bluuebunny/crossref_metadata_2025 huggingface dataset:
Cow and Calf Performance, per Hectare Productivity, and Persistence of Crownvetch under Grazing1
Authors: Burns J. C. , Cope W. A. , Barrick E. R.
Published: July 2010

Crownvetch (Coronilla varia L.) has been observed to be somewhat less sensitive to midsummer stress in the Piedmont region of the Southeastern USA than other cool season legumes and has produced good ruminant daily gains. These factors suggest that crownvetch offers potential as a grazing forage, yet quantitative data on animal responses and stand persistence are lacking.

The objective of this study were to further evaluate crownvetch as a grazing forage by considering cow and calf performance from pure stands as compared with that from tall fescue (Festuea arundinacea, Schreb. cv. ‘Ky 31’) and to determine the per hectare productivity [(total digestibue nutrients (TDN)], calf gain and animal days) and the persistence of crownvetch when continuously grazed.

Calf daily gains (kg/head/day) from crownvetch averaged 0.96 for the two‐year evaluation phase compared with 0.67 from tall fescue (P ≤ 0.05). Cows grazing crownvetch also averaged 0.96 kg/head/day compared to 0.31 from tall fescue (P ≤ 0.05) with consistently higher average daily cow and calf gains from crownvetch throughout the grazing season.

Crownvetch yielded 3,375 and 325 kg/ha of TDN and calf gain respectively, when stocked at 2.63 (season average) cow‐calf units/ha.

By the end of the fourth year (spring 1972) crownvetch stand counts in the grazed paddocks were reduced 86%, as estimated from fixed points, or 89%, as estimated from random points. Crownvetch stands in plots fenced off and harvested mechanically (not grazed) after 2 years of grazing were reduced only 59% which is considerably less than that from continuous grazing.

The animal‐gain data indicated that crownvetch is a very satisfactory forage for grazing. However, agronomically, crownvetch failed at this location when continuously grazed. Stands were extremely difficult to establish and were severely weakened at the end of the second grazing season. Before crownvetch can be agronnomically reliable for grazing in much of the Piedmont region, considerable effort must be given to increasing seedling vigor thereby aiding stand establishment and to develop more persistent plants to prolong stand survival.
Prediction of Late Season Nitrate‐Nitrogen Content of Sugarbeet Petioles1
Authors: Giles J. F. , Ludwick A. E. , Reuss J. O.
Published: July 2010

Nitrate nitrogen levels in sugarbeet (Beta vulgaris L.) petioles have been used as an aid to diagnose nutritional status of the plants. The purpose of this study was to evaluate a theoretical approach to the prediction of the rate of change in NO3‐N concentration of sugarbeet petioles. Petiole samples were collected from sugarbeet N fertilizer trials conducted over a 2‐year period on cooperator farm sites in central and eastern Colorado. Results showed the NO3‐N concentration of sugarbeet petioles through the growing season decreased exponentially. The rate of change was a function of soil NO3‐N content (0‐120 cm depth) measured in the spring and the amount of N applied as preplant fertilizer. Calculation of the rate of change with this function and the measurement of one early petiole sample enables the prediction of the NO3‐N concentration during the remainder of the growing season.
A Power Parabola for an Asymmetrical Response1
Authors: Adams Carol J. , Hills F. J.
Published: July 2010

As plant density increases, crop yield often increases, reaches a plateau, then decreases at a different rate. It is difficult to find a simple equation that will adequately describe this situation. A FORTRAN IV program is presented which can be used to fit a parabola to such an asymmetrical response by the transformation of abscissa and ordinate values to calculated powers, i.e. Yw = a + bXz + c(Xz)2. The procedure is illustrated with the response of sugar beet (Beta vulgaris L.) root yield to plant density in field plots and resulted in a power parabola of excellent fit (R2 = 0.955).
Effect of Increasing Foliage Reflectance on the CO2 Uptake and Transpiration Resistance of a Grain Sorghum Crop1
Authors: Moreshet S. , Stanhill G. , Fuchs M.
Published: July 2010

The investigation reported here was designed to provide a physiological explanation for the grain yield increases which resulted from whitening of dryland sorghum crop canopy (Sorghum bicolor L. Moench ‘Hazera 726’) by a kaolin suspension spray. Two years of field measurements of labelled CO2 uptake rates, on kaolin‐coated and uncoated sorghum leaves, showed that the kaolin coating caused a 23% decrease of net photosynthesis similar to the 26% reduction of solar radiation absorption measured with a spectrophotometer immediately after the spray. The reduction in net photosynthesis persisted for several weeks and was actually larger 6 weeks after the last kaolin application.

Measurements of the dynamics of light dependent CO2 uptake made on leaves of different ages with a series of neutral filters and independent measurements of green leaf area confirmed enhanced senescence of the kaolin‐coated leaves.

By contrast, field measurements with a diffusion porometer demonstrated only minor reductions in the leaf surface diffusion resistance of kaolin‐coated leaves.

It is concluded that, for the sorghum crop examined, the primary effect of kaolin sprays was to reduce the rate of photosynthesis, both by decreased light absorption and by enhanced senescence. Finally, a possible explanation is offered to reconcile the reduction in photosynthesis with the observed increase in the grain yield of the treated crop.
Nitrogen, Chloride, and Water Balance with Irrigated Russet Burbank Potatoes in a Sandy Soil1
Authors: Saffigna P. G. , Keeney D. R. , Tanner C. B.
Published: July 2010

Large applications of sprinkler irrigation and N fertilizer have been implicated in causing nitrate contamination of ground water in central Wisconsin.

Field and lysimeter experiments were established in 1972 and 1973 on the Plainfield loamy sand to determine the effect of reducing the amount of sprinkler‐irrigation and fertilizer N on potato (Solanum tuberosum L., var. ‘Russet Burbank’) tuber yields and on the field water and N balance. Two main treatments were used. The conventional (CON) treatment received irrigation water and N fertilizer according to current recommendations. The improved (IMP) treatment received less irrigation water than the CON treatment in both years. In both years fertilizer N was applied more frequently to the IMP treatment and in 1973 the total amount applied was less in the IMP treatment than in the CON treatment. Chloride (as KCl) accompanied N on a one‐to‐one weight basis to provide an independent ion for tracing. Additional subtreatments included planting potatoes without hilling in a furrow, additional application of N late in the season, and cropping a high N fertility area.

The overall average fresh weight tuber yield was 515 q/ha. Total yields were the same in both CON and IMP treatments for both years. However, grade A tuber yields were greater on the IMP treatment than the CON treatment in 1973 when irrigation was applied every 3 rather than every 5 days, and fertilizer N was applied in 11 rather than three doses. The greater grade A tuber yields occurred despite a decrease in fertilizer N from 260 to 170 kg N/ha and a decrease in irrigation water applied from 45 to 27 cm. Evapotranspiration and N uptake by tubers were not appreciably affected by irrigation and N management.

In 1973 most of the N applied at planting was leached except where S‐coated urea was used to provide a source of slow‐release fertilizer N. Application of fertilizer N and Cl with the irrigation water resulted in substantial variability in inputs over the plot area due to variation in the water distribution. The average coefficient of variation for inputs of fertilizer and water was 19% and the average uniformity coefficient (Cu) was 85%.

A satisfactory mass balance of water, N and Cl for potatoes grown in the dosimeters was obtained. Drainage accounted for considerable amounts of the water, N, and Cl outputs with nearly all of the remainder going to and plant uptake. The carefully managed IMP treatment decreased NO3‐N leaching from 200 to 120 kg N/ha and lowered the overall average NO3‐N concentration of the leach ate from 23 to 16 mg N03‐N/liter. However, the additional costs required to effect a small savings in N fertilizer is probably not justified.
Crownvetch‐Grass Mixtures under Frequent Cutting: Yields and Nitrogen Equivalent Values of Crownvetch Cultivars1
Authors: Hart Richard H. , Thompson A. J. , Hungerford W. E.
Published: July 2010

Crownvetch (Coronilla varia L.)‐grass mixtures are recommended for pastures, but data were needed on forage yields under frequent severe defoliation, and on yields of crownvetch‐grass mixtures vs. grass fertilized with N. ‘Penngift’, ‘Chemung’, and ‘Emerald’ crownvetch were seeded with ‘Ky‐31’ tall fescue (Festuca arundinacea Schreb.), ‘Potomac’ orchardgrass (Dactylis glomerata L.) and Kentucky bluegrass (Poa pratensis L.) in 1965 in a field trial on a fine‐loamy, mixed mesic Fluvaquentic Dystrochrept. Mixtures were clipped every week, 2 weeks, or 4 weeks, leaving a 5‐ or 10‐cm stubble, in 1968 and 1969. In 1970, we removed crownvetch from some plots with herbicide. In 1970 and 1971, we applied N at 112 or 224 kg/ha to the resulting pure grass plots, and cut all grasses and mixtures every 2 weeks. Only fescue and fescue‐crownvetch mixtures were studied in 1972 and 1973. Fifty‐six, 112, 168, and 224 kg N/ha were applied, and all entries were cut every 2 weeks.

In 1968 and 1969, yields of all mixtures increased as the interval between cuttings increased. Yields of all mixtures in 1968 and 1969, and of grass plus N in 1970 and 1971, were higher when cut back to 5‐cm rather than 10‐cm stubble height. Penngift‐grass mixtures outyielded Chemung‐ and Emerald‐grass mixtures at both stubble heights from 1968 to 1971, and at the 5‐cm stubble height in 1972. Over 4 or 6 years, Penngift‐grass mixtures produced about 30% more forage than Chemung‐ or Emerald‐grass mixtures. Bluegrass‐crownvetch often outyielded orchardgrass‐ or fescue‐crownvetch in 1968 and 1969, but total yields over 4 years of bluegrass‐, orchardgrass‐, and fescue‐crownvetch mixtures were almost the same. Fescue plus Penngift produced as much forage as fescue plus 155 and 62 kg N/ha in 1970 and 1973, respectively (mean of 5‐ and 10‐cm stubble). Corresponding N equivalent values were 69 and 39 kg/ha for Chemung and 88 and 25 kg/ha for Emerald.
Effects of Paraquat on Yield and Quality of Coastal Bermudagrass1
Authors: Monson Warren G.
Published: July 2010

Paraquat (1, l'‐dimethyl‐4‐4‐bypyridinium ion) has been utilized as a pasture renovation tool and to provide “cured” standing forage for later utilization. This study was undertaken to determine the amount of standing ‘Coastal’ bermudagrass (Cynodon dactylon L.) forage that can be successfully desiccated with paraquat. Subsequent effects on yield and quality of the grass were assessed.

Accumulated Coastal bermudagrass up to 4 metric tons/ha can be effectively desiccated with paraquat. Quality of Coastal hay desiccated with paraquat decreased by more than 20%, within 1 week after treatment, indicating that this is not a practical means of providing cured forage in situ in the humid southeastern United States. Paraquat plus burning can be used to remove accumulated forage and redistribute some of the dry matter production or provide succulent regrowth in late summer if moisture is adequate. Paraquat plus burning to remove forage reduced yields significantly P < 0.05 when compared to mowed plots.
Sequential DCPA Treatments for Weed Control in Turfgrasses1
Authors: Johnson B. J.
Published: July 2010

In the southeastern USA, herbicides have not generally given consistent preemergence control of large crabgrass [Digitaria sanguinalis (L.) Scop.] and annual bluegrass (Poa annua L.). DCPA (dimethyl tetrachloroterephthalate) was applied as single and repeated treatments over a 3‐year period for large crabgrass control at Griffin and Blairsville, Georgia, and for annual bluegrass control at Griffin. The soil types were Cecil sandy loam (Typic Hapludult) or sandy clay loam at Griffin and Hatboro loam (Typic Fluvaquents) or sandy loam at Blairsville.

None of the DCPA treatments controlled large crabgrass or annual bluegrass consistently at the, rates included in these studies. Treating plots with DCPA at 11.2 kg/ha in both March and June gave the greatest control in 2 of 3 years at each location. A significant multiple correlation between temperature prior to treatment and weed control ratings indicated that poor control of large crabgrass was related to germination of crabgrass prior to treatment. High temperatures that induced germination of crabgrass during 2 weeks prior to time of treatment resulted in less control than in years with lower temperatures. This emphasizes the need for early application of DCPA in Georgia.
Effect on Plant Growth of Constricting Forces Applied to the Upper Part of Roots1
Authors: White Everett M.
Published: July 2010

Contraction forces developed by soils as they dry may compress roots and reduce growth. In order to evaluate this effect on growth, plants were placed with their upper roots between two rigidly fixed adjacent plastic tubes that could be inflated against the roots with 0 to 15 bars air pressure. Root and top growth of corn (Zea mays L.), oats (Avena sativa L.), and western wheatgrass (Agropyron smithii Rydb.) decreased gradually as a constricting force on the upper part of the roots was increased from about 4 to 15 bars. At pressures lower than about 4 bars, growth was larger than growth of the plants in loose sand, which applies little if any constricting force on roots. When wet puddled soil was dried around the upper roots of corn or oat seedlings, growth was decreased in some experiments and increased in others possibly because the pressure was larger or smaller, respectively, than 4 bars. The effect that drying of poor soil structure has on compressing roots and reducing plant growth needs to be investigated.
Effects of Natrustoll (Solonetz) Soil Horizons and Nitrogen on Growth of Tall Wheatgrass1
Authors: McGinnies William J. , Ludwig Jim R.
Published: July 2010

Vast hectarages of potentially valuable pasture land in Colorado and Wyoming are dominated by saltgrass (Distichlis stricta (Torr.) Rydb.), an undesirable pasture component. Saltgrass meadows could possibly be revegetated with a more valuable forage species such as tall wheatgrass (Agropyron elongatum (Host) (Beauv.). A greenhouse study was conducted to evaluate the effects of the A, B, and C horizons of a solonetz soil on herbage yield of tall wheatgrass; the effect of N application was also investigated. Yields of plants grown in soils from the A horizon were highest, those from the B horizon where somewhat lower, and those from the C horizon were very low. Mixtures of A and B horizons usually produced higher yields than the A or B alone. Plants grown in any soil mixture which included the C horizon showed reduced yields. The deleterious effect of the C horizon was attributed to its high Na‐salt content. Nitrogen, applied at rates equivalent to 56 to 448 kg N/ha, significantly increased herbage yield. Compared to no N application, the highest rate resulted in a three‐fold increase in yield. The highest N efficiences in terms of total biomass produced per unit of N applied were obtained from rates of 112 and 224 kg N/ha which produced 39 and 37 kg of additional biomass per kg of N applied, respectively.
Soaking Procedures and Hydroseeder Damage to Common Bermudagrass Seeds1
Authors: Kay Burgess L. , Evans Raymond A. , Young James A.
Published: July 2010

Hydroseeding is increasingly important as a technique for vegetating roadside, industrial, and residential areas. Presoaking of seeds in solutions of growth regulators has proven valuable as a germination accelerator in the laboratory, but has not been previously field tested. The objectives of these studies were: 1) to develop production procedures for presoaking seeds of hulled common bermudagrass [Cynodon dactylon (L.) Pers.] in solutions of growth regulators, 2) to determine whether presoaked seeds were damaged in a commercial hydroseeder, and 3) to demonstrate the effectiveness of presoaking under field conditions. We undertook these studies because hydroseeding is extensively used in the USA, and presoaking seeds has been shown to be valuable to this industry. To determine optimum procedures, seeds were soaked for 24 through 96 hours in an aqueous solution containing 1.0 mmole/liter KNO2, 0.035 mmole/liter GA3 and 0.01 mmole/liter kinetin at seed‐to‐solution ratios by weight of 1:1, 1:2, 1:5, 1:10, 1:20, and 1:30, some with aeration (1:5 and 1:30). To determine damage, seeds were soaked in water for 0, 36, 60, and 96 hours and then agitated in a commercial hydroseeder for I hour, with samples removed at intervals. Germination in petri dishes was not affected by different ratios of seeds to solution varying from 1:1 to 1:30 if soaking was limited to 24 hours. With longer soaking the higher ratios decreased germination. Soaking for 36 hours in water before agitation did not alter seeds to the extent that damage was excessive even after 30 min in the hydroseeder. Damage of both soaked and dry seeds by cracking or rubbing was negligible at the agitation times normally used in hydroseeding. In field testing, seedling numbers were increased when seeds were presoaked with growth regulators. The technique of presoaking seeds in hydroseeders appears to be effective and practicable.
Effect of Photoperiod and Size at Flowering on Vegetative Growth and Seed Yield of Soybean1
Authors: Patterson David T. , Peet Mary M. , Bunce James A.
Published: July 2010

In comparisons of soybean [Glycine max (L.) Merr.] ‘Ransom’ from growth chambers and field plots, seed yield per plant was generally lower in the chambergrown plants. To determine the limiting factors, we studied the effects of photoperiod and plant size at flowering on final seed yield in controlled environment rooms at 26/20 C (day/night) temperatures. To obtain plants of three size classes at time of flowering, a 37‐day period of photoinductive 8‐hour days was used at three ages: (22, 30, and 38 days after planting; three, six, and nine main stem trifoliolate stages respectively). Delaying the beginning of photoinduction for 8 days increased total seed weight 34%. When photoinduction was delayed 16 days there was an 84% increase in seed weight. The increased yield was primarily associated with an increase in the number of axillary nodes produced as photoinduction was delayed. Delayed photoinduction had little effect on the average numbers of pods per node, numbers of seeds per pod, or weight of individual seeds. When the plants were grown under 16‐hour daily periods of full illumination, after photoinduction was completed, final seed yield was significantly greater than under 12‐hour daily periods of full illumination, but vegetative growth was not significantly increased. It was concluded that by controlling flowering times in chamber‐grown plants, seed yields per plant and per unit area could match similar yields in field plants.
Corn Forage Production in No‐Till and Conventional Tillage Double‐Cropping Systems1
Authors: Nelson L. R. , Gallaher R. N. , Holmes M. R. , Bruce R. R.
Published: July 2010

Double‐cropping systems involving feed grains are becoming increasingly important for the long growing season in the Southeast and to meet consumer demands for food. Therefore, corn (Zea mays L.) forage production and quality were evaluated in double‐cropping systems following wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). These systems were evaluated at two locations in Georgia Upper Coastal Plain (soil is member of the clayey, kaolinitic, thermic family of Typic Hapludults) regions. Variables in this study were no‐till (NT) vs. conventional tillage (CT), irrigated vs. non‐irrigated, and early vs. late planting date. Forage yields from corn NT planted in small grain stubble (harvested for silage) in April were about equal to those from CT‐planted corn. Corn forage yields when NT was planted in small grain stubble in mid‐June were reduced compared with that planted in April in the Coastal Plain Region of Georgia, while forage yields in the Piedmont Region were nearly equal for corn planted early and late. The lower yields of late planted corn were related to a lower percentage of ears in the forage than early planted corn. Forage yield increases due to irrigation varied from zero to over 100%, depending on season and location. A high forage yield potential for double cropped NT corn planted early (mid‐April) throughout the Southeastern USA is evidenced. With present varieties and known management, forage yields of late planted (June corn) will usually be lower than those for early corn in the Coastal Plain region.
Barley Yields and Tissue N, P, and K with High‐Low N Supply for Different Growth Periods1
Authors: Suzuki Michio , MacLeod L. B.
Published: July 2010

Grain production with minimum use of N has been a major concern of producers. Since physiological characteristics of a barley plant having high N utilization efficiency (grain yield/supplied N) have not been fully elucidated, grain yields and chemical components of Herta barley (Horedum distichon L.) from hydroponic cultures with high and low N supply for different growth periods were determined. A high rate of N at 75 ppm was applied for 0 (check), 1, 2, 3, 4, 5, 6, 7, and 12 weeks after emergence and low rate of N at 20 ppm for the remaining period to maturity. The highest grain yield and N utilization efficiency occurred by supplying the high rate of N for 5 weeks after emergence. In the primary tiller of the productive and efficient plant at 9 weeks after emergence the leaf‐to‐stem‐N ratio was approximately 7:3, and the P concentrations of the fifth leaf was twice as high as of the second top leaf. This study suggests that an ideal N supply would involve applications of a low rate of N for 1 week after emergence, a high rate of N for the following 4 or 5 weeks until the first node of the stem becomes visible on the primary tiller and then a low rate of N for the remaining period to maturity.
A Technique of Monitoring Acidity of Silage during Preservation and Storage1
Authors: Sprague Milton A. , Taylor B. Brooks
Published: July 2010

Measurement of the rate of drop in pH of silage is important in research since it indicates the kind of fermentation which takes place. Ability to monitor pH changes without opening the silo permits a time‐development study of agronomic factors which affect the efficiency of preservation of different kinds of forages. pH electrodes were placed within plastic silos and electrode lead wires extended through the plastic to a portable pH meter outside. In addition, a KCI agar‐salt bridge was inserted and led to a calomel electrode outside the silo. Its perormance was compared closely with where both electrodes were placed in the silo (r = 0.995). The method is demonstrated with data from 12 silos of orchardgrass fertilized with 28, 140 and 364 kg/ha of N and harvested at early and late stages of maturity. Medium N forage harvested at late maturity attained a pH of 4.2 within 15 hours, whereas that harvested early required 2 days. High N forage of early maturity remained above pH 4.2 for 103 days and butyric acid was detected. Dry matter content of forage below 30% is required for best operation of the electrodes.
The Gompertz Function as a Model for Cotton Hypocotyl Elongation1
Authors: Pegelow E. J. , Taylor B. B. , Horrocks R. D. , Buxton D. R. , Marx D. B. , Wanjura D. F.
Published: July 2010

Successful modeling of cotton (Gossypium hirsutum L.) seedling emergence requires a model capable of simulating hypocotyl growth under a wide range of soil environments. A previous model used an autocatalytic growth equation which was satisfactory for relatively favorable soil environments. We report here the use of the Gompertz equation as a hypocotyl elongation model which should have adaptability to greater environmental extremes than the autocatalytic model. A three parameter form of the Gompertz equation was applied to a comprehensive set of cotton hypocotyl elongation data, obtained over a range of steady‐state soil environments. The form used was y = A exp {—exp [b(c—t]} where y is hypocotyl length at time t, A is maximum (potential) hypocotyl length under prevailing soil conditions, b is the weighted mean relative growth rate, and c is the time at which maximum growth rate is attained. This function describes an asymmetrical sigmoid curve in which all parameters can be assigned physiological meaning. Best‐fit estimates of the Gompertz parameters were derived for hypocotyl elongation in each environment by a non‐linear least squares program. Multiple linear regression analyses of the estimated Gompertz parameters (in ) with soil temperature, physical impedance, and moisture were used to examine the influence of soil environment on the parameters. Each of the three Gompertz parameters were adequately described by a cubic regression model involving these soil factors. The regression models were used to develop a Gompertz model in which each parameter was responsive to fluctuating changes in soil environment. The model should be adaptable to simulating cotton hypocotyl elongation under a wide range of soil conditions, including those resulting in seedling stress.
Guttation Deposits on Turfgrass1
Authors: Duell Robert W. , Markus Denes K.
Published: July 2010

The infrequently observed, and insufficiently documented phenomenon of guttation and accumulations is herein related to environmental specifics to better comprehend responses observed. Three applications of 367 kg/ha of 10‐4.4‐8.3 were made at 12 and 13‐day intervals to low maintenance turfgrasses on a regraded field of sandy loam. The second of the series resulted in the accumulation of guttation deposits. The white solids were concentrated on the abaxial surface of the distal 1 to 1.5 cm of the tips of certain grasses. Deposits were most conspicuous on certain broad‐bladed cultivars of Poa pratensis and were confined to inconspicuous white spheres on the tips of blades of a large series of several species of Festuca and other turfgrasses. The absence of such deposits on the same grasses receiving similar fertilizer treatments 12 days earlier or 13 days later was attributed to their dissolution by rainfall after fertilization. No injury related to the deposits could be discerned; hence, no remedy is needed, but irrigation or the next rain will eliminate the deposits.
Temperature Gradient Effects on in situ Hygrometer Measurements of Water Potential1
Authors: Wiebe Herman H. , Brown Ray W. , Barker Jerry
Published: July 2010

The effects of temperature gradients on water potential measurements with various commercial and laboratory soil hygrometers were tested in a soil column at —18 bars or in a sponge column wetted with a —18 bar sodium chloride solution. Temperature gradients were induced in the medium by warming or cooling either the base or the top of the column for several hours. Hygrometers in which the measuring (wet) junction was located in the middle of the cylindrical sample surface gave small temperature gradient errors, less than 3 bars when the temperature gradient in the surrounding medium was 1 degree cm−1. Locating the measuring thermocouple near the base of the cylindrical sample surface gave errors ranging from 10 to 18 bars per gradient of 1 degree cm−1. Hygrometers with an “end window” sample surface gave errors ranging from 23 to 62 bars. Water potential readings were consistently too low (dry) when the sample surface was cooler than the measuring junction, and too high (near zero) when the sample surface was warmer. Accurate water potentials were obtained with all models when medium temperature was uniform. Double junction, so called “temperature compensated” units, gave the largest temperature gradient errors. The zero offset voltage of single junction models was a systematic function of the temperature gradient in the medium, and could be used as a warning that temperature gradients exist and in calibrating individual sensors.
A Flotation Method for Determining Root Mass in Soil1
Authors: Al‐Khafaf S. , Wierenga P. J. , Williams B. C.
Published: July 2010

Root weight is commonly determined as a criterion of root response to the environment. Determination of root weight by soaking soil and associated roots, and washing over sieves may result in losses of root material. In this study the distribution of cotton roots with depth and time was determined by soaking soil and roots in a solution containing 40 g/liter sodiumhexametaphosphate in a 1:5 soil solution ratio. The density of the resulting soil suspension was increased to 1.5 g/cm3 by adding dry, 78% pure CaCl2 in a ratio of 1 g CaCl2 to 2 g soil suspension. Roots floated to the surface and were skimmed from the surface with a fine wire strainer. By subsequent washing in tap water roots and organic debris ,were separated. Distributions of fine roots (mean diameter 0.25 mm) and total root mass for field grown cotton is shown at various times and depths.
Influence of Subsurface Layered Herbicides on Horsenettle and Various Crops
Authors: Banks P. A. , Santelmann P. W.
Published: July 2010

Horsenettle (Solanum carolinense L.) is a perennial weed species of increasing importance in much of the southern and eastern U. S. Experiments were conducted to determine the usefulness of subsurface layering (SSL) of herbicides for the control of horsenettle in several crops. Herbicides were applied to horsenettle infested fields with spray nozzles mounted beneath a 2.4 m wide sweep type plow operated about 20 cm below the soil surface. Crops were then planted. Picloram (4‐amino‐3,5,6‐trichloropicolinic acid) and dicamba (3,6‐dichloro‐o‐anisic acid) were successful for horsenettle control but severely injured broadleaved crops planted over the SSL. Dinitroaniline herbicides generally suppressed emergence of horsenettle plants up to 82 days. Postemergence treatments of 2,4‐DB [4‐(2,4‐dichlorophenoxy)butyric acid] plus SSL dinitroaniline treatments did not enhance horsenettle control above that achieved with 2,4‐DB alone. Trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) and fluchloralin [N‐(2‐chloroethyl)‐2,6‐dinitro‐N‐propyl‐(decrease in yields of cotton (Gossypium hirsutum L.), soybeans (Glycine max L. Merr.), and peanuts (Arachis hypogaea L.) when used SSL. Butralin [4‐(l,l‐dimethylethyl)‐N‐(1‐methylpropyl)‐2,6‐dinitrobenzemamine] caused the least yield reductions. Trifluralin was more soil persistent as a SSL than dinitramine (N4N4‐diethyl‐α,αα‐trifluoro‐3,5‐dinitrotoluene‐2,4‐diamine). These two herbicides were also more persistent when applied deeper in the soil.
Analysis of Potato Growth Under Differing P Regimes. II. Time by P‐status Interactions for Growth and Leaf Efficiency1
Authors: McCollum R. E.
Published: July 2010

Few full‐season studies of potato (Solanum tuberosum L.) growth under mid‐latitude environments have been conducted. Furthermore, published reports about effects of nutrient status on leaf efficiency in any species are inconclusive. Hence, the effects of factorially combined levels of initial soil P (SP = 35, 66, and 110 kg/ha) and row‐applied fertilizer P (FP = 0, 28, and 56 kg/ha) on dry matter accumulation, leaf‐area generation, leaf efficiency, and partitioning of assimilates by potatoes were studied via growth‐analysis concepts. Tops and tubers of field‐grown ‘Pungo’ potatoes (40,000 plants/ha on Portsmouth fsl—Typic Umbraquult, fine‐loamy, mixed, thermic) were harvested weekly, and all parameters essential to a detailed growth analysis were derived.

Growth curves for P‐adequate plants (Sp ⋝ 66, FP > 0) were typically sigmoidal with three post‐emergent ontogenetic phases: 1) pre‐tuber vegetative (emergence − 28 days); 2) tuber initiation and early bulking concurrent with rapid leaf growth (28 to 50 days); and 3) continued tuber growth during rapid leaf loss followed by death of haulms. Plants on the low‐P extreme (SP = 35, FP = 0) never entered the third phase; they produced in 80 days only 50% of the “normal” leaf canopy (LAI = 1.6 vs. 3.2 at optimal P) and lost none of it. Curves for plants with moderate P supplies lay between these extremes. Row‐applied P enhanced early growth; but it also hastened leaf senescence and, if initial soil P was low, shortened the duration of tuber bulking.

Leaf growth rate was maximal with 0.35% P in foliar tissue. Tuber growth rate was a quadratic function of leaf area during most of the tuber bulking period, but the estimate of 3.4 as optimal LAI was tenuous because no treatment generated a LAI greater than 3.2. Tuber yield was linearly related to leaf‐area duration (LAD); doubling the LAD resulted in a 45% increase in yield.

Phosphorus deficiency reduced mean net assimilation rate (NAR) during early growth, had no statistically measurable effect during mid‐season [NAR (35 to 63 days) = 7.76 gm−2 day−1], but markedly increased NAR during late growth stages. Instantaneous estimates of NAR derived from growth equations suggested that effects of low P on leaf efficiency were even more severe and longer‐lasting than indicated by NAR's. Initiation of tubers as an additional metabolic sink halted a downward trend in NAR, and partitioning of assimilates between tops and tubers during bulking depended on P supply and the manner of supplying it.
Arsenic Pollution from Underdrainage and Runoff from Golf Greens1
Authors: Duble R. L. , Thomas J. C. , Brown K. W.
Published: July 2010

Modern golf greens are subject to intense management which includes frequent pesticide applications. Tricalcium arsenate, Ca3(AsO4)2, is commonly used on a regular basis for control of grubs and Poa annua even though the As losses associated with leachate and runoff have not been established. This study was thus undertaken to develop data on As losses from golf greens.

A field study was conducted using four lysimeters each 3 m by 3 m) containing a Tabor sandy loam soil (Udertic Paleustales) and 16 lysimeters containing different sand‐soil‐peat mixtures, each equipped with a gravel underdrainage system. The lysimeters having a sandy loam soil simulate older greens built of sandy soil placed over a gravel drainage system while those lysimeters having mixtures of sand, soil and peat typify modern greens. Bermudagrass (Cynodon dactylan L.) turf was maintained at a height of approximately 1 cm throughout the investigation. Sprinkler irrigation was used to apply approximately 1 cm of water daily. Tricalcium arsenate was applied on two dates at a rate of 88 kg ha−1. Leachate and runoff water from individual plots was collected in 208 liter barrels. This was measured and sampled on a regular basis and more frequently when required by rainfall.

Arsenic was found in significant concentrations in both drainage and runoff from lysimeters. Particularly high concentrations were found in the drainage from plots previously cored for soil samples. Concentrations of 8 ppm As were found in the drainage water from these plots. Concentrations of As in the runoff were as great as 14 ppm when a heavy rain occurred shortly after application of Ca3(AsO4)2. Drainage from the plots typically contained 1 to 3 ppm and decreased slowly with time. Arsenic concentrations of 0.8 ppm were still found in the drainage 115 days after application. Concentrations of As in the runoff and drainage from all the plots exceeded acceptable limits for irrigation water established by the U. S. Public Health Service.
Influence of N Nutrition on Flower and Pod Abortion and Yield of Soybeans1
Authors: Brevedan R. E. , Egli D. B. , Leggett J. E.
Published: July 2010

The number of seed produced by a soybean (Glycine max (L.) Merrill) community is one of the important determinants of yield. Since soybeans usually abort a high percentage of their flowers and pods, this study was undertaken to investigate the influence of N nutrition on flower and pod abortion. Experiments in which the N supply to the soybean plant was varied during flowering and pod filling were conducted in the greenhouse and field. The greenhouse experiment was conducted in a hydroponics system with 5 meq NO3‐/liter in the nutrient solution. Some plants were shifted to 12.5 or 18.0 meq NO3‐/liter at initial bloom and maintained at these levels until maturity, while others were exposed to the high NO3‐/levels only until the end of bloom. Treatments in the field consisted of (1) 168 kg N/ha as NH4NO3 applied at initial bloom, (2) 168 kg N/ha at the end of bloom, and (3) 168 kg N/ha at both growth stages (total of 336 kg N/ha). The field experiments were conducted on a maury silt loam soil (Typic Paleudalts). Increasing the N supply to the plant during the period from initial bloom to the end of bloom increased yield 33% in the greenhouse and 28 to 32% in the field. Yields were not affected by high levels of N during the filling period. In the greenhouse experiment and one field experiment all of the yield increase resulted from an increase in seed per plant, which was due to an increase in the number of nodes and a reduction in flower and pod abortion. Flower abortion ranged from approximately 55% on the controls to approximately 45% on the treatments giving the maximum yield increase. In a second field experiment, the yield increase came partially from an increase in seed size and partially from an increase in seed number. The data demonstrate the importance of an adequate supply of N to the plant during the period of flowering and pod set for maximum yield.
Weed Control in Reduced Tillage Corn Production Systems1
Authors: Moomaw R. S. , Martin A. R.
Published: July 2010

Till‐planting and slot‐planting are two reduced tillage corn (Zea mays L.) production systems used in Nebraska and other states. Farm operators frequently encounter existing weed populations at planting time with these systems when tillage does not precede the planting operation. Our research investigated weed control in tillplanted and slot‐planted corn with preplant translocated and contact herbicides, broadcast or band applications of preemergence herbicides, and a cultivation variable. Field experiments utilized previously undisturbed ridges of old corn rows for till‐planting or slot‐planting corn. Applications of 2,4‐D[(2,4‐dichlorophenoxy)acetic acid] ester and paraquat (l,l'‐dimethy 1‐4,4'‐bipyridinium ion) were used in combination with preemergence herbicide treatments that were either row banded or broadcast. One or two cultivations were imposed on the two tillage systems. Till‐planting resulted in more soil surface tillage and less dependence on herbicides than did slot‐planting. Maximum corn yield was achieved in the till‐plant system by row banding several preemergence herbicide treatments, coupled with one cultivation. Slot‐planting resulted in less soil disturbance with the planter than did till‐planting and required more herbicide usage. With slot‐planting, a preplant application of 2,4‐D was essential to remove the predominantly broadleaf weed population and maximize corn yields. When preplant 2,4‐D was used with slot‐planting, corn yields were not significantly different between band and broadcast applications of the preemergence herbicides used. Two cultivations rather than one tended to increase yields of slot‐planted corn.
Alfalfa Water Use and Production on Dryland and Irrigated Sandy Loam1
Authors: Bauder J. W. , Bauer A. , Ramirez J. M. , Cassel D. K.
Published: July 2010

Field studies were conducted during a 4‐year period to determine “Vernal“ alfalfa (Medicago satva L.) dry matter yield in response to irrigation and fertilization variables. In the Northern Great Plants alfalfa forage production contributes significantly to overall agricultural land use; consequently optimization of resources use is desirable. Limited available information has created a need for such research.

This study was carried out on a Maddock sandy loam soil, a member of the sandy, mixed frigid Udorthentic Haploboralls. Four irrigation levels, ranging from dryland to excessive irrigation, were established as whole plots in a randomized block, split plot design. Eight different fertilizer treatments of P, K, and S were applied to split plots during the 1st year of the study. Under a three harvest per season management system dry matter yield was significantly affected by harvest number and irrigation treatment each year. Within the dryland and deficient irrigation treatment by year, yields decreased with each cutting; with optimum and excessive irrigation, yields varied inconstantly with cutting; yields increased 14 to 330% over dryland by increasing irrigation applications. Total seasonal crop water use, or evapotranspiration (ET), was determined using a water balance approach. Drainage (DRAIN) was calculated, using flux gradients calculated from tensiometer data, and appropriate soil properties. Other inputs, including irrigation (IRR), growing season precipitation (PPT), and soil water depletion (DEPL), were measured. In addition, water use efficiency (WUE) was calculated by treatment by year. Multiple linear regression analyses were used to relate actual dry matter yield (YIELD) and relative yield (RELY) to several independent variables. When plant water stress existed throughout the growing season, RELY correlated with relative evapotranspiration (RELET) in a near perfect, linear manner. Under nonstress conditions IRR, PPT, and DEPL required consideration to attain nearly perfect correlation of RELY with RELET. The results of this study indicate that under plant water stress conditions, alfalfa dry matter yield is a linear function of plant water use.
Relative Yield Totals and Yield Components of Intercropped Sorghum and Soybeans1
Authors: Wahua T. A. T. , Miller D. A.
Published: July 2010

A 2‐year field study was conducted to determine how total grain yield per unit of land area could be maximized by intercropping sorghum (Sorghum bicolor (L.) Moench) and soybeans (Glyycine max (L.) Merrill). These two species are being intercropped more frequently through‐out the world to increase protein yield per unit of area and utilize available moisture. Grain yields, yield components, and relative yields were analyzed. Two sorghum cultivars, grain type ‘DeKalb BR‐44’ (semi‐dwarf) and dual purpose ‘DeKalb FS‐16’ (tall), were intercropped with soybean cultivars ‘Calland’ (Group III) (constant plant density) at 16 sorghum population densities, ranging from 1.38 to 33 plants/m2. The soil was a Flanagan series, a fine, montmorillonitic, mesic Aquic Argiudoll.

Intercropping changed the response patterns of sorghum yield components as plant population changed and reduced yields of FS‐16 and BR‐44 by 14 and 74%, respectively. Sorghum yield components were reduced more in mixtures of BR‐44 than in mixtures of FS‐16; with number of heads per plant being the most affected. Intercropping also reduced the compensatory alterations in sorghum yield components as population changed. In mixtures, tillering ability and population density were the main determinants of grain yield.

Highest yields in monoculture were obtained at densities higher than 25 plants/m2 for FS‐16. and between 12 and 15 plants/m2 for BR‐44. Grain yields of both sorghum cultivars increased linearly with increases in plant population in the mixture. lntercropping soybeans with FS‐16 and BR‐44 reduced soybean yields by 75 and 17%, respectively; primarily due to reduced pod number.

Relative yield curves indicated that the highest relative yield totals might be obtained by planting soybeans 5 cm apart between rows of sorghum planted at a density of 5 plants/m2 at a spacing of 74 ✕ 74 cm.
Description of an Inexpensive Forage Sample Dryer1
Authors: Swain R. H. , Jones E. R. , Walpole E. W.
Published: July 2010

Forage sample dryers are often needed but may not be available in many outlying stations. The purpose of this paper is to describe a dryer design suitable for modest sized research programs or for use in remote locations. The dryer cabinet is 1.22 m2 × 2.44 m high with controls, blower, and air ducts mounted on the exterior of the cabinet. Design features include limited power surge, adaptability to various drying regimes, and use of readily available materials and limited construction skills. Approximately 175, 0.45 kg forage samples can be dried to constant weight in 72 hours.
Measuring Symbiotic Nitrogen Fixation in Rangeland Plots of Trifolium subterraneum L. and Bromus mollis L.1
Authors: Phillips Donald A. , Bennett James P.
Published: July 2010

Accurate assessment of seasonal nitrogen fixation in improved rangeland is an important objective for researchers investigating N budgets and management impact. The 15N A‐value technique and the acetylene reduction method were compared for their accuracy in determining seasonal symbiotic N2 fixation on a ground area basis in rangeland plots of Trifolium subterraneum L. and Bromus mollis L. To simulate range management practices, seeds were planted at 10, 141, or 1970 seeds/m2 in pure stands or 50:50 mixtures in Laughlin loam, a member of the fine‐loamy, mixed, mesic family of Ultic Haploxerolls. Amounts of N2 fixed, calculated by the 15N A‐value technique, varied significantly with planting density and proportion of clover at different densities. Seasonal, symbiotic N2 fixation, calculated from the acetylene reduction method, did not vary significantly with either planting density or proportion of clover. It is concluded that with appropriate studies on possible differences in isotope accumulation by a grass and a legume, including morphological, physiological, and biochemical differences, the 15N A‐value technique should be more quantitative and discriminatory than the acetylene reduction technique. The single seasonal sampling requirement of the 15N A‐value technique also is more amenable to the overall goal of determining the effect of range management systems on symbiotic N2 fixation.
Effect of Soil Matric Potential and Seeding Depth on Emergence of Barley1
Authors: Sepaskhah A. R. , Ardekani E. Raessi
Published: July 2010

Adequate crop stands resulting from vigorous seedling emergence is important for optimum crop production. Seedling emergence is usually influenced by soil water potential and seedling depth as well as other environmental factors. The effects of soil matric potential and seeding depth on emergence percent and rate of emergence of barley (Hordeum vulgare L.) were investigated. Seedling emergence of ‘Zarjo’ cultivar of barley was measured in a Calcixerollic Xerochrept soil at −0.6 to −30.0 bars soil matric potentials and at 2 to 12 cm seedling depths in the greenhouse. Cultivar response to seeding depth was determined by seedling emergence measurements of ‘Torsh’, Zarjo, and ‘Shaneii’ cultivars at seeding depths of 2 to 12 cm under the same experimental conditions. Soil matric potential of ‘30.0 bars reduced the seedling emergence of Zarjo and resulted in the lowest emergence rate. However, soil matric potentials of −0.6 and −1.5 bars also reduced Zarjo emergence at the 12‐cm seeding depth. Seedling emergence and emergence rate of Zarjo were lower at the 12 cm seeding depth at all levels of soil matric potentials. The emergence rate was also reduced at the 8‐cm seeding depth, but only at −30.0 bars. Seedling emergence of Shaneii was found to be lower than that of the Torsh and Zarjo cultivars. The rates of emergence of the cultivars were not greatly different at the various seeding depths.