bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Tillage Practices on Phosphorus Distribution and Forms in Three Ultisols
Authors: Weil R. R. , Benedetto P. W. , Sikora L. J. , Bandel V. A.
Published: July 2010

Many studies have indicated that organic matter levels in soils tend to rise when no‐till (NT) management replaces plowing. It was hypothesized that organic P may thus play a more important role in the plant availability of P in NT soils. A laboratory study was conducted to investigate the organic and inorganic forms of P and their cycling in NT and conventionally tilled (CT) silt loams. Soils from three long‐term field experiments were sampled in the fall of 1984, obtaining core segments from 0 to 2, 2 to 4, 4 to 8, 8 to 12, 16 to 20, and 24 to 28 cm. Soil analyses indicated significant differences in the distribution with depth of macro‐nutrients between tillage systems. Total P, dilute acid‐extractable P (DA‐P), total N, and organic matter were more concentrated in the 0‐ to 2‐cm layer under NT compared to CT management. Organic P did not accumulate to the same extent as did organic N and C, resulting in a lower organic P/organic C ratio under NT than under CT management. With increased rates of P fertilization on one soil, total P and DA‐P increased dramatically in the upper soil layers, but a similar increase and stratification of organic P was not observed. Samples taken in the spring of 1985 indicated that, despite significantly higher microbial respiration in NT cores, there was no consistent change in the solubility of P over a 75‐d incubation period. Thus, it was concluded that the incubation procedure inadequately measured P mineralization in these soils. However, water‐soluble P was significantly greater in the upper 5 cm under NT, even where no P fertilizer had been applied. This may have been a result of interference with P‐adsorption reactions by accumulated organic matter. This study provided no evidence that organic P is of more importance to plant P availability under NT.
Forage Sorghum Production on a Witchweed‐Infested Soil in Relation to Cutting Height and Nitrogen
Authors: Bebawi Faiz F.
Published: July 2010

Little is known about forage sorghum [Sorghum bicolor (L.) Moench] and forage sorghum‐sudangrass [S. bicolor × S. sudanense] hybrid production in soil infested with witchweed [Striga hermonthica (Del.) Benth]. The objective of the present study was to evaluate the immediate effects (first harvest) and aftereffects (second and third harvest) of two cutting heights (0.1 and 0.3 m) and five N treatments (0,60 + 60,120,120 + 120, and 240 kg N ha−1) on witchweed management in forage sorghum (cv. Abu Sabeen) and forage sorghum‐sudangrass (cv. Pioneer 988) hybrid. Field studies were conducted at Shambat, Sudan, in 1984 and 1985 on a heavy alluvial clay soil (montmorillonitic, isohyperthermic Vertic Camborthid) heavily infested with witchweed. Pioneer 988 was more tolerant of witchweed than Abu Sabeen at first harvest, but less tolerant of witchweed at later harvests. The shorter cutting height resulted indirectly in a larger number of tillers (26%) and a higher forage greenchop yield (37%) at first harvest. Nitrogen increased forage tiller density approximately twofold and forage greenchop yield by approximately ten‐fold at the first harvest. There was a concurrent, approximately fivefold reduction in witchweed shoot weight. At second harvest, forage tiller density, forage greenchop yield, and witchweed shoot weight were increased with N. Both forage sorghum and witchweed were dead in the zero N plots at third harvest. No differences were detected between single and split applications of N, or between low (120 kg N ha−1) and high (240 g N ha−1) rates of N. Forage tiller density, forage greenchop yield and witchweed shoot weight were reduced at the second and third harvests compared to the first harvest.
Yield, Soil Nitrogen Uptake, and Nitrogen Fixation by Soybean from Four Maturity Groups Grown at Three Elevations
Authors: George Thomas , Singleton Paul W. , Bohlool B. Ben
Published: July 2010

The exploitation of the soybean [Glycine max (L.) Merr.] ‐Bradyrhizobium juponicum symbiosis in varied environments requires an understanding of factors that may affect fixed and soil N assimilation. Temperature affects both soybean maturity and N requirement, and soil N availability. Five soybean varieties belonging to four maturity groups (00, IV, VI, and VIII) and their respective nonnodulating isolines were planted at three sites along an elevational transect in Hawaii to study the effect of elevation‐associated changes in temperature on yield, soil N uptake, and N2 fixation. The mean soil/air temperatures during the experiment were 24/23,23/21, and 20/18°C, with 7, 8, and 9°C differentials between mean maximum and mean minimum air temperatures at elevations of 320,660, and 1050 m, respectively. The soils of the two lower sites were Humoxic Tropohumults and that of the highest site was Entic Dystrandept. The seeds were inoculated at planting with B. japonicum. Plants were harvested at physiological maturity. Average dry matter yield and N accumulation at the highest site was only 48 and 41%, respectively, of that at the lowest site. Early maturing varieties were relatively more affected by high elevation than were later varieties. Within each site, late‐maturing varieties produced greater yield and accumulated more N than did the early varieties. Nitrogen fixation contributed 80, 66, and 97% to total plant N at the lowest, intermediate, and highest sites, respectively. Differences between sites in the proportion of N from fixation were due to differences in the availability and uptake of soil N. Although total N assimilation between varieties differed in some cases by more than 400%, the proportions of N derived from fixation were similar within a site. On a per‐day basis, N accumulation was similar among varieties at a site. Since the different maturity groups had similar average N assimilation rates per day within a site, and since soil N mineralization rate per day at a site can be assumed to be constant, the proportion of total N derived from N2 fixation is necessarily constant. Since the proportion of N derived from fixation is yield independent at a site, it may be possible to predict the relative contributions of soil N and symbiotic N2 fixation to soybean through characterization of the processes that affect N availability at a site. Data from in vitro soil N mineralization and a greenhouse pot test indicated that low temperature may have decreased root growth and uptake of soil N, or soil N availability more than it reduced N2 fixation.
Effect of Salinity on Grain Yield and Quality, Vegetative Growth, and Germination of Triticale
Authors: Francois L. E. , Donovan T.J. , Maas E. V. , Rubenthaler G. L.
Published: July 2010

Development of high yielding triticale (X Triticosecale Wittmack) cultivars may promote an increased acreage of this crop on irrigated soils in the western United States. Often these soils are, or have the potential to become, highly saline. Because of the lack of information on salinity effects on vegetative growth and seed yield of triticale, the salt tolerance of two cultivars (Beaguelita ‘s’ and Cananea 79) was determined in a 2‐yr field plot study. Six salinity treatments were imposed on a Holtville clay [clayey over loamy, montmorillonitic (calcareous), hyperthermic Typic Torrifluvent] by irrigating with waters salinized with NaCl and CaCl2, (1:1 by weight). Electrical conductivities of the irrigation waters were 1.8,2.6, 5.1, 7.5,9.6, and 12.2 dS/m the first year, and 1.4, 3.9, 7.9, 12.0,16.0, and 20.3 dS/m the second year. Grain yield, vegetative growth, and germination were measured. Relative grain yield for both cultivars was unaffected by soil salinity up to 7.3 dS/m (electrical conductivity of the saturated‐soil extracts in the rootzone). Each unit increase in salinity above 7.3 dS/m reduced grain yield by 2.8%. These results place triticale in the salt‐tolerant category. Yield reduction resulted primarily from a reduction in spike number rather than from lower weight per spike or lower weight per individual seed. Salinity reduced vegetative growth less than grain yield in Cananea 79 but more in Beaguelita ‘s’. Both cultivars were slightly less salt tolerant at germination than they were after the three‐leaf stage of growth.
Effect of Incrementing Nitrogen Application on Sucrose Yield of Sugarbeet
Authors: Anderson Frank N. , Peterson Gary A.
Published: July 2010

Nitrogen fertilization of sugarbeet (Beta vulgaris L.) usually increases root yields but decreases sucrose concentration. Therefore, management strategies must aim at an optimization of both that leads to maximum sucrose yield and not root yield. This study explored the value of applying N in increments to increase sucrose production and decrease top growth and impurities of the sugarbeet crop. The soil was depleted of N by cropping with corn (Zea mays L.) each year prior to the sugarbeet production year. Total N rates from 30 to 300 kg ha−1 N were applied in increments of 30,60, and 90 kg ha−1 over a time span of 16 wk each year of the experiment for 3 yr on a Tripp very fine sandy loam (coarse‐silty, mixed, mesic Typic Haplustoll). A series of hail storms in the second year of the experiment caused the N requirement to be higher for that year, as N in the leaves removed by the hail did not recycle. The first and third years demonstrated a normal pattern of greater top growth, lower sucrose concentration, and lower purity as N rates increased. Optimum N rates were 50 kg ha−1 higher for root yields than for maximum sucrose production. Delaying N supply by incrementing fertilizer applications favored root development and sucrose production but did not affect top growth.
Yield, Lodging, and Growth Characteristics in Sweet Corn as Influenced by Ethephon Timing and Rate
Authors: Gaska J. M. , Oplinger E. S.
Published: July 2010

Summer storms frequently lodge sweet corn (Zea mays L.), making harvest difficult while reducing yields. Ethephon (2‐chloroethylphosphonic acid), a plant growth regulator, has the potential to be an anti‐lodging agent in sweet corn. Field research was conducted on a Plano silt loam soil (fine‐silty, mixed, mesic Typic Argiudoll) at the Arlington Research Station near Arlington, WI, in 1985 and 1986 to determine the effect of ethephon timing and rate on sweet corn. Four rates (0, 140, 280, and 420 g ha−1) of ethephon were applied at three application timings [tassel elongation (TE), TE + 4 to 6 d, and TE + 9 to 13 d] to two plant densities of ‘Jubilee’ sweet corn. In 1985, plant densities of 49 400 and 66 700 plants ha−1 were used. In 1986, an additional ethephon rate of 70 g ha−1 and plant densities of 59 200 and 73 900 plants ha−1 were used. In hand‐harvested plots, ethephon altered yield and plant growth both years. High rates of ethephon reduced lodging by 87%, plant and ear height by 16 and 13%, respectively, and increased brace root development by 50%. High plant densities increased yields 8% and lodging 23%. Timing of ethephon application on yield had variable results. Yields were reduced 13% with the high rate of ethephon at the early and middle application times, but were not altered at the late application time. When the potential for lodging is high, ethephon at the higher rates and late application times may be effective in preserving sweet corn yields.
Interactive Water and Nitrogen Effects on Senescence of Maize. II. Photosynthetic Decline and Longevity of Individual Leaves
Authors: Wolfe D. W. , Henderson D. W. , Hsiao T. C. , Alvino A.
Published: July 2010

Stress‐induced senescence is frequently alluded to, but interactive effects of water and N deficits on leaf longevity and on physiological changes associated with leaf aging have received little attention. A 2‐yr field experiment with maize (Zea mays L.) was conducted on Yolo loam (fine‐silty, mixed, nonacid, thermic Typic Xerorthents) with four treatments: N fertilized (180 kg N/ha) with (NI) and without (ND) irrigation; and no N applied with (OI) and without (OD) irrigation. Size and longevity measurements were made of leaves at all nodal positions, and leaves 5, 11, and 15 (counting up from stem base) were monitored for changes in photosynthetic capacity (PC), N concentration, and chlorophyll content (CHL). Leaf PC was correlated with percent N during senescence in all treatments (r2 = 0.86), but an occasional midday depression in PC, unrelated to leaf N status, was observed in severely water stressed plants. Chlorophyll and percent N were also correlated (r2 = 0.80), but initial onsets of decline in these two parameters often differed by several days. Nitrogen deficits were less severe in 1983 than 1982, but in both years lack of applied N had an early impact and reduced longevity of lower leaves. In 1982, N deficiency caused a 50% reduction in leaf peak values of percent N, CHL, and PC, and the decline in leaf 5 was most rapid in low N plants. Water stress intensified as stored soil water was gradually depleted, and the most rapid decline and earliest complete senescence of upper leaves (11 and 15) occurred in the ND treatment. These results indicate that early stress effects on leaf area and ear development affected subsequent demands for water and N, which in turn altered patterns of leaf senescence.
Response of Field Grown Alfalfa to Root Waterlogging and Shoot Removal. II. Nitrogen and Fermentation Metabolism
Authors: Barta A. L.
Published: July 2010

Shoot removal and root hypoxia are two stresses to which alfalfa (Medicago sativa L.) roots are often exposed. Because shoots are the primary energy source for all higher plant metabolism, clipping may have severe consequences on anoxic root metabolism. The objective of this study was to characterize aspects of N metabolism, especially polyamine accumulation, and fermentation metabolism when waterlogged roots are further stressed by shoot removal 2 or 12 d before soil saturation. Experiments were conducted on a fine, loamy, mixed mesic Typic Fragiudalf soil water‐saturated for up to 14 d. Seedling plants of ‘Vernal’ and ‘Answer’ alfalfa were used at the flowering stage of growth. There was no relationship between flooding injury and root N content or amino‐N concentration, although both were significantly affected by flooding. Putrescine concentrations increased significantly with flooding, but there was no correlation with flooding injury among the shoot treatments. Root ethanol concentrations increased in all flooded treatments but were not correlated with root injury. Glucose‐6‐P concentration increased under hypoxia and did not appear rate limiting for fermentation. Root ATP concentrations were significantly reduced by both clipping and root flooding, while the ATP/ADP ratio was affected only by flooding. Because both the ATP concentrations and the ATP/ADP ratios were similar in tissues with differing flooding injury, a quantitative relationship between energy availability and flooding tolerance is not a probable characteristic of the tolerance mechanism.
Winter Wheat Response to Nitrogen and Irrigation
Authors: Eck Harold V.
Published: July 2010

Winter wheat (Triticum aestivum L.) is grown on the Southern Great Plains under dryland conditions and under varying irrigation regimes. Relationships between water and fertilizer needs are not well defined. Field studies were conducted to determine: (i) the interacting effects of N fertilization and irrigation on N and P needs, wheat yields, and yield components; and (ii) the effects of riming of water deficit periods on N and P needs, wheat yields, and yield components. Studies were conducted on a Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). Respective N and P rates ranged from 0 to 210 kg ha−1 and 0 to 40 kg ha−1. Irrigations were applied or withheld to allow the crop to be nonstressed (I‐1), stressed during heading and grain filling (I‐2), stressed during tillering and jointing (I‐3), and stressed throughout spring (I‐4). Two‐year average data showed that 140 kg N ha−1 was sufficient for maximum grain yields on treatment I‐1, while 70 kg N ha−1 was sufficient on treatments on I‐2 and I‐3, and no N response occurred on treatment I‐4. Compared to treatment I‐1, grain yields were 27, 32, and 52% less on treatments I‐3, I‐2, and I‐4, respectively. Water use efficiency (WUE) increased with increments of N through 140 kg ha−1 on treatment I‐1, and through 70 kg ha−1 on treatments I‐2, and I‐3 but applied N did not affect WUE on treatment I‐4. In 1981, WUE was highest on treatment I‐1 and lowest on treatment I‐4; in 1982, however, WUE was highest on treatment I‐4 and lowest on treatments I‐1 and I‐3. For limited irrigation, irrigating during tillering and jointing would be preferable to allowing stress then, and irrigating during heading and grain filling, because there is still potential for high yields if precipitation occurs during heading and grain filling.
Stubble Burning Effects on Winter Wheat Yield and Nitrogen Utilization under Semiarid Conditions
Authors: Rasmussen P. E. , Rohde C. R.
Published: July 2010

Although cereal residues are reportedly burned to accelerate vegetative growth, reduce disease or weed competition, or prevent microbial immobilization of N, there may be no yield enhancement in semiarid regions where drought stress limits yield. Experiments were initiated in 1979 and 1980 in a winter wheat (Triticum aestivum L.)—fallow rotation to determine burning effects on wheat yield and N utilization on a Walla Walla silt loam soil (coarse‐silty, mixed, mesic Typic Haploxeroll). Burning versus not burning wheat stubble was examined at three N levels (0, 45, and 90 kg ha−1) over 6 yr (three crops in each wheat‐fallow secquence). Wheat stubble was burned on designated plots in the spring of the fallow year, then all plots were plowed 0.22 m deep. Nitrogen as NH4NO3 was applied in October prior to wheat seeding. Stubble burning had no effect on grain yield or grain N uptake in any of the 6 yr. Burning tended to increase straw yield when wheat was fertilized with N but had no effect on straw N uptake. Overall, burning did not increase total N uptake. Nitrogen fertilization increased yield and N uptake in all years. Six‐year grain yield averages for 0, 45, and 90 kg N ha−1 were 3.1, 4.7, and 5.3 Mg ha−1. Stubble burning did not decrease foot rot (Pseudocercosporella herpotrichoides) incidence or severity in either of the 2 yr that it was present. Burning did reduce downybrome (Bromus tectorum) density in the 1 yr that it was not effectively controlled by mechanical tillage.
Effects of Moisture Stress on Nitrogen Fertilizer Response in Dryland Wheat
Authors: Korentajer L. , Berliner P. R.
Published: July 2010

Long‐term N fertilizer trials with dryland wheat (Triticum aestivum L.) are frequently confounded by large year‐to‐year variability in yields resulting from moisture stress fluctuations. To account for this variability, an N fertilizer study was conducted in which the magnitude of moisture stress was monitored. The experiment was carried out during 1983 and 1984 (389 and 136 mm of seasonal rainfall, respectively) on a Plinthustalf loamy fine sand soil, with wheat (cv. Betta), using a completely randomized block design with four replicates and five levels (N) of N fertilizer: 0, 30, 60, 90, and 120 kg N ha−1. The seasonal moisture stress index, S, was estimated from a weighted product of ET/ETp ratios (actual to potential evapotranspiration) obtained for the different phenological wheat growing periods. The ET was estimated from soil moisture (monitored by means of a neutron moisture meter), whereas ETp was calculated from meteorological measurements using Penman's equation. The response to N in both years was significant; the mean yields were 3.18 and 1.7 Mg ha−1, for the 1983 and 1984 seasons, respectively. The data were statistically analyzed by means of a postulated multiple regression model, with N and S levels as the explanatory variables. The model was validated using yield and meteorological data from several other 2‐yr N response studies. A good correlation (R2 = 0.63, standard error of the estimate = 0.27 Mg ha−1) was obtained between the predicted and the observed yields. The results of the study highlight the need for moisture stress measurements to be included in fertilizer trials conducted in areas of large seasonal rainfall variability.
Root Growth Dynamics of a Rice Cultivar Grown at Two Locations
Authors: Beyrouty C. A. , Wells B. R. , Norman R. J. , Marvel J. N. , Pillow J. A.
Published: July 2010

Root growth dynamics of rice (Oryza saliva L.) under submerged soil conditions are poorly understood. Two field experiments were conducted in 1986 to compare root growth of rice at two locations on different soils. The rice cultivar Bond was seeded in leveed plots on a Captina silt loam (fine‐silty, siliceous, mesic Typic Fragiudults) at Fayetteville, AR, and on a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualfs) at Stuttgart, AR. Plots contained rectangular Plexiglass root observation tubes oriented at a 45° angle from the soil surface and extending 0.57 m (Captina) and 0.44 m (Crowley) below the soil surface. Root recordings were taken during vegetative and reproductive growth. Root growth was most rapid during vegetative growth at both locations, with maximum root length occurring at panicle initiation. Root lengths either plateaued or declined during reproductive growth. Root lengths were greater on the Captina soil than on the Crowley soil. The pattern of root length densities (RLD) was similar between soils; however, RLDs were generally lower on the Crowley soil. During early stages of rice growth, a greater percentage of rice roots was measured in the upper 20 cm of the Crowley soil. By harvest, about 50% of the rice roots occurred in the top 20 cm in both soils. Harvesting appeared to reduce the percentage of roots found below 20 cm on the Crowley soil, and to have little effect on the Captina soil. Results suggest that rice root growth can vary dramatically between soils, and is influenced by soil profile characteristics, soil moisture, air temperatures, and growth stage.
Carbohydrate Reserves and Tillering of Switchgrass Following Clipping
Authors: Anderson Bruce , Matches A. G. , Nelson C. J.
Published: July 2010

Stands of switchgrass (Panicum virgatum L.) often decline following defoliation, a response often attributed to a high fertile/vegetative stem ratio and a paucity of basal shoots and foliage. Information is lacking on interactions among meristem removal, tiller development, and energy reserves. Field studies on a Mexico silt loam soil (Udollic Ochraqualf) were conducted for 2 yr to examine tillering and total nonstructural carbohydrate (TNC) trends of ‘Pathfinder’ switchgrass following clipping. Harvests were taken on six dates between the vegetative and heading stage during two consecutive years. In Year 2, tiller density was determined periodically during the season. First‐harvest yield increased 699 kg ha−1, and regrowth yield decreased 281 kg ha−1 with each week delay of first harvest. When apical meristems were removed, TNC in aboveground tissue declined more (28 vs. 5 g kg−1) during regrowth and to a lower concentration (51 vs. 43 g kg−1) than when apical meristems remained intact. By the end of the growing season, all clipped plants had similar TNC concentrations, but uncut plants contained 22 and 40% more TNC in above‐ and belowground tissue, respectively, than clipped plants. Tiller development appeared to be unrelated to TNC or to date of first harvest when harvested between vegetative and heading stages. However, clipping during the first year reduced yield during the second year by 34 to 60%. Lengthy regrowth periods following severe defoliation, defoliation that allows apical meristems or leaf area, or both, to remain, and control of weeds are likely to enhance stand maintenance and plant vigor of switchgrass.
Bahiagrass Response to Sulfur on an Aeric Haplaquod
Authors: Mitchell C. C. , Blue W. G.
Published: July 2010

Sulfur fertilization of bahiagrass (Paspalum notatum Flugge ‘Pensacola’) has not been a common practice on northern Florida Spodosols. A 6‐yr study was begun in 1978 on an established sward of bahiagrass on Myakka fine sand (sandy, siliceous, hyperthermic Aeric Haplaquod) to determine if an S response could be obtained by intensive management of bahiagass and to evaluate N and S rates for this forage crop. Herbage yield, N and S uptake, the stolon‐root mass, and soil S were measured and evaluated at two rates of N fertilization (200 and 400 kg ha−1) and four rates of S fertilization (0, 10, 20, and 40 kg ha−1) as gypsum (CaSO4·2H2O). Splitting S into four applications had no effect on yield, S uptake, or N uptake over a single annual application. At the low N rate, a dry matter yield response did not occur until the fourth year of the study, with maximum yields thereafter predicted at an average annual S application between 27 and 33 kg ha−1. At the high N rate, a dry matter yield response occurred the second year with 10 kg S ha−1 applied, and by the fifth and sixth years, maximum dry matter herbage yield was predicted at an annual S application between 40 and 51 kg ha−1. The stolon‐root system accumulated N and S, but S treatments had no effect on extractable or total soil S. Sulfur removed in the herbage exceeded that applied at all but the highest S rate. Sulfur fertilization also enhanced N recovery. A critical S concentration of 1.61 g kg−1 was identified for bahiagrass herbage.
Water Deficit Timing Effects on Yield Components in Maize
Authors: Grant R. F. , Jackson B. S. , Kiniry J. R. , Arkin G. F.
Published: July 2010

This study was designed to determine the interval of sensitivity of maize (Zea mays L.) yield components to moisture stress, and to evaluate that interval using estimates of plant available water (PAW). Individual maize plants were grown in containers in a glasshouse. For each treatment, water was withheld until the accumulated water use in well‐watered control containers was 20 L, approximately twice the PAW in each container. Containers were well watered at all other times. Containers were weighed to determine water use rates and to estimate PAW. Moisture stress was assumed initiated when water use rates declined below the average for well‐watered containers. The interval when kernel number was sensitive to moisture stress began 2 to 7 d after silking and ended 16 to 22 d after silking. Stress initiated prior to silking but relieved within 2 d after silking did not reduce kernel number, kernel weight, or plant yield. The fewest number of kernels, 45% of the control, occurred for stress during the 7‐d period after silking. Kernel weight was reduced by stress during the grain filling period, and the lowest weight, 51% of the control, occurred for stress 12 to 16 d after silking. Water use rates in treatment plant containers were compared to estimates of the soil moisture stress index (SMI) determined as the percentage of PAW in the containers. Water use rates declined when SMI declined below thresholds of between 0.20 and 0.30. These thresholds were similar to those reported for other crops. Thus, this analysis demonstrated that parameters based on PAW can be useful for evaluating the timing of moisture stress on maize yield components.
Seeding Depth in Relation to Plant Development, Winter Survival, and Yield of No‐Till Winter Wheat
Authors: Loeppky Heather , Lafond G. P. , Fowler D. B.
Published: July 2010

Successful production of winter wheat (Triticum aestivum L.) on the Canadian prairies requires no‐till seeding into standing stubble (stubbling‐in) in order to trap snow and thereby prevent low temperature freezing injury of the young seedlings. In the present study, a total of 14 no‐till winter wheat field trials were seeded into standing stubble on several Saskatchewan soil types (Aridic, Typic, Vertic, and Udic Haploborolls, and Udic Agriborolls) to investigate the effect of seeding depth on plant growth and development. The influence of seeding depth and date on winter wheat growth and development were also investigated in a hand‐planted trial on conventional summerfallow. Increases in seeding depth as small as 17 mm resulted in significantly deeper crown placement and delayed plant emergence. Delayed seeding into cooler soils was associated with slower plant emergence and shorter sub‐crown internodes than earlier seeding at warmer soil temperatures. Consequently, delayed deep seeding resulted in very slow plant emergence, a reduction in the number of tillers plant−1 and fewer heads m−2 the following year. Winter survival was significantly higher for shallow seeded treatments in four of seven trials that experienced differential winterkill. A significant yield advantage (11%) was observed with shallow seeding in four of six trials that escaped serious winter damage. In contrast, improved winter survival and/or yield advantages were never obtained with increased seeding depths. These observations demonstrate that seeding shallow (10–25 mm) at the recommended date is necessary to optimize plant establishment in the fall, minimize the risk of winter damage, and maximize yield potential of no‐till winter wheat produced on the Canadian prairies.
Esophageal Plug and Fasting Effects on Particle Size Distribution and Quality of Extrusa from Grass Pastures
Authors: Fisher D. S. , Burns J. C. , Pond K. R.
Published: July 2010

Diet selection and mastication by cattle (Bos taurus L.) can be examined using extrusa from esophageal fistulas. Experiments were conducted to investigate the use of an esophageal plug and the influence of a 16‐h fast, prior to collection, on the particle size distribution and quality of masticated forage. Extrusa was freeze‐dried and sieved into seven size‐classes, and the weight of masticate in each class was determined. The proportions of large (>1.7 mm), medium (0.5–1.7 mm), and small (<0.5 mm) particles and the mean and median particle sizes were analyzed. Neutral detergent fiber (NDF) and in vitro dry matter disappearance (IVDMD) were also determined. In both experiments, significant differences between single pastures of Coastal bermudagrass [Cynodon dactylon L. (Pers.)] with 3500 kg ha−1 and flaccidgrass (Pennisetum flaccidum Griseb.) with 2900 kg ha−1 available forage were found in particle size, NDF, and IVDMD. Averaged over experiments, the proportions of large, medium, and small particles found in bermudagrass were 20, 54, and 26%, respectively, and 35, 47, and 18%, respectively, for flaccidgrass. The NDF of bermudagrass and flaccidgrass averaged 550 and 505 g kg−1, respectively, and the IVDMD averaged 640 and 700 g kg−1, respectively. Neither the esophageal plug nor the fasting had an influence on the particle size distribution, NDF, or IVDMD.
Soybean Field Losses as Influenced by Harvest Delays
Authors: Philbrook B.D. , Oplinger E.S.
Published: July 2010

Conflicts for time and machinery can postpone harvests beyond the initial time when optimum conditions exist. This study was conducted to determine the effects of delaying soybean [Glycine max (L.) Merr.) harvests on grain losses in the field. Field studies were conducted each year from 1983 to 1986 at Arlington, WI. Two cultivars from each of maturity groups (MG) 0, I, and II, one more susceptible to lodging than the other, were used. Initial harvest for each maturity group began 3 to 7 d beyond stage R8. Three additional harvests were made for each maturity group at 14, 28 and 42 d beyond their initial harvest. Average soybean field losses were 10% of the potential yield, but ranged from 5.5% in 1983 to 12.7% in 1984. Loss of potential yield increased linearly at a rate of 0.2% d−1 from an average of 6.1% at the initial harvest to 13.9% 42 d later. In 1984 and 1986 net yields were reduced 14 and 18 kg ha−1d−1, respectively. Harvest delays of 42 d resulted in plant deterioration and, in turn, lodging increased 20%, and preharvest, shatter, and stem losses increased 62, 95, and 70 kg ha−1, respectively. Shatter losses were influenced by moisture conditions at harvest, but plant deterioration also increased shattering beyond that accounted for by moisture. On the average the MG I cultivars Hardin and Northrup King S1346 lost only 7.3 and 8.3% of their potential yield versus 10.4 and 11.4% for the MG 0 cultivars Ozzie and Evans, and 10.8 and 9.2% for MG II cultivars Wells II and Corsoy 79. Both of the MG I cultivars exhibited slower rates of harvest loss increases. The proportion of potential yield lost was inversely related to potential yield, indicating that harvest efficiency was improved with higher yields. Harvest delays can ultimately result in plant deterioration, increased grain losses, increased harvesting difficulties, and reductions in net yield of 11 kg ha−1d−1.
No‐till Winter Wheat Production on the Canadian Prairies: Placement of Urea and Ammonium Nitrate Fertilizers
Authors: Fowler D. B. , Brydon J.
Published: July 2010

A practical snow management system, which utilizes no‐till seeding into standing stubble immediately after harvest of the previous crop has permitted the expansion of winter wheat (Triticum aestivum L.) production in western Canada. In the present study nine field trials were conducted on several Saskatchewan soil types (Aridic, Typic, Vertic, and Udic Haploborolls) from 1982 to 1986. The objectives were to compare stubbled‐in winter wheat grain yield (GY), grain protein yield (GPY), and protein concentration (PC) responses to urea and ammonium nitrate (AN) fertilizer banded and broadcast at seeding, or broadcast in the late fall or early spring. A prolonged dry period following spring broadcast of urea and AN delayed the availability of added N in one trial, which resulted in negligible GY response, limited GPY response, and large PC response to spring N applications. Reduced yield responses, which were probably due to N losses through denitrification, were also observed for both urea and AN broadcast in the late fall in one trial. Reduced CY and GPY responses for urea compared with AN in three trials indicated that, under some conditions, volatilization losses of greater than 50% can be experienced with broadcast urea. Fall banding prior to seeding was effective in reducing losses with urea, but this method of application presents other problems in the stubbling‐in production system and, in these trials, fall banding did not outperform AN broadcast at the same time.
Photosynthetic Rates of Six Maize Cultivars During Development
Authors: Dwyer L. M. , Stewart D. W. , Balchin D. , Houwing L. , Marur C. J. , Hamilton R. I.
Published: July 2010

Production estimates based on photosynthate accumulation are affected by changes in photosynthesis rates related to aging in different cultivars. The influence of leaf and plant age on photosynthetic rates was investigated in six maize (Zea mays L.) cultivars with maturity ratings ranging from <2300 to >3500 CHU (corn heat units). Photosynthesis and irradiance measurements were fitted to rectangular hyperbolas using a nonlinear fitting technique. These curves were analyzed as a function of cultivars, and leaf and plant age. For comparison among cultivars and age groups, photosynthesis was represented by P2000 (net photosynthetic rate at irradiance (I) = 2000 µmol m−2 s−1). In all cultivars, early leaves had lower P2000 values at a given leaf age than late maturing leaves. The P2000 values tended to increase to a maximum at the time of full individual leaf expansion and then decrease. The duration of maximum P2000 values for leaves nearest the ear were longer than for earlier or later developing leaves. Leaves nearest the ear for early maturing cultivars tended to have lower P2000 values than later maturing cultivars at comparable leaf ages. Plant photosynthesis patterns were the same for all cultivars in relation to plant age and phenological development. Photosynthesis (P2000) was low for the six‐leaf stage, reached a maximum just before tasselling, and then declined during brown silk, blister, and dent stages. A quadratic equation described the relationship between P2000 and plant age. The trend was for latermaturing cultivars to have significantly (P < 0.05) larger P2000 values than earlier‐maturing cultivars at comparable phenological stages. Significant cultivar differences were found in leaf development rate and length of vegetative period (P < 0.10).
A Conservation Tillage System for Profitable Cotton Production in the Central Texas High Plains
Authors: Harman W. L. , Michels G. J. , Wiese A. F.
Published: July 2010

Irrigation water supplies are dwindling in the southern High Plains and effective methods of conserving precipitation during fallow periods are needed. This study was conducted to compare soil water storage, yield of cotton, and profitability of conventional and notillage in a 2‐yr, double crop, irrigated barley (Hordeum vulgare L.)‐ dryland cotton (Gossypium hirsutum L.) cropping sequence with a 48 wk fallow from barley harvest and cotton planting. The soil was a Sherm (fine, mixed, mesic Torrertic Paleustolls) clay loam with 2.2% organic matter, a soil pH of 6.9, and 28, 31, and 41% sand, silt, and clay, respectively. Kochia [Kochia scoparia (L.) Schrad.], Russian thistle [Salsola kali (L.) var. tenuifolia Tausch], pigweed (Amaranthus blitoides S. Wats.), and witchgrass (Panicum capillare L.) were controlled during fallow with disk and field cultivator in conventional tillage. Herbicides used for no‐tillage were dicamba [3,6‐dichloro‐2‐methoxybenzoic acid], atrazine [6‐chloro‐N‐ethyl‐N′‐(l‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], fluometuron [N,N‐dimethyl‐N′‐[3‐(trifluoro‐methyl)phenyl] urea], and glyphosate [N‐(phosphonomethyl)glycine]. A 45 mm increase in soil water storage with no‐tillage increased dryland cotton yields 110 kg ha−1. Although herbicide costs were $155.00 ha−1 greater with no‐tillage, long‐term annual profit with no‐tillage increased $82.00 ha−1 over conventional tillage because of increased yield and lower machinery depreciation Costs.
Flood Duration Effects on Soybean Growth and Yield
Authors: Scott H. D. , DeAngulo J. , Daniels M. B. , Wood L. S.
Published: July 2010

Flooding is often a problem in areas of the southern USA with high rainfall and impermeable soils. A field study was conducted on two poorly drained, slowly permeable soils, a Sharkey clay (veryfine, montmorillonitic, nonacid, thermic Vertic Haplaquept) and a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf), to determine the influence of prolonged flooding on the growth and seed yield of eight determinate soybean [Glycine max. (L.) Merr.] cultivars. Soybean was continuously flooded 3 cm above the soil surface at either the V4 or R2 growth stage for 2, 4, 7, or 14 d. Soil water pressures were monitored at four depths in the Sharkey profile. Flood duration effects on the soybean plant were manifested in yellowing and abscission of leaves at the lower nodes, stunting, and reduced dry weight and seed yield. Canopy height and dry weight decreased linearly with duration of the flood at both growth stages. The growth rates were 25 to 35% less when soybean was flooded at R2 than at V4. The additional 4 wk of vegetative growth after flooding allowed the soybean flooded at V4 to recover to a greater extent than the cultivars flooded at R2. A linear relation was found between seed yield and monthly average crop growth rates for the 4 wk following flooding. A linear decrease in seed yield with flood duration was also found. On the Sharkey clay, rates of yield reduction were 157 and 124 kg ha−1 d−1 of the flood for the soybean flooded at R2 and V4, respectively. On the Crowley silt loam, yield reduction rates were 101 and 53 kg ha−1 d−1 of the flood duration for the soybean flooded at R2 and V4, respectively. Crop susceptibility factors (CS) were determined by dividing the decline in yield by the unstressed control, where the 2‐d flooded soybean cultivars were considered the controls. Values of CS ranged from 0.0 to 0.6 and were linearly related to flood duration after 2 d. The slopes of the lines were 1.5 times greater for the flood applied at R2 than at V4, and 2.4 times greater with soybean grown on the Sharkey clay than on the Crowley silt loam. The determinate soybean cultivars were more susceptible to prolonged flooding during early reproductive growth than early vegetative growth and when grown on the clayey soil than on the silt loam.
Salinity Effects on Rye Grain Yield, Quality, Vegetative Growth, and Emergence
Authors: Francois L. E. , Donovan T. J. , Lorenz K. , Maas E. V.
Published: July 2010

Although current rye (Secale cereale L.) grain production is concentrated mainly in the northern half of the USA and Canada, some rye grain is grown in the arid southwest. Soils in this area are, or have the potential to become, highly saline from the application of saline irrigation water. Since there is nearly a complete lack of information about the response of rye grown under saline conditions, a 2‐yr field plot study was conducted. Six salinity treatments were imposed on a Holtville silty clay (clayey over loamy, montmorillonitic [calcareous], hyperthermic Typic Torrifluvent) by irrigating with Colorado River water artificially salinized with NaCl and CaCl2 (1:1 by weight). Electrical conductivities of the irrigation waters were 1.1, 4.0, 8.0, 12.1, 16.0, and 20.1 dS m−1 the first year, and 1.1, 3.9, 7.5, 11.6, 15.6, and 19.8 dS m−1 the second year. Grain yield and vegetative growth were measured. Relative grain yield of two cultivars, Maton and Bonel, was unaffected up to a soil salinity of 11.4 dS m−1 (electrical conductivity of the saturation extract;κe). Each unit increase in salinity above 11.4 dS m−1 reduced yield by 10.8%. These results place rye in the salt‐tolerant category. Yield reduction was attributed primarily to reduced spike weight and individual seed weight rather than spike number. Bread quality decreased slightly with increasing levels of salinity. Straw yield was more sensitive to salinity than was grain yield. Plant emergence was determined in greenhouse sand cultures. Both cultivars were slightly less salt tolerant during plant emergence than during subsequent stages of growth.
Birdsfoot Trefoil Management. I. Root Growth and Carbohydrate Storage
Authors: Alison M. W. , Hoveland C. S.
Published: July 2010

Management research is lacking for birdsfoot trefoil (Lotus corniculatus L.) cultivars adapted to the southeastern USA. This study was conducted to determine the effect of harvest interval and stubble height on root growth and carbohydrate storage of five birdsfoot trefoil entries. Two field experiments were conducted on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult) soil near Athens, GA. One experiment consisted of two birdsfoot trefoil entries (‘Fergus’ and GA l), three harvest intervals (21, 28, and 42 d), and two stubble heights (5 and 10 cm). The other experiment had five birdsfoot trefoil entries (‘AU Dewey’, ‘Dawn’, Fergus, GA 1, and ‘Norcen’) harvested on 21‐d intervals at three stubble heights (3, 5, and 10 cm). The AU Dewey and GA 1 entries, selected in Alabama and Georgia, respectively, had greater root weights and diameter than the northern‐developed cultivars. In the spring following 2 yr of harvest, root weights of Fergus and GA 1 were reduced 17 and 26%, respectively, when the harvest interval of the previous 2 yr had been 21 instead of 42 d. Raising the stubble height reduced fluctuations in carbohydrate reserves during regrowth. Total nonstructural carbohydrate (TNC) levels were greater in midseason when the stubble height was 10 instead of 3 cm. A positive correlation was found between spring herbage yields and the mean TNC level of the 2 preceding years. This correlation suggests a cumulative effect by carbohydrate levels on vigor of birdsfoot trefoil stands and management should be designed to maintain relatively high TNC levels.
Growth Suppression of ‘Kenblue’ Kentucky Bluegrass Using Plant Growth Regulators and Degree Day Application Timing
Authors: Branham B. E. , Danneberger T. K.
Published: July 2010

Plant growth regulator (PGR) applications for seedhead and vegetative growth suppression have given inconsistent results from year to year when application timing is based on calendar days. Application timing based on growing degree days (GDD) should provide uniform and consistent results over time. These field studies were conducted to determine the window of application, based on GDD, for seedhead and vegetative growth suppression of Kentucky bluegrass. Mefluidide (N‐|2,4‐dimethyl‐5‐[[(trifluoromethyl)‐sulfonyl] amino] phenyl] acetamide) at 0.28 kg ha−1 and amidochlor (N‐[(acetylamino) methyl]‐2‐chloro‐N‐(2,6‐diethylphenyl) acetamide) at 2.8 kg ha−1 were applied to a uniform stand of Kentucky bluegrass [Poa pratensis (L.) ‘Kenblue’] at 25, 50, 75, 100, 125, and 150 GDD. Trials were conducted at East Lansing, MI in 1985 and 1986, and Columbus, OH in 1986. Soil type at East Lansing was an Owosso‐Marlette sandy loam complex (fine‐loamy, mixed, mesic Typic Glossoboric Hapludalf). Soil at Columbus was a Brookston silty‐clay loam (fine‐loamy, mixed, mesic Typic Agriaquoll). Application of PGR between 25 and 125 GDD provided excellent (>86%) seedhead control. Mefluidide and amidochlor applications at 150 GDD gave 31 and 24% seedhead control, respectively, indicating that seedhead control was lost with this application timing. Clipping weights at East Lansing varied between years with only the 150 GDD application in 1985 and the 75 GDD application in 1986 differing significantly from the other application timings. However, the 75 GDD treatment in 1986 had reduced PGR activity because of rainfall 5 h after application. Application timing of PGR appeared to have no significant effect on the degree of vegetative growth suppression. However, GDD timed PGR applications are a valid technique for seedhead control in Kentucky bluegrass.
Animal and Forage Responses on Rotationally Grazed ‘Floralta’ Limpograss and ‘Pensacola’ Bahiagrass Pastures
Authors: Sollenberger L. E. , Rusland G. A. , Jones C. S. , Albrecht K. A. , Gieger K. L.
Published: July 2010

‘Floralta’ limpograss [Hemarthria altissima Poir. (Stapf) et C.E. Hubb.] has the best combination of in vitro digestibility and persistence under grazing of four limpograss cultivars released in Florida. Limpograss crude protein (CP) concentration has been observed to be low in several studies and animal performance on continuously stocked pastures has not exceeded that observed on the industry standard, ‘Pensacola’ bahiagrass (Paspalum notatum Flugge). This study was conducted from 1984 through 1986 on soils of the Pomona (sandy, siliceous, hyperthermic Ultic Haplaquod) and Smyrna (sandy, siliceous, hyperthermic Aeric haplaquod) series. The objective was to compare animal performance on limpograss and bahiagrass when they were rotationally grazed to 20‐ to 25‐cm and 6‐ to 8‐cm stubble heights, respectively, and fertilized with N after each grazing. Seasonal average daily gain (ADG) did not differ between grasses in any year, and mean ADG over the 3‐yr period was 0.41 kg for steers (Bos sp.) grazing limpograss and 0.38 kg for those on bahiagrass. Hand‐plucked samples of Pensacola had higher CP than those of Floralta, averaging 116 and 83 g kg−1 dry matter (DM), respectively, but in vitro digestible organic matter (IVDOM) concentration of bahiagrass was 581 vs. 613 g kg−1 OM for limpograss.