bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficiency of Nitrogen Fertilizer Use by Shade Tobacco Improved by Timed Applications1
Authors: Rathier T. M. , Frink C. R.
Published: July 2010

Shade‐grown cigar wrapper tobacco (Nicotiana tabacumcv. ACC‐75) is fertilized annually with large amounts of organic N with little regard for residual N from previous crops. The potential for leaching of nitrate and consequent groundwater pollution can be high. In 1980, shade tobacco plants grown in Merrimac sandy loam (Entic Haplorthods) and fertilized with 67,134, and 202 kg ha−1of N, supplied as Ca(N03)2metered through overhead irrigation in small portions throughout the growing season, were compared with plants receiving a conventional organic N treatment of 252 kg ha−1. These plants had different N uptake patterns, but similar total N content at the end of the season. In 1982, Ca(N03)2was metered at 179 and 224 kg ha−1of N in amounts determined by the average N uptake over time in 1980 and compared with a conventionally fertilized organic source (224 kg ha−1of N) and with a treatment receiving no N. While total leaf yields for plots receiving no N were considerably lower than those receiving N, their N uptake closely matched the other treatments for about 45 days after transplanting, suggesting that residual N in the soil is available for plant growth early in the season. One treatment in 1983 was designed to utilize this residual N as a part of a metered program applying a total of only 140 kg ha−1of N. Leaf yields from this treatment were not significantly different from those receiving 224 kg ha−1of conventional N. These timed fertilization treatments reduced the potential for leaching of nitrate while not affecting leaf harvest yields.
Partitioning of Nitrogen‐15‐Labeled Biologically Fixed Nitrogen and Nitrogen‐15‐Labeled Nitrate in Cowpea During Pod Development1
Authors: Douglas L. A. , Weaver R. W.
Published: July 2010

Cowpea [Vigna unguiculata (L.) Walp] is an important grain legume that meets its N requirement for pod development from remobilization of N from vegetative tissue, biological N2fixation, and uptake and assimilation of NO‐3when it is available. To develop a better understanding of N sinks, plants grown in vermiculite medium and solution culture were pulsed with 15N2or 15NO‐3during early pod development. The fate of the incorporated 15N was followed during pod development by destructively sampling plants during a 19‐day period. Biologically fixed N was rapidly distributed throughout the plant; within 9 days 55% of it was contained in the pods, and at 19 days 65% was contained in the pods. Surprisingly, 15% of the labeled N remained in the leaves even though vegetative growth had ceased when the plants were pulsed with labeled N and N was being remobilized to the pods. Nitrate‐derived 15N was also distributed throughout the plant, but only 40% of it was recovered in pods 19 days after exposure. The roots and leaves retained 19 and 26%, respectively, of the 15N from NO−3. The results indicate that, during reproductive development, pods are not the only plant parts that serve as sinks for N, even though net gains in N within the other parts may not be evident.
Relative Efficiency of Two Randomized Block Designs Having Different Plot Sizes and Numbers of Replications and of Plots per Block1
Authors: Lin C. S. , Binns M. R.
Published: July 2010

Equations for estimating relative efficiency of two randomized block designs having different numbers of replications, plot sizes, and numbers of plots per block are presented. The purpose is to use information of past experiments to improve the proposed design either through increasing the number of replications, or plot size, or both. A decision rule is presented, based on the soil heterogeneity index, b when b < 0.2, increase the number of replications; when b > 0.7, increase the plot size; when b is between 0.2 and 0.7, changes in both numbers of replications and plot size will be effective. To simpliy the case, 0.2 < b < 0.7, two tables are presented: one shows the relative variance for various plot sizes, and the other shows the ratio of required number of replications and experimental area to obtain a desired relative efficiency. By judicious use of these two tables, the optimum combination of replicate number and plot size can be obtained. Examples are given to demonstrate how the basic equations can be used to answer specific design questions such as: can the efficiency be improved while using the same experimental area, and how can a design be obtained with the same relative efficiency and with no restriction on area.
Peroxide Coated Seed Emergence in Water‐Saturated Soil1
Authors: Langan T. D. , Pendleton J. W. , Oplinger E. S.
Published: July 2010

Anoxia is a major problem in waterlogged soil, and most crop plants suffer reduced growth and yield from it. Inorganic peroxides react with water and evolve oxygen, so peroxide seed coatings could supply oxygen to seeds and seedlings. Three greenhouse experiments tested the ability of peroxide seed coatings to improve emergence in flooded soil. Maize (Zea mays L.), soybean [Glycine max (L.) Merr.], wheat (Triticum aestivum L.), and barley (Hordeum vulgare L.) were grown in Piano silt loam soil (fine‐silty, mixed, mesic, Typic Argiudoll) in plastic trays. Soil moisture treatments included normal moisture and flooding for three days after planting. Calcium peroxide, zinc peroxide, and a formulation containing calcium peroxide were applied as seed coatings at rates of 12 and 25% wt/wt seed. The most significant effect of the peroxides was on percent emergence, and wheat showed the most favorable results. Calcium and zinc peroxides at 25% improved wheat emergence by an average of 42% in flooded treatments in two experiments. Zinc peroxide at 25% improved wheat emergence by 21% in the third experiment. Zinc peroxide at 25% significantly improved corn emergence with flooding in one experiment. Soybean emergence in flooded soil was improved slightly by zinc peroxide, and was decreased by calcium peroxide. Barley emergence was not affected by peroxide. Peroxides generally had no effect on emergence with normal soil moisture. Time to emergence, plant height, and plant dry matter were not affected by peroxide seed coatings. Peroxide seed coatings had variable effects on plant emergence, and wheat showed the most consistent positive response.
Refinement of Quicktest Methodology for Improved Potassium Fertilizer Recommendations1
Authors: Pichtel J. R. , McLean E. O. , Dick W. A. , Esmaeilzadeh H.
Published: July 2010

Potassium fertilizer recommendations that can be applied to soils that vary widely in K‐fixation tendencies, and that also provide adequate levels of K nutrition without costly excesses, are needed. The purpose of this study was to refine the soil quicktest methodology and to describe how the refined procedure can be used to make fertilizer recommendations that are based on the K‐fixation tendencies of individual soils. The fixation tendency is determined via a 2‐h equilibration of the soil with a 200 mg kg 1 KCl solution, followed by extraction with neutral molar NH4OAc. An initial recommendation is computed, based on the amount of the added K fixed, which is mathematically adjusted to provide a K fertilizer recommendation based on a longer (60‐day) equilibration. Using a population of 100 soils, preliminary observations that the 2‐h adjusted quicktest methodology provides similar K recommendations as those obtained by a 60‐day equilibration, were confirmed. A subsample of 20 soils selected on the basis of (i) K‐fixation tendency, (ii) soil test K level, and (iii) fertilizer K required for near maximum yield, was found to represent the 100‐soil population accurately. A regression equation relating quicktest and 60‐day equilibration data for the 20 soils was used to predict K requirement for additional soils collected in a field study. Potassium recommendations were considerably improved over those computed by the currently‐used procedure which assumes that a constant recovery of 60% of added K applies to all soils. A 16‐h (overnight) equilibration involving the same population of 100 soils also accurately predicted estimates of fertilizer K needs. This alternative procedure provides greater flexibility in use of laboratory space.
Evaluation of Dicyandiamide‐Amended Fertilizers on Kentucky Bluegrass1
Authors: Mosdell D. K. , Daniel W. H. , Freeborg R. P.
Published: July 2010

Dicyandiamide (DCD), a nitrification inhibitor, is a 67% N compound of low volatility that can be incorporated into fertilizer granules. Urea, ammonium sulfate (AS), and a complete fertilizer (COMP), all amended with DCD so that 10% of the N was derived from DCD, were evaluated in field studies at West Lafayette, IN, on ‘Wabash’ Kentucky bluegrass (Poa pratensis L.) grown on Toronto silt loam (fine‐silty, mixed, mesic Udollic Ochraqualfs). Urea, AS, sulfur‐coated urea (SCU), and isobutylidene diurea (IBDU) were included for comparison. Equal treatments were applied two or four times per season to provide 196 kg N ha−1yr−1. Clipping yields in response to DCD‐amended fertilizers were similar to those of urea and AS at both N regimes. Initial response to DCD‐amended fertilizers was rapid and response to residual N shorter than that of IBDU and SCU; however, recovery of applied N in the tissue was similar between DCD fertilizers and IBDU, and SCU. Averaged over 3‐yr, recovery of N ranged from 41.1% for IBDU to 36.4% for AS at 2 ✕ 98 kg N ha−1, and 39.0% for COMP + DCD to 32.6% for AS at 4 ✕ 49 kg N ha−1, respectively. Turf quality of plots receiving IBDU was superior to all N sources. Measurements 24 days after a 15 November application in 1984 indicated DCD inhibited NO‐3 formation at the 2 ✕ 98 kg N ha−1 rate (14.6 kg DCD ha−1). Fall‐applied DCD did not influence soil NO+4 and NO‐3 concentrations at 0 to 0.20 m the next spring. The short period of effectiveness of DCD would seldom warrant its use as a nitrification inhibitor in turf.
A Model to Estimate Harvest Losses Due to Taproot Breakage in Sugarbeet1
Authors: Cole D. F.
Published: July 2010

Sugarbeet (Beta vulgaris L.) yields can be reduced due to root breakage. These losses are difficult to estimate when the taproot is broken below the soil surface during harvest. The objective of this investigation was to develop a model to estimate harvest losses in sugarbeets due to taproot breakage. Sugarbeet roots of 14 and 13 cultivars were harvested manually from six environments in 1982 and 1983, respectively. Significant differences were detected among cultivars and environments for root weight, length, circumference, and diameter. Significant correlations between root weight, length, circumference, and diameter were observed. Several regression models were developed to estimate harvest losses based on the morphological data. The best single variable model was percent loss = −3.8 + 32.3 (diameter of the taproot break/root length) with a coefficient of determination R2 = 0.92. Regression coefficients were not affected by cultivars, however, they were affected by environments. This is the first model developed to estimate harvest losses in any crop using morphological data.
Bahiagrass Response to Lime and Nitrogen under Pines1
Authors: Teare I. D. , Wright D. L. , Stanley R. L. , Kidd B. T.
Published: July 2010

The fertilization of slash pine trees (Pinus eliotti Engelm), a practice initiated in the sixties, stimulates bahiagrass (Paspalum notatum Flügge) production, providing under‐canopy forage for the beef cattle industry of the Southeast on sandy, acid soils. Little research has been conducted to determine the production potential of limed and N fertilized bahiagrass growing under pine. The objectives of this research were to measure bahiagrass forage production under slash pine, comparing lime (2.24 Mg ha−1) vs. no lime, four N rates (28, 56, 112, 224, kg ha−1), and to observe changes in extractable soil P, K, and pH on a Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Paleudult). During the 4yr period, application of 2.24 Mg ha−1 lime empirically decreased bahiagrass forage yield under pines when averaged across N levels. Liming at 2.24 Mg ha−1 yr−1 for 4 yr did change the soil pH from 5.0 to 6.1. Nitrogen rates did not affect bahiagrass forage production the first year, but without lime, we found a quadratic response to N rates each year thereafter. The highest yields of bahiagrass forage with lime were obtained with 56 kg ha−1 N. Economic analysis shows the greatest net return ($441 over 4 yr) for no lime at 112 kg ha−1 N and with lime ($211) at 56 kg ha−1 N.
Alkaloid and Nitrate Concentrations in Pearl Millet as Influenced by Drought Stress and Fertilization with Nitrogen and Sulfur1
Authors: Krejsa Beverly B. , Rouquette F. M. , Holt E. C. , Camp B. J. , Nelson L. R.
Published: July 2010

Pearl millet [Pennisetum americanum (L.) Leeke] forage, which had been previously reported to become unpalatable under drought stress conditions, also contained high levels of nitrate and total alkaloids. This study was conducted to determine the effect of irrigation, drought stress, and drought stress elimination, as well as fertilization with 0 and 56 kg S ha−1, and 112, 224, and 336 kg N ha−1, on alkaloid and nitrate levels in pearl millet. ‘Millex 24’ hybrid millet was grown in the field during a hot, dry summer on a Darco soil (loamy, siliceous, thermic Grossarenic Paleudult) in East Texas. Chemical analyses for nitrate and total alkaloid levels were conducted on leaf blades and stems plus sheaths of vegetative plants. Alkaloid levels increased in pearl millet after extended drought and with increasing N fertilization rate. Total alkaloid concentration was higher in leaf blades (46 mg kg−1) than in stems plus sheaths (16 mg kg−1). Nitrate levels increased with improving plant water status and with increasing N fertilization. At the lowest N fertilization rate, nitrate concentrations were similar in irrigated and nonirrigated millet. At the highest N fertilization rate, nitrate was nearly two times higher in irrigated than in nonirrigated millet due to accumulation in stem portions. Nitrate concentration was higher in stems plus sheaths (14 g kg−1) than in leaf blades (5.1 g kg−1), but nitrate levels were highly correlated (r=0.90**; n=48) among plant parts. Sulfur application had no effect on either alkaloid or nitrate levels. A significant interaction between S and N rate occurred in stem plus sheath nitrate concentration (P<0.01). Whole plant alkaloid and nitrate levels were significantly correlated under N fertilization and irrigation but were not correlated under moderate drought stress or under drought stress elimination.
Nitrogen Fertility and Irrigation Influence on Grain Sorghum Nitrogen Efficiency1
Authors: Zweifel T. R. , Maranville J. W. , Ross W. M. , Clark R. B.
Published: July 2010

Little of the research concerning efficient use of N by crops has examined genotypic variation for the amount of dry matter produced per unit of N absorbed by a plant. A replicated field experiment was conducted for 2 yr to determine the influence of N fertility and irrigation on the N use efficiency of selected grain sorghum [Sorghum bicolor) L.) Moench] hybrids. Thirty‐six F1 hybrids, produced from six female and six male inbreds, were grown under dryland or irrigated conditions with 0 or 112 kg ha−1 N. Samples of the aboveground dry matter were harvested after physiological maturity, separated into leaf, stalk, and grain fractions, and analyzed for reduced N. Hybrid N efficiency was evaluated by ratios of dry weight to plant N content. Significant differences were found among the hybrids and their common parent averages for efficiency ratios, dry weight, and N content. Irrigation had little effect on N utilization efficiency and produced no significant change in the relationship among hybrids for N efficiency. Hybrid N efficiency values were over 30% higher in plots without N fertilizer. Interactions among hybrids and N levels were significant for N efficiency traits and grain weight. Alternate definitions of N efficiency emphasized different characteristics, but the potential for selection of sorghum hybrids with improved efficiency of N use was evident.
Herbicide Selectivity among Grain and Weedy Amaranthus Species1
Authors: Endres C. S. , Longer D. E.
Published: July 2010

The cultivation and evaluation of the grain amaranths Amaranthus hypochondriacus and Amaranthus cruentus as potential field crops has been initiated by several investigators worldwide. Because of their similarity to the grain amaranths, the pigweeds (Amaranthus spp.) represent a potential weed‐control problem. To date, no research on chemical weed control in grain amaranth has been reported. Greenhouse herbicide screening studies were conducted on a Captina silt loam soil (fine‐silty, siliceous, mesic Typic Fragiudults) to evaluate herbicide selectivity for control of smooth pigweed (Amaranthus hybridus L.) and Palmer amaranth (Amaranthus palmeri S. Wats.) without injury to the grain amaranths. Of the herbicides tested, bentazon [3‐(1‐methylethyl)‐1H‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide], naptalam [2‐[(1‐naphthalenyl‐amino)carbonyl]benzoic acid} + dinoseb [2‐(sec butyl)‐4,6‐dinitrophenol], and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] exhibited a degree of selectivity towards A. cruentus or A. hypochondriacus. These findings offer encouragement for further studies on the effects of rates and time of application on herbicide selectivity for grain amaranths.
Improved Data Collection Program for a Notebook‐Size Microcomputer1
Authors: Jackson H. O. , Stone J. A.
Published: July 2010

The use of notebook‐size microcomputers for field and laboratory entry of data in agronomy and soils research is limited by the availability of data collection and formating programs. Data collection programs were written in BASIC for the Epson HX‐20 and PX‐8 notebook‐size microcomputers. The programs accept treatment identifiers and response variables for most experimental designs used in agronomy and soils research, and output column‐ and line‐formatted data suitable for analysis without further editing. Once the program is set up for an experimental design, numerical data may be entered in any number of sessions. Data are permanently saved in the microcomputer's internal memory between sessions, but may also be saved on an internal microcassette, transferred to another computer, or transferred to a printer via the units' RS232C ports. These data collection programs improve the efficiency and accuracy of transferring data from field and laboratory observations to analysis programs that accept formatted ASCII input.
Root Trimming Influence on Elongation, Development, and Potassium Influx of Corn Roots
Authors: Mullins G. L. , Edwards J. H.
Published: July 2010

The partitioning of assimilate between vegetative and reproductive plant parts of soybean [Glycine mar (L.) Merrill] during flowering and fruit set could be related to fruit and seed number, and yield. Experiments were conducted in the field (cv. Cumberland) for 2 yr to investigate the effect of alterations in plant growth on the distribution of dry matter during flowering and fruit set. Alterations in plant growth were created by reducing the insolation (63%) during flowering and fruit set by using commercial shade cloth and by low density plantings (spaced plants, approximate equidistant spacing with 0.9 m between plants). The control and shade treatments were grown in 0.76‐m rows (0.71‐m in 1984), and conventional cultural practices were used. Partitioning ratios (reproductive mass/total biomass) were calculated from four samples collected between R1 and R6. Leaves (uppermost fully expanded leaf and the leaf four nodes below it) were sampled during flowering and fruit set for carbohydrate and N analysis. Shade reduced crop growth rate (Rl‐R5), vegetative mass at R5, seed number per square meter, and yield. The spaced plants were much larger and had nearly 80% of their reproductive mass on the branches at R6 compared with 5% for the control plants. Leaf starch and soluble sugar concentrations tended to be reduced by the shade treatment and increased in the spaced plants. There were no treatment effects on leaf N concentration. The treatments had a minimal effect on the partitioning ratios, indicating that distribution of dry matter between vegetative and reproductive plant parts was relatively constant across large differences in plant size and growth rate. This suggests that the fruit and seed numbers may be more closely related to crop growth rate than to the partitioning of assimilate.
A Simple Pump for Extracting Water from Neutron Access Tubes and Mini‐Rhizotrons
Authors: Shouse Peter J.
Published: July 2010

Water in neutron‐probe access tubes and mini‐rhizotrons impedes the acquisition of accurate data under wet field conditions. When such situations arise, water must be extracted before data can be taken. The objective was to design, construct, and use a pump that would be easy to operate, portable, and inexpensive. The pump was found to be a useful tool for extracting undesired water from access tubes and mini‐rhizotrons. Only one to three strokes of the pump were necessary to remove all but about 0.05 to 0.1 L of water from a 2.5‐m‐long neutron access tube that was completely filled with water. The pump, which is easily constructed with materials available at any hardware store, proved to be an easy‐to‐use and cost‐effective tool for field use.
Development and Testing of a Versatile Fluid Fertilizer Applicator
Authors: Haby V. A. , Davis J. V. , Smith K. L.
Published: July 2010

An applicator was needed for evaluation of fluid fertilizers including spray broadcasting and dribble banding clear liquids and suspensions at selected band spacings, rates, and methods of application. The number of treatment combinations and rates required a system that could be quickly purged, washed, and reset for the next treatment. A three‐point hitch, tractor‐mounted applicator was designed and constructed by the authors to dispense fluid fertilizers from pressurized containers. A regulated air supply was provided by a tractor‐powered compressor. Specific fertilizer rates were regulated by tractor speed, air pressure, changing 3‐m‐long booms that differed in orifice plate spacings and sizes, and by changing nozzle sizes on a spray boom. A second application system on the unit consisted of individual quick‐coupling nozzles that injected pressurized fluids into a flow divider. Gravity moved the fluids from the flow divider to back‐swept knives mounted behind the coulters. Additional features of the applicator included systems to sparge suspension fertilizers, solubilize and mix fluids, spray wash, and apply foliar fertilizers and pesticides.
Photographic Technique for Grass Seedling Root Systems
Authors: Newman P. R. , Moser L. E.
Published: July 2010

In descriptive studies of seedling root morphology a seedling root system must be clearly visible to develop clear photographs. A technique for photographing grass seedling root systems has been developed for morphological‐developmental studies. Seedlings were carefully washed from the growing media and placed in a thin tank with two glass sides filled with water and with a grid pattern on one side. The lower stem and root system were immersed in the water where the natural buoyancy of the root system in water allowed the root to spread out, which improved visibility. Photographs were taken of the illuminated seedling root system and grid pattern with a camera positioned on the shaded side of the tank. Detailed diagrams of the tank and placement of the camera, lights, and shades are presented. This technique produced high‐quality photographs of grass seedling root systems that show seedling root morphology clearly.
Subcrown Internode Length of Spring Wheat and Barley as Influenced by Light and Soil Temperature
Authors: Martin J. M. , Smith C. W. , Ferguson A. Hayden
Published: July 2010

Biological theory and some field observations during a dry spring suggest that small grains have an adaptive advantage in an environment with dry surface soil if the crown sets near the seed, because crown roots would have a better chance of forming in moist soil. Our objective was to measure how subcrown internode length in spring wheat (Triticum aestivum L.) and spring barley (Hordeum vulgure L.) responds to soil temperature and light regimes. Eight cultivars of both wheat and barley were evaluated at each of two light intensities and four soil temperature regimes. Both wheat and barley had shorter subcrown internodes when subjected to light as opposed to shade. Decreasing soil temperatures produced shorter subcrown internodes in both species. When averaged over the light and soil temperature regimes, there was a wide range of subcrown internode lengths among the cultivars, with values ranging from 28.1 to 8.3 mm for wheat and from 34.7 to 0.2 mm for barley. Wheat cultivars responded similarly to light and soil temperature treatments, but a differential response to light and temperature was observed with barley. One barley entry initiated its crown at or near the seed across all light and soil temperature regimes. These data suggest that under semiarid conditions, plant breeders should consider subcrown internode length as a selection criterion for spring cereals.
Frost Heave of Alfalfa as Affected by Harvest Schedule
Authors: Van Keuren R. W.
Published: July 2010

Frost heave of alfalfa (Medicago sativa L.) occurs periodically in northern areas of the United States, and frequently results in serious stand losses. Studies were conducted at Wooster, OH, to determine the effect of date of initial harvest, harvest frequency, and date of final harvest on yield and persistence of alfalfa on a Wooster silt loam (fine‐loamy, mixed, mesic Typic Fragiudalf), a frost heave susceptible soil. Late‐autumn harvests (late October) were a major factor associated with frost heave in this research. An average of 38 and 28% frost heave occurred in 1986 and 1987, respectively, compared to 5 and 7% with no late‐autumn harvests for the same years. The extent of frost heave was not related to average root weight, percent of roots branched, or percent total nonstructural carbohydrates. The two winters had high soil moisture, soil temperatures slightly below freezing, and no snow cover for relatively long periods, factors previously recognized as related to frost heave. Soil cover provided by leaving the autumn regrowth appeared to be the major effect in reducing the amount of frost heave that occurred by modifying the soil temperature. The practice of late‐autumn harvesting has become widespread in recent years. Producers with soils subject to heaving must consider the value of leaving the regrowth as protection against frost heave damage and potential loss of the alfalfa stand, against the value of the harvested forage.
Nodulation and Early Growth of Soybean Mutants with Increased Nodulation Capacity Under Acid Soil Infertility Factors
Authors: Alva A. K. , Edwards D. G. , Asher C. J. , Carroll B. J. , Gresshoff P. M.
Published: July 2010

Nitrate tolerant symbiotic (nts) mutants have exhibited a greatly increased capacity for nodulation under nonacidic conditions. To evaluate the potential for growing the mutants in acid soils, the nodulation and growth of the mutants were investigated in this study under acid soil infertility factors. The effects of pH, Ca, and Al on nodulation and early growth of ‘Bragg’ soybean [Glycine max (L.) Merr.] and two mutants (nts382 and nts1116) with increased nodulation capacity were evaluated in nutrient solution experiments. In both experiments, the mutants nodulated more quickly than Bragg under conditions conducive to nodulation. The first experiment examined effects of pH (4.0, 4.5, 5.0, and 6.0) and Ca concentration (0.05 and 1.0 mM). At pH 4.0, nodulation was completely inhibited in all lines at 0.05 mM Ca, but only in Bragg at 1.0 mM Ca. Nodule number and nodule weight per plant increased significantly with an increase in solution pH from 4.0 to 5.0, and were much greater in the mutants than in Bragg, particularly at pH 4.5,5.0, and 6.0. Shoot and root weights in Bragg and ntslll6 generally increased with an increase in solution pH. However, there was a strong reduction in shoot and root weight of nts382 at pH 5.0 and 6.0 associated with greatly increased nodule numbers. The second experiment examined the effects of the sum of activities of monomeric Al species (∑aAl mono) up to 70 iiM. The mutants nodulated much more prolifically than Bragg in solutions with ∑a Al mono 32 μM, and only failed to nodulate at 70 μM. Bragg failed to nodulate at 32 μM. Stronger inhibitory effects of lower ∑a Al mono were observed on nodule number and nodule weight than on early shoot growth. Thus, a ∑a Al mono from 0.1 to 0.4 μM reduced nodule number and weight by 10%, whereas 5 to 10 μM was required to reduce shoot weight by 10%.
Response of Ladino White Clover to Sulfur at Cool Temperatures
Authors: Hern J. L. , Peck R. L. , Staley T. E.
Published: July 2010

Effective production of quality legumes during the cool portions of the growing season is of importance to animal production systems. However, it is unclear to what extent fertility requirements change under sub‐optimal environmental conditions. Ladino white clover (Trifolium repens L.) was grown in pots with a Lily silt loam (fine‐loamy, siliceous, mesic Typic Hapludult) soil under three temperature regimes. Environmentally controlled growth chambers were employed to approximate conditions common to the hilly terrain of Appalachia (mean air temperatures of 10.7°C, 14.7°C, and 18.2°C) Yield, tissue mineral composition, soil nutrient levels, and P‐, S‐, and N‐uptake were evaluated to determine the effects of S (0, 25, and 50 kg S ha−1 as MgSO4) on Ladino white clover at minimal and adequate P levels [75 and 450 kg P ha−1 as Ca(H2PO4)2·H20]. Shoot dry matter production for the initial 144‐d growth period and two subsequent 22‐d regrowths was significantly higher for the 450 kg P ha−1 rate at all temperatures; however, yield increase resulting from an increase in S was minimal (<10%) and inconsistent. Sulfur application increased uptake of S and N. Estimated N2‐fixation by acetylene reduction at three growth stages following the first harvest was significantly greater for the high rate of S under all temperature regimes. These studies suggest that Ladino white clover may recover faster during cool temperatures and assimilate more S and N with high applications of S.
Corn Growth and Yield as Affected by Surface and Subsoil Compaction
Authors: Voorhees W. B. , Johnson J. F. , Randall G. W. , Nelson W. W.
Published: July 2010

Wheel traffic of harvesting operations on agricultural fields often carries compactive loads in excess of 8 Mg. Consequently, soil physical properties may be affected to depths of 60 cm, and these effects of compaction may persist for a number of years. In addition, smaller compactive forces that affect only the surface layer of soil are applied annually during spring tillage and planting operations. A replicated field study was conducted on a Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquolls) in southern Minnesota, and two Ves clay loams (fine‐loamy, mixed, mesic Udic Haplustolls) in southwestern Minnesota to assess the effects of surface and subsoil compaction on the growth and yield of corn (Zea mays L.). A total of six compaction treatments was imposed; subsoil compaction of control (no subsoil compaction), 9 Mg per axle, and 18 Mg per axle loads, each with and without annually applied interrow surface compaction of <4.5 Mg per axle. During the first year after high axle loading, 9 and 18 Mg per axle loads significantly decreased final grain yield by 9 and 30%, respectively, on the Webster soil. For the second year, the 18 Mg per axle treatment significantly reduced yield by 12% as compared with the control treatment. Soil water loss data indicated a more shallow rooting depth and/or reduced root activity in the 18 Mg per axle treatment. High axle loads on a dry Ves soil caused little subsoil compaction; grain yield was reduced by only 6% the first year after high axle loading. High axle loads on a relatively wet Ves soil compacted the soil to a depth of 60 cm. However, relatively dry climatic conditions the following year negated any potential adverse effects of subsoil compaction and yields were not affected. Surface layer compaction from annual interrow wheel traffic did not cause a significant yield response consistently at any site.
Nitrate Reductase Activity and Nitrate Concentration in Cotton Plant Leaf Blades and Petioles
Authors: Chu Chang‐chi , Graham Lucy E. , Bariola Louis A.
Published: July 2010

Greenhouse studies were conducted to determine the potential of nitrate reductase activity (NRA) as an indicator of the change of N concentration of cotton (Gossypium hirsutum L.) shoots. The results showed that cotton petiole in vivo NRA was not significantly different from NRA in leaf blades during vegetative growth. Nitrate reductase activity (in vivo) in cotton petioles was significantly higher than in leaf blades during reproductive growth. When plants were in the three‐mature‐leaf stage, petiole NRA contributed 16% of total cotton shoot NRA. The petiole biomass was 14% of total shoot fresh weight and 8% of total shoot dry weight. Petiole NRA of plants in the vegetative growth stage increased from 39 to 68 pmol NO−2 g1− FW (fresh weight) s−1 when supplemented with nitrate‐N. These results indicate that cotton petiole NRA is significant and its assay has potential for incorporation into monitoring systems that determine the change of N concentration in cotton shoots.
Herbicide × Annual Fertility Programs Influence on Creeping Bentgrass Performance
Authors: Johnson B. J.
Published: July 2010

Creeping bentgrass (Agrostis palustris Huds.) is increasing in the use of golf greens in the upper South where heat and drought stress occurs. Research was initiated to determine the effects of annual fertilizer programs on performance of creeping bentgrass treated with spring and fall‐applied herbicides. Treatments were arranged in a split‐split block with subunits in strips. Fertilizer programs were the main block and the blocks were stripped by spring and fall herbicide treatments. Soil type was an artificial rootzone mix. Creeping bentgrass performed best the first 26 wk of each year when fertilized at the high (490‐20‐195 kg NPK ha−1 yr−1) fertility level and best the last 26 wk of each year when fertilized at the medium (294‐12‐124 kg NPK ha−1 yr−1) fertility level. The quality of creeping bentgrass fertilized annually at the low (98‐6‐52 kg NPK ha−1 yr−1) fertility level was unacceptable. The quality of creeping bentgrass was reduced less at the medium fertility level than at the low fertility level when treated with oxadiazon {3‐[2,4‐dichloro‐5‐(1‐methylethoxy)phenyl]‐5‐(1,1‐dimethylethyl)‐1,3,4‐oxadiazol‐2‐(3H)‐one} and bensulide {O,O‐bis(1‐methylethyl)‐S‐[2‐[(phenylsulfonyl)amino]ethyl]phosphorodithioate} + oxadiazon. Ethofumesate [(±)‐2‐ethoxy‐2,3‐dihydro‐3,3‐dimethyl‐5‐benzofuranyl methane‐sulfonate] applied in the fall 1986 maintained the highest quality ratings at the high fertility level until mid‐April when the quality was the same whether fertilized at the medium or high level. In most instances in 1987, the quality of creeping bentgrass treated with ethofumesate at the medium fertility level was equally as good as when treated with the same herbicide but at the high fertility level. When fertilizer by herbicide interaction occurred, creeping bentgrass maintained a higher quality at the medium to high fertility level than at the low fertility level.
Fall‐Seeded Legume Cover Crops for No‐Tillage Corn in the Humid East
Authors: Holderbaum J. F. , Decker A. M. , Messinger J. J. , Mulford F. R. , Vough L. R.
Published: July 2010

No‐tillage systems utilizing winter cover crops can reduce erosion and leaching losses. Fall‐seeded legumes can also supply significant amounts of N to subsequent corn (Zea mays L.) crops. The suitability of 14 fall‐seeded legumes, three small grains and four legume/grass mixtures was evaluated for winter covers from 1982 through 1985 on Matapeake silt loam (fine‐loamy, mixed, mesic, Typic Hapludult) and Mattapex silt loam(fine‐silty, mixed mesic, Aqualfic Normuldult) Coastal Plain soils as well as Delanco silt loam and Chester silt loam (fine‐loamy, mixed, mesic, Aquic Hapludult) Piedmont soils. Hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.) and Austrian winter peas [Pisum sativum (L.) Poir.] were the most promising cover crops. Fall growth and early soil coverage was highest with crimson and lowest with vetch which had higher winter survival and spring growth. Peas and, to a lesser extent, crimson clover stands were damaged in some years by Sclerotinia trifoliorum Eriks. In some years top growth of vetch contained up to 350 kg N/ha. While N concentration varied among species, total N production was determined more by dry matter yield. Legume cover crops had a greater influence on corn grain yields on the heavier textured soils and longer growing season of the Coastal Plain. In 1985, N contribution to the subsequent corn crop was reduced when small grains were seeded with annual legumes. Results from these studies show that winter annual legumes can reduce N costs while providing better soil protection during winter months.
Cupric Ion as a Tracer to Measure Spray Application Efficiency
Authors: Nichols R. L. , Gaines T. P. , Stephenson M. G.
Published: July 2010

The uniformity and efficiency of agricultural chemical spray solutions on plants, such as sucker control chemicals on tobacco (Nicotiana tabacum L.), needs to be determined. This study was conducted to determine if cupric ion could be used as a tracer to measure the spray applicaton efficiency of a tobacco sucker control chemical. Chlorpropham (1‐methylethyl 3‐chlorophenylcarbamate) was amended with 1.92 mmol of cupric sulfate (CuSO4˙5H2O) to determine the relationship between leaf Cu concentration and tobacco sucker control, as measured by per unit reduction of sucker Weights. Leaf Cu was correlated positively with sucker control (r = 0.70) and negatively with sucker weights (r = −0.69). These results indicate that cupric ion can be used as a tracer to measure the spray application efficiency of agricultural chemicals on plants.
Soybean Phosphorus and Potassium Requirement Evaluation by Three M‐DRIS Data Bases
Authors: Hallmark W. B. , Beverly R. B. , Sumner M. E. , DeMooy C. J. , Morris H. F. , Pesek John , Fontenot J. D.
Published: July 2010

Modified‐diagnosis and recommendation integrated system (MDRIS) soybean (Glycine max L.) norms are now available for select, large, and regional data bases. It is unclear which of these data bases is more accurate in evaluating nutritional needs of soybean. A study was conducted to compare the ability of select, narrow‐based (S); large, broad‐based (L); Midwest (MW); and Southeast (SE) MDRIS data bases to diagnose P and K nutrition in four soybean cultivars grown in a limestone by a P by K soil fertility study in Iowa. Greater accuracy by L, MW, and SE vs. S in evaluating plant P and K status was attributed to spuriously high P and K concentrations in S, which resulted in excessive P and K deficiency diagnoses. Diagnostic accuracy for L and MW did not differ. Greater accuracy of MW vs. SE in detecting P deficiencies was attributed to the larger norm mean for P. The SE performed better than L or MW in determining K nondeficiencies, resulting in superior overall K diagnoses and overall P plus K diagnoses. This was attributed to relatively larger CVs for norms involving K (vs. the average CV for nutrient expressions involving DM) in the SE data base compared to those in the L and MW data bases, which resulted in less incorrect diagnoses by SE where K was nondeficient. Diagnoses by MW were not superior to those for L and SE; therefore, data do not support the suggestion that regional data bases will improve soybean diagnoses for P and K. Data do support the assumption that MDRIS norms from large, broad‐based (L) data sets are more accurate than norms from select, narrow‐based (S) data sets in evaluating plant nutrient requirements.
Prediction of Time to Anthesis of a Selection of Sunflower Genotypes
Authors: Goyne P. J. , Schneiter A. A. , Cleary K. C.
Published: July 2010

Synchronization of anthesis of male and female sunflower (Helianthus annuus L.) inbreds to be crossed is important for successful hybrid seed production. The use of weather‐related models, which predict anthesis dates in scheduling planting times could assist in this synchronization. The field plantings of 16 sunflower genotypes in locations from 32°51' S to 64°50' N lat. during 1982 and 1983 were used to develop an anthesis predictive model. This model which related mean daily screen temperature to daily rate of development accounted for genotypes classified into developmental response groups as very quick, quick, medium and slow. The model had satisfactory predictive ability when validated on independent data. The model requires refinement to account for temperature by photoperiod interactions when additional data are available.
Canopy Response of Soybean Affected by Growth Habit and Late Season Competition
Authors: Weil R. R. , Khalil N. , Thomison P. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] isolines that differ only in regard to determinacy have been developed as tools for better understanding the differential responses of determinate and indeterminate types to environmental factors. This study was conducted to investigate the effect of growth habit on soybean yield components at different canopy levels, and on the response of these yield components to environmental conditions during critical reproductive growth stages. Three pairs of near‐isogenic lines (determinate and indeterminate) were grown at three Maryland (USA) locations and subjected to a thinning treatment at the R4 growth stage to release the plants from competition for light, water, and nutrients after pod set was completed. In each plot, six plants were divided into four canopy levels at maturity and hand harvested. For unthinned soybean there was no consistent difference in yield between growth habits. Under low‐moisture conditions at the Beltsville site, the determinates responded more to release from competition than did the indeterminates, indicating that the latter are more buffered against unfavorable growing conditions. Generally seed yield and seed size near the bottom of the canopy was greater in determinates than in indeterminates, but the opposite was true near the top. Thus, the determinate growth habit shifted yield production toward the bottom canopy level. The effect of thinning was nearly uniform at all canopy levels for both stem termination types, increasing the yield of determinates by 38.2 and indeterminates by 13.8%.
Seasonal Growth Rate Patterns for Orchardgrass and Tall Fescue on the Appalachian Plateau
Authors: Denison R. Ford , Perry H. Douglas
Published: July 2010

Information about the seasonal distribution of forage growth rates and variability among years is needed to design improved grazing systems for the Appalachian Plateau. Growth rate and the influence of weather may depend on regrowth stage. Therefore, the objectives of this study were to develop a method to give separate seasonal growth rate curves for plots in the 1st and 3rd wk of regrowth, and to derive such curves for the Appalachian Plateau. The new method, which required 12 harvest schedules (identical except for starting date), was applied to orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.) growing on a Gilpin silt loam (Typic Hapludult) near Beckley, WV, in 1986 through 1988. Growth rates were highest in spring each year, especially for plots in the 3rd wk of regrowth. Growth rates of plots in the 1st wk of regrowth showed a clear summer slump only in 1987 (during a prolonged drought). For plots in the 3rd wk of regrowth, periods of very low growth rate (apparently due to drought) occurred in both 1987 and 1988, but timing differed by approximately 4 wk between years. Growth rates in fall were generally less than or equal to summer growth rates, except in comparison to drought periods. Grazing strategies based on the expectation of higher growth rates in fall are unlikely to succeed on the Appalachian Plateau.
Leaf Area Development and Dry Matter Production of Cassava
Authors: Manrique Luis A.
Published: July 2010

Most published work on cassava (Manihot esculenta Crantz) plant growth and yield responses to environment has been conducted at high latitudes. Little is known of cassava responses to environment when grown at lower latitudes. A field experiment was conducted in Hawaii (21°N lat) during 1986 summer and 1987 winter to study leaf area development and efficiency of dry matter partitioning of cassava when grown under seasonal regimes of temperature and solar radiation. Plants were grown under optimum moisture and nutritional conditions. A series of biomass harvests were collected throughout the growing season to examine effects of temperature and solar radiation on leaf area index (LAI), top and root dry yield, and dry matter partitioning. Maximum LA1 values of about eight and six were attained by 240 d after planting (DAP) in summer and winter, respectively; maximum root growth rates of 17.1 and 13.5 g m−2 d−1 were attained at 240 and 300 DAP in summer and winter. Dry matter partitioning to roots had little seasonal variation and increased with plant age; dry matter partitioning to branches was more sensitive to environment and substantially increased during the summer months. Overall, leaf and root growth proceeded almost similarly in both summer and winter; differences in root yield between seasons were largely determined by differences in dry matter allocation to branches.
Identifying Individual Plants or Plants Parts during Shoot and Root Evaluations
Authors: Douglas C. L. , Toll T. R. , Klepper B. L. , Wilkins D. E.
Published: July 2010

Identity of individual plants or plant parts is often required when making shoot and root measurements. Normally parts from each plant are coded with colored paper clips or put in individually labelled paper or plastic sacks. Both procedures are time consuming and costly. The objective of this project was to develop a method of individual plant or plant part identification that is simple, accurate, economical, and efficient. Materials used are tape and waterproof marker. Individual plants or plant parts are placed on a strip of tape in the order in which they are analyzed. They can then be passed on to another evaluator for further analyses, retaining individual plant identity. This method doubles the number of plants processed/hour and reduces materials cost from approximately$0.13 to less than $0.01/plant.
Leaf Dark‐Adapter for Measuring Chlorophyll Fluorescence in Situ during Daytime
Authors: Selmani A. , Wassom C. E.
Published: July 2010

Chlorophyll a fluorescence is used as an indicator of stress damage to growing plants. Plants or plant samples first must be transported to a laboratory and dark adapted. If stress (e.g., drought) has not been severe enough to permanently damage the photosynthetic apparatus, plants may recover during dark adaption and stress may not be detectable. In situ readings are more reliable. Dark adaptation takes place after the onset of total darkenss. The objective of this work was to develop a device that would enable the dark adaptation of plant leaves in situ during hours when stress could occur. A thin, light weight sheet of metal was developed to clip onto corn (Zea mays L.) leaves and allow dark adaptation during daylight. A sliding shutter was provided to expose a section of the leaf to light emitted from the fluorometer probe. Using the device, field measurements of daytime chlorophyll a fluorescence were obtained on attached leaves. Measurements were also taken at night on the same plants after dark‐adaptation. In situ day measurements were significantly lower than those taken at night, indicating that stress during daytime influenced the fluorescence response and that plants tended to recover before nighttime readings were taken. Daytime in situ measurements provide an opportunity to detect non‐permanent damage to the photosynthetic apparatus that may show transient drought effects and lowel photosynthetic activity.