiple burrow systems at once with this machine. Trapping and aluminum phosphide were more efficacious than was the PERC machine. When costs were amortised over time, trapping was the most cost-effective approach even with longer application times, given high efficacy. Multiple treatment applications were needed to maximise the efficacy of management programs. Conclusions. For small-scale management efforts, aluminum phosphide was a cost-effective and efficacious option. For a greater number of treatments, trapping was the most successful and cost effective. However, a modest increase in efficacy could make the PERC machine a preferred tool as well. We also stress that regardless of the management approach, multiple treatment applications will generally be needed to manage pocket gopher populations. Implications. The present study provides growers with information needed to determine efficient and cost-effective methods for managing pocket gophers. This information can be used to craft an integrated pest-management approach to manage damaging pocket gopher populations.

Estimating Evapotranspiration of Fully-and Deficit-irrigated Alfalfa in Commercial Fields with the Eddy Covariance and Surface Renewal Methods

Evapotranspiration (ET) of fully irrigated and deficit irrigated (no irrigation in July, August, and September) was measured in four commercial alfalfa fields with the eddy covariance (EC) and surface renewal (SR) energy balance methods. Both EC and SR methods were used in the fully irrigated part of the fields, while the SR method only was used in the deficit irrigated part. Deficit irrigation reduced ET, but the amount of reduction was highly site specific. Good agreement was found between the EC and SR methods. However, patterns of the daily differences between the EC and SR methods differed between the four fields.