bluuebunny/crossref_metadata_2025 huggingface dataset:
Corn Growth Response to Temperature and Photoperiod II. Leaf‐Initiation and Leaf‐Appearance Rates1
Authors: Warrington I. J. , Kanemasu E. T.
Published: July 2010

The prediction of evapotranspiration and canopy photosynthesis, for example in crop simulation modeling and in remote sensing applications, requires a quantitative description of the influence of environmental factors such as temperature and photoperiod on leaf area development. The objectives of this study were to define the temperature response curves and the responses to photoperiod for two components of leaf area development in corn (Zea mays L.), namely leaf‐initiation rate and leaf‐appearance rate. Plants of two corn hybrids, W346 and XL45, were grown in controlled environments under 17 day/night temperature regimes ranging from 16/6 to 38/33°C (12 h photoperiod) and under three photoperiod regimes (12, 14, and 16 h) at two selected temperatures (constant 18 and 28°C). Leaf‐initiation rates, determined from frequent dissections, were constant from seedling emergence until tassel initiation in all treatments. Similarly the appearance rate of the first 12 leaves was constant from seedling emergence onward, but after leaf 12, appearance rate increased, presumably as a consequence of rapid stem elongation and because the upper stem leaves were smaller and required less time to expand. Both cultivars had similar leaf‐initiation and leaf‐appearance rates under each day/night temperature regime. Data from the day/night temperature regimes were used to derive rate of leaf‐initiation (leaf primordia/day) vs. temperature and rate of leaf‐appearance (leaves/day) vs. temperature response curves which could be described by third and fourth‐degree polynomial equations, respectively. Previously published values for leaf‐appearance rates have varied by up to three or four‐fold at any particular temperature, primarily because of different definitions that have been used for appearance rate. Values for the rate of change in leaf appearance rate with temperature within the 16 to 26°C range, however, were more similar ranging from 0.21 to 0.30 leaves day−1°C−1 and were similar to a value of 0.23 leaves day−1°C−1 obtained in this study. Both leaf‐initiation and leaf‐appearance rates increased with an increase in photoperiod, particularly under constant 18°C conditions. Cultivar W346 appeared to be more responsive to photoperiod than XL45.
Seeding Rate and Seeding Date Effects on Spring Seeded Small Grain Cultivars1
Authors: Ciha A. J.
Published: July 2010

Over the past 15 to 25 years the plant characteristics of small grains have changed; however, little is known in the Pacific Northwest about the production practices necessary to maximize grain yields with these short statured, early maturing, lodging resistant small grain cultivars. A 4‐year (1977 to 1980) field study at Pullman, Wash. on a Palouse silt loam (fine‐silty, mixed, mesic pachic Ultic Haploxerolls) examined grain yield and test weight responses to three seeding dates (early, normal, and late) and three seeding rates (40, 75, and 110 kg/ha). Five spring barley (Hordeum vulgare L.), three spring oats (Avena sativa L.), and five spring wheat (Triticum aestivum L.) cultivars were tested. Significant cultivar × seeding date and cultivar × seeding date × year interactions existed for grain yield. Seeding date delays past the normal date significantly reduced grain yield and test weight for the majority of the cultivars when averaged over the 4‐year period. However, several cultivars showed yield reductions with seeding date delays past the earliest date. Several cultivars showed yield reductions with the lowest or highest seeding rate. Reduced yields with the 110 kg/ha seeding rate were caused by lodging. The non‐significant seeding rate × seeding date and cultivar × seeding rate × seeding date interactions for yield indicate that increasing the seeding rate with later seeding dates was not beneficial in increasing grain yield. Test weight values for the small grains averaged over years were generally reduced with late seeding dates.
Alfalfa Stem and Leaf Growth during Water Stress1
Authors: Brown P. W. , Tanner C. B.
Published: July 2010

Alfalfa (Medicago sativa L.) requires irrigation in semiarid and arid regions and improved yields often result from irrigation in subhumid and humid areas. Despite the importance of optimizing water management for alfalfa leaf and stem growth, no field study has been reported which relates alfalfa leaf expansion or stem extension to plant water deficits. The objective of our research was to determine how leaf expansion, stem elongation, and stomatal response of alfalfa related to the water potential in alfalfa, field‐grown on Plainfield loamy sand (mixed, mesic Typic Udipsamment). Periodic measurements of alfalfa stem extension and leaf expansion (area derived from length and width measurements) were related to leaf water potential (ΨL) measured with a pressure chamber, soil matric potential (Ψm, measured with tensiometers, and stomatal conductance measured with porometers. For wellwatered alfalfa, expansion curves of individual leaves were sigmoid‐shaped, while internode extensions were nearly exponential with time through about 95% of the total extension. The primary leaf attached at the top of an internode expands to nearly full size before the internode begins rapid extension. The growth of individual leaves and internodes collectively results in nearly constant rates of leaf expansion and stem extension during vegetative regrowth. When Ψm at 30 cm decreased to −0.35 bar, afternoon ΨL decreased to about −8 bars, about 2 bars below irrigated alfalfa, and both the growth rate (GR) and relative growth rate (RGR) of stressed leaves and stems were significantly less (p < 0.1) than well‐watered leaves and stems. In stressed treatments, wilting, gray‐green canopy color, decreased afternoon stomatal conductance, and a 50% decrease in RGR as compared to irrigated treatments resulted when afternoon ΨL decreased to about −15 bars even though Ψm exceeded −0.1 bar at 90 and 150 cm. Alfalfa extracted 85% of its total water from the 1st meter of soil prior to the onset of decreased afternoon stomatal conductance, but nearly equal percentages from each of the top 2 m of soil afterward. Little shoot growth occurred when ΨL dropped below −10 bars. Development of water stress 2 weeks after cutting reduced alfalfa leaf size, internode length, and dry matter production, but not leaf and internode number or stem density. The percentage of total forage dry weight in leaves (LPDW) decreased linearly with stem height resulting in higher LPDW and a better quality forage in stress‐stunted forage. Cool night temperatures limited growth of well‐watered alfalfa.
Steer Performance and Association of Acremonium coenophialum Fungal Endophyte on Tall Fescue Pasture1
Authors: Hoveland C. S. , Schmidt S. P. , King C. C. , Odom J. W. , Clark E. M. , McGuire J. A. , Smith L. A. , Grimes H. W. , Holliman J. L.
Published: July 2010

Poor animal performance on tall fescue (Festuca arundinacea Schreb.) pasture may be associated with toxic products produced by the fungal endophyte Acremonium coenophialum Morgan‐Jones and Gams (previously identified and referred to as Epichloe typhina (Fries) Tulasne). The object of this study was to determine steer performance on ‘Kentucky 31’ tall fescue pastures which were either heavily infested or relatively free of the fungal endophyte. Replicated 1.2 ha paddocks were located in west central Alabama on three soils, Sumter clay (fine silty, carbonatic, thermic Rendolic Eutrochrept), Houston clay (very fine montmorillonitic, thermic Typic Chromudert), and Eutaw clay (very fine, montmorillonitic, thermic Entic Pelluderts). They were fertilized annually with 224 kg N ha−1 and grazed with yearling steers. The grazing season during the 4‐year period averaged from 23 October to 24 December and 26 February to 16 June. Tall fescue, averaging 94% of plants fungus infested, produced 768 animal days ha−1 and produced 384 kg beef ha−1 with an average daily gain (ADG) of 0.50 kg. Tall fescue with less than 5% of plants infested produced 593 animal days ha−1 and produced 492 kg beef ha−1, with an ADG of 0.83 kg. Rectal temperatures were 0.8 °C higher and hair coats much rougher on steers which grazed fungus‐infected grass rather than grass free of the fungus. Results of the study furnish further evidence that the fungal endophyte, A. coenophialum, is associated with low performance of steers on tall fescue pasture. In the absence of the fungal endophyte, ADG of steers on tall fescue is high and similar to that on small grain pastures.
Central Appalachian Hill Land Pasture Evaluation Using Cows and Calves. I. Ordinary and Generalized Least Squares Analysis for an Unbalanced Grazing Experiment1
Authors: Burns J. C. , Giesbrecht F. G. , Harvey R. W. , Linnerud A. C.
Published: July 2010

In formal grazing trials, especially those involving cow‐calf test units, the land area needed and cost of initiation and operation limit the number of treatments simultaneously evaluated. Often it is desirable to terminate and add a new treatment or simply add a new treatment during the trial. The analysis of the resulting unbalanced data poses several difficulties. The objective of this paper was to evaluate a two‐step statistical procedure to analyze cow‐calf responses from an unbalanced grazing trial. Per animal and per hectare responses and pasture characteristics were obtained from a 6‐year study conducted in the Appalachian hill land region. Soils ranged from a Typic Hapludult to a mixed, mesic Hapludult. Pastures were a mixture of Kentucky bluegrass (Poa pratensis L.), white clover (Trifolium repens L.), and orchardgrass (Dactylis glomerata L.) and 12 agronomic or animal management treatments were evaluated. Some of the original treatments were deleted and new ones added, but not always on fields already in the study or in equal replication. The full 6‐year unbalanced data set contained two balanced subsets used to evaluate results from the two‐step analysis. The statistical procedure involved a fist step of estimating variance components for year and field effects. These were applied in a second step as a weighted adjustment through a generalized least squares analysis. The variance components, treatment mean adjustments and associated standard deviations from the two‐step analyses were compared with ordinary least squares (OLS) analyses where years were fixed effects and fields ignored (OLS1) or year and field effects were both ignored (OLS2). Year and field variances for cow and calf daily gains, pasture productivity estimates and pasture measurements from the 6‐year unbalanced data had similar magnitude and structure from the two‐step procedure compared with the two balanced data subsets. The residual error from OLS1 and OLS2 compared with the two‐step analysis were consistently larger. The two‐step analysis (unbalanced data) gave biologically rational adjustments of treatment means and offers much potential for use in experiments requiring high resources and where unbalance is likely for maximum treatment evaluation.
Soybean Water Status and Canopy Microclimate Relationships at Four Row Spacings1
Authors: Sojka R. E. , Parsons J. E.
Published: July 2010

There is little field data relating plant water status and canopy microclimate of determinate soybean [Glycine max (L.) Merr.] cultivars grown in humid environments. Also, few observations of these parameters have been reported for the period prior to complete canopy closure. A field study was conducted in South Carolina in 1979 to determine these basic relationships for two determinate soybean cultivars, Davis (Group VI) and Coker 338 (Group VIII) grown in 1.02, 0.76, 0.51 and 0.36‐m row spacings. The experiments were conducted on a Norfolk loamy sand (fine‐loamy, siliceous, thermic, Typic Paleudult). Thermistor‐determined leaf temperatures (TL) and ambient temperatures (TA) were highly correlated, and no significant improvement in the correlation resulted from treating row spacing or diurnal periods separately. Both TL and ΔT (TL – TA) were highly correlated with pressure chamber determination of xylem pressure potential (ΨX). Parallel leaf diffusive resistance (R5) was not highly correlated with any of the canopy microclimate or water status parameters observed. Atmospheric vapor pressure deficit (VPD) was correlated with ΔT. Xylem pressure potential was very highly correlated with leaf vapor pressure deficit (LVPD). No row spacing effect on Ψx was observed, but mean seasonal midday Ψx was 0.10 MPa lower for Coker 338 than for Davis (P≤0.001) and osmotic potential was 0.20 MPa lower for Coker 338 than for Davis (P≤0.01). The authors propose that the slope of ΔT vs. VPD may be influenced by high prevailing relative humidity and heating of the canopy from exposed soil between rows in the period prior to complete canopy coverage.
Nitrification of Anhydrous Ammonia Related to Nitrapyrin and Time‐Temperature Interactions1
Authors: Gomes S. L. , Loynachan T. E.
Published: July 2010

The effects of time and temperature, with and without nitrification inhibitor, were evaluated on the rate of nitrification for field‐applied anhydrous ammonia on a Webster clay loam soil (fine loamy, mixed, mesic Typic Haplaquoll) in central Iowa. The purpose of the study was to document factors influencing the production of oxidized N, forms of N more easily lost from the soil by leaching or denitrification. Anhydrous ammonia at 180 kg N/ha was applied at three application dates in the fall of 1979 (9 October, 27 October, and 14 November) and three application dates in the spring of 1980 (15 April, 2 May, and 25 June). Plots with and without 0.56 kg/ha nitrapyrin were established on each date. Ammonium was found to be concentrated within a 5‐cm radius of the injection zone. The accumulation of heat units (HU), calculated by the summation of temperature (°C) multiplied by time (days), was shown to have a negative correlation with recoverable NH4‐N and followed the equation: %NH4‐N = −0.07 HU + 76.4, R2= 0.84*, significant at the 0.05 level. Thus, much of the variability of recovered NH4‐N could be explained by a time by temperature interaction. This suggests that a grower's decision to apply anhydrous ammonia in the fall when soil temperatures reach a given level, commonly 10˚C, should be tempered by the date. In early fall, more time is available for nitrification to occur before freezing of the soil, and a greater conversion of NH4‐N to N03‐N would be expected. In the presence of a nitrification inhibitor, higher percentages of NH4‐N were recovered for a similar heat‐unit accumulation. Regression equations predicted an 84% recovery with 233 accumulated heat units in the presence of nitrapyrin, compared with a 60% recovery without nitrapyrin. For an equal percentage of NH4‐N recovery the following spring, a grower could apply anhydrous ammonia earlier in the fall if nitrapyrin was used. According to the equations developed in this study for the 1979‐1980 season, a 9 October application of anhydrous ammonia with nitrapyrin would have resulted in approximately a 70% NH4‐N recovery in the spring of 1980, compared with the same recovery for a 23 November application without nitrapyrin.
Maturity Effects on Genotype × Environment Interactions in Grain Sorghum1
Authors: Saeed Mohammad , Francis C. A. , Rajewski J. F.
Published: July 2010

Genotype × environment (GE) interaction is an important consideration in plant breeding because of its effects on progress from selection. This study examines the effects of genotype maturity on GE interaction for grain yield and yield components. Fifty‐four grain sorghum [Sorghum bicolor(L.) Moench] genotypes included in three maturity groups, early, medium, and late, were evaluated in 48 environments across Nebraska and Kansas in 1978 and 1979. The soil ranged from sandy types (mixed, mesic Typic Ustipsamment) to intermediate types as represented by Typic Haplustoll, course‐silty, mesic and fine‐silty, mixed, mesic, Aridic Argiustoll, to clay loam at the opposite extreme (deep with high water holding capacity) as represented by fine, montmorillonitic mesic, Typic Argiuboll. In the analysis of variance combined over years and environments within year, genotype, genotype × year, and genotype × environment within year sums of squares were partitioned into components representing within and among maturity groups. More than half of the interaction effects sums of squares was attributed to differences among maturity groups. The GE interaction increased with an increase in duration of plant growth (maturity). Genotypes showed larger interaction with environments within year than with years, irrespective of maturity. The results suggest that a reliable evaluation of relative genotype performance can be made if the genotypes under test do not include a wide range of maturity. Minimizing differences in maturity among genotypes reduces GE interaction. Testing at more locations or environments at given locations should be done rather than testing in more years. For a desired level of precision, the amount of testing required for a set of genotypes with a wide range of maturity and long‐growth duration is greater than that required for genotypes with a narrow range of maturity and short‐growth duration. Increasing number of replications per test more than two, environments in a year more than eight, and years of testing more than two, was not effective in increasing efficiency in genotype evaluation, especially in early and medium maturing genotypes.
Leaf Area Development in Field‐Grown Soybeans1
Authors: Sinclair T. R.
Published: July 2010

Leaf area is critical for crop light interception, and thereby has a substantial influence on crop yield. In this research an attempt was made to characterize the development of soybean [Glycine max(L.) Merr.] leaf area by examining the process in two phases. First, the rate of increase of plastochron index as a function of temperature was evaluated under field conditions. A total of seven cultivars was studied during three cropping seasons on Arredondo fine sand (loamy siliceous hyperthermic Grossarenic Paleudalf). A linear response was confirmed in the rate of increase in plastochron index to temperature with a base temperature of 9 to 11°C for most cultivars. Second, an allometric model for predicting plant leaf area from plastochron index was developed. The same medel with differing coefficients was found to work well for all cultivars. A simplified procedure for estimating the coefficients of the model was developed and found to result in good predictions of leaf area from plastochron index.
Zinc Nutrition Related to Critical Deficiency and Toxicity Levels for Sorghum1
Authors: Ohki K.
Published: July 2010

Sorghum [Sorghum bicolor(L.) Moench] production has increased in the Southeastern United States as a second crop in many double‐cropping systems. Guidelines are needed for Zn concentration in leaf blade tissue for the diagnosis and correction of Zn deficiency and toxicity problems. The Zn critical deficiency level (CDL) and critical toxicity level (CTL) are the minimum and maximum concentrations, respectively, associated with a 10% yield reduction from maximum yield due to Zn deficiency and toxicity. Sorghum was grown in nutrient solutions containing Zn concentrations ranging from 0.0 to 91.78 nmol L−1in 14 increments in the greenhouse. Individual blades were sampled at 49 days growth and analyzed for Zn concentration by atomic absorption spectrometry. The Zn CDL values in blades were 10, 10, 9, 13, and 24 µg g−1for blades 1 (top), 2, 3, 4, and 5 (bottom), respectively, as calculated from the exponential relationship of Zn concentration in blades and top dry weight. The Zn CTL values in blades were 64, 68, 80, 100, and 195 µg g−1in blades 1, 2, 3, 4, and 5, respectively. For tissue sampling to diagnose Zn deficiency and toxicity, blade 1 is recommended. The Zn CDL and CTL are 10 and 64 µg g−1, respectively, sampled at growth stage 2 and near maximum vegetative growth harvested at this time is expected if the Zn concentrations are within the CDL and CTL.
Estimating Absorbed Photosynthetic Radiation and Leaf Area Index from Spectral Reflectance in Wheat1
Authors: Asrar G. , Fuchs M. , Kanemasu E. T. , Hatfield J. L.
Published: July 2010

Some plant growth models require estimates of leaf area and absorbed radiation for simulating evapotranspiration and photosynthesis. Previous studies indicated that spectral reflectance, absorption of photosynthetically active radiation (PAR), and leaf area index (LAI) are interrelated. The objective of this study was to establish a procedure by which spectral reflectance can be used to simultaneously estimate PAR absorption and LAI. A method is presented for estimating the quantity of absorbed PAR by wheat (Triticum aestivumL.) plants and their LAI based on the normalized difference (ND), transformation of the near infrared (ρn= 800 to 1100 nm) and red (ρr= 600 to 700 nm) canopy reflectances. The results, from a theoretical analysis and field measurements, indicated that ND correlates with the fraction of PAR absorbed by wheat canopies. Bare soil reflectance and scattering of near infrared radiation by foliage elements were the major factors that influenced the relation between ND and PAR absorption. The estimated PAR absorption values, based on the ND, and four classes of assumed leaf angles (45°, 60°, 75°, and spherical), were used to indirectly evaluate LAI of wheat for three different geographical locations. The standard deviation on mean predicted to measured LAI's for the three locations varied from 0.5 to 0.9 for a range of 0 to 6 LAI. The method is considerably less sensitive in predicting LAI above 6.0 since the sensitivity of ND to changes in LAI becomes small (<0.01), due to small changes in canopy reflectance.
Soil Testing, Foliar Analysis, and DRIS as Guides for Sugarcane Fertilization1
Authors: Elwali A. M. O. , Gascho G. J.
Published: July 2010

Foliar analysis has been practiced widely in sugarcane (a complex trispecies hybrid of Saccharum) for planning and evaluation of fertilizer programs and harvest schedules. On the mainland of the USA, sugarcane farmers have traditionally relied on soil testing to plan fertilizer programs. Soil testing remains an excellent preplant practice but its reliability for the successive ratoon crops has been questioned. Results of foliar analyses are usually interpreted on the basis of the Critical Nutrient Level (CNL) approach. Recently, the Diagnosis and Recommendation Integrated System (DRIS) was introduced as an alternative approach for foliar diagnosis. The present study was conducted to evaluate the effectiveness of soil testing and foliar analysis interpreted by the CNL approach and by the DRIS as guides for sugarcane fertilization. Standard nutrient levels and DRIS norms were established for N, P, K, Ca, Mg, Fe, Mn, Zn, and Cu in the top visible dewlap leaf laminae of sugarcane. Comparison of the three methods was conducted in eight fields of ratoon sugarcane representing the major sugarcane soils in south Florida. Soil samples were collected in May and leaf samples in May, July, and September. Fertilizers were applied in May and July as indicated by each method. Foliar analysis interpreted by either method revealed a need for applying one or more micronutrient(s) to all fields, a practice which had not previously been recommended for ratoon sugarcane in Florida. Application of N was also recommended for the first time on Torry muck soil (euic, hyperthermic Typic Medisaprist) by foliar analysis using both methods. Fertilization according to the DRIS significantly increased both cane and sugar yields compared with those obtained when fertilization was guided by foliar analysis using the CNL approach or soil testing. Differences were not significant between foliar analysis using the CNL approach and soil testing. The high cane and sugar yields obtained by DRIS‐guided fertilization were attributed to the better nutrient balance as revealed by DRIS indices late in the season. Foliar analysis using the DRIS proved to be a better guide for fertilization of sugarcane than the soil testing method currently in use.
Effect of Planting Date and Plant Population on Sunflower Performance1
Authors: Miller B. C. , Oplinger E. S. , Rand R. , Peters J. , Weis G.
Published: July 2010

Sunflower (Helianthus annuus L.) is an alternate cash crop in the northern humid USA. Sunflower responds variably to planting date and plant population in different production areas. Field experiments were conducted for 3 years to determine the effect of planting date and plant population on sunflower seed yield and other plant characteristics under the humid growing conditions in the north central USA. In Exp. I, three planting dates, from early May to late June, were established with two hybrids at 30,000, 45,000, 60,000 and 75,000 plants ha−1 at Arlington (1978 to 1980) and Spooner (1978 to 1979), Wis. In Exp. II, two hybrids were established at three populations, 30,45, and 60,000 plants/ha, under irrigated and dryland conditions at Hancock (1978 to 1980), Wis. The soil types were silt loam (Typic Argiudoll) at Arlington, and sandy loam (Typic Udipsamment) at Spooner and Hancock. Planting in early and mid‐May at Arlington, and mid‐May at Spooner maximized seed yield, seed weight, seeds head,−1 oil concentration, oil yield, and test weight. Sunflower seed and oil yields were not influenced by plant populations ranging from 28,700 to 73,200 plants ha−1. Relatively constant yields were a consequence of reduced seed weight and seeds head−1 as plant population increased. The yield response of sunflower to increasing plant population, among planting dates and hybrids was more variable under the northern, cooler climate at Spooner. Yield and plant height were much higher under irrigated conditions on the sandy soils at Hancock. Although seed oil concentration under the dryland conditions at Hancock was 1.8% higher, the oil yield was 172 kg ha−1 lower, than under the irrigated conditions.
Tillage System × Planting Date Interactions in Corn Production1
Authors: Eckert D. J.
Published: July 2010

Little information is available concerning the effect of no‐tillage (NT) production on development of corn (Zea mays L.) through harvest, or on appropriate planting dates for NT corn. In this study, NT and conventional tillage (CT) (moldboard plow) corn were planted on a series of planting dates over a 3‐year period, on a moderately well‐drained Canfield silt loam (fine‐loamy, mixed, mesic Aquic Fragiudalfs) located at Wooster, Ohio. Under these conditions, tillage system had no effect on development or yield when data were averaged over 3 years. However, CT corn often silked earlier than NT corn under cooler conditions and yielded more in a wetter than normal year. No‐tillage corn silked earlier and yielded more than CT corn in a drier than normal year. Later silking did not result in wetter grain at harvest in NT corn, but often did so in CT corn. Date of planting had the same effect on yield in both tillage treatments.
Nonstructural Carbohydrates and Dehydration Tolerance of Blue Grama Seedlings1
Authors: Khan Sultan M. , Wilson A. M.
Published: July 2010

Blue grama [Bouteloua gracilis (H.B.K. Lag ex Steud.] seedlings are susceptible to dehydration during warm dry winds, even when the seminal root has extended into a moist soil profile. The objective of this study was to determine relationships between total nonstructural carbohydrates (TNC) and dehydration tolerance of seedling crowns (lower 3‐cm of stem base). The greenhouse and controlled environment study included growth of seedlings for accumulation of TNC, use of shade and sunlight after shade to change TNC percentage in crowns, dehydration of crowns, and evaluation of the effects of dehydration treatments on tiller survival and production of adventitious roots. Soil was a fine‐loamy, mixed, mesic Aridic Argiustoll. Percent TNC in crowns from various shade and light treatments were as follows: control, 10.1; 2 days shade, 7.5; 4 days shade, 5.9; 4 days shade + 2 days light, 9.0; 4 days shade + 4 days light, 10.4. After dehydration treatments, the numbers of surviving tillers per pot in treatments receiving no shade (control), 2 days shade, 4 days shade, 4 days shade + 2 days light, and 4 days shade + 4 days light were 42, 22, 14, 33, and 42, respectively. Number of surviving tiller decreased with an increase in dehydration stress. Path coefficient analysis indicated a significant relationship (p < 0.01) between TNC and tiller survival (p = 0.35). Thus establishment and persistence of blue grama on semiarid lands may depend on maintenance of adequate levels of TNC.
Premature Flowering in Soybean Yield Reductions at Nonoptimal Planting Dates as Influenced by Temperature and Photoperiod1
Authors: Board J. E. , Hall W.
Published: July 2010

The optimum time for soybean [Glycine max (L.) Merr.] planting in the southeastern USA is from early May to early June. Planting at other times has consistently resulted in seed yield losses which have been blamed on premature flowering induced by short photoperiods. Objectives in this study were to characterize the photoperiod response of soybean cultivars commonly grown in the southeastern USA, determine if daylength differences between optimal and nonoptimal planting dates in the southeastern USA are great enough to cause premature flowering, determine the interaction of photoperiod and temperature factors on the length of the vegetative stage, and evaluate the ability of delayed flowering genotypes to avoid yield losses at nonoptimal planting dates. The studies were conducted in both growth chambers (to provide daylengths of 12 to 16 h and temperatures of 21 to 30°C) and in the field (Aquic Fragiudalf soil). Group V cultivars had smaller increases in vegetative period as daylength increased and had a longer daylength beyond which flowering did not occur compared to Group VI, VII, and VIII cultivars. The critical daylength using constant photoperiod durations for achieving an adequate vegetative period was determined to be between 14 and 14½ h in ‘Forrest’, ‘Centennial’, and ‘Tracy‐M’, while ‘Bedford’, ‘Davis’, ‘Ransom’, ‘Bragg’, and ‘Braxton’ had a critical photoperiod between 13½ and 14 h. Based on these studies, daylength encountered by soybeans planted early (e.g., early April) is short enough to cause premature flowering. Daylength encountered by some cultivars planted late (e.g., mid‐June) is not short enough to cause premature flowering. However, daylength is short enough to cause premature flowering in most cultivars at a July planting date. Field data supported these predictions. Evaluation of delayed flowering genotypes in photoperiod and field studies showed promise for avoidance of yield losses caused by short‐day induced premature flowering. Temperature photoperiod interaction studies showed that warm temperature (27°C) compared to cold temperature (21°C) decreased the time to first flowering and had its greatest effect under short rather than long days. This effect was greater in Group VI and VII cultivars compared to Group V cultivars.
Behavior of Steers Grazing Several Varieties of Tall Fescue During Summer Conditions1
Authors: Bond J. , Powell J. B. , Weinland B. T.
Published: July 2010

Fescue (Festuca arundinacea Schreb.) toxicosis during summer grazing is characterized by decreased tolerance to environmental stress. The purpose of this study was to determine if this reduced tolerance causes changes in the behavioral patterns of steers (Bos spp.) grazing fescue pastures during summer conditions as has been shown under other conditions of environmental stress and sickness. During a 3‐year experiment to measure chemical characteristics of four lines of tall fescue and to study physiological responses of steers grazing these fescue varieties, observers monitored the behavior of steers at 1300 h daily and during two 24‐h periods on 9 Sept. and 12 Oct. 1978. Categories with the highest frequency included grazing, lying in the field and shade, and standing in the field and shade. Steers on G1‐307 (an experimental line which contained a low level of perloline) showed symptoms of fescue toxicosis and grazed 20% less, laid in the field 4% less, and laid and stood in shade 8 and 17% more, respectively, than the steers that grazed ‘Kentucky 31’, ‘Kenhy’, and G1‐306 (high level of perloline). All steers spent less time lying in field and more standing in shade on 9 September than 12 October. Results suggest that the grazing behavior of steers varied as a function of variety of tall fescue grazed, particularly during periods of climatic stress.
Simple Beta Distribution Representation of Leaf Orientation in Vegetation Canopies1
Authors: Goel Narendra S. , Strebel Donald E.
Published: July 2010

It is shown that a two‐parameter beta distribution represents very well the leaf angle distribution for a variety of vegetation canopies. Comparison to theoretical distributions as well as field data suggests that this distribution be considered as a candidate for a “universal” leaf angle distribution. The parameters of the distribution can then be used to identify and classify intermediate canopy types and possibly to quantify canopy changes caused by environmental stress.
Syringing Effects on the Canopy Temperatures of Bentgrass Greens1
Authors: DiPaola J. M.
Published: July 2010

Syringing of fine turf, particularly bentgrass golf greens, is practiced throughout the USA. The literature indicates that this procedure offers some potential to moderate turfgrass canopy temperature. The practical utility of syringing from canopy temperature reduction under the warm, humid conditions of the southeastern USA was examined in this study. A ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) green constructed to U.S. Golf Association (USGA) specifications and located in Raleigh, NC was subjected to eight rates of water applications (0, 0.05, 0.1, 0.7, 1.4, 2.7, 4.1, and 5.5 mm) as syringing treatments at one of two times (1100 or 1300 h) during the day. Green soil construction consisted of mixing 9 parts sand with 1 part of a Typic Hapludult Clayey, kaolinitic, thermic (Cecil gravelly sandy loam) soil and 1 part peat. The objective of a second study was to evaluate canopy temperature changes following a syringing treatment of 2.7 mm of water applied as single or multiple applications. In the absence of wilt, bentgrass canopy temperatures were not significantly altered 1 h after syringing regardless of the water volume or timing of the syringing application. Therefore, in the absence of wilt, the routine syringing of bentgrass greens must be reevaluated given the substantial economic cost of this procedure, particularly for labor and water.
Contribution of Genetic Improvement to Recent Wheat Yield Increases in the USA1
Authors: Feyerherm A. M. , Paulsen G. M. , Sebaugh J. L.
Published: July 2010

Genetic yield potential of wheat (Triticum aestivum L. and T. turgidum L. var. durum) has increased markedly during recent decades, but its impact on production has not been well documented. Studies were conducted to measure the effect of genetic improvements from 1954 through 1979 on growers' yields of wheat in states where each major class is grown. Differential yielding ability (DYA) values were calculated for popular cultivars from a broad data base of performance trial yields and weighted by the mix of cultivars in production in each state. Yield increases attributed to changing cultivar mixes in spring wheat states ranged from 268 kg ha−1 in Montana to 550 kg ha−1 in Minnesota. Increases in the hard red winter wheat region were greatest in Nebraska (416 kg ha−1), Oklahoma (368 kg ha−1), and Kansas (348 kg ha−1) and were smallest in Texas (233 kg ha−1), Colorado (228 kg ha−1), and Montana (193 kg ha‐'). Soft wheat yield increases ranged from 739 to 854 kg ha−1 in Corn Belt states and 734 kg ha−1 in Washington State. We concluded that the impact of genetic improvement was inversely related to environmental constraints, that substantial yield improvement in unfavorable environments requires greater emphasis on stress resistance, and that no slowing of the rate of yield improvement is evident.
Stem Excision as a Means of Simulating Hail Injury on ‘Alaska’ Peas1
Authors: Miller D. G. , Muehlbauer F. J.
Published: July 2010

Accurate assessment of stem hail injury in peas (Pisum sativum L.) resulting from excised stems is difficult to make and can cause problems in hail adjustment methods. This study evaluated stem excision and its effect upon subsequent growth and yield in fieldgrown peas. Four levels of simulated hail injury were applied to ‘Alaska’ peas previously thinned to 13, 20, 26, or 33 plants m−2. Injury treatments were made by cutting the primary stem and removing all tissue above the point of excision on plants at the rate of 0, 5, 10 or 20% of the total plant population when plants were in the eighth node (vegetative) and full‐bloom (reproductive) growth stages. Plants in the vegetative stage were excised between the fourth and fifth node (Treatment 1). Those in the reproductive stage were excised between the fist and second flowering node (Treatment 2a) or immediately below the first flowering node (Treatment 2b). Individual plant performance at all treatments showed that damaged plants had delayed maturity, reduced plant height, increased branching, and reduced seed weight when compared to undamaged plants. Seeds pod−1 were similar on damaged and undamaged plants except at Treatment 2b, where a significant reduction in seeds pod−1 was noted on damaged plants. Pods plant−1 were reduced for Treatments 1 and 2a, but not for Treatment 2b. Damaged plants recovered by initiating branches from lateral buds; however, they required 6 to 7 days more than untreated plants to reach dry seed maturity. When peas were treated in the vegetative stage, yield declined 0.41% for each 1% increase in damaged plants. Yield declines of 0.59% for Treatment 2a and 0.85% for Treatment 2b were obtained for each 1% increase in damaged plants in the reproductive stage. This information concerning plant recovery from excised stem damage and yield compensation by undamaged plants should make hail damage adjustment in peas more precise.
Harvesting Losses of Spring Wheat in Windrower/Combine and Direct Combine Harvesting Systems1
Authors: Clarke John M.
Published: July 2010

Harvest loss of cereal crops has been reported to be reduced by windrow‐drying prior to combing compared to direct combining, but few comparisons of the two systems have been made. Field studies were conducted in order to compare harvesting losses of five wheat (Triticum spp.) cultivars of varying shattering resistance in direct combine and windrower/combine harvesting systems on a Swinton loam soil (Aridic Haploboroll). Cutting treatments were initiated when kernel water concentration was about 670 g water per kg kernel dry weight and continued for at least 2 weeks after kernel water concentration reached 170 g kg−1. Natural shattering losses and cutting losses were measured at each cut; combine pick‐up losses were measured when the windrows were combined. Cutting and pickup losses did not change with cutting time and there was no consistent variation among cultivars. Cutting losses ranged from 0.75 to 3.03 g m−2; pick‐up losses ranged from −0.10 to 0.98 g m−2. Natural shattering losses varied with cultivar and year; cummulative loss ranged from a low of 4 to a high of 27 g m−2 over a period to some 2 weeks after kernel water concentration reached 170 g kg−1. Harvesting losses were similar for the two harvesting systems for cultivars resistant to shattering, but greater for the direct combine than for the windrower/combine system for cultivars susceptible to shattering. An earlier start to direct combining (at kernel water concentrations of 170 to 250 g kg−1) narrowed the difference between the systems for cultivars susceptible to shattering as did delayed windrowing.
Emergence of Inbred and Hybrid Corn Following Flooding1
Authors: Fausey N. R. , McDonald M. B.
Published: July 2010

While it is commonly accepted that the Occurrence of excess soil water following planting adversely affects the establishment and early growth of corn (Zea mays L.) seedlings, the effect of flooding duration, soil temperature at time of flooding, and cultivar have not been determined. Such information would be useful to drainage system designers and corn breeders. The objective of this study was to determine whether pregermination flooding duration and soil temperature at time of flooding affect the emergence of selected inbred and hybrid corn cultivars. Five popular inbred [A632, B37, B73, H60, and Mo17] and five hybrid [(A635 ✕ A632)Mo17, B73 ✕ H60, (H95 ✕ H99) A632, (OH514 ✕ OH7B)H95, Mol7 ✕ B73] corn cultivars grown in Ohio were exposed immediately following planting to differing durations of flooding (0,48,96, and 144 h) at two temperatures (10 and 25 °C) in the laboratory and at cold (near freezing) and warm (approximately 25 °C) temperatures in a silty, clay, loam Typic Argiaquoll soil in the field. Seedlots were selected which possessed a germination percentage above 90. Laboratory and field results showed inbred cultivars to be more tolerant of flooding than hybrid cultivars. Flooding damage as measured by reduced emergence was noted in both inbred and hybrid cultivars after only 48 h flooding in both laboratory and field studies. The severity of flooding damage was enhanced for both cultivar groups when flooding temperature was increased from 10 to 25 °C.
Nitrogen from Forage Legumes: Harvest and Tillage Effects1
Authors: Groya F. L. , Sheaffer C. C.
Published: July 2010

Increasing interest in forage legumes as green manures in crop rotations has emphasized the need for information on harvest and tillage management of modern cultivars. Our objectives were to: 1) determine the effects of four seeding year harvest managements on sweetclover [Melilotus officinalis (L.) Lam.], red clover (Trifolium pratense L.), and alfalfa (Medicago sativa L.) herbage and root dry matter (DM) and N yields, and on DM yield and N recovery by a subsequent sudangrass [Sorghum bicolor (L.) Moench] crop, and 2) determine the effect of moldboard or chisel plowing on DM yield and N uptake by sudangrass grown following incorporation of alfalfa residues. Two separate experiments were conducted on a fine‐silty over sandy‐skeletal, mixed, mesic Typic Hapludolls. With a hay harvest management (three or four harvests), legumes had similar total season herbage N yields (261 kg ha−1), and root DM (1.4 Mg ha−1) and N yields (30 kg ha−1), and total plant N yields (325 kg ha−1). Unharvested sweetclover had greater fall whole plant N yields (348 kg ha−1) than alfalfa (195 kg ha−1) and greater root DM (5.1 Mg ha−1) and N yields (175 kg ha−1) than alfalfa or red clover (average root DM and N yields of 1.9 Mg ha−1 and 48 kg ha−1, respectively). Nitrogen incorporation (272 kg ha−1) was greater when legume herbage was accumulated in situ than when herbage was removed and only fall regrowth and/or crowns and roots incorporated (86 kg ha−1). Legume species selection within harvest management had little effect on sudangrass DM yield or N uptake. Tillage method had no consistent effect on sudangrass, DM yield, or N uptake. Since fallowing resulted in sudangrass yields similar to those from the best legume treatments, it might be considered as an alternative to legume production for diverted cropland on some soils.
Predicting Rice Grain Yield from Dry Matter Production at Late Tillering1
Authors: Gilmour J. T.
Published: July 2010

It was hypothesized that grain yield of rice (Oryza sativa L.) was related to dry matter accumulation at late tillering. Using published data from N rate and timing studies conducted in Arkansas on Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf) and in the Philippines, this hypothesis was tested by regressing relative grain yield against relative dry matter production at late tillering. A linear, highly significant relationship which had a slope of 0.52 and intercept of 40% was obtained. In this equation, the dry matter and grain yield were expressed as a percentage of an unfertilized control. The mean relative growth rates after late tiilering were relatively constant irrespective of N management which explained, in part, the influence of dry matter at late tillering on grain yield for these data. Application of this relationship to specific plant‐soil‐climate situations to predict and/or increase grain yield are potential uses of these findings.
New Hand‐Operated Press for the Extraction of Tissue Sap for the Measurement of Osmotic Potential1
Authors: Markhart Albert H. , Lin Tsai‐Yun
Published: July 2010

Conventional methods of extracting sap from leaf tissue for the measurement of osmotic potential are time consuming and often result in changes in sap concentration due to evaporation or enzymatic activity. In this paper, a simple hand operated press is described which facilitates rapid extraction and filtration of tissue contents with either direct deposition on a filter paper disk for osmotic potential measurement or collection in a suitable vial for future analysis. A complete measurement is made in 5 min. Triplicate measurement of samples with the same osmotic potential differed by an average of 0.05 MPa at an osmotic potential of −0.7 MPa. Osmotic potentials measured with a vapor pressure osmometer on expressed sap were 10% higher than values derived from pressure volume carves. This error is most likely due to dilution of the protoplasm by the cell wall water. Convenience and reliability make this new press a useful tool for the water relations laboratory.
Linear Increase in Soybean Harvest Index during Seed‐Filling1
Authors: Spaeth S. C. , Sinclair T. R.
Published: July 2010

Grain‐to‐stover ratio and harvest index (the ratio of seed mass to total aboveground mass) were studied during soybean [Glycine max (L.) Merr.] seed‐filling to determine the potential for using these normalized expressions of yield to improve measurements of the seed‐filling period. For example, if either grain‐to‐stover ratio or harvest index increased linearly during seed‐filling, it could be used to calculate an effective filling period. However, calculation of an effective filling period requires a linear approximation. Thus, the specific objective was to determine whether grain‐to‐stover ratio or harvest index increased as a linear function of time for various genotypes and environments. First, C and N assimilation and distribution rates within plants were simulated. Simulations predicted that harvest index increased linearly throughout seed filling, while grain‐to‐stover ratio increased curvilinearly. Next, simulations were compared with data from field‐grown plants at three northern locations. Cultivars included determinate and indeterminate types, and a range from early to late maturities. To a good approximation, harvest index increased linearly during the seed‐filling period for all but the early cultivars. The early cultivars approached maximum values of harvest index curvilinearly. Therefore, harvest index has potential for use in calculations which require linear approximations.