bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stand Dynamics and Yield Components of Alfalfa as Affected by Phosphorus Fertility
Authors: Sanderson Matt A. , Jones Ronald M. 
Published: July 2010

AbstractStand maintenance of alfalfa (Medicago sativa L.) relies on the persistence of the original plants. Yield (yield per plant, yield per shoot) and stand components (plants per square meter, shoots per square meter, shoots per plant) were studied in two experiments designed to determine yield response to P on a low P soil (Windthorst fine sandy loam; fine, mixed, thermic, Udic Paleustalfs) near Stephenville, TX. Three preplant incorporated rates of P (0, 29, and 59 kg ha−1) and five annual surface broadcast rates of P (0, 7, 15, 29, 59 kg ha−1) were applied to two field experiments established in September 1988 and 1989. The experimental design was a split plot in four randomized blocks. Whole plots were incorporated P rates and subplots were annual broadcast P rates. Plants and shoots per square meter were counted 4 and 8 wk after planting in 1988 and 1989, at each harvest in 1989 and 1990, and at the beginning and end of the season in 1991. Relative distribution of root mass to a 90‐cm depth was determined in the fall of 1990 and 1991 for selected treatments. Phosphorus incorporated before planting increased alfalfa dry matter (DM) yields more efficiently than did broadcast P. Plant and shoot densities did not differ among treatments; thus, low yields at low P levels were a function of reduced yield per shoot. Delayed application of P on fall‐planted alfalfa did not affect plant density. Under 0‐P, root mass was concentrated in the upper 20 cm of soil, whereas under adequate to high P, more root mass was distributed throughout the upper 40 to 50 cm.
Endophyte Effects on Growth and Persistence of Tall Fescue along a Water‐Supply Gradient
Authors: West C. P. , Izekor E. , Turner K. E. , Elmi A. A. 
Published: July 2010

AbstractEcophysiology of the endophyte (Acremonium coenophialum Morgan‐Jones and Gams)‐tall fescue (Festuca arundinacea Schreb.) association needs to be understood in order to promote environmental fitness traits of the association while reducing its deleterious effects on ruminants. Our objective was to determine the influence of endophyte on drought stress tolerance, persistence, and yield components of field‐grown tall fescue on a Typic Hapludalfs soil. A water supply gradient was established during 1988 and 1989 with line‐source irrigation on established populations of 0 and 80% endophyte‐infected tall fescue. Whole plots consisted of endophyte infection status, across which a gradient of water was applied in a strip‐split fashion with eight replicates. Tiller population density and herbage yield were determined every 28 d and yield components were measured on selected dates. Relative to populations receiving high irrigation (375‐650 mm applied), tiller density in nonirrigated stands (0‐50 mm applied) from July to October 1988 was reduced an average of 42% in infected tall fescue and 55% in noninfected tall fescue. Tiller density of nonirrigated, infected populations recovered fully to that of high irrigation treatments by 17 November, whereas that of nonirrigated, endophyte‐free populations recovered to only 62% of irrigated treatments. The advantage in population density due to endophyte infection continued throughout 1989, a relatively wet year. A benefit in total forage yield due to endophyte infection was not consistently evident because of greater yield per tiller in endophyte‐free stands in 1989. Enhanced tiller density and survival were associated with endophyte infection during severe water deficit, and this advantage continued throughout the subsequent year. Endophyte infection confers population stability in tall fescue during drought stress through improved tiller and whole plant survival.
Rooting Depth and Dry Matter Development of Sunflower
Authors: Jaafar M. N. , Stone L. R. , Goodrum D. E. 
Published: July 2010

AbstractThe use of modeling and computers increases the potential to estimate crop water use and irrigation requirements. However, for that potential to be realized, data on root growth are needed for model development and/or input. Few field studies have included direct measurement of sunflower (Helianthus annuus L.) root development. Our objective was to examine plant development, with emphasis on rooting depth, of field‐grown sunflower. The study was in 1985 and 1986 near Manhattan, KS on deep, barrier‐free, Muir silt loam soil (fine‐silty, mixed, mesic Cumulic Haplustoll). Regression analysis was applied to data on root growth and aboveground development. The resulting equations were then used to examine growth patterns and rates of development. Canopy height reached its maximum of 2.40 m during the latter part of disk flowering. The maximum rate of height increase was 72 mm d−1 and occurred during early bud formation. Roots reached the deepest soil depth of 2.18 m late in the growing season (95% of the total of thermal units from emergence to physiological maturity). Roots reached 1.88 m at the beginning of disk flowering and 2.02 m at the completion of disk flowering. Rate of advance of the deepest observed root decreased linearly from 43 mm d−1 during mid June (eight leaves emerged). Green leaf area index (LAI) reached its maximum immediately prior to disk flowering. Dry mass of leaves, stems, and heads reached maximums at late disk flowering, back of head yellow with bracts still green, and physiological maturity (no green on head), respectively. Total aboveground dry mass reached its maximum at 85% of the total of thermal units from emergence to physiological maturity. The rate of total aboveground dry mass yield was greatest near mid season (48% of total thermal units). The data on sunflower rooting depth reported in this article will assist in estimation of crop water use.
Growth, Yield, and Quality of Forage Maize Under Different Nitrogen Management Practices
Authors: Cox W. J. , Kalonge S. , Cherney D. J. R. , Reid W. S. 
Published: July 2010

AbstractMaize (Zea mays L.) forage producers need more information on how N management affects dry matter (DM) yield, forage quality, and residual soil NO−3 ‐N concentrations. Studies were conducted in New York to evaluate three hybrids under different sidedress N rates (0, 56, 140, and 255 kg N ha−1 at the V4 stage) and timing (70 + 70 kg N ha−1 at V4 and V8 and 75 + 75 + 75 kg N ha−1 at V4, V8, and R1 stages). The DM yields, which averaged 25% lower in 1991 (12.3 Mg ha−1) compared to 1990 (16.9 Mg ha−1), responded curvilinearly to N rates with maximum economic yields of 140 and 160 kg N ha−1, respectively. Whole‐plant neutral detergent fiber (NDF), acid detergent fiber (ADF), and N concentrations responded linearly to N rates in 1990 indicating that forage quality improved with each additional increment of N. Higher N rates, however, increased residual soil NO−3‐N concentrations in the upper 0.3 m soil depth in 1990 (0, 3, 30, and 32 mg kg−1) and 1991 (0, 0, 17, and 17 mg kg−1 for the 0, 56, 140, and 225 kg N treatments, respectively). Split‐N applications compared to respective single rate N applications did not increase DM yields, improve forage quality, or decrease residual soil NO−3‐N concentrations. When applying higher rates of N fertilizer, maize forage producers must balance potential benefits of higher DM yields and improved forage quality with the potential risk of increased residual soil NO−3‐N concentrations.
Penetration of Soybean Roots by Soybean Cyst Nematode at High Soil Water Potentlals
Authors: Johnson A. B. , Scott H. D. , Riggs R. D. 
Published: July 2010

AbstractSoil water is an important factor in the movement and development of soybean cyst nematode (Heterodera glycines Ichinohe). Plant growth and soybean cyst nematode (SCN) population density were measured to determine the effects of soil water potential (Ψ8) on root penetration by SCN of ‘Essex’, a suspectible cultivar of soybean [Glycine max (L.) Merrill]. Soybean seeds were planted in growth containers and subjected to constant Ψ8 of −5, −10, −20, −30, −40, and −50 kPa at SCN levels of 12 000 eggs and second‐stage juveniles (J2) per kg soil or no SCN for the controls for 16 d. The soil used was a Captina slit loam (fine‐silty, mixed, mesic Typic Fragiudult) with 23, 68, and 9% sand, silt, and clay, respectively. Soybean was inoculated with eggs and J2 at the cotyledon growth stage (VC). Average soil temperature during the study was 25.5 °C. Leaf water potential (Ψ1) and soil oxygen diffusion rate (ODR) were significantly affected by Ψ8 < (P > 0.01) after 16 d of exposure to SCN. In the infested treatments Ψ1 was reduced at a more rapid rate with decreasing Ψ8 than in the non‐inoculated controls. The increase in SCN penetration of the soybean root system corresponded positively to the increase in soil ODR and corresponding decrease in Ψ8. Recovery of SCN from the soil decreased with a decrease in Ψ1. A mechanistic, nonlinear mathematical model was used to describe the relationship between Ψ8 and SCN penetration of soybean roots. A quadratic regression model was used to describe the relationship between Ψ8 and SCN recovery from the soil.
Sward Height and Vertical Morphological Differentiation Determine Cattle Bite Dimensions
Authors: Flores Enrique R. , Laca Emilio A. , Griggs Thomas C. , Demment Montague W. 
Published: July 2010

AbstractTo identify and quantify the influence of sward structure on the intake of grazing animals requires an understanding of sward‐animal interactions at the bite level. We tested the hypothesis that bite dimensions on vertically heterogeneous swards are determined by structural characteristics of the top leaf stratum, independent of those of a bottom layer of pseudostem or stem. Dallisgrass (Paspalum dilatatum Poir.) microswards were constructed by hand in a factorial combination of two lamina lengths (5 and 8 cm) and two sward heights 8 and 16 cm). Tillers consisted of a top segment of lamina and a bottom one of pseudostem (Exp. 1) or stem (Exp. 2) of length equal to the difference between sward height and lamina length. Treatments were replicated over three steers (Bos taurus) of 750 kg avg. body weight. Bite area and depth increased with sward height in swards with pseudostem but were not affected by lamina length. Pseudostems were not a barrier to defoliation and did not affect bite dimensions. Steers restricted grazing of tillers with stem to the upper lamina horizon. Bite depth was limited by stems only when lamina length was less than half of sward height. Bite area was reduced by the presence of stems because tillers bent at ligule height, restricting the animals to gather fewer tillers in each bite than when tillers bent at the base. Bite weight was reduced severely in swards with stem, relative to those with pseudostem. Results confirmed the importance of stem horizons and their relative positions in the sward as determinants of bite weight.
Growth, Boll Opening Rate, and Fiber Properties of Narrow‐Row Cotton
Authors: Heitholt James J. , Pettigrew William T. , Meredith William R. 
Published: July 2010

AbstractRow spacing has the potential to affect agronomic traits of upland cotton (Gossypium hirsutum L.). Although narrow‐rows can pose numerous management challenges (e.g., cultivation and harvesting), the benefits of narrow‐rows may justify their use. Unfortunately, the extent and consistency of cotton's response to narrow‐rows is variable, which makes management decisions more difficult. The objective of this study was to determine whether row spacing affected the earliness (date at which 65% of the lint was on open bolls), fiber properties, and vegetative dry matter of normal‐leaf and okra‐leaf cotton. In 1989 and 1990, an okra‐leaf genotype and its normal‐leaf isoline were grown in field experiments on a Bosket fine sandy loam, using 0.5‐ and 1.0‐ m row spacings in early and late plantings each year. During midand late‐bloom, the vegetative dry matter was determined. At maturity, seed cotton in open bolls was picked at approximately 10‐d intervals, ginned, and earliness (date when 65% of total lint was on open bolls) calculated. Okra‐leaf grown in 0.5‐m rows reached 65% open 3 d earlier than okra‐leaf grown in 1.0‐m rows in the early planting of 1990. Otherwise, earliness was not affected by row spacing. Except for a small increase in the 2.5% span length of normalleaf grown in 1.0‐m rows above that in 0.5‐m rows, the other fiber properties, vegetative dry matter, vertical boll distribution, and average seed mass were unaffected by row spacing. Since many agronomic traits were unaffected by row spacing, management practices (e.g. date of defoliation) of narrow‐rows might be expected to similar be to that of conventional rows.
Agronomic Practices that Affect Corn Kernel Characteristics
Authors: Ahmadi M. , Wiebold W. J. , Beuerlein J. E. , Eckert D. J. , Schoper J. 
Published: July 2010

AbstractAgronomic practices affect corn (Zea mays L.) grain yield and may affect physical and chemical characteristics of corn kernels. These characteristics affect feed, food, and industrial uses of corn grain. Four field experiments consisting of planting date and population combinations were conducted to determine the effect of these agronomic practices on grain yield, kernel N concentration, and kernel hardness. Kernel hardness was estimated by kernel weight, kernel density, and grinding resistance. A fixed ear hybrid, B73 × LH38, was used in all four experiments. Two of the four experiments also included LH119 × LH51, a flexible ear hybrid. Planting date affected yield in only one experiment. In this instance, delaying planting 4 wk decreased yield 55%. Yield reduction from planting delay was greater for B73 × LH38 than for LH119 × LH51. In two experiments, increasing population increased yield quadratrically; whereas, in the other two experiments the effect of population on yield was linear. No interaction between hybrid and population occurred. Delayed planting increased kernel N concentration in one experiment. In all four experiments, increasing population resulted in a linear decrease in kernel N concentration. Few effects from either planting date or population on kernel weight and density were found. Grinding resistance was increased by delayed planting in one experiment but was not affected by plant population in any of the four experiments. Inverse relationships between yield and important kernel physical and chemical characteristics were found. Emphasis on high yield may result in less desirable grain. End‐users that require high grain quality may need to provide incentives to growers.
Residual Effects of Soil Profile Modification on Water Infiltration, Bulk Density, and Wheat Yield
Authors: Unger Paul W. 
Published: July 2010

AbstractFine‐textured soils of the Southern High Plains, of which Pullman (fine, mixed, thermic Torrertic Paleustolls) is the dominant series,/ have inherently low water infiltration rates. Pullman soils have a moderately permeable surface horizon overlying and slowly‐permeable Bt horizon, which limits deep water penetration, thus hampering water conservation efforts and reducing water‐use efficiencies for crop production. In 1964, Pullman clay loam was profile‐modified (PM) to 0.9‐ and 1.5‐m depths. The objective of the 1990–1991 study was to compare soil bulk density (Db), water infiltration, plant available water (PAW) content, and winter wheat (Triticum aestivum L.) yield on PM and unmodified soil. Soil Db values were similar near the surface, but decreased with increasing depth of PM at depths greater than 0.3 m, except for the deepest increment (1.50–1.80 m), were Db values were 1.56 Mg m−3 for all treatments. Time required for 240 mm of applied water to infiltrate was 28.6 h on unmodified soil, and 8.4 h with 0.9‐ m and 6.3 h with 1.5‐m PM. The PAW contents in October and March were significantly greater for the mean and at some depths in PM plots than in unmodified plots. The differences were attributed to greater evaporative losses from the unmodified soil. After wheat harvest in June, mean PAW contents were not significantly different, but water extraction occurred to greater depths on modified than on unmodified soil Wheat grain yields tended to increase with PM (2.81 Mg ha−1 on unmodified and 3.07 mg ha−1 with 0.9‐m and 3.37 Mg ha−1 with 1.5‐m deep PM). This study showed that PM imposed on the Pullman soil in 1964 is still highly effective for increasing water infiltration. Although wheat yields were not significantly increased, grain sorghum [Sorghum bicolor (L.) Moench] and alfalfa (Medicago sativa L.) responded favorably to PM in previous studies. Considering the long‐term benefits, PM should be cost‐effective if the cost is prorated over the lifetime of the benefits and if crops that respond favorably to PM are grown.
Inadequacy of the Liebig Limiting‐Factor Paradigm for Explaining Varying Crop Yields
Authors: Sinclair Thomas R. , Park Wayne I. 
Published: July 2010

AbstractHistorically, the limiting‐factor paradigm has been used to describe how crop yields may be constrained by the individual input resources required by plants. The limiting‐factor paradigm proposes that plant growth is constrained only by a single resource whose availability is so low that it solely inhibits greater growth or growth rates. However, this paradigm ignores the great flexibility of plants to acclimate morphologically and physiologically to changing environmental conditions. In view of the inadequacy of the limiting‐factor paradigm, an analysis analogous to that used in economic studies to describe well‐managed businesses was developed. Investment of capital reserves (i.e., photosynthate) is allocated to obtain various input resources (i.e., water, minerals, etc.) in order to maximize output (i.e., crop growth). The important criterion in the allocation of reserves is that the capital reserves should be allocated to the resources with the greatest marginal returns. Since the marginal return for each resource is likely to change as the crop develops and the environment changes, resource allocation (i.e., plant development and physiology) is predicted to be dynamic and continually adjusting through the plant life cycle. An interesting outcome predicted for this acclimatable plant development is that under many conditions a number of resources will be simultaneously limiting crop growth. It is suggested that the types of data and analyses required to assess resource limitation on crop yield need to be reevaluated.
Forage Intake and Ingestive Behavior of Cattle Grazing Old World Bluestems
Authors: Forbes T. D. A. , Coleman S. W. 
Published: July 2010

AbstractMany native and introduced warm‐season grasses are being seeded as a consequence of crop reduction programs; however, little is known about the intake and ingestive behavior of cattle (Bos taurus L.) grazing such grasses. The influence of differences in herbage mass, sward height, and morphological composition of old world bluestem (Bothriochloa spp.) pastures on herbage intake and ingestive behavior of steers were examined over the course of two grazing seasons at El Reno, OK. Soils were fine‐silty Pachic Haplustolls of the Dale series. Swards of ‘Caucasian’ [B. caucasica (Trin.) C.E. Hubb.] and ‘Plains’ [B. ischaemum (Hack.) Celarier & Harlan var. ischaemum (L.) Keng.] old world bluestem were maintained within the range of 0.5 to 5 Mg ha−1 by continuous variable stocking. Five grazing trials were conducted using a total of 20 swards over the 2 yr. In both years, pastures were grazed from mid‐May to late September by steers with an initial weight of ≈250 kg. Results showed that changes in sward height had little influence on organic matter intake or ingestive behavior, but changes in herbage mass, green mass, total green leaf proportion, and leaf proportion had more effect. Diet digestibility was most influenced by the proportion of green leaf in the sward. Organic matter intake increased with increasing green leaf mass to 1.07 Mg ha−1 and then decreased. Intake per bite and grazing time also increased as proportion of green leaf and herbage mass increased, respectively. These two measures of ingestive behavior were highly influential on intake. Management of old world bluestems should aim to maintain swards with a high proportion of green leaf.
Nonstructural Carbohydrate Utilization by Wheat Shaded during Grain Growth
Authors: Kiniry J. R. 
Published: July 2010

AbstractWheat (Triticum aestivum L.) is commonly grown in dryland conditions, where environmental stress during grain filling can increase the dependency on stored assimilate. The objective of this study was to quantify the loss of total nonstructural carbohydrates (TNC) from wheat leaves and stems and the increase in seed dry mass when severe shading stress occurred after anthesis. Beginning 10 to 11 d after anthesis, severe shading was imposed on ‘Mit’ wheat in the field at Temple, TX, in 1991 and 1992. During shading, plants with spikes had reductions in stem dry mass of 290 g kg‐1 in 1991 and 140 g kg‐1 in 1992. Leaf dry mass decreased 240 g kg‐1 in 1991 and increased 10 g kg‐1 in 1992. Fructan and sucrose comprised the largest proportion of the storage carbohydrate reduction in stems and leaves. Starch in stems and leaves was not remobilized during shading. Estimates of maintenance coefficient were 4.3 mg carbohydrate g−1 dry mass d‐1 in 1991 and 1.8 in 1992. Maintenance respiration consumed 68% of the TNC present at the start of shading in 1991 and 18% in 1992. There was 0.68 g of grain produced per gram of assimilate lost from leaves, stems, and the nongrain portions of spikes in 1991 and 0.78 in 1992. When estimated costs of maintenance respiration were removed, 0.82 and 0.93 g of grain was produced per gram of assimilate that disappeared. Stored carbohydrate represented an important buffer for yield production when stress occurred during grain filling.
Seedling Emergence Model for Velvetleaf
Authors: Forcella Frank 
Published: July 2010

AbstractConsistent postemergence weed control requires information on the timing of weed emergence. Information is especially important for velvetleaf (Abutilon theophrasti Medikus), which interferes with many crops over a broad geographic range. The objective of this study was to develop a model that predicts the timing and proportional extent of velvetleaf seedling emergence. Environmental effects on seed germination and seedling emergence, used to construct the model, were determined in growth chambers or from published sources. Two variables drive the model: average daily soil temperature of the seed zone (5‐cm soil depth) and daily rainfall. The model requires initialization by four seed zone parameters: (i) soil water content at the start of the simulation period, (ii) soil water holding capacity, (iii) soil bulk density, and (iv) a water retention curve relating percent soil water to soil water potential. The model was validated using field data collected in Illinois in 1967 and 1969 and in Minnesota in 1990. Regressions of predicted and observed seedling emergence resulted in r2 values of 0.91, 0.97, and 0.98 for 1967, 1969, and 1990, respectively. Correspondence (regression coefficients) between predicted and observed seedling emergence was 0.83, 1.01, and 1.01 for 1967, 1969, and 1990, respectively. Both sets of statistics indicate the model predicts velvetleaf seedling emergence reliably.