bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and Physiological Responses of Greenhouse‐Grown Blue Grama to Atrazine
Authors: Morgan J. A. , Knight W. G. 
Published: July 2010

AbstractBlue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] is an important native forage and the dominant C4 species on the shortgrass prairie. Sublethal concentrations of the herbicide atrazine (6‐chloro‐N‐ethyl‐N1‐[1‐methylethyl]‐1,3,5‐triazine‐2,4‐diamine) have increased range production, tissue N, and drought survival of blue grama. The mechanisms(s) for these responses are not well understood. This experiment was conducted to evaluate C exchange rates, water use, and productivity of blue grama to variable concentrations of atrazine. Plants were grown from seed (Lovington cv.) in soilpacked, column‐lysimeters. Treatment concentrations of 0.0, 0.5, 1.0, and 2.0 mg of atrazine per column were achieved by irrigating columns containing 8‐wk old plants with solution atrazine and/or tap water. Nine days following the initial atrazine application, CO2 exchange rates of plants treated with intermediate and high rates of atrazine averaged 28 μmol plant−1 s−1, 43% lower than rates observed for control and low atrazine treatments. This depression, which persisted for 30 d, was due to inhibition of leaf photosynthetic capacity. As a result, aboveground productivity of the intermediate and high atrazine treatments was inhibited 28% compared to the control. Similar atrazine‐induced reductions in evapotranspiration were noted. By the end of this period, chlorophyll concentrations of all atrazinetreated leaves had increased to an average 0.41 g m−2 compared to 0.33 g m−2 in control leaves. Shoot N concentrations were also affected by atrazine, averaging 23.3 g kg−1 in intermediate and high atrazine leaves and 14.9 g kg−1 in control leaves. Thirty‐seven days after the initial atrazine application, all remaining plants were clipped to 5‐cm height to begin a regrowth cycle. Twenty days after clipping, regrowth of low atrazine‐treated plants was 22% greater than controls. During the initial (2 wk) regrowth period, both increased plant photosynthesis and increased evapotranspiration rates were observed, but only for the intermediate treatment plants. Over the final period studied (2‐4 wk regrowth), no differences, compared to controls, were found for any parameters measured. No evidence for a direct stimulatory effect or hormonal‐type mode of action was found for atrazine.
Peanut Yield as a Result of Fifty Years of Breeding
Authors: Wells Randy , Bi Tin , Anderson William F. , Wynne Johnny C. 
Published: July 2010

AbstractBreeding for increased yield is known to indirectly alter other plant characteristics in many crop species, including peanut (Arachis hypogaea L.). This 2‐yr, field study examined growth and dry matter allocation to various plant organs of 10 Virginia‐type peanut genotypes bred for increased yield in North Carolina, Genotypes representing the period from 1944 to the present were grown in 1988 and 1989. Growth was measured on five dates in each year. Genotypes expressed as the minimum number of breeding cycles from an indigenous germplasm exhibited a yield increase of 30 g m2 per breeding cycle. Genotypes developed from a greater number of breeding cycles tended to have smaller vegetative mass and shorter main stem lengths. However, concurrent increases in reproductive allocation, measured as pod mass and reproductive‐to‐vegetative ratios (RVR), were evident. Correlation analysis at 133 d after planting (DAP) between the number of breeding cycles and measurements of main stem length, total dry weight (DW), vegetative DW, stem DW, leaf area index (LAI) and RVR resulted in significant correlation coefficients of −0.67,0.38, −0.67, −0.71, −0.42, and 0.74 respectively. At 71 DAP, reproductive growth, measured as peg number, pod number, pod mass, and RVR was correlated with the number of breeding cycles, with significant correlation coefficients of 0.53, 0.52, 0.46, and 0.46, respectively. Reproductive to vegetative ratio continued to be positively related to both breeding cycle number and year of cultivar release throughout reproductive growth. The data indicate greater reproductive dry matter allocation by more recently released genotypes. Further, the allocation in reproductive growth appears related to an earlier transition from vegetative to reproductive development
Path Analysis of Rice Yield and Yield Components as Affected by Seeding Rate
Authors: Gravois K.A. , Helms R.S. 
Published: July 2010

AbstractUnderstanding relationships among rice (Oryza sativa L.) yield and yield components (panicle density, filled grain per panicle, unfilled grain per panicle, and grain weight) is critical to utilizing these relationships effectively. Interrelationships among rice yield and yield components for direct‐seeded rice cultural systems using path‐coefficient analysis that describes a priori cause‐and‐effect relationships have not been shown. Our objective was to study direct‐seeded rice yield and yield component relationships as affected by seeding rates using path‐coefficient analysis. ‘Lemont’, a semidwarf rice, was seeded at 43, 85, 128, 170, and 213 kg ha−1 in four environments between 1986 and 1988. The seeding rate by environment interaction was nonsignificant for all traits, indicating stable performance across environments. As seeding rates increased, panicle density increased significantly, and filled grain per panicle decreased significantly, an indication of the compensatory nature between these two traits. Higher panicle densities at the lower seeding rates were due in part to increased tillering of the rice plants. Path‐coefficient analysis revealed that panicle density had the largest positive direct effect on rice yield, even at low seeding rates where filled grain per panicle increased to compensate for decreased panicle density. Direct effects for filled grain per panicle and grain weight were of secondary and/or tertiary importance in determining rice yield. Unfilled grain per panicle had negligible effects on rice yield. To achieve optimum rice yields and grain quality in a direct‐seeded cultural system, adequate panicle density per unit area of uniform maturity must be achieved.
Soybean Biomass Accumulation and Leaf Area Index in Early‐Season Production Environments
Authors: Savoy B. R. , Cothren J. T. , Shumway C. R. 
Published: July 2010

AbstractSome indeterminate soybean [Glycine max (L.) Merr.] cultivars are adaptable to early plantings in the southern USA (<35°N lat). The purpose of this study was to determine the effects of inter‐row spacing and soil moisture level on dry matter accumulation, leaf area index, and plant height of an early‐planted indeterminate soybean in southcentral Texas. Soybean (‘Williams 82’, Maturity Group III) was planted in mid‐April in 1988 and 1989 near College Station, TX (30° 32'N lat). Harvest maturity occurred in late August. Soil moisture levels were irrigation and no irrigation; inter‐row spacings were 0.36 and 1.02 m. Soil moisture level treatments did not affect any of the measured dry matter or leaf area traits. Reproductive (pod and seed) dry matter production was greater in 0.36‐m rows near physiological maturity in both years. Total dry matter accumulation in 0.36‐m rows was greater than in 1.02‐m rows in 1988, but not in 1989. Leaflet, stem, and petiole dry matter accumulation was similar across soil moisture Levels and inter‐row spacings. Maximum leaf area index was greater in 0.36‐m rows than in 1.02‐m rows in 1988, but not in 1989. Narrow rows had greater radiation use efficiencies (0.48 g MJ−1 in 1988, 0.42 g MJ−1 in 1989) than wide rows (0.35 g MJ−1 in 1988, 0.37 g MJ−1 in 1989). Mean plant height was greater in 1.02‐m rows than in 0.36‐m rows in 1989, but not in 1988. Adequate levels of dry matter accumulation, leaf area production, and plant height were obtained using an adaptable indeterminate soybean in an early‐planted, early‐maturing production environment in south‐central Texas.
Delayed Seeding of Alfalfa Avoids Autotoxicity after Plowing or Glyphosate Treatment of Established Stands
Authors: Tesar Milo B. 
Published: July 2010

AbstractRe‐establishment of alfalfa (Medicago sativa L.) has often been unsuccessful because of autotoxic effects of the crop on seedlings. This study was conducted at East Lansing, MI on an Udallic Ochraqualfs, fine loamy, mixed, mesic soil. The first objective was to determine the days required to eliminate autotoxic effects for 1‐, 4‐, and 6‐yr old stands of alfalfa with 1.4 Mg ha−1 dry weight of topgrowth after treatments of plowing or glyphosate [N‐(phosphonomethyl)glycine]. The second objective was to determine autotoxic effects of 1.4, 2.7, and 4.0 Mg ha−1 dry weight of topgrowth from year‐old alfalfa plowed prior to seeding the same day. Check treatments were seedings after plowed Kentucky bluegrass (Poa pratensis L.), corn (Zea mays L.), or fallow. Alfalfa was seeded for Objective 1 on 23 June 1982, 12 d after plowing alfalfa and 19 d after glyphosate application on 6‐yr‐old alfalfa; on 5 June 1984 and 29 May 1985, 0, 7, 14, 21, 28, and 195 d (29 May 1985 only) after plowing alfalfa or glyphosate application on year‐old alfalfa; and on 11 June 1986, 7, 14, 21, and 28 d after plowing alfalfa or glyphosate application on 4‐yr‐old alfalfa. Seedings for Objective 2 were made on 5 June 1984. Densities and yields of seedings equaled checks when made at least 14 d after plowing alfalfa or 21 d after glyphosate application on established alfalfa. Seedling densities were similar, but lower than the check, after three levels of alfalfa topgrowth were plowed and seeded the same day. Results indicate alfalfa can be re‐established without significant autotoxicity if seedings are made at least 2 wk after plowing or 3 wk after glyphosate application on established alfalfa or after seeding failure. For maximum killing of old alfalfa and to avoid autotoxicity, plowing of alfalfa and seeding at least 2 wk after plowing, or early‐fall or spring glyphosate application on alfalfa followed by no‐till seeding at least 3 wk after glyphosate application, are recommended.
Cowpea Water Relations and Growth Response on a Toposequence Water Table Gradient
Authors: Timsina J. , Garrity D. P. , Pandey R. K. 
Published: July 2010

AbstractCowpea sown after wetland rice in tropical monsoon climates is frequently subjected to soil saturation and a high water table during early growth. We compared the effects of variation in water table regime on the shoot and root growth, and plant water relations of two medium‐maturing (cv. TVX3236‐01G and TVX3410‐02J) and two early maturing (cv. BS6 and IT82D‐889) cowpea [Vigna unquiculata (L.) Walp] cultivars in three water table depth regimes on a Typic Tropudalf toposequence. Our objective was to elucidate the possible mechanisms of differential cultivar adaptation to shallow water table conditions. The shallow water table regime (SWT) significantly reduced the total dry matter accumulation and harvest index for BS6, an early maturing cultivar (reductions in stems, leaves, pods, and total dry matter by 82, 77, 88, and 84% respectively), while the least reductions (reductions by 44, 3, 57 and 55%, respectively) was observed for TVX 3410‐02J, a medium‐maturing cultivar. Roots of the medium cultivars were more concentrated in the top 0.2m in the SWT Site than those of the early‐maturing cultivars. Roots of the medium cultivars later penetrated to 0.8‐m maximum depth compared to 0.6‐m maximum depth for the early cultivars, and extracted soil water from 20 cm deeper in the soil profile than the early maturing cultivars. The medium‐maturity cultivars maintained higher leaf water potentials and lower canopy temperatures throughout the season. This was associated with greater end‐of‐season total soil profile water extraction. The medium‐maturing cultivars showed better adaptation to shallow water table conditions due to superior plant water status, rooting pattern, and biomass production and partitioning.
CARICE: A Rice Model for Scheduling and Evaluating Management Actions
Authors: Miller Baird C. , Foin Theodore C. , Hill James E. 
Published: July 2010

AbstractCrop growth modeling can be useful in crop management, but previous rice crop models lack the morphologically accurate phenological detail needed for practical application. We designed a rice crop management model, CARICE, for scheduling management actions on the farm and evaluating consequences of alternative management strategies. A simple rice crop productivity model was expanded to include (i) phenology, based on leaf stage; (ii) tiller development, to establish yield components (iii) assimilate partitioning by developmental stage, (iv) assimilate partitioning patterns of California cultivars; and (v) a direct‐seeded cultural system. The key phenological events were accurately simulated: leaf stage development followed the expected pattern; predicted 50% heading was within 6 d of the actual heading dates; and grain filling predictions were within 1 to 11 d of field observations. Cultural management strategies simulated included delayed planting, and managing barnyardgrass (Echinochla spp.; BYG) competition by increasing water depth and seeding tale. Simulated yield results were within the range of field observations, although total aboveground biomass was overestimated. The model simulated a 27% loss in grain yield from a 21‐d delay in planting, which is close to the 21% loss measured in the field. At 11 and 54 BYG plants m−2, the model simulated 20.6 and 54.6% yield reductions relative to the control, as compared with 32.5 and 57.5% reported in the literature. The model predicted the interactive effect of rice seeding rate and water depth management for reducing barnyardgrass competition. The morphologically accurate phenology submodel and the yield‐component approach to calculating yield are keys to using CARICE for scheduling and evaluating management actions and strategies.
Field Response of Alfalfa to Harvest Frequency, Cultivar, Crown Pathogens, and Soil Fertility: II. Crown Rot
Authors: Gossen B. D. 
Published: July 2010

AbstractDecline in stand density and productivity of alfalfa (Medicago sativa L.) over time in Canada and the USA has been attributed, in part, to crown and root diseases. In 1985, an experiment was initiated at three locations in Saskatchewan to examine the interaction of (i) harvest frequency, (ii) alfalfa cultivar, (iii) inoculation with fungal crown rot pathogens (Coprinus psychromorbidus, Phoma sclerotioides, or Fusarium spp.), and (iv) K nutrition on the etiology, lesion initiation, incidence, and severity of crown rot of alfalfa. Plant samples were collected from the plots in early spring and late fall each year, starting 1 yr after seeding. The pattern of symptom initiation and lesion expansion were similar at all sites. Lesions were observed initially at the base of senescing stems, and spread laterally into the crown and vertically into the tap root. Lesions were observed on plants at all sites on the first sampling date (> 70% of plants affected at Loon Lake and Saskatoon and 32% at Melfort), but severity was low. By the fall of the following year (1987), incidence was near 100% at all sites, and severity had increased markedly. Harvest frequency and K fertility did not affect crown rot at any location. Inoculation with C. psychromorbidus resulted in small increases in crown rot severity at two sites, but inoculation with the other pathogens had no effect. ‘Nordica’ alfalfa was more resistant to crown rot than ‘Beaver’. These results indicate that resistance to crown rot may be advantageous if long‐term persistence is required, but resistance is not required in short‐term rotations. Also, crown rot and crown bud rot, two alfalfa diseases that have previously been described as distinct entities, appear to be a single disease complex, based on similarities in symptom development and the organisms associated with affected plants.
Influence of Plant Growth Regulators and Mowing on Two Bermudagrasses
Authors: Johnson B. Jack 
Published: July 2010

Abstract‘Tifway‘ hybrid bermudagrass [Cynodon transvaalensis Burtt‐Davy × C. daetylon (L.) Pers.] and common bermudagrass [C. dactylon (L.) Pers.] are popular turfgrasses used throughout the southern USA. When both grasses are managed as a medium‐ to high‐quality turf, frequent mowings are needed to limit vegetative growth and seedhead emergence. Plant growth regulators offer the potential to reduce the number of mowings needed by bermudagrass. Therefore, experiments were conducted on Tifway and common bermudagrasses to determine the effects of plant growth regulators on vegetative growth, seedhead suppression, and mowing requirements. Flurprimidol {α‐(1‐methylethyl)‐α‐[4‐(trifluoro‐methoxy) phenyl]‐5‐pyrimidine‐methanol}, paclobutrazol, {(±)‐(R*R*)β‐[(4‐chlorophenyl) methyl]‐α‐(1,1‐dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol}, and trinexapac‐ethyl [4(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxocyclohexanecarboxylic acid ethyl ester] plant growth regulators were each applied at various rates in three applications at 4‐wk intervals. When Tifway bermudagrass was treated initially with trinexapac‐ethyl at 0.2 kg ha−1, and followed by 0.1 kg ha−1 at 4 and 8 wk, vegetative growth and seedheads were suppressed for 12 wk and the number of mowings were reduced by 70 and 67% during 1992 and 1993, respectively. However, the quality of Tifway bermudagrass as significantly lowered in plots treated with trinexapac‐ethyl at this rate at four rating dates during 1992 and three rating dates during 1993, when compared with turfgrass treated initially at 0.1 kg ha−1, and followed by 0.05 kg ha−1 at 4 and 8 wk. Common bermudagrass was less affected by these treatments. Neither flurprimidol nor paclobutrazol applied in three applications during a 12‐wk period provided consistent vegetative growth and seedhead suppression of common bermudagrass during 1992 and 1993.
Evaluation of a Model to Predict Nutrient Uptake by Field‐Grown Rice
Authors: Teo Yan Hock , Beyrouty Craig A. , Gbur Edward E. 
Published: July 2010

AbstractThe Barber‐Cushman model has not been evaluated under flooded conditions. A field study was conducted on a Crowley silt loam to evaluate the ability of the model to predict NH+4, P, and K uptake by rice (Oryza sativa L.). Total nutrient uptake and root and soil parameters were measured at vegetative (active tillering, maximum tillering, and 1.25‐cm internode elongation) and reproductivec (booting and heading) stages of development of three cultivars (Katy, Mars, and Lemont). The model accurately predicted nutrient uptake during vegetative growth but underpredicted nutrient uptake during reproductive growth. About 90% of the total NH+4 P, and K uptake and root length of the rice cultivars occurred within the surface 20 cm of soil, suggesting that samples collected for routine soil tests should be from the top 20 cm. Ammonium and P uptake in the 0‐ to 20‐cm soil depth were most sensitive to root competition, root radius, nutrient solution concentration, and buffer power. However, K uptake was most sensitive to maximum influx rate, root radius, Michaelis constant, and root growth rate throughout the top 40‐cm soil depth. These findings indicate that NH+4 and P uptake can be enhanced by increasing levels of fertilization in the top 20 cm of soil where these nutrients are found to be limiting. Fertilization should increase the NH+4 and P solution concentrations, thus reducing root competition for these elements. Potassium soil levels were not low enough to limit uptake by the cultivars selected for this study.
Temperature and Soil Water Effects on Dormancy and Mortality of Subterranean Clover Seed
Authors: Fairbrother Timothy E. , Rowe Dennis E. 
Published: July 2010

AbstractGermination tests were conducted to investigate possible causes for a reestablishment failure of subterranean clover (Trifolium subterraneum L.). ‘Mount Barker’ subterranean clover seeds were germinated on blotters and on the soil surface or at 1 cm depth in nonfumigated and fumigated soil at four constant temperatures for 14 d, followed by constant 15°C for 8 d. Fumigation had no effect on germination. Germination on blotters was reduced to 11.1% at 25 and 30°C, compared with 94.5% at 15°C. Emergence of seedlings was reduced to 37.9% at 30°C, compared with 92.5% at 15°C. Emergence of seedlings at 30°C from soil was greater after 14 d than germination on blotters. In a second experiment, seeds buried 1 cm were germinated at soil water levels ranging from 0.0 to 0.816 kg kg−1. Temperatures were 15 or 30°C for 7 d, then 15°C for 7 d more. Seeds failed to germinate at either temperature in dry or saturated soil. Emergence after 7 d was reduced at 30°C compared with 15°C at soil moisture levels from 0.204 to 0.544 kg kg−1. After 7 more d at 15°C, emergence was similar between temperatures at soil moisture levels from 0.0 to 0.544 kg kg−1. Under saturated soil conditions, 28.5 and 80.8% of the seed rotted at 15 and 30°C, respectively. Our results suggest that subterranean clover seeds can survive in pasture soil for 14 d in an embryo dormant condition during the summer, unless the soil is saturated, in which case soft seeds tend to decay.
Residue Removal Method and Herbicides for Tall Fescue Seed Production: II. Crop Tolerance
Authors: Mueller‐Warrant George W. , Young William C. , Mellbye Mark E. 
Published: July 2010

AbstractIncreased reliance on herbicides for controlling weeds is a significant component of the ongoing transition from open‐field burning (FB) to nonburn systems for grass seed production in the Pacific Northwest. Volunteer crop seedlings are the most abundant weeds present in many certified grass seed fields, but herbicide treatments to control them also have the potential to injure the established crop. Fourteen herbicide treatment sequences plus an untreated check were examined in five residue removal systems at two field sites during two consecutive growing seasons to determine their effect on tall fescue (Festuca arundinacea Schreb.) seed yield and harvest index. Herbicide treatments were applied preemergence (PRE) to seedling grasses in mid‐October, postemergence (POST) in early December, or at both times. Tall fescue seed yield was not affected over a two‐year period by competition from volunteer seedlings. Seed yield was reduced by herbicide injury, particularly in the second year. PRE applications of oxyfluorfen [2‐chloro‐1‐(3‐ethoxy‐4‐nitrophenoxy)‐4‐(trifluoromethyl)benzene] reduced seed yield by 87 and 151 kg ha−1 in 1990 and 1991, respectively, compared with the average for three other PRE herbicides, pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine], metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐l‐methylethyl) acetamide], and trifluralin [2,6‐dinitro‐N,N‐dipropyl‐4‐(trifluoroniethyl)benzenamine]. The untreated check yielded 122 kg ha−1 more seed than the average of all 14 herbicide treatments in 1991. The least injurious herbicide treatment was PRE pendimethalin applied without subsequent POST herbicide. When applied following PRE herbicides, POST applications of 2.7 kg a.i. ha−1 diuron [N'‐(3,4‐dichlorophenyl)‐N,N‐dimethylurea] or 0.14 kg a.i. ha−1 oxyfluorfen plus 1.8 kg ha−1 diuron did not differ in yield or harvest index. An aggressive system for mechanical removal of straw, seed, and postharvest regrowth, vacuum sweeping (VS), reduced tall fescue seed yield and harvest index in 1991 compared with other, less aggressive, mechanical methods, and compared with two methods of burning. Some herbicide treatments applied to control volunteer crop seedlings had a greater effect on tall fescue seed yield than the adoption of nonburn methods of residue removal.