The preferences of broiler and layer strains of fowl for four different intensities of incandescent luminaire (6, 20, 60 and 200 lux; Osram, 60W, pearl) were tested at 2 and 6 weeks of age. With each strain, four replicates of 12 birds were each allowed to move freely between four compartments illuminated continuously at the different intensities for 6 days. The distribution of light intensities among the compartments was changed daily. After 2 days of conditioning, the birds’ location and behaviour were recorded once every 15min over 23h on each of the remaining 4 days. The other hour was devoted to changing light intensities and refilling the feeders and drinkers. Six, mutually exclusive behaviours were defined: resting, perching, feeding, drinking, litter-directed activity and locomotion.

With both strains, most time was spent in the brightest (200 lux) environment at 2 weeks of age. but in the dimmest (6 lux) at 6 weeks. This apparent change in preference was associated only with the two behaviours which took up most time, resting and perching, whereas the highest intensity was consistently preferred for all other behaviours. Older birds thus preferred to be in dim light when they were relatively inactive.

The finding that older birds prefer to spend much of their time in a light environment of < 10 lux intensity, depending on behaviour, is contrary to current recommendations that minimum light intensities for broilers and laying hens should be increased to as much as 20 lux. Some variation in the spatial or temporal distribution of ambient light intensity, to provide both dimly (< 10 lux) and brightly (eg > 50 lux) lit environments, might benefit the welfare of older poultry, although further work is needed to establish their optimal light environment.

Guidelines for the housing of dairy cows do not address the provision of supplementary lighting in passageways, other than for inspection of the animals. Two experiments were conducted to investigate whether lighting passageways to various intensities influenced the locomotion of dairy cows. The first experiment compared the locomotion of dairy cows in a dark or lighted passageway as they walked back to their accommodation from milking. When the passageway was dark, the cows took shorter but more rapid steps - which probably increased their stability. In the second experiment, cows walked down a cubicle passageway to receive a food reward, with the light intensity in the building varying from 0-250 lux. Step length and stepping rate were recorded, as well as the angles of the cows’ leg joints (which were measured from video recordings). Once again, the cows increased their stepping rate in the dark, and this resulted in an increased walking rate, perhaps because they wished to return more rapidly to other members of their group and found the darkness aversive. In addition, the arcs of travel of the metacarpophalangeal joint and of the fore- and hindfeet angles to the floor were reduced in the dark, probably increasing the cows’ stability, and were greatest at 119 lux. The slowest walking rate was observed at 39 lux. Hence, the optimum illumination for dairy cow locomotion may lie approximately between 39 and 119 lux, as measured by our technique.

We conclude that during locomotion in dark passageways cows have to modify their walking behaviour significantly, so that the provision of at least a low level of lighting is desirable at night.

It has been shown that, in small groups of intact male domestic turkeys, supplementary ultraviolet (UV-A) radiation, visual barriers, and added straw (environmental enrichment) minimize the incidence of injurious pecking under incandescent light at 5 lux. This paper describes two experiments, each involving eight groups of 100 non beak-trimmed birds up to 5 weeks of age, that assessed the effectiveness of these procedures at higher light intensities and with fluorescent light. Experiment 1 examined 5 or 10 lux of incandescent or fluorescent light. Experiment 2 studied responses to 5, 10, 36 or 70 lux of fluorescent light. Individual inspections of the birds, for wing, tail and head injuries due to pecking, were conducted daily.

Fluorescent light significantly reduced the incidence of tail injuries (P = 0.03), and tended to reduce those to the wings (P = 0.08), compared with incandescent light. No difference was observed between 5 and 10 lux for either tail or wing injuries. In Experiment 2, the incidence of tail and wing injuries was significantly and positively correlated with light intensity (tail, P = 0.05; wing, P = 0.02). Injuries to the head were minimal in all treatments. These results suggest that turkey poults may be kept with minimal injurious pecking, under fluorescent light at an intensity of 10 lux, with appropriate environmental enrichment.

Quizalofop-resistant rice allows for over-the-top applications of quizalofop, a herbicide that inhibits acetyl-coenzyme A carboxylase. However, previous reports have indicated that quizalofop applied postemergence may cause significant injury to quizalofop-resistant rice. Therefore, field experiments were conducted to evaluate the response of quizalofop-resistant rice cultivars to quizalofop applications across different planting dates. Under controlled conditions, the effects of soil moisture content, air temperature, and light intensity on quizalofop-resistant rice sensitivity to quizalofop were investigated. In the planting date experiment, injury of more than 11 percentage points was observed on early-planted rice compared with late-planted rice at the 5-leaf stage, with higher injury observed under saturated soil conditions. However, quizalofop applications at the labeled rate caused ≤16% reduction in yield regardless of planting environment. Quizalofop-resistant cultivars exhibited more injury by at least 25 percentage points when soil was maintained at 90% or 100% of field capacity because rice cultivars ‘PVL01’, ‘PVL02’, and ‘RTv7231 MA’ exhibited ≥42%, 30%, and ≥54% injury, respectively, compared with ≤10%, ≤5%, and ≤22% injury, respectively, at 40% or 50% of field capacity, pooled over rating timing. Greater injury ranging from 18% to 31% was observed on quizalofop-resistant rice grown under low light intensity (600 µmol m−2s−1) compared with 5% to 14% injury under high light intensity (1,150 µmol m−2s−1). The injury persisted from 7 to 28 d after 5-leaf stage application (DAFT), averaged over quizalofop-resistant cultivars and air temperatures (20/15 C and 30/25 C day/night, respectively). At 7 DAFT, greater injury (by 5 to 21 percentage points) was observed on quizalofop-resistant cultivars; PVL01, PVL02, and RTv7231 MA exhibited 33%, 9%, and 58% injury, respectively, under 20/15 C temperature conditions compared with 13%, 4%, and 37% injury, respectively, under 30/25 C day/night conditions averaged over light intensities. Overall, quizalofop is likely to cause a greater risk for injury to quizalofop-resistant rice if it is applied under cool, cloudy, and moist soil conditions.

Environmental conditions surrounding herbicide applications are known to affect weed control and crop response. Variable levels of rice injury caused by florpyrauxifen-benzyl have been observed across cropping systems and environmental conditions, warranting research in which single environmental and management strategies are isolated to understand the effect of each factor on rice injury and subsequent reductions in rice growth. A field study was conducted to determine the effects of planting date, rice cultivar, and florpyrauxifen-benzyl rate on rice injury, maturity, and yield. Two greenhouse studies were conducted to determine the effect of soil moisture and time of flooding after florpyrauxifen-benzyl application on rice injury caused by the herbicide. Growth chamber experiments were conducted to isolate the effects of temperature and light intensity on rice injury caused by florpyrauxifen-benzyl. In the field study, levels of injury varied across planting dates in both years, indicating the influence of environment on the crop response to florpyrauxifen-benzyl applications. Under dry (40% soil moisture) and saturated (100%) soil conditions, rice injury increased to 36% and 35%, respectively, compared with 27% and 25% injury at 60% and 80% soil moisture, respectively. Flooding rice 0 to 6 d after florpyrauxifen-benzyl application reduced visible injury; however, a reduction in rice tiller production occurred when the rice was flooded the same day as application. Visible rice injury increased when florpyrauxifen-benzyl was applied under low light intensity (700 µmol m−2 s−1) and high temperatures (35/24 C day/night). Based on these findings, applications of florpyrauxifen-benzyl are least likely to cause unacceptable rice injury when applied to soils having 60% and 80% saturation in high light, low temperature environments, and the crop is flooded 3 to 6 d following application.

Weed control of paraquat can be erratic and may be attributable to differing species sensitivity and/or environmental factors for which minor guidance is available on commercial labels. Therefore, the objectives of this research were to quantify selectivity of paraquat across select weed species and the influence of environmental factors. Experiments were performed under controlled conditions in the greenhouse and growth chamber. Compared with purple deadnettle (dose necessary to reduce shoot biomass by 50% = 39 g ai ha−1), waterhemp, Palmer amaranth, giant ragweed, and horseweed were 4.9, 3.3, 1.9, and 1.3 times more sensitive to paraquat, respectively. The injury progression rate over 3 d after treatment (DAT) was a more accurate predictor of final efficacy at 14 DAT than the lag phase until symptoms first appeared. For example, at the 17.5 g ha−1 dose, the injury rate of waterhemp and Palmer amaranth was, on average, 3.6 times greater than that of horseweed and purple deadnettle. The influence of various environmental factors on paraquat efficacy was weed specific. Applications made at sunrise improved control of purple deadnettle over applications at solar noon or sunset. Lower light intensities (200 or 600 μmol m−2 s−1) surrounding the time of application improved control of waterhemp and horseweed more than 1,000 μmol m−2 s−1. Day/night temperatures of 27/16 C improved horseweed and purple deadnettle control compared with day/night temperatures of 18/13 C. Though control was positively associated with injury rates in the application time of day and temperature experiments, a negative relationship was observed for waterhemp in the light-intensity experiment. Thus, although there are conditions that enhance paraquat efficacy, the specific target species must also be considered. These results advocate paraquat dose recommendations, currently based on weed height, be expanded to address sensitivity differences among weeds. Moreover, these findings contrast with paraquat labels stating temperatures of 13 C or lower do not reduce paraquat efficacy.

In the rapid response (RR) biotype of glyphosate-resistant (GR) giant ragweed (Ambrosia trifida L.), exposure to glyphosate elicits H2O2 production in mature leaves, resulting in foliage loss and reduced glyphosate translocation. When glyphosate is applied with POST herbicides intended to improve control of A. trifida, the RR to glyphosate has the propensity to antagonize these herbicide combinations. This research documents how transient changes in air temperature, soil moisture, and light intensity during a 6-d period surrounding herbicide application regulate induction of the RR and the effect on POST herbicide interactions with glyphosate. Air temperature had the greatest influence on H2O2 accumulation in leaf disks following treatment with glyphosate, as plants at 30 C produced more than twice the amount of H2O2 at 2.5 h after treatment compared with 10 C. Plants under field capacity conditions accumulated nearly 50% more H2O2 than those at one-third field capacity, while those under no shade had only 18% more H2O2 compared with those in a shaded environment. Despite these initial results, dry weight reduction at 21 d after treatment never differed by more than 8% between levels of environmental factors, thus indicating a negligible influence on glyphosate efficacy. The magnitude of glyphosate-induced antagonism was generally greater at 30 C (12% to 21% less than expected control) versus 10 C (11% to 16%) on atrazine, cloransulam, dicamba, and topramezone and was greater at field capacity (20% to 24%) versus one-third field capacity (11% to 15%) on cloransulam and topramezone. These results indicate air temperatures and soil moisture levels conducive to optimal plant growth accelerate the RR to glyphosate, thereby increasing the likelihood of glyphosate-induced antagonism on several translocated herbicides.

Translocation of 14C-glyphosate [N-(phosphonomethyl) glycine] in johnsongrass [Sorghum halepense (L.) Pers.] was examined in relation to time and illuminance. Plants were treated with 14 C-glyphosate and harvested 3 days and 6 days after treatment. Translocation increased significantly between the 3 day and 6 day harvest. The greatest accumulation of 14 C occurred in areas of meristematic growth. The concentration of 14C recovered in rhizomes nearly doubled between the 3 day and 6 day harvest. Plants harvested after 3 days of treatment in the dark translocated 1.3% of the applied 14C, while plants exposed to full light translocated 4.7%. Plants harvested after 6 days of treatment in the dark translocated 2.1% of the applied 14C, while plants exposed to full light translocated 5.8%. Translocation data indicated that movement of glyphosate in johnsongrass was via the phloem. Accumulation of 14C in roots and rhizomes was significantly greater in plants exposed to full light compared with plants exposed to either darkness or shade.

Wild and cultivated proso millet (Panicum miliaceum L. ♯ PANMI) showed increased height and dry mass with increasing photoperiod and flowered under all photoperiods. Increasing planting density decreased height and dry mass and slowed seedhead development in both types. Shading increased plant height and decreased dry mass of both millets and increased germination compared to unshaded treatments. Planting date did not affect germination of freshly collected seed of either millet. Wild proso millet seed had a low germination rate until 8 weeks after panicle emergence, and the rate increased to 22% after 10 weeks. Germination of cultivated proso millet seed was low for 5 weeks after panicle emergence and increased to 92% after 10 weeks.

Comparative growth, development, and resource allocation of triazine - susceptible and triazine - resistant biotypes of common groundsel (Senecio vulgaris L.), grown under two light regimes, were studied over a 7 - week period. Dry-matter production, height, number of leaves, and leaf area of the susceptible biotype were greater than those of the resistant biotype at all harvests under both light regimes. Root/shoot ratios were lower in the resistant than in the susceptible biotype under high light. Lower values for these parameters in resistant plants are due to lowered photosynthetic capacity, which limits growth and lowers relative root production. Net assimilation rate (NAR) was lower in resistant than susceptible plants when grown under high light, but mean leaf area ratio over a harvest interval (L) of resistant plants was higher than that of susceptible plants under high light. Relative growth rate (RGR) was higher for susceptible plants before day 42 and higher for resistant plants after day 42 under high light. A lower plastochron index (PI) of resistant plants up to 5 weeks old, relative to susceptible plants of the same age, suggests that, when grown under high light, resistant plants are developmentally at least 2 days behind susceptible plants. Shading lowered dry-weight production, height, number of leaves, leaf area, NAR, RGR, PI and root/shoot ratios of both biotypes. Values for these growth parameters for susceptible plants were similar to or larger than for resistant plants when grown under low light. In both biotypes, resource allocation patterns and L shifted towards increased shoot and leaf production in response to shading.

Controlled environmental chamber experiments were conducted for a 14-d incubation period to measure the effect of temperature, light, light intensity, water potential, and pH on eclipta seed germination. In full light, seed germinated over a range of 10 to 35 C; however, germination was highest at 83% at 35 C. Seeds were strongly photoblastic with none germinating in the dark. Seeds germinated in light intensities between 6 and 100% of full light. Seeds germinated 78 to 88% in water potentials of 0.0, −0.1, and −0.2 MPa. In distilled water (pH ∼ 5.5) and a buffered solution pH 6 and 7, seeds germinated 85 to 89%; however, some seeds germinated in a buffered solution pH range of 5 to 8. After the first 14-d incubation period, ungerminated seeds were transferred to distilled water and incubated at 35 C in full light for 4 to 6 d as a second incubation period. Seeds germinated 89 to 96% after this second incubation period when first incubation was at temperatures 10 to 35 C in full light or darkness, light intensities 0 to 100% of full light, water potentials 0.0 to −0.8 MPa, and buffered solution pH levels of 5.5 to 7.

Growth chamber and greenhouse studies were conducted to evaluate effects of long-term low-light intensity on wild oat control with imazamethabenz and fenoxaprop. Seventy percent shading imposed during the entire experimental period resulted in enhanced activities for both herbicides applied at early and later growth stages. Such shading also reduced wild oat regrowth following application of imazamethabenz and fenoxaprop. When applied to plants exposed to 70 to 90% prespraying shading, both herbicides had phytotoxicity similar to, or better, than plants grown under continuous shading. Postspraying shading has less effect on herbicidal activity than prespraying shading or prolonged shading, especially with imazamethabenz. Full-light treatment more adversely affected fenoxaprop activity than imazamethabenz activity.

The influence of temperature, soil moisture, and light intensity on the tolerance of spring wheat, durum wheat, and spring barley to imazamethabenz and safened fenoxaprop-p-ethyl was determined in growth chamber experiments. Imazamethabenz at 500 g/ha reduced plant height and shoot fresh weight of durum and spring wheats grown under prolonged 70% shade. The height of durum and spring wheats was reduced by imazamethabenz under a low temperature regime. Compared to the plants grown under standard conditions, the shoot weight of spring and durum wheat plants was not reduced by imazamethabenz under drought, or high and low temperature conditions. Barley tolerance to imazamethabenz was not affected by environment. All three spring cereals were tolerant to fenoxaprop-p-ethyl plus a safener at 92 g/ha; and such tolerance was not greatly affected by various environments examined.

Yellow nutsedge (Cyperus esculentus L.) and purple nutsedge (C. rotundus L.) were grown in clay pots in the field to investigate the effect of sunlight intensity, planting date, and harvesting date on growth and development. Reducing the length of the growing season by delayed planting or early harvesting reduced the growth (dry matter accumulation) and tuber production of both species. Purple nutsedge growth (dry matter accumulation) was linearly reduced at 30 and 73% shade, but yellow nutsedge growth at 30% shade was not different from that at full sunlight. Tuber production in both species began about August 1, with slight delays in the initiation of tuber growth as planting date was delayed. At the end of the growing season a significant number of tubers were formed in both species even at the latest planting date under 73% shade.

The effect temperature, light intensity, time to initial light exposure, relative humidity, and the presence of dew have on CGA-248757 and flumiclorac efficacy was evaluated in laboratory trials. Increasing temperature from 10 to 40 C increased CGA-248757 and flumiclorac activity on common lambsquarters by 79 and 87%, respectively. Similarly, increasing temperature from 10 to 40 C increased CGA-248757 and flumiclorac activity on redroot pigweed by 68 and 60%, respectively. Increasing light intensity from 0 to 1,000 μmol m−2 s−1 increased CGA-248757 activity on common lambsquarters and redroot pigweed by 92 and 93%, while flumiclorac activity increased 91 and 99%. Time to initial light exposure and relative humidity did not affect CGA-248757 or flumiclorac activity on common lambsquarters and redroot pigweed. The presence of dew reduced herbicidal activity of both compounds on common lambsquarters by 5% and redroot pigweed control with CGA-248757 and flumiclorac by 21 and 20%, respectively. Field applications of CGA-248757 or flumiclorac at 6:00 A.M., 2:00 P.M., and 10:00 P.M. indicate environmental conditions at application strongly influence soybean tolerance and weed control with CGA-248757 and flumiclorac. The greatest soybean injury occurred from CGA-248757 or flumiclorac applications at 6:00 A.M. compared with applications at 2:00 P.M. or 10:00 P.M. Common lambsquarters control was greatest when CGA-248757 or flumiclorac was applied at 6:00 A.M. or 2:00 P.M. compared with 10:00 P.M. However, redroot pigweed control was greatest when CGA-248757 or flumiclorac was applied at 2:00 P.M. Application time of day did not affect velvetleaf control with either herbicide.

Corn and soybean were planted in narrow- and wide-row spacings to study the effects of glyphosate application timing and row spacing on light interception and subsequent weed growth. Corn planted in narrow rows (38 cm) had greater light interception than corn planted in wide rows (76 cm) from 35 to 55 d after crop emergence. Soybean planted in narrow rows (both 19 and 38 cm) had greater light interception throughout the growing season than soybean in 76-cm rows. At maximum canopy closure, narrow-row soybean (both 19 and 38 cm) intercepted more light than narrow-row corn. Biomass of weeds emerging after glyphosate application was greater when soybean was planted in 76-cm than in 19- or 38-cm rows. However, weed biomass was generally similar in both row spacings of corn. Sequential glyphosate applications reduced weed biomass in corn each year compared with a single glyphosate application at the 5-cm weed height. Sequential glyphosate applications that followed initial glyphosate application to 10- or 15-cm-tall weeds did not reduce weed biomass compared with a single application.

Controlled environment experiments showed that velvetleaf plants grown under drought stress or low temperature (LT) treatments had greater leaf epicuticular wax (ECW) deposition compared to plants grown in soil with moisture at field capacity (FC) or a high temperature (HT) regime. Light intensity did not affect ECW deposition; however, increasing light intensity decreased the leaf ECW ester content and increased the secondary alcohol content. Plants grown at an LT regime or under FC had leaf ECW with fewer hydrocarbons and more esters than those grown at an HT or drought stress regime. Velvetleaf absorption of acifluorfen increased as light intensity decreased for plants grown in adequate soil water content, while the opposite was true for drought-stressed plants. Velvetleaf absorption of acifluorfen was approximately 3 and 10 times greater, respectively, with the addition of 28% urea ammonium nitrate (UAN) in comparison to crop oil concentrate (COC) or no adjuvant, regardless of the environmental treatments. Plants absorbed more acifluorfen when subjected to the LT regime in comparison to the HT regime when UAN was the adjuvant, while the opposite was true when COC was the adjuvant. Velvetleaf absorption of acifluorfen was not affected by drought stress when COC or no adjuvant was used and varied between studies when UAN was used. Velvetleaf absorption of bentazon was greatest for plants grown under HT/FC or high light/FC treatments and least with plants grown under HT/drought stress or low light/drought stress treatments, regardless of the adjuvant. However, bentazon absorption was higher with the addition of an adjuvant and for plants grown at a high light intensity or FC condition compared with medium to low light intensity or drought stress treatments.

Kudzu is an aggressive, nonnative vine that currently dominates an estimated 810,000 ha of mesic forest communities in the eastern United States. To test an integrated method of weed control, abundances of kudzu and other plant species were compared during 4 yr after six herbicide treatments (clopyralid, triclopyr, metsulfuron, picloram + 2,4-D, tebuthiuron, and a nonsprayed check), in which loblolly pines were planted at three densities (0, 1, and 4 seedlings m−2) to induce competition and potentially delay kudzu recovery. This split-plot design was replicated on each of the four kudzu-dominated sites near Aiken, SC. Relative light intensity (RLI) and soil water content (SWC) were measured periodically to identify mechanisms of interference among plant species. Two years after treatment (1999), crown coverage of kudzu averaged < 2% in herbicide plots compared with 93% in the nonsprayed check, and these differences were maintained through 2001, except in clopyralid plots where kudzu cover increased to 15%. In 2001, pine interference was associated with 33, 56, and 67% reductions in biomass of kudzu, blackberry, and herbaceous vegetation, respectively. RLI in kudzu-dominated plots (4 to 15% of full sun) generally was less than half that of herbicide-treated plots. SWC was greatest in tebuthiuron plots, where total vegetation cover averaged 26% compared with 77 to 111% in other plots. None of the treatments eradicated kudzu, but combinations of herbicides and induced pine competition delayed its recovery.

Controlled-environment experiments were conducted to determine giant foxtail epicuticular wax (ECW) deposition and fluazifop-P absorption under different environmental conditions and with two adjuvants. Drought stress and low temperature increased leaf ECW content, whereas low light intensity decreased ECW content compared with medium light intensity. Drought stress conditions decreased the fatty acid and primary alcohol content of ECW and increased the hydrocarbon content compared with field capacity. Compositional changes would make the ECW more hydrophobic and reduce leaf wetting by herbicide spray. Increasing air temperature decreased the aldehyde content of ECW, whereas decreasing light intensity increased ECW fatty acid and aldehyde content while decreasing primary alcohols and esters. Compositional changes under low light intensity would make the ECW more hydrophilic and increase leaf wetting by a herbicide spray. Drought stress reduced fluazifop-P absorption regardless of the temperature but could not further reduce fluazifop-P absorption under low light intensity. Fluazifop-P absorption by plants under low light and drought stress conditions was similar to plants under low or medium light intensity and field capacity conditions. Similarly, the rate of fluazifop-P absorption was less under drought stress and low light conditions. Fluazifop-P absorption was greater when crop oil concentrate was added compared with 28% urea ammonium nitrate or no additive. Crop oil concentrate, added to the herbicide solution, overcame reduced fluazifop-P absorption under the low light conditions and in one of the two drought stress regimes but could not overcome reduced fluazifop-P absorption with the high temperature regime.