bluuebunny/crossref_metadata_2025 huggingface dataset:
Corn Grain Yield and Nutrient Response to Foliar Fertilizer Applied during Grain Fill1
Authors: Harder H. J. , Carlson R. E. , Shaw R. H.
Published: July 2010

Recently there has been renewed interest in foliar fertilization of field crops, but little work with foliar application of nutrients on corn (Zea mays L.) during the grain filling period has been reported. This study was conducted to observe the effect of foliar fertilizer on corn grain yield, yield components, and nutrient content in the grain at harvest, while plants were subjected to moisture stress imposed after silking in one, two, or three successive stress periods.

Experiments were conducted in the movable rain shelter facility at Ames, Ia., in 1976 and 1977. In this facility corn plants were grown in containers containing 100 liters of a Nicollet loam soil (an Aquic Hapludoll, fine‐loamy mixed mesic). Foliar fertilizer was applied three times in the post‐silking period with a pressurized hand sprayer.

In 1976, foliar fertilizer application commenced 4 weeks after silking, and no significant effect of foliar fertilizer on yield, or yield components was measured. In 1977, foliar‐fertilizer application commenced as early as 2 weeks after silking, and a significant, 6.4% yield reduction occurred in foliar‐fertilizer treatments. This decrease occurred in both hybrids used and in all moisture‐stress treatments. There was no evidence for an interaction between post‐silking moisture stress and foliar‐fertilizer application. In 1977, the effect of foliar fertilizer was to reduce mass/kernel in one hybrid, while in the other, neither mean mass/kernal nor kernels/plant were significantly reduced, but total grain yield was reduced. This difference was related to the number of days after silking when foliar fertilizer was first applied. Foliar fertilizer seemingly produced a stress on these plants, and the deleterious effect of this stress was expressed by the yield component being primarily determined at the time the stress occurred. Foliar fertilizer applications resulted in a significant increase in the percent N (10%) and in the percent P (4.7%) in the grain at harvest. There was, also, an increase in N yield (5.1%) in the grain despite a grain yield decrease in one hybrid.
Consumptive Water Use by Sub‐irrigated Turfgrasses under Desert Conditions1
Authors: Kneebone William R. , Pepper Ian L.
Published: July 2010

Irrigation is essential for turfgrass growth in the arid southwest. Water conservation is equally essential. To irrigate properly, levels of consumptive water use and the factors which affect them must be known. This study evaluated effects of management, local climate, species, and cultivars upon water use. Three bermudagrasses (Cynodon dactylon L. Pers.), a zoysiagrass (Zoysia japonica Steud.), St. Augustinegrass [Stenotophrum secundatum (Walt.) Kuntze], and tall fescue (Festuca arundinacea Schreb.) were grown in a local washed mortar sand in percolation lysimeters with measured subirrigation at Tucson, Ariz. There were no significant differences in consumptive water use among the bermudagrasses and zoysiagrass at either of two managements. Raising the water table 10 cm and overseeding with annual ryegrass in winter significantly increased consumptive use. St. Augustinegrass and tall fescue used significantly more water than the bermudagrasses and zoysiagrass. Consumptive water use varied with evaporative demand as measured by Class A pan. Consumptive use values expressed as percentage of evaporative pan losses ranged from 42 to 80% depending upon management and grass. Mean annual percentages were 46 for bermudagrasses and zoysiagrass, 58 for St. Augustinegrass, and 64 for tall fescue grown with the same water table. The same percentage was 58 for bermudagrasses and zoysiagrass overseeded with ryegrass in winter and maintained with a 10 cm higher water table.
Allelopathic Effects of Tall Fescue on Birdsfoot Trefoil as Influenced by N Fertilization and Seasonal Changes1
Authors: Luu K. T. , Matches A. G. , Peters E. J.
Published: July 2010

Difficulties in obtaining successful establishment of birdsfoot trefoil (Lotus corniculatus L.) in sods of tall fescue (Festuca arundinacea Schreb.) cannot be fully explained by competition for water, nutrients, and light. The difficulty may be due to allelopathy that has been shown to exist in tall fescue. Laboratory and greenhouse experiments were conducted at Columbia, Mo., to characterize the influence of N fertilization and seasonal changes on the intensity of allelopathic effects of tall fescue on birdsfoot trefoil. Trefoil seeds were germinated in water extracts of fescue herbage (15 g herbage/100 ml H2O) applied to filter paper in a 23.3 C germination chamber and also in sand or soil (fine, montmorillonitic, mesic Udollic Ochraqualf) media in the greenhouse. Extracts of fresh herbage caused inhibition of germination and seedling growth, but ashing of the fresh herbage prior to extraction eliminated the inhibition. Previous N fertilization of tall fescue increased inhibition of germination and seedling growth. Percent germination and root and hypocotyl lengths of birdsfoot trefoil seedlings treated with the June through September extracts were 10, 13, and 7 times greater, respectively, than were those obtained from herbage sampled from January through May. Soil reduced the inhibitory effects of extracts, but root growth was still suppressed 54.7% in soil + extract as compared with the soil + water control. Growth of trefoil roots were reduced more by allelopathic substances than either germination or hypocotyl growth.
Immobilization, Nitrification, and Losses of Fall‐applied, Labeled Ammonium‐Nitrogen during Growth of Winter Wheat1
Authors: Olson R. V.
Published: July 2010

A field experiment was conducted to follow immobilization, nitrification, movement, and loss of fall‐applied N during growth of winter wheat (Triticum aestivum L.). On 4 Oct. 1979, small plots on a Pachic Argiustoll soil received 80 kg N/ha broadcast as (NH4)2SO4 containing 5.97 atom % 15N. Plants and soil samples (to a depth of 150 cm) were removed from four randonly selected plots at each of four samplings. Leaching to depths below 150 cm was calculated from N contents of soil water and drainage values derived from an evapotranspiration equation.

Of the applied N, 26% was immobilized by 6 Dec. 1979 and 40% by 21 May 1980. Amounts of inorganic N from fertilizer declined steadily as a result of immobilization, plant uptake, and losses. At maturity, 81.9% of the fertilizer N remaining in the 150‐cm profile was immobilized. The surface 10‐cm layer contained more than 70% of the fertilizer N in the soil profile at each sampling time. Amounts of fertilizer N as NO−3 were greatest 6 December and were always less than amounts as NH+4 −N.

Concentrations of fertilizer N in inorganic forms decreased with time in the 0‐ to 10‐cm and 10‐ to 20‐cm layers. Between 20 and 110 cm, concentrations peaked in April, whereas amounts below 110 cm peaked in May. Unusually high precipitation for this location in late March resulted in the leaching of 6.5% of the fertilizer N below 150 cm. Losses of 10 to 18%, apparently from denitrification, occurred soon after the fertilizer was applied. The crop used 41.6% of the applied N. At maturity, more than half of the applied N remained in the soil and crop residue. Because that was largely in organic forms, only slight additional loss would he expected as the N was slowly mineralized.
Surface Area Measurement of Corn Root Systems1
Authors: Smika D. E. , Klute A.
Published: July 2010

The density or amount of roots per unit of soil is important when evaluating the use of soil water and nutrients by plants. The most commonly used measurement of roots is mass, but more recently root length measurements have been reported. We believe root surface area is of critical importance in assessing water and nutrient uptake. We are presenting a method whereby this characteristic can be determined using roots washed from soil cores which are photographed followed by the developed film being scanned with an Image Analyzer to determine the area. This value is multiplied by π assuming the roots are cylindrical to give the total surface area of the roots. The accuracy of the technique was checked by calculating the root length using an average root diameter of 0.05 cm. The calculated lengths were comparable to published values giving credibility to the technique.
Survival of Rhizobium phaseoli in Six Carrier Materials1
Authors: Sparrow S. D. , Ham G. E.
Published: July 2010

Peat is the most commonly used base material for Rhizobium sp. (rhizobia) inoculants; however, suitable sources of peat are not available in many developing countries. Other materials have been evaluated as alternatives to peat as carriers of rhizobia, but few of these studies have included Rhizobium phaseoli. In this study, survival of three strains of R phaseoli was evaluated in peat, ground peanut hulls, ground corn cohs, charcoal, vermiculite, and polyacrylamide gel at 4, 25, and 45 C. Numbers of viable cells of rhizobia were determined in the carrier materials by the plate count procedure at time zero and periodically up to 30 weeks. Survival of each strain was much better in peat, charcoal, and vermiculite than in peanut hulls or corn cohs. Die‐off in polyacrylamide gel was rapid for strain CIAT 75 survival was better for strains 3644 and 650R, but bacterial contamination was a severe problem. For peat, charcoal, and vermiculite, survival was good at 4 and 25 C for strain 3644; for CIAT 75 and 650R survival was good in these carriers at 25C but not at 4 C. Survival was very poor in all carriers at 45 C; no viable cells were detected after 3 days. None of the materials tested was superior to peat as carriers of R phaseoli, but the results indicate that charcoa and vermiculite can be used as inoculant carriers with relative success. Storage of inoculants in these carriers is feasible at room temperature.
Effect of Folicote Antitranspirant Application on Field Grain Yield of Moisture‐Stressed Corn1
Authors: Fuehring H. D. , Finkner M. D.
Published: July 2010

Little has been done on the practical use of antitranspirants to increase the yield of field crops. The objective of this study was to determine the yield response of moisture‐stressed corn to the application of an antitranspirant. Folicote, a hydrocarbon film‐type antitranspirant, was foliarly applied on moisture‐stressed field corn (Zea mays L.) grown on Pullman silty clay loam (fine, mixed, thermic Torrertic Paleustoll) soil. Single seasonal applications (foliar spray with ground rig just prior to tasseling) resulted in average yield increases of 11 and 17 %. Fields where both the upper and lower leaf surfaces were sprayed required 1.93 L/ ha for maximum yield response, 42 % less than required where spraying was from the top only. The response was curvilinear with definite yield depression when rates were too great, indicating the need to determine optimum application rates according to the method of application. It was concluded that antitranspirant application is a feasible method of increasing corn yield under the conditions of this study.
Heat Tolearance Screening of Field‐Grown Cultivars of Kentucky Bluegrass and Perennial Ryegrass1
Authors: Minner D. D. , Dernoeden P. H. , Wehner D. J. , McIntosh M. S.
Published: July 2010

The quality of cool‐season turfgrasses frequently declines during periods of high temperature stress. Simple tests are needed to rapidly identify heat tolerant germplasm for incorporation into breeding programs. Facilitative screening tests have been devised, however, in the few studies that have been performed only immature and greenhouse or growth chamber‐grown plants have been evaluated. To be of practical value, results of screening tests, employing plants grown under artificial conditions, should correlate closely with results of tests involving field grown plants. The objective of this research was to evaluate the heat tolerance of several cultivars of Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.) grown in the field under four different regimes of N fertilization (0, 98,148, or 196 kg ha−1 yr−1) in a Typic Hapludults, fine silty, mixed mesic soil for comparison with published results in which greenhouse and growth chamber‐grown material was used. On six sampling dates, plants representing all cultivar and N combinations were exposed to 42, 44, and 46 °C by immersion in a water bath. Heat tolerance of the cultivars was compared using the mean percent recovery weight for the three temperatures. The Kentucky bluegrass cvs. Sydsport, Vantage, and Pennstar were more heat tolerant than the perennial ryegrass cvs. Pennfine, Citation, and Caravelle. When data were averaged over 2 years, it was shown that Sydsport was significantly more heat tolerant than all other genera and cultivars tested. Pennfine had higher recovery weights than the other two ryegrasses on four of six sampling dates. When data were averaged, however, no significant heat tolerance differences among the ryegrasses were discerned. The results from the screening of field grown material followed the same trends as published results using greenhouse or growth chamber‐grown samples. This investigation therefore provides strong evidence that laboratory screening tests may be used to identify accurately and rapidly heat tolerant cultivars of Kentucky bluegrass and possibly perennial ryegrass. The overall heat tolerance of the cultivars on each sampling date correlated with the amount of precipitation (r=−0.91) and the average high temperature (r=0.93) for the period just prior to and during sampling. The moderate N fertility regimes imposed had little effect on the heat tolerance of the grasses.
Evapotranspiration and Yield Estimation of Spring Wheat from Canopy Temperature1
Authors: Diaz R. A. , Matthias A. D. , Hanks R. J.
Published: July 2010

Canopy temperature indices have been shown to be related to evapotranspiration (ET) and grain yield (Y) for many crops at various locations. The purpose of this study was to evaluate three indices at a location different from where the indices were developed. The indices were the stress‐degree‐day (SDD), temperature‐stress‐day (TSD), and the crop‐water‐stress index (CWSI), and were tested at Logan, Utah on spring wheat (Triticum aestivum L. var. Fieldwin). Planting dates were 14 Apr., 28 Apr., and 19 May 1980. Canopy temperatures in differentially irrigated plots (36 × 3 m) were measured by infrared thermometry at midday from growth stages of heading to maturity. Net radiation, wind speed, humidity, and air temperature data were collected. Neutron meter measurements were used to calculate ET. Summations of SDD (∑SDD) and TSD (∑TSD) and mean values of CWSI were calculated. Linear regression analysis for each planting showed large goodness of fit (r2 ≥ 0.93) for ET vs. ∑TSD, and for ET vs. ∑SDD (r2 ≥ 0.86). Large r2 values were obtained with Y vs. ∑TSD and Y vs. ∑SDD data. For the combined data from all plantings, r2 ranged from 0.90 for the ET vs. ∑SDD data to 0.21 for the Y vs. ∑TSD data. Slopes and intercepts of individual regression lines were significantly (α = 0.05) different. Goodness of fit of relative ET deficit with mean CWSI for the combined plantings was r2 = 0.86, and for relative Y decrease with mean CWSI, r2 = 0.78. Results indicate that SDD may be most suitable for wheat yield assessment and water management in northern Utah.
Moisture Stress and N Redistribution in Soybean1
Authors: Egli D. B. , Meckel L. , Phillips R. E. , Radcliffe D. , Leggett J. E.
Published: July 2010

The redistribution of N from vegetative plant parts to the developing seed of soybean [Glycine max (L.) Merr.] may influence the duration of seed filling and yield. The objective of this study was to investigate the effect of moisture stress during various developmental stages on N redistribution. Soybean (cv. Williams) was grown in the field at Lexington, Ky., for 3 years (1979 to 1981) on a Maury silt loam (fine, mixed, mesic Typic Paleudalf) soil. Irrigated controls were compared with moisture stress treatments from planting to beginning seed fill (growth stage R5), during seed filling (growth stage R5 to R7) or throughout the growing season. Stress was applied by not irrigating until the soil water potential reached – 300 9 kg−1 or by covering the soil with black plastic after emergence to allow severe stress to develop. Plant weight at growth stage R5 and yield were affected by the moisture stress treatments; however, moisture stress had only a limited effect on N concentration in the plant tissue. The proportion of seed N that came from redistribution varied among treatments and years from 33 to 102% and there was no consistent relationship between the level or timing of moisture stress and the contribution of redistributed N to seed N. The proportion of the N in the vegetative plant and pod walls that was redistributed was nearly constant across treatments and years. The data suggest that the contribution that redistributed N makes to the seed N at maturity is more closely related to the amount of N available for redistribution than it is to the ability of the plants to obtain N from the soil or via N2 fixation during seed filling.
Nitrogen and Yield as Related to Water Use of Spring Barley1
Authors: Kallsen C. E. , Sammis T. W. , Gregory E. J.
Published: July 2010

The water‐production function is the relationship between marketable crop yield and seasonal evapotranspiration. Variability in the parameters of the function for different growing seasons result in error in estimating the effect of a water management strategy on yield. The present study was conducted to determine if the parameters describing the functional relationship between transpiration and yield for field‐grown spring barley (Hordeum vulgareL.), was stable for different levels of nitrogen fertility and seasonal differences in the atmospheric evaporative demand. A sprinkler‐line‐source was used to impose different irrigation treatments and seasonal evapotranspiration resulting from these treatments was calculated by a water budget technique. Soil‐water evaporation was estimated using equations taken from the literature and transpiration was calculated by subtracting the estimated evaporation from evapotranspiration. The experiment was done on a sandy loam soil, Typic Calciorthid (coarse, loamy, mixed, calcareous, mesic family), which resulted in frequent light irrigations being applied to maintain the barley at the sprinkler line under non‐moisture stress conditions. The water‐production function was found to vary significantly among N‐fertility levels, and between seasons. However, a constant linear relationship existed between grain yield and transpiration, independent of seasonal differences in evaporative demand, or the level of nitrogenfertility in the field.
Comparison of Experimental Designs Used to Detect Changes in Yields of Crops Exposed to Acidic Precipitation1
Authors: Evans Lance S. , Thompson Keith H.
Published: July 2010

abstract

A comparison of experimental designs used to detect changes in yield of crops exposed to simulated acidic rain was performed. Seed yields were determined from field‐grown soybeans (Glycine max L.) exposed to simulated rainfalls in which all ambient rainfalls were excluded by automatically moveable rainfall exclusion shelters. When all eight, 4 ✕ 4 , latin squares were used, simulated rainfalls of pH 4.1,3.3, and 2.7 exhibited yields 10.6,16.8, and 23.9%, respectively, below yields of plants exposed to pH 5.6. The linear component of pH treatment differences showed a highly significant decrease in yield (p < 0.001). The eight latin squares analyzed as individual experiments yielded erratic conclusions. However, when all eight latin squares were combined a satisfactory evaluation can be made. The low probability value for differences among latin squares (p < 0.005) indicates that field locations are a legitimate source of stratification. Sources of variation are also highly significant for both pooled among rows within squares (p = 0.0028) and the pooled among columns within squares (p = 0.0168) indicating that the two stratifications within each latin square was doubly effective in reducing the residual error term. The relative efficiency of the latin square to a randomized complete block design, and a completely randomized design was 132‐146 and 162%, respectively.
Protein and Mineral Concentrations of Selected Wild Sunflower Species1
Authors: Seiler Gerald J.
Published: July 2010

Although wild sunflowers (Helianthusspp.) can be components of pastures, hay, and silage, limited information is available on the forage‐quality of sunflower species. The objective of this study was to evaluate wild species of sunflower for protein and mineral concentrations. The experiment had a completely randomized design with three replications. The plots were planted in Pullman clay loam (fine, mixed, thermic Torrertic Palenstolls) soil. The leaves and stems of 26 perennial and one annual wild Helianthusspp., and a commercial annual sunflower hybrid planted in pure stands were evaluated at vegetative, flowering, and fruiting stages to ascertain their nutritive value for ruminants. Crude protein (CP) of 140 g kg−1and above occurred in the leaves of 11 of the 26 perennial species at the vegetative stage. At the flowering stage, only two of the 26 perennial species had CP concentrations above 140 g kg−1in the leaves. Willow‐leaf sunflower (Helianthus salicifoliusDieter) had the highest leaf CP (180 g kg−1) at the vegetative stage. Wild annual sunflower (H. annuusL.) and the commercial ‘Hybrid 894’ had leaf CP concentrations above 140 g kg−1at all stages of maturity. Crude protein concentrations generally declined as plants matured. Crude protein concentrations of seeds were higher in most of the perennial sunflower species than in the wild annual or commercial sunflower. Nutritionally, adequate amounts of Ca (2 to 5 g kg−1), Mg (2 g kg−1), and K (8 g kg−1) were present in the leaves and seed of all wild sunflower species and commercial sunflower. The leaves and stems of all species except the Arizona sunflower (H. arizonensisR. Jackson) had sub‐optimum P levels for high‐producing ruminants. Nutritionally adequate amounts of P (3 g kg−1) were present in seeds of all sunflowers examined. At the vegetative stage, nutrient level of some of the wild perennial sunflowers is comparable to that of cultivated sunflower. Ruminants most likely would not graze pure stands of wild sunflower, but would graze it in mixed stands with other forbs and grasses. The wild sunflower species may also be incorporated in hay or silage and still offer a satisfactory nutrition level.
Predicting Sand Content of Modified Soil Mixtures from Sand, Soil, and Peat Properties1
Authors: Taylor D. H. , Blake G. R.
Published: July 2010

Obtaining a specified texture in a sand‐soil‐peat mixture after mixing by a contractor requires some assumptions on the part of the soil/turf scientist. Its estimation depends on calculations based on analysis of the individual components and knowledge of bulk density values for the sand, soil, and peat. Its conformance to the specifications depends on the skill and care of the mixing operator as well as on the accuracy of the analyses. The purpose of this research was (1) to determine the mean values and variation of bulk densities of sand, soil, and peat found at construction sites and, (2) to determine the effects on sand content of the resulting mixture of variations in the following: mixing volume ratio of sand, soil, and peat; sand content of the soil component; sand content of the peat; and bulk densities of the individual components. The mean bulk densities of sands and soils found at soil mixing sites were 1.57 and 1.19 Mg/m3, respectively. The bulk densities of peats with organic contents greater than 75% by weight varied from 0.11 to 0.20 Mg/m3. A simulation model showed that the volume ratio needed to obtain a specified sand content varied considerably depending on the texture of the soil used in the mixture. To achieve 90% sand in the mixture using a hypothetical silt loam required a sand‐soil‐peat volume ratio of 7‐1‐1 while a mixture using a sandy loam soil required a volume ratio of 3‐1‐1. Relative to mixing volumes and soil texture, other variables had minor effects on the sand content of the resulting mixture. A simulation nomograph allows one to specify a sand‐soil‐peat mixing ratio to obtain a given sand content in the resulting mixture.
Drought and Flooding Effects on N2Fixation, Water Relations, and Diffusive Resistance of Soybean1
Authors: Bennett J. M. , Albrecht S. L.
Published: July 2010

Symbiotic N2fixation depends on an interaction between bacteria and a host plant and is affected by both aerial and below‐ground environments. The specific objectives of this study were to determine the effects of drought and flooding on nitrogenase activity of soybeans [Glycine mar(L.) Merr.] growing in sandy soils and to relate the changes in activity to the availability of soil water and to observed stress responses of the shoot. Three greenhouse experiments were conducted in which plants were subjected to drought or flooding for 14 days. During the stress periods, midday measurements of gravimetric soil water content, leaf water potential (ΨL) leaf diffusive resistance, nodule water potential (Ψmod) and nitrogenase activity were collected. Flooding of soybeans for 14 days had little effect on (ΨL), leaf diffusive resistance, or (Ψmod). Although some initial leaf yellowing and structural alterations of the root and crown were apparent in the flooded plants, the nitrogenase activities of nodules after removal from the flooded environment were similar to those of the controls by the termination of the experiment. Data from drought stressed plants indicated a very sensitive response of nitrogenase activity to reductions in (Ψmod) and further suggest that nodules surrounded by dry soil may desiccate to water potentials lower than those observed for leaf tissue. Even after water deficits reduced midday N2fixation to near zero for several days, rewatering restored activities to values equal to or above those of well‐watered plants. Reduced rates of nitrogenase activity were observed as (ΨL) decreased and diffusive resistance increased.
Establishment Characteristics of Kentucky Bluegrass‐Perennial Ryegrass Turf Mixtures as Affected by Seeding Rate and Ratio1
Authors: Brede A. D. , Duich J. M.
Published: July 2010

Mixtures of grass species are desirable in a lawn for genetic diversity and to help ensure against establishment failures. Furthermore, it has been suggested that mixtures may potentially outperform monocultures of their components in terms of foliar density and possibly other factors. The purpose of this study was to determine the effects of various seed ratios (1:0, 3:1, 1:1, 1:3, 0:1) and rates (60 to 480 field‐viable seeds dm−2) of Kentucky bluegrass (Poa pratensis L., cv. Touchdown) and perennial ryegrass (Lolium perenne L., cv. Penfine) on leaf area index (LAI), shoot density, shoot size, species composition, ground cover, and clumping of the two grasses in the field. The treatments were based on field‐ viable‐seed ratios, which required data on the field survival, purity, and seeds g−1 of the seedlots. The soil was a Hagerstown silt loam (a fine, mixed, mesic Hapludalf). A shoot‐sizing technique was developed for the rapid measurement of LAI in turf stands. Using this method, results could be obtained with accuracy similar to direct area measurements but in less time. Mixtures tended to outperform monocultures by 8% in LAI, by 14% in shoot density (2 months after establishment), by 11 and 6% in foliar ground coverage (at 1.4 and 3 months, respectively), and by 44% in spring greening. A bluegrass ‐ ryegrass mixture containing 70 to 95% bluegrass field‐viable seeds provided the best compromise between adequate establishment of the bluegrass and minimal clumping of the ryegrass, which often occurs at low ryegrass seed densities. A seeding rate of 196 field‐viable seeds dm−2 produced a peak LAI value at 2 months after planting. No benefit was derived, in terms of leaf area, shoot density, or shoot size, from exceeding this rate. Low seeding rates of bluegrass and high rates of ryegrass tended to produce plants with the thinnest leaves during establishment. Shoot number, mass, and size of the two species were also affected by seeding rate and ratio.
Foliar Application of N and Fe to Kentucky Bluegrass1
Authors: Yust A. K. , Wehner D. J. , Fermanian T. W.
Published: July 2010

The goal of the professional lawn care industry is to provide the homeowner with a dark green weed‐free lawn. Members of this industry are interested in techniques to enhance the color of a turfgrass stand in lieu of excessive N fertilization. The purpose of this research was to evaluate the use of foliar applications of Fe alone or in combination with N on the color response of Kentucky bluegrass (Poa pratensis L.). Iron sulfate or an iron chelate was applied at the rate of 1.1, 2.2, or 4.5 kg Fe ha−1 in combination with either 0, 25, or 49 kg N ha−1 to a mixed ‘Columbia’/‘Touchdown’ Kentucky bluegrass turf growing on a Catlin silt loam (flne‐silty, mixed, mesie Typic Argiudoll). Color ratings and clipping weights were determined on a weekly basis until treatment effects were no longer significant. In a separate experiment, both sources of Fe were applied at rates of 1.1 to 72.4 kg Fe ha−1 to Kentucky bluegrass to evaluate phytotoxicity. The color enhancement due to Fe applications without N lasted from several weeks to several months depending on the weather following application. Use of Fe during cool wet periods enhanced turf color for only 2 to 3 weeks and therefore, was considered of limited value. Iron applications during cool dry periods enhanced turf color for several months. The treatment of 2.2 kg ha−1 of Fe from iron chelate was judged to be the most effective Fe treatment because the color enhancement was usually equal to that provided by a 4.5 kg rate of either source but it did not result in any discoloration as was found with the 4.5 kg rate. Combining Fe with the 25 kg ha−1 rate of N resulted in color enhancement equal to that caused by applying 49 kg ha−1 of N alone. The results of the study indicate that combining Fe with N can result in acceptable turfgrass color with lower rates of N. No permanent damage was caused to turfs receiving Fe at rates up to 72.2 kg ha−1 although foliar phytotoxicity was observed.
Regional‐Scale Estimates of Surface Moisture Availability from GOES Infrared Satellite Measurements1
Authors: Carlson Toby N. , Rose Fred G. , Perry Eileen M.
Published: July 2010

A method for obtaining remotely a measure of surface moisture, called moisture availability, is derived here using satellite infrared surface temperature measurements in conjunction with a numerical boundary layer model. Results are presented largely in the form of a statistical comparison between rainfall (antecedent precipitation index) and soil moisture patterns. Moisture availability patterns were determined from Geostationary Operational Environmental Satellite (GOES) thermal infrared temperature measurements for 12 days during the dry summers of 1978 and 1980 over eastern Kansas and southeastern Nebraska. Representative analyses of moisture availability are presented, along with a summary of results for all cases. A significant correlation was found between M and the antecedent precipitation (API) for virtually all 12 days analyzed. The relationship between M and API can be expressed as a log‐linear one: API (cm) = 0.32 (2a, where n = a + bM and a ∼ 0.9 and b ∼ 2.2. Agreement between M and API was poorest on the smallest scales, for reasons which are discussed in the text. The relatively narrow range of API values over which M is sensitive to changes in rainfall suggest that the infrared method is most suitable for deriving surface moisture availability over plains or semiarid vegetation and where there are large horizontal precipitation gradients. The accuracy of the method may permit inference of percent soil moisture over the rooting depth of plants to within plus or minus 10 to 20%, at least when averaged over a regional‐scale domain.
Salt Effects on Seedling Growth and Ion Uptake of Three Pecan Rootstock Cultivars1
Authors: Miyamoto S. , Gobran G. R. , Piela K.
Published: July 2010

Salt damage is often reported in irrigated cultivation of pecans (Carya illinoensis K.), yet little is known about the concentration or the salt element present in soils, which causes the damage. This study was conducted to evaluate the effects of salinity, Na and Cl on growth and ion uptake of pecan seedlings used as rootstock. The seedlings of three cultivars (‘Apache’, ‘Burkett’, and ‘Riverside’) were grown for 2 years in outdoor lysimeters containing fine loamy sand (calcareous, mixed, thermic, Typic Torripsaments). They were irrigated with eight different qualities of water; four of which had salinity levels of 0.8, 2.1, 3.4, and 6.2 dS m−1 and the additional four containing greater proportions of Na, Cl, or CaSO4. Seedling growth evaluated in terms of leaf, stem, and root weights was inversely related to Na concentrations in soil solutions as well as Na contents of seedling leaves with r values generally exceeding 0.90. The concentrations of Na in soil solutions corresponding to 25% reduction in seedling growth were approximately 40 mmol L−1 for Apache and Burkett, and 50 mmol L−1 for Riverside. Leaf Cl contents correlated neither with Cl concentrations in the soil solutions nor with seedling growth. Seedlings of Riverside absorbed substantially lesser amounts of Na and produced equal or greater root mass, and may be better suited as rootstock in saline areas.
Preharvest And Postharvest Dormancy In Spring Triticale
Authors: Salmon D. F. , Helm J. H.
Published: July 2010

Susceptibility to sprouting is a major production problem for spring triticale (X TriticosecaleWittmack) grown in areas of Canada with high rainfall during the harvest period. During 1982 and 1983, seven spring triticales and three spring wheats (Triticum aestivumL. em. Thell) were evaluated for preharvest and postharvest dormancy. for the evaluation of preharvest dormancy, primary, secondary, and tertiary spikes were collected 1 week prior to harvest. Seed was germinated for up to 96 h at a temperature of 18 ± 1 °C. Postharvest dormancy was based on seed from random spikes collected at harvest and stored for 3 months on the shelf and in a freezer at approximately 20 and − 20 °C, respectively. Seed from each storage temperature was rated for germination using temperatures of 18 and 30 ± 1 °C for up to 72 h. In both years, primary, secondary, and tertiary spike seed provided similar rankings of lines and cultivars for preharvest sprouting. The sprouting‐resistant red seeded wheat line, RL4137 the red seeded utility wheat cultivar Glenlea, and the triticale line 7431A‐68E4 showed the most consistent levels of preharvest as well as postharvest dormancy over the 2‐yr period. The 30 °C germination temperature identified lines and cultivars with low levels of dormancy not expressed at 18 °C. Regardless of the seed source, collection date, or germination temperature, none of the experimental lines and cultivars approached the dormancy of RL4137.
Potato Top Growth as Influenced by Day‐Night Temperature Differences1
Authors: Benoit G. R. , Grant W. J. , Devine O. J.
Published: July 2010

Past work has considered plant growth as a function of average or constant temperatures and has not evaluated the affect of diurnal temperature variations on growth. This study was conducted to evaluate the growth response of potato plant tops (Solanum tuberosumL.) to exposure to 72‐h controlled‐temperature treatments consisting of 14 different day‐night temperature combinations. Day‐night temperature differences ranged from 0 to 30°C with no night temperature ever exceeding a given day temperature. Ten potato plants were grown in individual pots in a greenhouse for each treatment with the treatment accomplished by inserting the plants into a growth chamber for 72 h at two stages of vegetative growth. Plants were maintained under “nonlimiting” soil moisture conditions. Growth was measured as increase in plant height and leaf area during the treatment period. Developed equations (all significant at P<0.01) express plant growth (plant height and leaf area) as a function of the combined influence of maximum and minimum temperatures at both growth stages. The data suggest that each maximum daytime temperature has an optimum night temperature for growth. In general, the difference in temperature between the maximum temperature and its optimum minimum temperature increases as the maximum temperature increases. Plant growth models should incorporate functions that include day‐night temperature effects on growth.
Yield and Regrowth Characteristics of Alfalfa Grazed with Sheep. I. Spring Grazing1
Authors: Allen V. G. , Wolf D. D. , Fontenot J. P. , Cardina J. , Notter D. R.
Published: July 2010

Grazing alfalfa (Medicago sativa L.) in early spring would provide high quality pasture prior to using the forage for subsequent hay production. ‘Arc’ alfalfa grown on Groseclose silt loam (clayey, mixed, mesic Typic Hapludult) at Blacksburg, VA, was grazed by sheep beginning 6 Apr. 1981 and 1982 for four grazing durations (GD) of 0,2,4, and 6 weeks. Two experiments were conducted which differed in level of available forage (AF); high (to maintain about 0.9 Mg ha−1 and low (to maintain less than 0.4 Mg ha−1). The GD's were replicated four times within each AF as two experiments on adjacent sites. Non‐grazed alfalfa was harvested as hay at late bud stage. Regrowth on all treatments was harvested at 1/10 bloom during the remainder of the season. Increasing GD at either AF had no adverse effects on alfalfa stands in 1981. In 1982, grazing for 6 weeks at either AF reduced plant regrowth compared to non‐grazed alfalfa. Respective yields of two hay harvests in 1983 were 5.5,5.3,4.6, and 5.9 Mg ha−1 for 0‐, 2‐, 4‐, and 6‐week GD treatments at high AF, and 5.8,6.2, 5.5, and 5.1 Mg ha−1 at low AF. Results indicate that alfalfa in similar soil‐climatic regions can be grazed beginning in early spring for 4, and possibly 6, weeks for two consecutive years with minimal influence on stand longevity and productivity, particularly if AF is maintained at about 0.9 Mg ha−1.
Development of a Weather‐yield Function for Winter Wheat1
Authors: Feyerherm Arlin M. , Paulsen Gary M.
Published: July 2010

Crop models require detailed knowledge of weather relationships for estimating and predicting yields. Objectives of this research were to develop a weather‐yield function (WYF) for winter wheat (Triticum aestivum L.) that had stable coefficients and minimal bias over a wide range of climates. The WYF was derived by regressing 966 location‐years of plot yields, adjusted for genetic gain, on candidate sets of weather‐related variables, applied N, location‐related variables, and time. Applied N, location, and time variables were included to reduce bias in coefficients of weather‐related variables. The portion of the regression function that included only weather‐related variables became the WYF. Observations used for regression came from a wide range of climates with high interannual variance. Values of WYF ranged from 546 to 2765 kg ha−1; they reflected deleterious effects of high and low temperatures and of inadequate and excessive moisture during the crop yield. Besides estimating the impact of weather on yields, the WYF can be applied to identifying yieldlimiting factors and managing wheat for increased productivity.
Evaluation of Cultivar and Nitrogen Management Options for Malting Barley1
Authors: Varvel G. E. , Severson R. K.
Published: July 2010

Malting barley (Hordeum vulgare L.) requires constant evaluation of N management practices for individual cultivars because applied N directly affects both yield and malting properties. Knifed‐in versus broadcast applications of 0, 56, 112, and 168 kg N ha−1 were compared on Morex and Glenn cultivars in field experiments during 1981, 1982, and 1983 on a Hegne silty clay loam soil (fine, frigid Typic Calciaquolls). An additional cultivar, Robust, was added during 1983. Early plant, forage, and grain N concentrations, forage and grain yields, and percent plump kernels were measured. Cultivar and N rate main effects explained most differences in yield and malting quality after significant cultivar ✕ year, and N rate ✕ year interactions were found to be caused by differences in initial NO3‐N levels. Method of N application was not significant. Grain N concentrations never exceeded 21.6 g kg−1, a maximum set by the malting industry, during the 3 yr. On the basis of grain yields and percent plump kernels, Glenn was superior to Morex overall, but in 1983, Robust surpassed both Glenn and Morex at all levels of applied N. Each cultivar attained high yield levels and maintained malting quality with careful N management.
Effect of Tillage on Soybean Growth and Seed Production1
Authors: Webber C. L. , Gebhardt M. R. , Kerr H. D.
Published: July 2010

Soybean [Glycine max (L.) Merr.] grown without tillage often produces less grain on silty clay loam soils than soybean produced under conventional tillage. A 3‐yr (1982, 1983, and 1984) study was conducted to gain a better understanding of the factors affecting yield differences between conventional and no‐till soybean production systems on silty clay loam soils. The study was conducted near Columbia, MO, on a Mexico silt loam soil (Udollic and Mollic Ochraqualf). Conventional tillage consisted of spring moldboard plowing and secondary tillage. The no‐till treatment received a foliar application of glyphosate [N‐(phosphonomethyl) glycine] at the time of planting. Soybean grain yields were less for no‐till in 1982 (1890 kg/ha vs. 2260 kg/ha) and greater in 1983 (2310 kg/ha vs. 1510 kg/ha) and 1984 (1870 kg/ha vs. 1670 kg/ha). Seasonal rainfall was above average in 1982 and below average in 1983 and 1984. In 1983 and 1984, soybean in the no‐till plots depleted greater soil moisture at soil depths of 840 and 990 mm and had less plant water stress during podfilling, with afternoon leaf water potential measurements averaging 0.11 MPa greater in 1983 and 0.34 MPa greater in 1984, than soybean grown under conventional tillage. Conventionally tilled soybean had a greater yield potential due to greater vegetative growth, but with less than adequate rainfall the soybean in no‐till had less plant water stress, resulting in greater yields.
Design and Use of a Fully Automated Portable Rain Shelter System
Authors: Kvien C. S. , Branch W. D.
Published: July 2010

Automated rain shelters are usually fixed to one site. A three‐unit, portable, fully automated rain shelter system has been constructed for plant water stress research in Georgia. Each structure has a roof 8.6 by 7.2 m attached to four posts. Welded to the end of each post is an automotive wheel and tire assembly. Two smaller wheels (drive shaft driven by a geared‐down 746‐W 220 VAC motor) contact and drive the larger wheels. Two parallel irrigation pipe bumper rails guide the shelters. Movement onto and off of plots is controlled by one rain sensor and two limit switches. In studies with four sequential drought periods and a control, the total useful plot area is 0.05 ha.
Peanut‐Corn Intercrop Performance as Affected by Within‐Row Corn Spacing at a Constant Row Spacing
Authors: Calavan Kay M. , Weil Ray R.
Published: July 2010

The advantages of intercropping a cereal with a grain legume are often limited by the dominance of the cereal, which severely inhibits the legume. A field experiment was conducted in 1983 and 1984 in southern Maryland to determine the effects of within‐row corn (Zea mays L.) spacing on a peanut (Arachis hypogaea L.)‐corn intercrop. ‘Southern States 35A’ corn was planted in rows 1 m apart, with a double row of ‘Florunner’ peanut planted midway between. Peanut spacing was uniform, but within‐row corn spacing varied from 0.125 to 0.335 m in a systematic design with spacing in adjacent pairs of corn rows differing by 0.03 m. Separate sole‐crop plots of either four corn rows with 0.155‐m spacing or four double rows of peanut were used as controls. Yield components of both crops, shading on the peanut canopy, and nitrogenase activity of the peanut were measured. Averaged across corn spacings, intercropping reduced peanut yields by 44 and 64% in 1983 and 1984, respectively. Corn yields were not significantly affected by intercropping, but decreased linearly from 4.2 to 3.5 Mg ha−1 with decreased population density of corn. Conversely, peanut pod yield per hectare, pods per plant, and nitrogenase activity per plant increased linearly with decreased corn population density. Because of these countervailing trends, the combined yield and the land equivalency ratio (LER) (1.49 in 1983, a dry year, and 1.28 in 1984, a wetter year) of the intercrops were little affected by corn spacing. The 0.125‐m within‐row corn spacing resulted in the highest corn and combined dry seed yields, while the 0.335‐111 within‐row corn spacing resulted in the greatest combined economic value because of greater peanut yields. Peanut in monoculture gave the greatest economic value. This study pointed out that very low corn densities («30 000 plants ha−1) should be considered in peanut‐corn intercrops and that an LER >1.0 does not necessarily imply an economic advantage to intercropping.
Problems with Porometry: Measuring Net Photosynthesis by Leaf Chamber Techniques
Authors: Idso S. B. , Allen S. G. , Kimball B. A. , Choudhury B. J.
Published: July 2010

Prior experiments with cotton (Gossypium hirsutum L.) and water hyacinth [Eichhornia crassipes (Mart.) Solms] demonstrated that porometer chamber conditions may significantly perturb the measurement of leaf stomatal conductance. Thus, this study was conducted to determine if net photosynthesis rate measurements of water hyacinth and cotton leaves were similarly perturbed by leaf chamber conditions and, if so, to devise a method to correct for the instrument‐induced error. Several net photosynthesis rate and concurrent canopy environmental data sets for these two plant species were analyzed at Phoenix, AZ within the context of the non‐water‐stressed baseline paradigm, which relates foliage‐to‐air temperature difference to air vapor pressure deficit. It was found that leaf chamber measurements of net photosynthesis rate were subject to the same type of measurement error as that associated with porometer measurements of leaf stomatal conductance. For plants transpiring at potential rates, photosynthesis rates can be corrected by using ancillary data obtained by the leaf chamber system. However, the proper adjustment of net photosynthesis rates of water‐stressed plants measured with leaf chambers required free‐air foliage and air temperatures, as well as the free‐air humidity. It was demonstrated that concurrent infrared radiation thermometry, as well as simultaneous measurements of air wet‐ and dry‐bulb temperatures, are required to correctly evaluate, by leaf chamber techniques, the net photosynthesis rates of plants that are experiencing any degree of stomatal closure due to some aspect of their normal environment.