bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship Between Laboratory Cold‐Test Methods and Field Emergence in Maize Inbreds1
Authors: Burris J. S. , Navratil R. J.
Published: July 2010

Reliable estimates of field emergence under adverse planting conditions are required for maximum crop management. The “cold‐test” is widely used as such a parameter. Various versions of the laboratory cold‐test for corn (Zea mays L.) were studied on 15 inbred lines. Substrates ranged from sterile Kimpak to sand‐soil mixtures to a test utilizing pure soil. All procedures incorporated a 10 C 7 day stress period followed by a grow‐out period at approximately 25 C. Variability between test results on the same sample was as much as 60%. The lowest coefficient of variability was achieved with a method incorporating a cellulose substrate covered with a small amount of soil. The test utilizing the sterile substrate was found to have laboratory performance characteristics similar to the soil tests. It appears that for the inbreds studied, much of the cold‐test response is due to the temperature stress and little to the soil.

The ability of any of the tests to predict field emergence was quite variable. The lowest correlation and predictability was recorded with the method suggested by the AOSA Vigor Committee, while the sterile substrate test exhibited intermediate correlation performance compared to the other methods involving soil or soil mixes.

The cold‐test is not a consistently reliable predictor of early field emergence. The variability inherent in the test makes comparison between laboratories difficult.
Evaluation of Temperature Effects on K Uptake by Corn1
Authors: Ching P. C. , Barber S. A.
Published: July 2010

Changes in both plant uptake and soil supply parameters with temperature may restrict K uptake from cold soils. The objective of this research was to determine the effect of temperature on each of the soil and plant parameters used in a model simulating K uptake by corn (Zea mays L.). Then, using these measurements, to compare predicted by the simulation model with observed uptake. The parameters used in the simulation model were for the plant: root length at the start of the experiment; root growth rate; mean root radius; K influx as affected by K concentration outside the root; water influx; and for the soil: initial K concentration in soil solution; buffer power of K on the solid phase for K in solution; and the effective diffusion coefficient for K in the soil. The soil parameters were measured after equilibration of soils at 15 and 29 C in the laboratory. Where no additional K was added to the soil, soil solution K at 15 C was one‐half, buffer power was 1.7 and the effective diffusion coefficient was 0.4 of that at 29 C.

The plant growth experiments were conducted in a controlled climate with an air temperature of 29 C and root temperatures of 15 C and 29 C. The K influx characteristics of corn roots as affected by root temperature were determined in solution culture experiments. Potassium influx at 15 C was one‐half that at 29 C. Root length increase while plants were subjected to root temperature differentials for 6 days (age 10 to 16 days) was 8 tunes greater at 29 C than at 15 C. These two factors resulted in a shoot K of 8.1% at 29 C and 3.7% at 15 C. Root growth rate, root radius, and mean water influx were measured for plants growing in soil at 15 and 29 C. Potassium uptake predicted by the simulation model was correlated (R2 = 0.98) with observed K uptake. A sensitivity analysis predicted the effects on K uptake of changes in the parameters used in the model that were due to temperature changes.
Evaluation of Cluster Analysis for Comparing Treatment Means1
Authors: Willavize Susan A. , Carmer S. G. , Walker W. M.
Published: July 2010

Univariate cluster analysis of treatment means is considered as an alternative to the least significant difference for those experiments where pairwise multiple comparisons are applicable. Although cluster analysis procedures produce distinct, non‐overlapping groupings of the treatments, little previous study has been made of their statistical behavior. The objective of the present research was to examine statistical properties of four clustering algorithms in terms of their power and Type I and III error rates for several patterns of homogeneity among treatment means. The Scott‐Knott (SK) divisive procedure and three agglomerative procedures based on single linkage (SL), complete linkage (CL), and unweighted pair group averages (UPG), respectively, were compared to the least significant difference (FLSD) when a preliminary F test of overall treatment effects is performed.

Results of simulation studies indicate that the overlapping nature of the groupings of treatments obtained with the FLSD provides considerable protection against Type I and Type III errors. Both types of errors occurred with higher frequencies for all four clustering algorithms than for the FLSD. Furthermore, comparisonwise Type I error rates for the FLSD are determined by the researcher's choice of significance level, while the rates for cluster analysis are dependent on both the significance level and the degree of precision of the experiment. Consequently, researchers should contemplate with caution any possible adoption of cluster analysis as a replacement for a pairwise multiple comparison procedure such as the FLSD.
Topsoil and Subsoil Potassium Calibration with Leaf Potassium for Fertility Rating1
Authors: Woodruff J. R. , Parks C. L.
Published: July 2010

Plants obtain K from both topsoil and subsoil, but soil testing is usually performed on surface soil. Interpretation of subsoil tests for available K has also been limited by insufficient calibration of subsoil K level with plant growth response. Leaf K response was used to calibrate topsoil and subsoil K levels for fertility rating.

A 4‐year corn (Zea mays L.) — soybean (Glycine max L.) rotation on Marlboro loamy sand (Typic Paleudult) using various rates of K showed a buildup of K in the top 4 cm of B2 horizon with moderate annual K fertilization, but little change in Ap horizon K. Leaf K contents were sufficient where soil tests showed low topsoil and medium subsoil K. No yield response to K was obtained even after 4 years without K fertilization.

A 1‐year corn experiment on Orangeburg sand and Faceville loamy sand (Typic Paleudults) using various rates of K showed increased K in both Ap and subsurface horizons 50 and 70 days after K application. No yield response to K additions was obtained on either soil, even though the Orangeburg Ap horizon tested low in available K. The lack of yield response at low K ratings suggested a need for adjustment in the rating.

A 3‐year survey of the relationships among corn and soybean leaf K, and available K in Ap and top 10 cm of B2 horizons was made in the Middle Coastal Plain. Most of the soils were Typic Paleudults except for eight Psammentic Paleudults. A range of K application rates was not used at each site, preventing examination of relative yield response to soil K. Correlations were found between leaf K in both corn and soybeans and K in Ap and B2 horizons. To examine the contribution of K from each horizon, soil test calibration was achieved by multiple linear regression of leaf K on Ap and B2 available K values. Soil K fertility ratings were established from the regression equation using values for critical and sufficient leaf K to mark low and high soil test values.

This work indicated that soybeans may obtain K from B2 horizons at greater depths than corn and that available K in the B2 horizon should be considered along with Ap soil test K to characterize the soil fertility status, particularly in cases where coarse‐textured topsoils occur over finer‐textured subsoil material.
Nitrogen and Rhizobium Effects on Establishment of Legumes via Strip Tillage1
Authors: West Charles P. , Martin N. P. , Marten G. C.
Published: July 2010

abstract

The success of interseeding pastures with forage legumes via strip‐tillage is limited by the rate and degree of seedling establishment. Before biological nitrogen (N) fixation is initiated, the legume plant must depend on combined N from the soil or seed for establishment. Soils under permanent grass sod are known to contain very low levels of combined available N.

Field studies were initiated to determine the effects of seed rhizobium inoculum level and N fertilizer level on the establishment of three forage legumes introduced into grass pastures via strip‐tillage. 'Ramsey' alfalfa (Medicago sativa L.), 'Arlington' red clover (Trifolium pratense L.), and 'Carroll' birdsfoot trefoil (Lotus corniculatus L.) were interseeded into pastures at two locations (L 1 and L 2) with differing soils (Typic Haplaquoll and Typic Hapludoll, respectively). Location 1 had predominantly Kentucky bluegrass (Poa pratensis L.) , and L 2 had a mixture of Kentucky bluegrass and smooth bromegrass (Bromus inermis Leyss.). The grass was temporarily suppressed by a broadcast application of glyphosate [N‐(phosphonomethyl)glycine] at 0.84 kg/ha. Inoculum treatments consisted of 4,000 and 40,000 rhizobia seed. The four fertilizer levels applied at seeding were 0, 30, 60, and 90 kg N/ha.

Legume establishment was not affected by seed rhizobium inoculum level. Seedling vigor, first cutting leg ume, and total herbage yields increased significantly with added N fertilizer at both locations. Legume percentage in the sward followed a quadratic pattern with N level in the second cutting of the first year at L 2 and in the first cutting of the second year at L 1; legume percentage increased at the intermediate N levels and decreased at the highest N level in these cases. Increasing the N level resulted in either negative linear or quadratic changes in crude protein concentration in the 1st year, depending on location. Neutral detergent fiber concentrations in the total forage increased linearly with inoreased N at both locations in the first year. Herbage in vitro dry rnatter digestibility concentration was quadratically influenced by N level in the regrowth of the first year only at L 1.

We conclude that the application of 30 to 60 kg N/ha before interseeding legumes into a grass sod having low soil N availability may enhance early legume seedling growth and increase the initial legume contribution to the sward herbage yield, as well as total herbage yield.
An Automated Sample Weighing System1
Authors: McLaughlin N. B. , Townley‐Smith T. F.
Published: July 2010

A rapid weighing system was developed in order to eliminate reading and transcription errors during the recording of weights of large numbers of plot samples. The weighing system described consists of a digital electronic scale with parallel BCD outputs, an interface (described in detail), and an IBM 029 card punch. Computer cards were prepunched with the same identification code as the labels on the samples and are arranged in the same order. When initiated, the interface automatically reads the BCD output on the scale, converts it to a serial decimal form and sequentially supplies signals to the card punch simulating pressing the corresponding numeric characters on the card punch keyboard. When all digits have been punched, the card punch program automatically releases the card, feeds the next card and advances it to the correct column for the next weight to be punched.
Preparation of Customized Pressure Chamber Seals for Irregularly‐Shaped, Succulent Organs1
Authors: Simonelli Mary L. Neat , Spomer L. Art
Published: July 2010

The pressure chamber is commonly used to evaluate plant water status. The compression sleeves supplied with commercial units provide inadequate seals on irregularly‐shaped, succulent stems or petioles of organ samples. This makes accurate measurements of the water status of organs difficult, if not impossible. This note briefly describes a technique for making customized seals by molding them out of silicone rubber directly onto representative stems or petioles. Such seals have been demonstrated to provide superior sealing action with little or no tissue change.
Occurrence of Al and Mn in Grass Tetany Cases and Their Effects on the Solubility of Ca and Mg In Vitro1
Authors: Allen Vivien G. , Robinson D. L.
Published: July 2010

Although many factors associated with forages have been demonstrated to affect Mg balance in ruminants, none of the factors has been shown to cause grass tetany consistently. This investigation was begun with the objective of identifying mineral imbalances associated with individual grass tetany cases. Soil and forage samples were collected from tetany‐producing pastures and samples of rumen contents were collected from animals that had died with grass tetany. Rumen content samples were also collected from fistulated steers and cows grazing under non‐tetany conditions. Tetany pastures were found to contain areas where forages commonly contained 2,000 to 8,000 ppm Al. All rumen content samples from dead tetany animals contained high levels of Al, averaging 2,373 ppm. Samples from non‐tetany animals averaged 405 ppm Al. The rumen content samples from tetany and non‐tetany animals averaged 306 ppm and 139 ppm Mn, respectively.

In view of evidence that ruminant animals absorb Mg primarily in the reticulo‐rumen, an in vitro experiment was designed to determine the effects of Al ana Mn on the solubility of Mg and Ca in various combinations of ryegrass, rumen fluid, and buffer solution. Seven treatment combinations of Al and Mn were used: control, 1,000 and 2,000 pm Mn, 4,000 and 8,000 ppm Al, 1,000 ppm Mn plus 4,000 ppm Al, and 2,000 ppm Mn plus 8,000 ppm Al. After 48 hours of incubation, added Al had reduced Mg and Ca in solution by 56 and 74%, respectively (P ≤ 0.01). Manganese decreased Ca in solution when added alone, but had no effect on Mg or Ca when added with Al (P ≤ 0.05). This research indicates that high Al levels in forages and rumen contents are actively involved in the etiology of grass tetany in ruminants.
Afternoon Water Deficits and Grain Yields in Old and New Soybean Cultivars1
Authors: Boyer J. S. , Johnson R. R. , Saupe S. G.
Published: July 2010

Plant water deficits affect many metabolic processes, and soybean (Glycine max L. Merr.) is subject to water deficits during midday even when soil water is adequate under field conditions. Our objective was to determine if yield improvement by plant breeding has been associated with avoidance of these deficits in soybean. A 3‐ year experiment was conducted on highly productive soils in central Illinois with two soybean maturity groups each represented by four cultivars. The cultivars had been released between 1911 and 1968 in the USA.

Soil water availability was high in all 3 years. However, leaf water potentials were frequently below −11 bars at midday, which we defined as a water deficit. Cultivars with low yields experienced larger water deficits than those with high yields. The largest water deficits were found in the oldest cultivars and were present in all the fully illuminated leaves of the canopy. The deficits were large enough to be potentially inhibitory to afternoon photosynthesis and other metabolic processes.

Considerable yield improvement was apparent in the newer cultivars of both maturity groups when their yields were compared with those of older cultivars in the common environment represented by this experiment. Rooting densities of two cultivars showing extremes of midday water deficits indicated that the cultivar with the least water deficit (‘Wayne’) had a greater root density than the cultivar with the largest deficit (’Richland’).

The data suggest that old cultivars experience yield inhibiting water deficits at midday in central Illinois in soil containing adequate water. Breeding soybean for high yield has, at the same time, selected for superior shoot water status in midday, perhaps as a result of increased root densities.
Manure and Inorganic Fertilizer Effects on Sorghum and Sunflower Growth on Iron‐Deficient Soil1
Authors: Mathers A. C. , Thomas J. D. , Stewart B. A. , Herring J. E.
Published: July 2010

Iron chlorosis occur in grain sorghum [Sorghum bicolor (L.) Moench] and other Fe‐inefficient crops on calcareous soils in spots throughout the Great Plains. Economical control of Fe deficiency in these crops will allow them to be grown in places where they are otherwise not adapted.

Grain sorghum (‘Dekalb E‐59’) and sunflower (Helianthus annuus L. ‘Hybrid 896’) crops were grown on Arch fine sandy loam (Ustochreptic Calciorthid of the fineloamy, mixed thermic family) to compare their growth on calcareous soil and to study the effects of soil treatments with beef feedlot manure (11 and 33 metric tons of dry matter/ha), and inorganic N, P, and Fe (168‐56‐22) kg/ha) fertilizer. Sunflower seed yield was not changed significantly by any of the treatments. In 1977, the second year of the study, sorghum grain yield where N + P was applied was about half that of the check plot. However, in 1978 forage yield was reduced only about 10% below the check by N + P. Iron‐deficiency symptoms in sorghum were very severe on both check and N + P treatments; many sorghum plants died and others did not produce heads. When 22 kg/ha Fe was added with the N + P, grain yield was increased 66% over the check in 1977, and forage yield was twice that of check in 1978. Sorghum grain yield where manure was applied was three times the yield on check Plots in 1977, indicating that manure keeps both Fe and P available for use by grain sorghum on calcareous soil. The study also showed that sunflower is not highly sensitive to iron deficiency and could serve as an alternative crop for iron‐deficient soils.
Effectiveness of Nitrapyrin with Surface‐Applied Fertilizer Nitrogen in No‐Tillage Corn1
Authors: Frye W. W. , Blevins R. L. , Murdock L. W. , Wells K. L. , Ellis J. H.
Published: July 2010

Nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine] has been shown to slow the nitrification process by selectively inhibiting nitrifying soil bacteria, thus keeping N less susceptible to losses by leaching and denitrification. Since nitrapyrin is volatile, the manufacturer recommends incorporation into the soil immediately after applying. However, in no‐tillage production of corn (Zea mays L.), fertilizers usually are not incorporated. The objective of this study was to determine the effectiveness of nitrapyrin sprayed onto granular ammonium nitrate and urea fertilizers which were then applied to the soil surface for no‐tillage corn. Eight field experiments were conducted at four locations in Kentucky over a 5‐year period on soils that are usually wet during the spring. Nitrogen fertilizers were applied at rates ranging from 0 to 180 kg/ha of N. The rate of nitrapyrin application was 0.56 kg/ha. Nitrapyrin resulted in increased corn yields in most cases where N fertilizers were applied at yield‐limiting rates. This study indicated that nitrapyrin functions effectively for no‐tillage corn when applied directly to N fertilizer granules and broadcast on the soil surface. It was thought that volatilization of nitrapyrin was not great enough to render it ineffective when concentrated in the soil with the NH4+. Grain yield response in notillage corn may be expected when environmental conditions would cause severe leaching or denitrification losses and plant growth limitation without nitrapyrin.
Temperature Effect on the Inclination of Lateral Roots of Soybeans1
Authors: Kaspar T. C. , Woolley D. G. , Taylor H. M.
Published: July 2010

Genetic and environmental factors influence the size and shape of soybean (Glycine max (L.) Merr. root systems. Ten soybean lines were grown in sand culture at four different sand temperatures (10.0, 15.6, 21.1, and 26.7 C) to determine if temperature affects the angle of inclination of soybean lateral roots. The plants were grown in a growth chamber set for a constant air temperature (± 2.4 C) equal to the treatment temperature. The treatments were imposed until the unifoliate leaves had spread apart and unfolded. The sand was then washed from the roots, and a tracing on acetate was made of the root sysem, which was suspended in water at the time. The inclination of the lateral roots of each plant was determined from the acetate tracings by averaging the measured angles between the horizontal and the 10 up permost lateral roots. The effects of temperature, lines, and the interaction of temperature and lines were significant. The maximum angles of inclination occurred at either 26.7 or 21.1 C, and the minimum values at 10.0 C for most of the lines. ‘Hawkeye’ was not affected by temperature and had the largest angle of inclination averaged over the four temperature treatments. ‘Clark 63’ had the largest increase in the angle of inclination with an increase in temperature.
Basic Cation Saturation Ratios as a Basis for Fertilizing and Liming Agronomic Crops: I. Growth Chamber Studies1
Authors: Eckert D. J. , McLean E. O.
Published: July 2010

Basic cation saturation ratios are often used as a basis for making fertilizer and lime recommendations; however, little expermental evidence is available to support or refute the concept. This study was conducted to evaluate crop growth as influenced by varying soil cation ratios. A Loudonville silt loam (Ultic Hapludalf, fine loamy, mixed, mesic) was amended with K. and Mg to the following levels: 2.5 and 5% base saturation of K; 4, 8, and 16% Mg; and with Ca as Ca(OH)2 to pH 5, 6, and 7. The soil was then cropped with German millet (Setaria italica L. Beauv.) and alfalfa (Medicago saliva L.). Maximum yield of German millet was obtained at several soil K/Mg/Ca ratios. Yield increased as soil and plant Mg/Ca ratios increased, except where high soil Mg and low soil Ca levels induced Ca deficiency in the plants. Alfalfa also grew well at several ratios, particularly at the higher soil pH levels. The data indicated that balance of cations in the soil was unimportant, except at the extremely wide ratios where deficiencies of one element were caused by excesses of others. Hence, no best ratio existed for either or both crops.
Effects of N Fertilization and Cutting Schedules on Stockpiled Tall Fescue. II. Forage Quality1
Authors: Collins Michael , Balasko J. A.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) is the coolseason grass used most frequently to extend the grazing season in mid‐latitude states of the midwestern and eastern United States. Insufficient information is available regarding the influence of fertilization and harvest management on the quality of stockpiled tall fescue forage available during winter. Results of two field experiments dealing with the influence of cutting and N fertilization management on stockpiled tall fescue quality and chemical composition are reported.

In Exp. I, treatments consisted of four N rates: 0, 60, 120, and 180 kg/ha applied as split applications of one‐half in March and one‐half in August; three dates when stockpiling began (1) mid‐June, (2) early July, and (3) mid‐July; and three autumn and winter harvest dates (1) mid‐December, (2) mid‐January, and (3) mid‐February. The soil used in Exp. I was a well‐drained loam (Typic Hapludults) with high levels of P and K. The treatment with the greatest influence on in vitro dry matter disappearance (IVDMD) was winter harvest date. Forage IVDMD decreased from 47.3% hi mid‐December to 41.1% by mid‐February. Crude protein (CP) concentration increased from 7.4% at 0 N to 10.4% at the 180 kg/ha N rate averaged over all other treatments and 2 years. Forage P and Mg concentrations were below minimum requirements for dry beef cows by late whiter.

In Exp. II, conducted on a silt loam soil (Typic Fragiudalfs), treatments included four N rates: 0, 75, 150, and 225 kg/ha applied at the last summer or autumn cutting which occurred in either early September, mid‐September, or early October. In this experiment, all accumulated forage was harvested in late winter. Nitrogen fertilization increased forage IVDMD and CP, water soluble carbohydrate, K, and Mg concentrations in the stockpiled forage. Data from the two experiments Indicate that supplementation of energy, P, and Mg may be necessary in utilizing stockpiled tall fescue during January and February.
Competition Between Adjacent Fruiting Forms in Cotton1
Authors: Kerby T. A. , Buxton D. R.
Published: July 2010

Cotton plants (Gossypium hirsutum L.) produce more fruiting forms that can be supplied assimilates, and competition and abortion occurs. The relationship is accentuated with narrow‐row, high population culture. This study was conducted to determine the extent that fruiting forms compete and influence abscission of adjacent fruiting forms. The study was also designed to determine if plant leaf type or plant density altered the effects of competition.

Normal, Okra, and Super Okra‐leaf cotton plants were grown in rows 51 cm apart in irrigated basins at 11.2 and 18.5, and 10.0 and 20.0 plants/m2 in 1973 and 1974, respectively. The soil type was a coarse‐loamy, thermic, Typic Torrifluvent (a member of the Gila series). Fruiting positions reaching anthesis were tagged daily. Fruiting positions on sympodial branches were identified as L1 for the first position and L2 for the second position.

Averaged over genotypes, plant densities, and years, 25% of the positions at L2 retained bolls when L1 aborted as a square compared to only 10 and 11% when L1 aborted as a young boll or retained a boll until maturity, respectively. Averaged over plant densities and years, when bolls were retained at L1, 60% of the positions at L2 aborted as young bolls for Super Okra‐leaf plants compared to only 34% for normal‐leaf plants. However, normal‐leaf plants aborted 52% of the positions at L2 as squares compared to only 32% for Super Okra‐leaf plants. Averaged over genotypes and years, when L1 retained a boll, high plant densities aborted 45% of the positions at L2 as squares compared to 35% for low plant densities.

Under narrow‐row, high‐population culture it was apparent that adjacent fruiting forms competed for available assimilates, and that the potential for developing more than one boll per sympodial branch was low. The use of cultivars which produce long sympodial branches appears to be inefficient under this system.
Yield and Quality Changes with Maturity of Silage‐Type Sorghum Fodder1
Authors: Cummins D. G.
Published: July 2010

Maturity at harvest is a major factor in determining the quality of silage‐type sorghum [Sorghum bicolor (L.) Moench], and there is evidence of quality differences among hybrids at equivalent growth stages. The objectives of this study were to determine the effects of maturity in four height classes of sorghum hybrids and their interactions on dry forage yields and its composition, and to determine quality of heads, leaves, and stalks in terms of in vitro dry matter digestibility (IVDMD) and acid detergent fiber (ADF). Four hybrids, representing height classes of 4.5, 5.5, 6.5, and 7.5 m, were grown under conventional production practices and harvested at the late milk, early dough, dough, and hard dough stages of grain maturity. Dry matter accumulation in all hybrids remained similar after reaching 24.6%. The shorter hybrids had maximum head percentage earlier in maturity than the taller hybrids. The tallest hybrid had higher stalk percentage later in maturity than did the shorter hybrids. Head IVDMD of the short hybrids with high head percentage remained constant or increased with advancing maturity, while that of the tall hybrid with lower head percentage decreased later in maturity. Stalk IVDMD of the tallest hybrid increased with maturity while the other hybrids decreased with maturity. Stalk ADF of the tallest hybrid decreased with maturity, while that of the other hybrids remained relatively constant. Stalk IVDMD and ADF were negatively correlated (r = −0.63**). These results show the potential for improvement in quality of silage‐type sorghum hybrids through selection of breeding lines that maintain high stalk quality late into maturity.
Alfalfa Yield and Water Use When Forced into Dormancy by Withholding Water During the Summer1
Authors: Metochis Chr. , Orphanos P. I.
Published: July 2010

Under the hot (air temperature reaching 40 C) and dry conditions of the inland areas of Cyprus, alfalfa (Medicago sativa L.) yields decline markedly in July to August. Water‐use efficiency (kg DM/m3 of water taken up) decreases from 2.25 to 2.85 in March through May to 0.50 to 0.65 kg/m3 in July through August. This study evaluated several alternatives for increasing water‐use efficiency for alfalfa production.

Not irrigating the alfalfa for one growth period in July reduced yield during that period by 68%. However, not irrigating for a second or a third growth period resulted in no forage yield during these periods. When irrigation was resumed, plots not irrigated for one or two growth periods yielded as much as plots irrigated at all growth periods, but plots not irrigated for three growth periods produced 20% less yield during the first period following resumption of irrigation. In the following growth periods, however, these yielded as much as plots irrigated at all growth periods. Discontinuing irrigation for the three growth periods of July to August reduced annual dry matter yield to 17,700 kg/ha compared to 21,500 kg/ha when adequate water was applied throughout, but saved 610 mm of irrigation water out of a normal annual irrigation requirement of 1,400 mm. As a result, water‐use efficiency in 1978–1979 increased from 1.32 kg DM/m3 of water taken up when adequate irrigation was applied throughout the growing season to 1.60 when irrigation was withheld for the three growth periods of July to August. The corresponding figures for 1979–1980 were 1.41 and 1.81, respectively.
Relationships Among Components of Seed Yield in Blue Grama1
Authors: Wilson A. M. , Cuany R. L. , Fraser J. G. , Oaks W. R.
Published: July 2010

High caryopsis weight in forage plants generally increases seedling emergence, vigor, and establishment. Breeding for improved caryopsis weight in blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] can be successful only if variations in average caryopsis weight of a plant are not simply a result of variations in the components of caryopsis yield. The objectives of this study were to determine the effects of spikes/culm, spikelets/spike, and fertility on caryopsis weight and the effects of spikes/culm, spikelets/spike, fertility, and caryopsis weight on yield/culm. In a 1,080−plant, spaced field nursery, average caryopsis weight varied among plants from 25 to 70 mg/100. Multiple regression and path analysis indicated that spikes/culm, spikelets/spike, and fertility accounted for only 5% of the variation in caryopsis weight. These components of yield, with caryopsis weight, accounted for 86% of the variation in caryopsis yield/culm. In a polycross nursery of 60 plants selected from the previous nursery primarily for high caryopsis weight, blue grama clones differed significantly in all of the components of caryopsis yield/culm. Blocks in the polycross nursery differed significantly in all components of yield/culm except average caryopsis weight of a plant. These results suggest that it would be possible to select blue grama plants for both high caryopsis weight and high seed yields.
Salt Distribution and Water Consumption from a Water Table With and Without a Crop1
Authors: Saleh Hamed H. , Troeh Frederick R.
Published: July 2010

This study was undertaken to quantify the soil salinization process and relate it to soil depth, cropping, and water table variables. Such information has been needed but unavailable. Data were gathered by measuring the upward movement of water and salt from simulated groundwater. The work was done with 30‐cm square soil columns 50 and 75‐cm tall that were suspended in trays of artificial groundwater. The experiment was located in a greenhouse to create an arid environment. Sudangrass [Sorghum sudanense (Piper) Stapf.] was grown on half of the columns and the others were fallowed. Water consumption was increased by the shallower depth to groundwater, by the less saline groundwater (electrical conductivity 4 mmhos/cm vs. 11) and by the presence of a crop. The crop had little effect on the salt concentration at the moist surface of the 50‐cm columns but reduced the salt accumulation at the already drier and less salty surfaces of the taller columns. Salt accumulation in the root zone was increased by the presence of a crop.
No‐Till Soybeans in Forage Grass Sod1
Authors: Elkins D. M. , George J. D. , Birchett G. E.
Published: July 2010

No‐till planting of soybeans [Glycine mar (L.) Merr.] is a widespread practice in the midwestern and southern U.S.A. However, the vast majority of this hectarage is double‐crop soybeans planted in wheat (Triticum aestivum L.) or another small grain after grain harvest. Occasionally, soybeans have been planted in a chemically‐controlled winter cover crop. Little work has been reported on the possible merits of planting soybeans in a grass sod, which would offer the advantages of reduced soil erosion hazards and greater flexibility in soybean production systems.

Field studies were designed to investigate the success of no‐till soybean production in forage sod. The soils representing different sites and experiments were Weir silt loam (Typic Ochraqualf), Stoy silt loam (Aquic Hapludalf), Alford silt loam (Typic Hapludalf), and Ebbert silt loam (Argiaquic Argialboll). Soybeans were planted in a tall fescue (Festuca arundinacea Schreb.) sod for 4 years at the Carbondale location, and for 2 years in Kentucky bluegrass (Poa pratensis L.) at the Belleville location in southern Illinois. When rainfall was adequate, no‐till soybean production in grass sods was highly successful, with yields as much as 4,308 kg/ha in tall fescue in 1977 and 4,704 kg/ha in tall fescue and 4,119 in Kentucky bluegrass in 1979. In the 2 years of plentiful moisture, adjusted herbicide rates allowed persistence or autumn regrowth of up to 40% of the forage grass, which could be an important factor regarding autumn and winter grazing and erosion control.

The best herbicide treatments in these studies for allowing a combination of soybean yield and forage grass persistence or regrowth was paraquat (1, 1′‐dimethyl‐4,4′‐bipyridinium ion) alone at 0.6 kg/ha, paraquat at 0.6 kg/ha in combination with metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl) acetamide] at 3.4 or 4.5 kg/ha or with mefluidide{N‐[2,4‐dimethyl‐5‐[[trifluoromethyl) sulfonyl] amino] phenyl] acetamide} at 0.6 kg/ha. Another promising combination was glyphosate [N‐(phosphonomethyl) glycine] at 1.1 kg/ha plus metribuzin [4‐amino‐6‐tert‐butyl‐3(methylthio)‐as‐triazin‐5 (4H)‐one] at 1.1 kg/ha. All of these treatments resulted in no‐till soybean yields exceeding 4,000 kg/ha, when growing season rainfall was adequate, and tall fescue maintenance or regrowth resulting in 25 to 40% sod cover in the autumn.
Long‐term N‐P Fertilizer and Climate Influences on Morphology and Yield Components of Spring Wheat1
Authors: Black A. L.
Published: July 2010

The long‐term availability of one‐time, high‐rate, broadcast application of P fertilizer has not been adequately evaluated in relation to variable water supplies and N fertilization for optimum production of spring wheat (Triticum aestivum L.) on dryland. Additional knowledge of the interrelationship of plant morphological characteristics, plant growth, and components of grain yield to soil fertility will be useful in the development and validation of wheat yield models.

Spring wheat was grown for 12 years (winter wheat in 1 year) in two separate alternate crop‐fallow plot series on a Williams loam (fine‐loamy, mixed, Typic Argiborolls). Phosphorus fertilizer as treble superphosphate was broadcast at 0, 22, 45, 90, and 180 kg P/ha at the beginning of the study in 1967 or 1968. Ammonium nitrate was broadcast each crop year at 0, 45, and 90 kg N/ha. With relatively shallow sweep‐tillage, soluble P increased proportionate to rate of P applied and remained relatively high over the 12‐year period in the 0 to 15.2 cm soil depth. Significant grain yield responses to initial and residual P fertilization occurred up to a soluble P level of about 15 ppm independent of available water supplies. In contrast, yield responses to N fertilization increased as total available water supplies increased from 22.6 to 52.8 cm.

Number of heads/m2 could be predicted more reliably from number of adventitious roots/plant than from number of tillers. Number of head/m2 accounted for 86% of the yield variance associated with years (climate) and N‐P fertilizer treatments excluding one disease‐year when number of kernels/head was significantly decreased. Combining number of heads/m2 and kernels/head accounted for 91% of the yield variance associated with fertilizer treatments over all years combined. Predicting grain yields from dry matter production at tillering or heading was unsatisfactory compared to yield predictions based on total dry matter production or straw production at maturity.
Response of ‘Tifton 44’ and ‘Coastal’ Bermudagrass to Soil pH, K, and N Source1
Authors: Belesky D. P. , Wilkinson S. R.
Published: July 2010

A winter‐hardy bermudagrass [Cynodon dactylon (L.) Pers.], ‘Tifton 44’ with high productivity and nutritive quality should expand the range of bermudagrass production. Both productivity and winter survival are dependent upon soil fertility conditions. An investigation was designed to compare the productivity, winter survival, and mineral composition of ‘Coastal’ and Tifton 44 bermudagrass grown in Cecil sandy loam (Typic Hapludult, clayey, kaolinitic, thermic) soil as affected by pH level (4.1, 5.5, 6.5) rate of K (0, 70, 140 kg K/ha) and N source (NaNO3, urea) under greenhouse conditions. More sprigs of both cultivars survived establishment when treated with urea rather than NaNO3, regardless of K level. Survival was also improved at pH 5.5 and 6.5 over 4.1 for either cultivar. Coastal tended to outyield Tifton 44 when expressed on a yield per pot. Yield of Coastal was improved with increasing K rate regardless of N source while Tifton 44 yield was not improved by increasing K when NaNO3 was applied. Concentrations of K, Na, and Mg were greater in Tifton 44 than in Coastal, whereas Ca was greater in Coastal than in Tifton 44. Concentrations of Mg in both cultivars were higher with urea fertilization than with NaNO3 at pH 5.5 and 6.5. There were no significant trends for the micronutrients Cu, Mn, Fe, and Zn although increasing pH tended to decrease Mn and Zn concentrations for either cultivar. Winter survival was assessed by maintaining plants out of doors under field conditions at Blairsville, Ga., UGA Mountain Branch Experiment Station. Root and rhizome weights were significantly increased by applications of K to Tifton 44 which survived exposure to winter conditions at Blairsville, Ga. while Coastal did not survive winter exposure.
Analysis of Combined Experiments1
Authors: McIntosh M. S.
Published: July 2010

Most field experiments are conducted over two or more locations or years, yet statistical references do not contain sufficient detail for complete analysis. The purpose of this paper is to provide a reference for analysis of combined experiments. Tables include sources of variation, degrees of freedom, and F‐ratios for one factor and split‐plot experiments combined over locations and/or years. The F‐ratios are given for fixed, mixed, and random models.
Influence of pH on Yield and N and P Nutrition of Alfalfa Grown on an Andic Mission Silt Loam1
Authors: Mahler R. L.
Published: July 2010

Yields of alfalfa (Medicago sativa) average only 7500 kg/ha on ash‐influenced Mission silt loam (coarse‐silty, mixed, frigid Andic Fragiochrepts) in northern Idaho. This relatively poor growth is commonly attributed to the chemical characteristics of these andic soils. The objectives of this study were to: (1) determine the effect of soil pH on alfalfa establishment and growth, (2) N and P uptake, (3) Rhizobium meliloti survival, and (4) P availability in a Mission soil under greenhouse conditions. Aluminum sulfate and finely ground calcium carbonate were used to adjust soil pH. Soil pH values were 4.8, 5.1, 5.6, 6.2, 6.4, 6.9, 7.0, and 7.4. Alfalfa was grown in 150‐mm pots in the greenhouse and harvested five times at approximately 20‐day intervals. Yield was measured and plant material was analyzed for total N and P. Rhizobium meliloti populations were monitored using the most probable number (MPN) technique and available soil P was determined using sodium acetate extractant. Manipulation of pH in the Mission soil was found to have a significant effect on alfalfa growth, tissue N and P concentration, survival of R. meliloti in the soil, and on sodium acetate extractable soil P. In general, tested parameters increased with increasing pH. Greatest forage yield occurred at a pH of 7.4. The andic nature of the Mission soil requires a pH adjustment above pH 6.6 for acceptable alfalfa establishment and yields, probably because of the relatively high degree of Al saturation that occurred at pH values below 6.6. This is in sharp contrast to non‐andic northern Idaho soils where alfalfa yields are usually not adversely affected above pH 5.6.
Carbon Dioxide and Agricultural Yield: An Assemblage and Analysis of 430 Prior Observations1
Authors: Kimball B. A.
Published: July 2010

The probable effect of the increasing global atmospheric CO2 concentration on agricultural yields was evaluated. More than 430 observations of the yield of 37 species grown with CO2 enrichment were extracted from more than 70 reports published during the past 64 years. Most of the studies were performed in greenhouses or growth chambers. Open fields might respond less than greenhouses or growth chambers to increased CO2 because nutrient levels in general world‐wide agriculture are lower than those in the indoor studies, or open fields might respond more because light levels are generally higher outside. The data also were dominated by high value crops, but results should be applicable to the three‐fourths of the world agriculture represented by the C3 crops and possibly to the remaining C4 crops as well. Keeping these limitations of the data in mind, the analysis showed that yields probably will increase by 33% (with a 99.9% confidence interval from 24 to 43%) with a doubling of atmospheric CO2 concentration.
Costs of Measuring Leaf Area Index of Corn1
Authors: Daughtry C. S. T. , Hollinger S. E.
Published: July 2010

Leaf area index (LAI) is an important biophysical descriptor of crop canopies. Accurate measurements of W are laborious and time‐consuming. Many methods of measuring LAI of corn (Zea maysL.) have been reported and vary greatly in their accuracy, precision, bias, and ease of measurement. We examined the magnitude of plant‐to‐plant variability of leaf area of corn plants selected from uniform plots and evaluated four representative methods for measuring LAI. The number of plants required and the relative costs for each sampling method were calculated to detect 10, 20, and 50% differences in W using 0.05 and 0.01 tests of significance and a 90% probability of success (β = 0.1). The natural variability of leaf area per corn plant was nearly 10%. Additional variability or experimental error may be introduced by the measurement technique employed and by nonuniformity within the plot. Direct measurement of leaf area with an electronic area meter had the lowest coefficient of variance (CV), required that the fewest plants be sampled, but required approximately the same amount of time as the leaf area/weight ratio method to detect comparable differences. Indirect methods based on measurements of length and width of leaves required more plants but less total time than the direct method. Unless the coefficients for converting length and width to area are verified frequently, the indirect methods may be biased. When true differences in LAI among treatments exceed 50% of mean, all four methods are equal. The method of choice depends on the resources available, the differences to be detected, and what additional information, such as leaf weight or stalk weight, is also desired.
Growth and Water Use of Tall Fescue as Influenced by Several Soil Drying Cycles1
Authors: King M. J. , Bush L. P.
Published: July 2010

Many investigations have studied various physiological processes using plants watered on a schedule with the effect of this watering schedule seldom considered significant. An understanding of the effect of watering frequency on growth and water use is required to understand water stress tolerance of tall fescue (Festuca arundinacea Schreb.). Experiments were designed to evaluate the effect of watering schedule in greenhouse grown tall fescue on growth, water use, and meristem tissue water status. Growth and water use as well as water, osmotic, and turgor potential of the leaf meristematic region were measured on tall fescue seedlings that had been exposed to several Maury soil (a fine, mixed, mesic Typic Paleudalfs) drying cycles (stressed and daily watered). Growth, measured as leaf extension rate (LER), was greater for seedlings watered to field capacity every 4th day than daily watered seedlings when soil of both treatments was allowed to dry. No significant difference in water potential or osmotic potential was observed during the experiment, and the differential LER was not dependent on turgor potential of the meristematic area which was similar to both treatments. Water use was 50 to 100% higher in control seedlings during the first 48 h of a soil drying cycle than in stressed seedlings. After several soil drying cycles the enhanced growth of stressed plants increased as high as 280%, then declined over the next 24 days of daily watering to about 50% above the control. The enhanced LER did not result in greater shoot fresh weights, but, repeated soil drying depressed root development. Consequently, growth, water status, and water use by tall fescue plants during an experiment must be evaluated in terms of the plants prior water stress history.
Performance of Selected Soybean Cultivars in a Field Infested with Mixtures of Root‐Knot, Soybean Cyst, and Other Phytonematodes1
Authors: Weaver D. B. , Rodriguez‐Kabana R. , Robertson D. G.
Published: July 2010

Information on relative nematode resistance in soybean cultivars is needed because of recent Environmental Protection Agency action prohibiting the use of ethylene dibromide as a soil fumigant for nematode control. Performance of 10 soybean [Glycine max (L.) Merr.] cultivars was studied near Elberta, AL for 2 years in a Eustis loamy fine sand (sandy, siliceous, thermic, Psammentic Paleudults) that was heavily infested with Southern root‐knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] and lightly infested with race 3 of the soybean cyst nematode (Heterodera glycines Ichinohe). The objective was to determine relative resistance to nematodes among cultivars by measuring yield and nematode numbers in unfumigated plots and in plots fumigated with 18.7 L ha−1 ethylene dibromide. Seed yields of all cultivars were increased an average of 396% in 1982, and 138% in 1983 by fumigation. ‘Foster’ and ‘Kirby’ had the highest seed yields in unfumigated soil. All cultivars sustained significant nematode larval populations near harvest with greater numbers associated with the higher yielding cultivars. Foster and Kirby offer a practical approach to management of heteroderid nematodes in the absence of an economical, efficient nematicide.