bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Nitrogen, Narrow Rows, and Plant Population on Cotton Yield and Growth1
Authors: Koli Stephen E. , Morrill L. G.
Published: July 2010

Narrow row planting of cotton (Gossypium hirsutum L.) has the potential for improving yield and production efficiency. Fertilizer needs and other production technology for narrow row cotton have received little attention, especially the nitrogen (N) requirement. The objective of this study was to ascertain if N fertilizer, narrow row, and high population, has any effect on growth and yield of dryland cotton. The relationship between petiole NO−3‐N at various stages of development and yields was also investigated. Row spacing (25, 51, and 76‐cm), plant populations (123,550 and 173,000 plants/ha), and N rate (0, 45, and 90 kg/ha) variables were placed in a factorial arrangement of a randomized, complete block design with four replications. Low N treatments (45 kg/ha) produced no significant change in yield, but higher N rates reduced yield significantly. The 25 and 51‐cm row spacings produced significantly higher yield than 76‐cm rows. The range of plant populations used did not materially affect yield, but there was a significant N‐population interaction. Narrow rows reduced plant height. NO−3‐N levels in petioles increased with increased N rate, being highest at the square stage of plant growth and decreasing sharply at the flower and boll stages. There was no significant correlation between petiole NO−3‐N and yield. Narrow row cotton can result in higher yield and is especially of interest where the length of growing season is not optimum.
Seasonal Anhydrous Ammonia Comparison for Corn With and Without a Nitrification Inhibitor1
Authors: Boswell Fred C.
Published: July 2010

With increased interest in “off‐season” N application and emphasis on better management of N with respect to environmental pollution and economic considerations, information is needed relative to seasonal anhydrous ammonia comparisons for corn with and without an inhibitor.

Field studies compared rates of N applied preplant with December application either with or without the nitrification inhibitor, N‐SERVE (2‐chloro‐6‐(trichloromethyl) pyridine), to corn (Zea mays L.) on a Coastal Plain soil. The nitrification inhibitor (NI) did not affect yield, number of ears, average ear weight, and percent N, P, K, Ca, and Mg in the tissue or concentrations of various other elements in tissue sampled early in the growing season, at early silking, or in corn grain. Both low (90 kg/ha) and high (180 kg/ha) N levels increased yields above check plots (zero N) when applied in December for the three‐year average but both levels were significantly less than the high N level applied preplant. Ears per plant and ear weight were closely related to yields. Yield was more closely related to percent N in the tissue sampled at silking than tissue sampled early (ca 20‐cm height) or percent N in the grain.

On a 3‐year average, the low and high N rates applied in December were 84 and 82% as efficient as preplant applications.

These studies indicate that “off‐season” N applications as anhydrous ammonia are not as efficient as preplant applications. The NI did not influence micronutrient levels in the plant tissue, although N rates and time of application affected Mn, Fe, and Zn levels.
Endogenous Levels of Abscisic Acid in Water‐Stressed Cotton Leaves1
Authors: McMichael B. L. , Hanny B. W.
Published: July 2010

Studies relating diurnal changes in endogenous levels of certain plant hormones such as abscisic acid (ABA) diurnal patterns of plant water status are generally lacking. Since ABA has been implicated in the response of plants to stress conditions, the effects of plant water deficits on endogenous abscisic acid (ABA) levels in greenhouse and field‐grown cotton (Gossypium hirsutum L. ‘Deltapine 16’) were investigated. Greenhouse‐grown plants at the 7 to 8 leaf stage and leaves at node 18 of irrigated and nonirrigated field plants were used. Leaves were harvested at intervals throughout a 24‐hour period, frozen in liquid N and stored at −30 C. Samples wee then extracted in 80% methanol and assayed for ABA using newly developed, high.pressure, liquid chromatographic techniques. Plant water potential measurements were made at each sampling time. Stomatal diffusion resistance measurements were made on the leaves harvested from the field. A diurnal pattern in the ABA levels was observed in both field and greenhouse plants. Abscisic acid levels were low during the early morning hours when plant water potentials were high. During the day ABA levels increased as plant water potentials decreased, and reached a peak near sunset in both field and greenhouse. Levels of ABA then decreased as plant water potentials increased during the night and early morning hours. ABA levels were always higher in the stressed plants throughout the day in both field and greenhouse with the greater differences occurring in greenhousegrown tissue. The levels of ABA also increased as stomatal conductance increased in the field plants and continued to increase after conductance values began to decline in the afternoon in both stressed and well‐watered leaves which may reflect the measurement of ABA levels in whole leaves instead of guard cells alone. The larger differences between the conductance values in the stressed and nonstressed tissue late in the afternoon, however, may be associated with the differences in the ABA levels at that time. Since threshold potentials for initial ABA accumulation as well as diurnal patterns can be established, these assay techniques for ABA, developed specifically for cotton, may be useful in drought tolerance research as a tool for relating these parameters to variances in drought tolerance among genotypes.
Magnesium, Ca, and K Concentration in Temperate‐Origin Forage Species as Affected by Temperature and Mg Fertilization1
Authors: Gross C. F. , Jung G. A.
Published: July 2010

Additional information on Mg status of temperate‐origin forages under cool temperatures is needed if economic losses from grass tetany are to decrease. A greenhouse study was conducted to determine temperature and Mg fertilizer effects on herbage Mg concentration of one or more cultivars of tall rescue (Festuca arundinacea Schreb.), timothy (Phleum pratense L.), reed canarygrass (Phalaris arundinacea L.), smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), redtop (Agrostis gigantea Roth.), perennial ryegrass (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.), alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), ladino and white clover (T. repens L.), alsike clover (T. hybridum L.), birdsfoot trefoil (Lotus corniculatus L.), and crownvetch (Coronilla varia L.).

Plants were grown in Hagerstown soil, which belongs to the mixed, mesic family of typic Hapludalfs, in 4‐liter pots under natural daylength at cool (X̄ = 14 C), intermediate (X̄ = 18 C), and warm (X̄ = 26 C) ambient temperatures. Two levels of fertilizer Mg were used (0 and 672 kg Mg/ha as MgSO4). Grasses received 1,300 kg N/ha as NH4NO3 and both grasses and legumes were supplied K2SO4 to furnish 600 kg K/ha over a 13‐month growing period. Herbage was harvested at 2 to 3‐week intervals at a height of 5 cm.

Under cool temperatures, in both spring and autumn, and with added Mg, cultivars having high Mg levels were ‘Timfor’ timothy, ‘Nordstern’ orchardgrass, and ‘Viking’ birdsfoot trefoil. Species and cultivar rankings were similar for spring and autumn but Mg concentration was greater in autumn, indicating that cool temperatures, per se may be less limiting to Mg accumulation than previously thought.

Marked differences, five to seven‐fold, in Mg concentration occurred between species and cultivars of both grasses and legumes in response to Mg fertilizer. Low K/(Ca + Mg) ratios were obtained when the grasses were harvested under cool autumn temperatures. Yields were unaffected by Mg fertilization.

The consistency of cultivar ranking for Mg levels over a wide temperature range and different soil Mg levels, suggest that cultivar selection for Mg accumulation would be rewarding. Cultivars inherently efficient in Mg uptake, especially at cool temperatures, may help prevent grass tetany.
Alternate Drying and Rewetting Effects on Chemical and Physical Properties and Moisture‐Salinity Relationships of a Histosol1
Authors: Giskin M. , Levin I.
Published: July 2010

Under field conditions, cycles of drying and wetting take place naturally. Extreme fluctuations in the moisture content of Histosols have been reported to affect a number of soil processes and constituents. The purpose of the study was to investigate the possible influences on soil management of changes in chemical and physical properties resulting from a Histosol being carried through several successive dryings and wettings. Soil from the 0 to 30 cm layer of a low moor Histosol with a pH of 7.6 and organic matter content of 55.3% was used. The soil was put through three successive cycles of air‐drying and rewetting; subsamples were removed at each stage and physical and chemical determinations were carried out. The saturation percentage of the field sample decreased from 95.9 to 87.3% after the third drying cycle. The elecrtical conductivity of the saturation extract decreased at each drying stage, due to the large differences in the nitrate content between the dry and wet stages (8 vs. 380 ppm). Moisture retention curve data showed a 5% difference in available water between the moist field sample and the same sample after air‐drying. The data show that laboratory measurements of soil‐water relations for a Histosol change with time, i.e., with each exposure to drying and rewetting prior to sampling. This information will have a direct bearing on the management of a Histosol, i.e., when determining the amount of irrigation waters to be applied.
Influence of Growth Stage and Soil Conditions on Bermudagrass Susceptibility to Glyphosate1
Authors: Whitwell Ted , Santelmann Paul W.
Published: July 2010

Bermudagrass (Cynodon dactylon L.) is a perennial grass weed species in many crop and industrial situations. Glyphosate (N‐(phosphonomethyl) glycine) has provided some control of this weed, but results have been variable. Field and laboratory studies were conducted to evaluate the conditions under which bermudagrass is most susceptible to glyphosate. Fall, spring, or summer glyphosate applications were made for bermudagrass control in 1974, 1975, and 1976. Bermudagrass at five growth stages was also treated with 1.7, 3.4, and 5.0 kg/ha of glyphosate. In the laboratory the influence of temperature, soil moisture, and N stresses before or after glyphosate treatments were evaluated for their influence on the degree of control achieved. The soil type was a Teller sandy loam soil (Udic arguistoll; fine loamy, mixed thermic).

Glyphosate applications from July to early October, at a rate of 3.4 kg/ha or more, were the most effective for controlling bermudagrass. Spring glyphosate applications were ineffective even at 5.0 kg/ha. Substantial foliage (> 17 cm tall) had to be present to obtain the maximum control with August glyphosate applications. A 5‐day 20 C temperature pretreatment or cool temperatures during treatment did not decrease bermudagrass control with glyphosate. Dry soil conditions or wilted plants at treatment significantly reduced the effectiveness of glyphosate.

Effective bermudagrass control with glyphosate appears to require actively growing plants, with the major portion of the photosynthates moving into the stems and roots. Plant stress prior to treatment reduces the control obtained.
Nitrapyrin Degradation and Movement in Soil1
Authors: Touchton J. T. , Hoeft R. G. , Welch L. F.
Published: July 2010

Nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine] is applied with ammonium‐N fertilizers to control nitrification in soil. However, little information is available on the persistence or loss of field.applied nitrapyrin. The objective of this study was to monitor movement and degradation of nitrapyrin in soil. Nitrapyrin was applied with anhydrous ammonia in the fall of 1975 and spring of 1975 and 1976. These field studies were located on Drummer silty clay loam (Typic Haplaquoll) and Cisne silt loam (Mollie Albaqualf) soil, Detailed sampling from a concentric zone around the point of ammonia/nitrapyrin release in the soil was conducted periodically during the spring and summer. Measurable quantities of nitrapyrin were not found beyond 7.5 cm from the point of release in the soil. The distance that nitrapyrin moved from the point of release in the soil was not affected by nitrapyrin rates. Greater nitrapyrin movement was not detected in one direction from the point of release in the soil than in another direction. Increasing rates of anhydrous ammonia had no effect on nitrapyrin movement or degradation. The most rapid rate of degradation occurred soon after application and decreased with time. The highest concentrations of nitrapyrin were found within 2.5 cm from the point of release in the soil and a concentration gradient existed out to 7.5 cm. The greatest percentage of applied nitrapyrin was recovered within the concentric zone 2.5 to 5.0 cm from the point of release in the soil. Both nitrapyrin movement away from the point of application and degradation were less in a silty clay loan soil which had a relatively high organic matter level than in a silt loam soil which had a lower organic matter level. Relatively high concentrations of nitrapyrin were found in the soil after nitrification was completed and significant concentrations were found several months after application. The data suggest that nitrapyrin degradation and movement will depend on the physical and chemical characteristics of the soil. Even though degradation rates decrease with time, we did not find indications that soil accumulations of nitrapyrin will result from once‐a‐year applications.
Complete Neutralization of a Portion of Calcareous Soil as a Means of Preventing Iron Chlorosis1
Authors: Wallace A. , Mueller R. T.
Published: July 2010

Soybeans (Glycine max L. Merr., PI 54619‐5‐1) that are susceptible to Fe chlorosis, were grown in a glasshouse with calcareous (10% CaCO3) Hacienda loam soil (fineloamy, mixed, thermic aquic Natrargid) with a portion of the soil neutralized vs. equivalent mixing of sulfuric acid with all the soil. The objective was to determine if complete neutralization of only a small part of the mass of a calcareous soil could effectively prevent Fe chlorosis. Small acidified spots of soil, equivalent to as little as 0.4% of the CaCO3 in the 1,000 g of the soil used in each pot, placed 3 cm deep under seedlings, was sufficient to prevent the Fe chlorosis. These glasshouse results suggest that comparable procedures be tried for field experimentation with row crops which are susceptible to Fe chlorosis.
Effects of Planting Configuration on Water Use and Economics of Drip Irrigation Systems1
Authors: Singh S. D.
Published: July 2010

The drip irrigation system is expensive to install and warrants further study. To evaluate the cost of laterals needed and the amount of water used, cabbage (Brassica oleracea L.), cauliflower (Brassica oleracea L. var. Botrytis L.), tomato (Lycopersicum esculentum Mill.), and turnip (Brassica rapa L.) crops were grown on a loamy sand soil in rectangular, square, equilateral, and hexagonal planting geometries. The rectangular, both square and equilateral, and hexagonal planting geometries resulted in single, double, and triple row configurations and required four, two, and one drip lateral per 2.40 m plot width, respectively. The yield and quality of the produce were the same in both double and single row planting geometries. Thus, double row planting reduced cost and water use by 50%. The cost and water use were reduced 75% for the hexagonal planting geometry, but yields were 26 to 52% less than for the rectangular planting geometry; the produce quality was such that 37% heads of cabbage, 42% of cauliflower, and 23% of turnip balls were unmarketable. The quality of tomato, however, was not affected. Therefore, the hexagonal planting geometry in tomato with two separate laterals per 2.40 m should reduce cost and water use equal to that for double row planting and achieve a yield potential of twice the present production rate of 55 metric tons/ha.
Effects of Fluidized Bed Combustion Waste on the Ca, Mg, S, and Zn Levels in Red Clover, Tall Fescue, Oat, and Buckwheat1
Authors: Stout W. L. , Sidle R. C. , Hern J. L. , Bennett O. L.
Published: July 2010

Fluidized bed combustion, a desulfurization process for coal‐fired power plants, produces a waste that contains large amounts of calcium oxide and calcium sulfate. Since approximately 200 kg of fluidized bed combustion waste (FBCW) is generated per metric ton of coal burned, it represents a significant potential source of lime that must be evaluated before it can be properly utilized. In this study, FBCW was compared with calcium hydroxide as a lime source in a greenhouse study with red clover, tall fescue, oat, and buckwheat. The FBCW and calcium hydroxide were applied at rates calculated to adjust the pH of Westmoreland silt loam (Ultic Hapludalf, mixed, mesic) to 5.0, 5.5, 6.0, and 6.5. Though the loading rates from FBCW were higher than those from calcium hydroxide, FBCW treatments increased Ca levels more than did calcium hydroxide only in red clover. Only dry matter yields of buckwheat were higher for FBCW than for calcium hydroxide applications. All species showed higher FBCW‐induced Mg and S increases than hydrated lime. In spite of the Zn loading, Zn levels in herbage decreased as the pH levels increased as a result of FBCW application. Soil pH increases in FBCW and Calcium hydroxide treatments were comparable when the materials were applied in equivalent amounts. It was concluded that FBCW may be valuable as a lime, Mg, or S source when the effects of heavy metals in the material are evaluated.
An Analysis of the Relationship between Stem Diameter and Leaf Water Potentials1
Authors: So H. B.
Published: July 2010

Changes in stem diameter of a plant are known to follow those in its leaf water potentials; however, a time lag between them and the failure to account for it has been largely responsible for the lack of agreement between measured leaf water potentials and those calculated from stem diameters.

A dynamic method is described which infers leaf water potentials continuously from changes in stem diameter and is essentially nondestructive. The method is based on an analogy between a tensiometer‐soil and linear variable difference transformer (LVDT) plant system and requires continuous monitoring of stem diameters and at least two measurements of leaf water potentials as a calibration.

Using published data, the method was tested for cotton (Gossypium hirsutum L.) and red pine (Pinus resinosa Ait.) and good agreement was obtained between calculated and measured leaf water potentials. The method is simple, accurate, anl easily calculated. It would be useful for both laboratory and field measurements, particularly where a small number of plants is involved.
Genotypic Differences of Corn for Ion Uptake1
Authors: Baligar V. C. , Barber S. A.
Published: July 2010

Efficiency of fertilizer uptake may be improved by selecting genotypes that absorb a greater proportion of the nutrients in the soil. The objective of this investigation was to examine genotypic differences in ion influx (uptake rate per cm of root) properties of corn (Zea mays L.) roots that may influence efficiency of fertilizer uptake. Six genotypes developed in Florida and six genotypes developed in Indiana were investigated. Each represented two single‐cross hybrids and their parents. They were grown for 15 days in nutrient solution in a controlled climate chamber and the influx parameters of K, Ca, Mg, and P were determined by measuring the depletion of these ions from solution.

All hybrids exhibited heterosis in the growth of shoots and roots. Florida genotypes had finer roots than Indiana genotypes. Florida genotypes had higher average Imax (maximum influx) values for Ca and P. Parent lines of Florida hybrids had higher average Imax values for Ca and lower for K and Mg than hybrids. Indiana genotypes had higher average Km, Michaelis‐Menten, values for K uptake and lower Km values for P uptake than Florida genotypes. Florida genotypes had significantly higher average Cmin (concentration in solution where net influx is zero) values for Mg and P and lower for K than Indiana genotypes. Even though Florida and Indiana genotypes originated in different geographic regions they exhibited little difference in their average net influx rates for Ca and Mg, however, there were small but significant differences between these genotypes in average influx values for P and K. Florida inbreds with higher P influx rates tended to have hybrids with higher P influx rates. While the differences in this study were not large, investigation of a larger number of genotypes is needed to determine the possibilities of developing hybrids with roots that are more effective nutrient absorbers.
A Method for Obtaining Undisturbed Samples from Soil Columns
Authors: Mulchrone S. , Morgan M. A. , Mullen G. J.
Published: July 2010

Lack of a suitably simple technique to study the fate of nutrients applied to soil columns of given bulk density and water‐table exposure prompted the development of the apparatus described here. The system has a split pipe, containing the soil column, housed in an outer jacket. Peat or mineral soil can be packed into the split pipe to pre‐selected bulk density values which vary little with depth. The split pipe/outer jacket assembly can be subjected to various water‐table treatments according to the position of a drainage outlet in the associated water jacket, and drainage water from the assembly can be collected via the drainage outlet. Undisturbed soil samples are obtained after removing the split pipe from its jacket and breaking its watertight seal. The apparatus is economically constructed and may be used for a variety of experimental objectives.
Relation of Soil Properties and Other Environmental Factors to Grain Yield and Quality of Winter Wheat Grown at International Sites1
Authors: Karathanasis A. D. , Johnson V. A. , Peterson G. A. , Sander D. H. , Olson R. A.
Published: July 2010

Varied performance of different genotypes of winter wheat (Triticum aestivum L. em Thell) has been recognized in different areas of the world. It was the objective of this study to evaluate the role of measurable soil properties on the performance of 30 winter wheat varieties grown in nurseries at 31 international sites during 1975 and 1976. Soil samples from the rooting profile of these sites were collected and analyzed for carrying out this correlation study.

Despite substantial variability among nursery sites in soil type, climate, and soil management, 17 to 74% of the variation in the grain yield and 20 to 94% in the grain protein content was explained by the soil variables. Lowest grain yields were observed on soils with pH lower than 6.0 or on highly calcareous soils. Residual mineral N in the soil profile at most nursery sites was more than enough to produce maximum grain yield and protein, but soil P level appeared to be the main factor limiting yields of most cultivars. Soil K had positive influence on grain yield only at sites with <100 ppm exchangeable K and was generally negative in its influence on protein, while soil SO4‐S correlated positively with grain protein. The trace nutrients Zn, Cu, Mn, and Fe appeared to be important for the nutrition of certain cultivars. Winterkill was the main environmental factor depressing yields in some nurseries while seasonal rainfall had low significance or a negative effect on the yield and quality performance.
Trickle Irrigation and Fertilization of Tomatoes in Highly Calcareous Soils1
Authors: Kafkafi U. , Bar‐Yosef B.
Published: July 2010

Large areas of the world consist of marginal desert soils. Introducing these soils to agricultural production requires development of new irrigation and fertilization techniques. This study was conducted to test the hypothesis that such soils can be used provided one can control soil water content and nutrient concentration of the soil solution in the root zone by supplying nutrients daily through a trickle irrigation system.

Six fertilizer combinations at two irrigation levels were tested on a tomato crop of a determinate type of growth (Lycopersicum esculantum var. S‐5), grown on a virgin desert soil containing 85% calcium carbonate and EC of 7 mmho/cm. The highest yield, 80 tons/ha, was obtained with 400 mm water (40% of evaporation from a Class A pan) plus KNO3, superphosphate, and KH2PO4 fertilizers. In the root volume of this treatment the nitrate concentration in the soil solution was about 160 ± 30 ppm NO3‐N throughout the season. A total soil water potential of about −2 to −4 bars during the first month of growth resulted in a lower canopy yield but earlier fruit ripening as compared with total water potential of −1 to −2 bars.
Soil Test Correlation Problems with Two Phosphorus Methods on Similar Soils1
Authors: Varvel G. E. , Anderson F. N. , Peterson G. A.
Published: July 2010

Survey data on the fertility status of soils in western Nebraska, on which sugarbeets (Beta vulgaris) were grown, indicated that 78% of the fields tested were high in Bray P‐1 P. These results seemed questionable, especially when compared to the results being obtained on samples from the area by the NaHCO3 method. A study was then initiated to correlate and calibrate the Bray P‐1 and NaHCO3 methods on the soils in the area for sugarbeets. Observations from the first year of research indicated that a separation of the sites according to soil series, Mitchell or Tripp, despite their similarities in pH, CaCO3 content, organic matter, and texture, greatly improved correlation. Therefore, an additional objective was added to compare extractable P by both methods with sugarbeet response to P fertilization on each of the series. Twenty‐two field experiments were conducted from 1974 through 1976 on these soil series. The experiments consisted of six rates (0, 23, 45, 67, 112, and 224 kg/ha) of P on sugarbeets with four replications. Yields were determined from samples harvested in the fall of each year.

Correlation of crop response with soil‐test P levels by either soil test method was very poor when used across all locations. However, separation by soil series and the use of the Bray P‐1 and NaHCO3 methods on the Tripp and Mitchell series respectively, greatly improved the correlation. This improvement was obtained by using available soil classification data, which had already separated these soils, despite their similarity in many physical and chemical properties generally used to explain the problem.
A Comparison of Soybean Leaf Water Potential and Leaf Temperature under Progressive Drought1
Authors: Scott H. D. , Jung P. K. , Ferguson J. A.
Published: July 2010

Information is limited on the relationship between leaf water potential (Ψ) and leaf temperature (T) of soybeans [Glycine max (L.) Merr.] grown in the field. Therefore, measurements of Ψ and T were made with a pressure chamber and infrared thermometer, respectively, in five study periods during a field study in 1978. The season was characterized by progressive drought. ‘Forrest’ soybeans were grown at two moisture regimes on a Crowley silt loam (Typic Albaqualf).

Linear relationships were found between T and Ψ. Leaf temperature of the nonirrigated soybeans was more sensitive to changes in Ψ than that of the irrigated soybeans and became more sensitive as the drought progressed. The regression equations relating Ψ to T in each of the five study periods were not unique for a given moisture treatment. However, the regression equations expressing the Ψ vs. T relationship for the single linear equation would suffice for describing the Ψ vs. T relationship throughout the season for each moisture treatment, but a different one would be required to express that relationship for a different moisture treatment.
Mass and Energy Exchanges of a Soybean Canopy under Various Environmental Regimes1
Authors: Baldocchi Dennis D. , Verma Shashi B. , Rosenberg Norman J.
Published: July 2010

The environment of the east central Great Plains of North America can be very extreme during the course of a growing season. A field study was thus conducted during the summer of 1979 to examine the exchange of mass and energy between the atmosphere and a soybean canopy [Glycine max (L.) Merrill] for various environmental conditions experienced in the east central Great Plants of North America. The crop was planted in a Typic Argiudoll (Sharpsburg silty, clay loam) soil. Measurements of mass and energy exchange rates were made using the Bowen‐ratio energy balance technique.

Hot, clear days dominated by sensible heat advection limited CO2 exchange but increased latent heat flux. As a result, the CO2‐water flux ratio (CWFR), a measure of water‐use efficiency, was low. Cloudy days suppressed both CO2 and latent heat flux. This effect caused CWFR to be greater. Optimal conditions for photosynthesis and CWFR occurred in the absence of sensible heat advection on clear days with moderate temperatures.

Our measurements indicate that a developed soybean canopy (LAI of 4.1) did not become light saturated at photosynthetically active radiation (PAR) levels exceeding 400 Wm−2. Optimal air temperatures for CO2 exchange ranged between 29 and 32 C. Higher temperatures led to a reduction in CO2, exchange. The CWFR was found to be dependent on both net radiation and sensible heat advection.
Stand Establishment and Yield of Corn as Affected by Herbicides and Seed Vigor1
Authors: Johnson R. R. , Wax L. M.
Published: July 2010

Seed quality and herbicide injury are factors that might interact to affect corn {Zea mays L.) yields. Field studies were conducted to determine if corn grown from low‐quality seed was more susceptible to herbicide injury than corn grown from high‐quality seed. Seed lots with standard warm germinations above 90% but cold test germinations ranging from 50 to 96% were obtained for three U.S. Corn Belt hybrids. Herbicide treatments of cyanazine {2‐[[4‐chloro‐6‐(ethylamino)‐s‐triazin‐2‐yl] amino]‐2‐methylpropionitrile}, metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide], and EPTC+ [S‐ethyl dipropylthiocarbamate plus R‐25788 (N,N‐dially1‐2,2‐dichloroacetamide)] were preplant incorporated at rates ranging from one to three times those normally used for soil types common to these experiments. The soils were Drummer silty clay loam (Typic Haplaquoll) and Flanagan silt loam (Aquic Arguidoll). Seed quality, hybrid, and seedbed environment all interacted to affect emergence, herbicide injury, stand density at harvest, and grain yield. Seedlings from seed lower in vigor received greater herbicide injury in two of the five seedbed environments investigated, but this interaction was not significant for percent seedling emergence, plant density at maturity, and grain yield. Some herbicide treatments caused grain yield reductions of 4 to 13% but were limited to above‐normal rates of cyanazine and EPTC+ and were not associated with plant death. Visual symptoms of herbicide injury on seedlings were usually out‐grown with no resultant effect on grain yield. Grain yield reductions of up to 32% occurred from seed low in cold test germination. Yield reductions from low quality seed did not occur with all hybrids or in all seedbeds, but when yield reductions did occur, they were associated with decreases in plant density. We conclude that any interaction of corn seed quality with herbicides applied at recommended rates is minor compared with effects of poor seed quality per se, unwarranted high herbicide rates, hybrid differences, or limited soil moisture.
Soybean Tillage and Planting Method Effects on Yield of Double‐Cropped Wheat and Soybeans1
Authors: Touchton J. T. , Johnson J. W.
Published: July 2010

Wheat (Triticum aestivum L., em Thell) following soybeans (Glycine max L., Merr) is an important cropping system throughout the southeastern United States. In this system, notillage soybean production is becoming a common practice; however, the effects of no‐tillage soybean production on yield of double‐cropped wheat are not well documented. The objective of this study was to determine the effects of three tillage practices and planting methods for soybeans on yields of soybean and wheat grown on Appling (Typic Hapludult) and Cedarbluff (Fragiaquic Paleudult) soils. Three primary tillage systems for soybeans were no‐tillage, cbisel, and moldboard plow and the three planting methods were drilled (18 cm rows), in‐row subsoiling (69 cm rows), and conventional (without subsoiling, 61 cm rows). The entire experimental area was disked (8 cm deep) prior to drilling wheat.

In the three environments tested, no‐tillage soybean production without in‐row subsoiling reduced wheat grain yield an average of 509 kg/ha when compared to chiseling and moldboard plowing. Generally, planting soybeans with an in‐row subsoiler eliminated adverse effects of no‐tillage soybean production on wheat yield. No‐tillage soybean yields were not affected by planting methods except in 1 year where subsoiling increased yield 907 kg/ha (160%) over that obtained without subsoiling. Soybean yields were approximately equal for the chisel and plow treatments but wheat yields were often lower on the chiseled than on the plowed soil. The results suggest that plowing or at least chiseling prior to planting soybeans will result in higher yield of double‐cropped wheat than no‐tillage planted soybeans unless the soybeans are planted with an in‐row subsoiler.
Harvest Frequency and Fertilizer Effects on Yield, Quality, and Persistence of Eight Bermudagrasses1
Authors: Monson Warren G. , Burton Glenn W.
Published: July 2010

Bermudagrass [Cynodon dactylon (L.) Pers.] is a well adapted and widely used forage grass in southern U.S.A. As new cultivars and hybrids are developed there is a need to evaluate and compare their performance to that of the accepted cultivars. This study was initiated to evaluate three established cvs.. Coastal, Coastcross‐1, and Midland, two new cvs., Callie (C. nlemfuënsis Vander.) and Tifton 44 and three experimental hybrids designated Tifton 67, 68, and 84. A split‐split plot design was used to evaluate harvest frequency and fertilizer levels on performance of the grasses on a Plinthic Paleudult soil. The grasses were main plots, N fertilizer rates of 336 and 672 kg/ha were subplots and harvest frequencies of 1, 2, 4, and 8 weeks were sub‐subplots. Data were gathered on forage yield, in vitro dry matter digestibility (IVDMD), crude protein (CP) content, and persistence of the grasses. Dry matter yields were highest in the 1st year for the robust type bermudagrass cvs. Callie, Tifton 67, and Tifton 68. In the 2nd year, Coastal and Tifton 44 were superior due in part to stand losses of the more robust types. Increasing the N rate from 336 to 672 kg/ha significantly (P = 0.05) increased yields, but there were significant interactions with both harvest frequency and genotype. Annual dry matter yields increased with harvest interval except that in the 2nd year there were only small differences among the 1, 2, and 4 week interval.

Persistence of the bermudagrasses measured by a single harvest in the spring of the 3rd year ranked Tifton 44, Coastal, and Midland as the top three cultivars under both fertilizer regimes. The other cultivars yielded from 36 to 0.0% of Coastal at the lower N rate and from 57 to 0.0% at the higher rate. These data along with visual observations indicate the superiority of the rhizomatous cvs. (Coastal, Tifton 44, and Midland) in persistence and ability to produce early spring growth.
Differential Accumulations of Cadmium and Zinc by Corn Hybrids Grown on Soil Amended with Sewage Sludge1
Authors: Hinesly T. D. , Alexander D. E. , Redborg K. E. , Ziegler E. L.
Published: July 2010

Researchers have recognized that different varieties and cultivars of plants subjected to the same growing conditions frequently take up different amounts of essential and nonessential trace elements. Differences in uptake appear to be predisposed genetically. In designing studies to determine the nature of the inherited capacity of corn (Zea mays L.) to control the uptake of heavy metals some additional information was needed. The objectives of this study were to determine the extent to which Cd uptake was affected by the proximity of growing plants, whether or not maternal effects were present and the extent to which uptake patterns varied from year to year under normal field conditions.

Where corn inbreds known to accumulate relatively high amounts of Cd in leaves and grain were paired with those that took up low amounts in pots of Ipava silt loam (Aquic Argiudoll, fine, montmorillonitic, mesic, pH 5.5) containing 57 mg Cd/kg and 864 mg Zn/kg, supplied as constituents of sewage sludge, the uptake of Cd by individual inbreds was not altered. Using the same soil, reciprocal crosses of corn inbreds that accumulated high and low amounts of either Cd or Zn were grown for 6 weeks in pots. Regardless of which inbred was used as the female parent, concentrations of metals in leaves were not significantly different.

Two hybrids, differing only in their capacities to accumulate Cd, were grown in a field study for 3 consecutive years on replicated control and sewage sludge‐amended split plots. Initial annual applications of sludge were made 9 years prior to the study and were continued throughout the 3 years. At the beginning, where maximum rates of sludge had been applied, the soil surface contained 28 mg Cd/kg and during the study 31 kg/ha of sludge‐borne Cd were applied. Cadmium and Zn concentrations in leaves, grain, and stover from both hybrids were increased each year by increasingly higher applications of sludge, except in grain from the hybrid selected to take up low amounts of Cd. During the last year, grain from the low‐Cd accumulator grown on maximum‐sludge‐treated plots had Cd concentrations that were not significantly different than those in grain from the high‐Cd accumulator grown on control plots. Grain‐Cd concentrations for the high‐Cd accumulator were 13 to 18 times higher than for the low‐Cd accumulator when they were grown together on maximum‐sludge‐treated plots. Accumulative sludge applications did not cause increased Cd concentrations in grain from either of the two hybrids, but did cause increased levels of both Zn and Cd in leaves and stover of the high Cd accumulator. Phytotoxicity symptoms were not observed, even though concentrations of Cd ranged from 20 to 42 and 1.5 to 1.8 mg/kg in the leaves and grain, respectively, of the high accumulator grown on plots treated with maximum amounts of sludge.
A Simple Method to Calibrate an Infrared Thermometer1
Authors: Sadler E. J. , van Bavel C. H. M.
Published: July 2010

An infrared thermometer (IRT) was calibrated by simultaneously measuring the temperature of a black cavity with the IRT and with fine thermocouples, while the cavity was being heated from 5 to 50 C, over a 2‐hour period. Both temperatures were recorded on cassette tape by a microprocessor‐based data collector, transferred to computer disk storage, and used to determine the calibration equation. The entire procedure required about 4 hours from setup to completion, including production of a graph of the equation and the results.
Effects of Long‐Term, Annual Applications of N and P on Corn Grain Yields and Soil Chemical Properties1
Authors: Hooker M. L. , Gwin R. E. , Herron G. M. , Gallagher P.
Published: July 2010

Maximum yield production in monocultural cropping systems requires annual applications of fertilizer to maintain adequate soil nutrient levels. The rates of applied N and P fertilizers may vary from conservative to excessive applications. Experiments were established at two locations (Ardic Haplustoll and Aridic Argiustoll) to evaluate the effects of annual applications of N and P, over a period of several years, on corn (Zea mays L.) grain yields and the accumulation of these nutrients in the soil. Maximum grain yields were consistently maintained with N applications of 134 to 180 kg/ha and P applications of 20 kg/ha. Applications of N‐rates higher than the optimum resulted in accumulations of residual NO3‐N and subsequent leaching. At one location the soil P level was maintained constant for 21 years with the 20‐kg P rate. A similar trend was observed for the initial 10 years of the second experiment, however, for the last 4 years soil‐P has increased at the rate of 4 ppm annually.
Fertilizer Application and Irrigation Management of Broccoli Production and Fertilizer Use Efficiency1
Authors: Letey J. , Jarrell W. M. , Valoras N. , Beverly R.
Published: July 2010

Fertilizer and irrigation must be managed for efficient resource use and preservation of environmental quality as well as maximum production. Two furrow irrigation experiments growing broccoli (Brassica oleracea) were conducted. The first consisted of three N rates (90, 180, and 270 kg/ha), two irrigation treatments (replenishment of water lost by evapotranspiration and evapotranspiration plus 30%), and two N application procedures (application to the soil and in the irrigation water) on a sandy loam soil (coarse‐loamy, mixed, thermic Typic Xerofluvent). Plant growth increased with increasing N application. For a given N application, there was higher average production with the lesser amount of water application. The method of N application had very little effect on production under the lower irrigation treatment, but production was consistently higher for N application with water rather than to the soil when the higher water application treatment was used. The ratio of N in the plant to N applied decreased with increasing N application, decreased with higher water application, and decreased with application in the irrigation water as compared to soil application. The second experiment consisted of two N rates (115 and 225 kg/ba) and two N application procedures (application to soil and in the irrigation water) on a loam soil (fine‐loamy mixed, thermic Calcic Haploxeroll). Yield and N uptake were significantly higher with 225 as compared to 115 kg/ha of N. Conventional preplant and side‐dress N application to the soil resulted in significantly higher broccoli head yield than injecting N in the irrigation water. Leaching of N was not a factor under the experimental conditions.
Coefficients of Variation, Error Variances, and Resource Allocation in Soybean Growth Analysis Experiments1
Authors: Carter T. E. , Burton J. W. , Cappy J. J. , Israel D. W. , Boerma H. R.
Published: July 2010

Treatment differences are usually difficult to detect in soybean (Glycine max (L.) Merr.) plant growth analysis studies because of large experimental errors. However, no estimates of error variances, coefficients of variation (CVs), treatment × environment interactions, or numbers of replications required to show treatment differences have been reported. This report describes the error variances and CVs from five soybean growth analysis studies (field and greenhouse) conducted in the southeastern USA. We use these data to develop calculations which aid in planning growth analysis experiments. For dry weight traits the average CV was 0.256 and ranged between 0.13 and 0.50. Based on the average CV value of the dry weight traits and assuming no treatment × environment interaction, an average of 3, 16, and 65 replications is required in order to detect 50, 20, and 10% treatment differences, respectively, for a single sampling date. The average error variance for percent N traits was 0.035 and ranged between 0.00636 and 0.366. Based on this average variance for percent N traits, an average of 2 and nine replications is necessary to show 0.4 and 0.2 unit differences, respectively, for a single sampling date. For multiple sampling dates and again assuming no treatment × environment interaction, the above values may be considered as the minimum value of replication number (per sampling date) × the number of sampling dates needed to show specified treatment differences. Treatment × environment interaction variances (5 to 10 % of error variance) were detected for some traits in the two experiments conducted over multiple environments. Although our data are limited, it appears that moderate treatment × environment interaction should be anticipated wben planning growth analysis experiments; i.e., one should expect to test in multiple environments for a reliable ranking of treatments. In that regard, the presence of treatment × environment interaction variance (10% of error variance) indicates that testing in at least two environments is necessary to detect 20 % treatment differences, and that testing in at least seven environments is necessary to detect 10% treatment differences. There is no unique combination of environment, replication, and sampling date which is required for detecting specified treatment differences, however. Charts and tables are presented as an aid in determining combinations of environments, replications, and sampling dates which should enable detection of treatment differences. From these combinations, a researcher can choose an allocation of resources which will fit a program budget and also give reasonable chances for detecting treatment differences. It is efficient to have the number of test environments as large as is practicable. Only two of the five experiments reported here had the precision needed to detect 20 % treatment differences when moderate treatment × environment interaction was present.
Previous Crop Influence on Fertilizer Nitrogen Requirements for Double‐Cropped Wheat1
Authors: Hargrove W. L. , Touchton J. T. , Johnson J. W.
Published: July 2010

Few studies have addressed factors which affect wheat (Triticum aestivum L.) production in double‐cropping systems. This study was conducted for 4 years at two locations in Georgia (Limestone Valley and Coastal Plain regions) to determine the influence of the previous crop on fertilizer N requirements for double‐cropped wheat. The N fertilizer treatments were fall (0, 11, 22, 33, and 44 kg N ha−1 as ammonium nitrate) and spring (0, 22, 44, 66, and 88 kg N ha−1 as ammonium nitrate) N rates applied to wheat following soybeans (Glycine mar L. Merr.) or grain sorghum [Sorghum bicolor (L.) Moench]. The soil types were Cedarbluff silt loam (fine‐loamy, siliceous, thermic Fragiaquic Paleudult) in the Limestone Valley region and Greenville sandy clay loam (clayey, kaolinitic, thermic Rhodic Paleudult) in the Coastal Plain region. Plant samples were obtained each year at the time of the spring N application, and the N content of plant tissue was determined. In addition, whole plant and flag leaf N concentrations were determined on samples obtained during the boot and flowering stages in 1981. Grain yields and the N content of mature grain were also determined each year. The N concentration in plant tissue at the time of spring application was consistently greater for wheat following soybeans than for wheat following grain sorghum at equal fall N rates. In the Limestone Valley region, maximum yield was obtained with a total of 85 kg N ha−1 for wheat following soybeans and 105 kg N ha−1 for wheat following grain sorghum. In the Coastal Plain region, maximum yield was obtained with a total of 103 and 137 kg N ha−1 for wheat following soybeans and wheat following grain sorghum, respectively. Extractable soil N was not related to plant N status or grain yield. The N concentration in the flag leaf at flowering was significantly correlated with grain yields and may provide a useful diagnostic criterion for the N status of soft red winter wheat. Regardless of previous crop, location or N rate, maximum yields were obtained when flag leaf N concentration was 35 to 40 g kg−1. Results from this study indicate that wheat growth, N status, and grain yield are significantly influenced by the previous crop and are important to the management of double‐cropping systems.