bluuebunny/crossref_metadata_2025 huggingface dataset:
Tillage and Residue Effects on Infiltration into Soils Cropped to Cotton
Authors: Baumhardt R. L. , Keeling J. W. , Wendt C. W.
Published: July 2010

Greater infiltration of precipitation increases water available for cotton (Gossypium hirsutum L.), wheat (Triticum aestivum L.), and sorghum [Sorghum bicolor L. (Moench)] production on the semiarid Texas South Plains. The objective of this study was to determine the short‐term effects of tillage and crop residues on water infiltration into an Olton clay loam (fine, mixed, thermic Aridic Paleustoll), a Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll), and an Amarillo loamy fine sand (fine‐loamy, mixed, thermic Aridic Paleustalf). Cropping treatments included (i) conventional tillage of continuous cotton (CVT), (ii) no‐tillage, limited residue, of continuous cotton (C‐NTL), and (iii) no‐tillage of cotton grown in rotation with limited grain sorghum (S‐NTL), or (iv) wheat (W‐NTL) residues. Final infiltration rate (IR) and cumulative infiltration (CI) was measured on three soils during three successive years after applying well water at 80 mm h−1 for 1 h with a rotating disk‐type rainfall simulator. Cumulative infiltration varied between 40 and 60 mm and did not increase with increasing sand content among the three soils tested. Compared to CVT, neither W‐NTL nor S‐NTL resulted in significantly greater infiltration. Except on the Pullman soil, C‐NTL consistently had the lowest CI; however, its infiltration tended to increase with time to a level similar to the other rotations of reduced till crops. Results shown that infiltration into these soils at mid‐growing season was not affected by no‐tillage management of limited crop residues.
Spatial Nature of Randomization and Its Effect on the Outcome of Field Experiments
Authors: van Es H. M. , van Es C. L.
Published: July 2010

Many sites used for field trials exhibit a spatially‐dependent variance structure in that nearby observations are autocorrelated. This may affect treatment comparisons made at unequal distances. This study investigated (i) the probabilistic nature of randomization with respect to spatial distances in randomized complete block (RCB) designs and (ii) the effect of spatially unbalanced designs on the outcome of field experiments. The mean distance of treatment comparison increases linearly with the number of treatments in the experiment. The lack of spatial balance also increases and is inversely related to the number of replications. This may result in increases in Type II errors for short‐distance treatment contrasts and increases in Type I errors for long‐distance contrasts. Evaluation of two experimental RCB designs involving four and nine treatments and four replications showed that the randomization process does not ensure spatial balance. Two simulated experiments, each using 50 randomizations based on the Mercer and Hall data showed no adverse effect from spatially unbalanced treatment comparisons if the underlying variance structure is random, but significant effects if spatial autocorrelation is present. Expected variances for long‐distance comparisons (5.6% of all comparisons) were 51% higher than the error term resulting in tests of treatment differences at ɑ = 0.05 to actually be conducted at the 0.09 error level. Alternative design and analysis methods that ensure spatially balanced treatment comparisons are discussed.
Forage Yield, Quality, Compatibility, and Persistence of Warm‐Season Grass—Legume Mixtures
Authors: Posler G. L. , Lenssen A. W. , Fine G. L.
Published: July 2010

Development of compatible, persistent, warm‐season grass‐legume mixtures could increase forage yield and quality during summer months. We established a trial to determine forage yield, quality, species compatibility, and persistence of binary mixtures of warm‐season grasses with selected legumes, five of which are native to the central USA. Grass entries were switchgrass (Panicum virgatum L.), sideoats grama (Bouteloua curtipendula Michx.), and indiangrass [Sorghastrum nutans (L.) Nash]. Legume entries were purple prairieclover [Dalea purpurea Vent.; syn. Petalostemon purpureum (Vent.) Rydb.], roundhead lespedeza (Lespedeza capitata Michx.), leadplant (Amorpha canescens Pursh), Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill., B. Robins. & Fern.], catclaw sensitive brier [Schrankia nuttallii (DC.) Standl.], and cicer milkvetch (Astragalus cicer L.), a cool‐season species. Unfertilized grass plots without legumes also were included. The experiment was on a Haynie very fine sandy loam soil (coarse‐silty, mixed, calcareous, mesic Typic Udifluvents). All mixtures containing purple prairieclover, roundhead lespedeza, Illinois bundleflower, or catclaw sensitive brier yielded more forage than did grasses grown alone or with leadplant, except for pure switchgrass in 1986. All legumes increased the crude protein concentration of forage compared to that of grass‐alone plots, except for leadplant with switchgrass in 1986. Inclusion of catclaw sensitive brier and cicer milkvetch with grasses consistently improved in vitro digestible dry matter concentration (IVDDM), while inclusion of roundhead lespedeza, leadplant, and Illinois bundleflower generally resulted in decreased [VDDM concentration of forage. Purple prairieclover generally did not influence IVDMD of mixtures. Persistence of all legumes was good. Cicer milkvetch was not compatible with these grasses because it developed a thick, dense canopy prior to initiation of growth by these grasses.
Yield Contribution of Apical and Subapical Ears in Prolific and Nonprolific Corn
Authors: Durieux R. P. , Kamprath E. J. , Moll R. H.
Published: July 2010

Previous studies have demonstrated higher corn (Zea mays L.) yield potential for prolific corn hybrids (more than one ear) compared to nonprolific hybrids (one ear). However, little is known about the relative contribution of the second ear to total yield at various N levels. This study compared yield responses to N rates of 56, 140, and 224 kg N ha−1 of prolific Hybrids A (I202 × Mo17) and B (I117 × B73) with responses of nonprolific Hybrid C (Pioneer 3320) at a uniform low plant population density. All three hybrids gave a positive yield response to N applications. The prolific hybrids increased both in apical ear weight and in subapical ear weight and number in response to N rate. Averaged over N rates, Hybrid A yielded 24% and Hybrid C 14% higher than Hybrid B in 1987. In 1988, they yielded 13 and 10% higher than Hybrid B. Yield of single ears of nonprolific hybrid was higher than that of the apical ears in the prolific hybrids. Total potential yield in response to N application appears to be highest in Hybrid A because of second ear formation. Factors contributing to to yield increases from N applications in prolific Hybrid A included, in order of importance, an increase in the number of subapical ears, an increase in apical ear weight, and an increase in the subapical ear weight. Contrary to previous reports, apical and subapical ear weight increased simultaneously, with increasing N rates
Temperature Effects on Pima Cotton Leaf Growth
Authors: Reddy K. R. , Hodges H. F. , McKinion J. M.
Published: July 2010

Temperature is a primary environmental factor affecting cotton growth. Information on temperature effects on Pima cotton (Gossypium barbadense L.) growth is limited. The objective of this paper is to provide quantitative estimates of temperature effects on leaf emergence rates, the duration of leaf expansion, and rate of expansion. Pima cotton plants were grown from seed in naturally lit controlled environments with unlimited water and nutrients under five day/night temperature regimes ranging from 20/12 to 40/32 °C. Weighted average daily temperature was calculated from 900‐s average temperatures. Carbon dioxide was maintained at 350 µL L−1 during the daylight hours. Leaf area expansion and biomass accumulation were monitored from emergence to 64 d after emergence. Leaf initiation took about 2 d longer for prefruiting nodes at near optimum temperatures than for leaves formed after square initiation. Fruiting leaf initiation required about 4.5 d leaf−1 at 20 °C and about 2.5 d leaf−1 at 30 °C. Leaves expanded in excess of three times more rapidly at 31.3 °C than at 18.9 °C. The optimum temperature for leaf expansion was 31.3 °C. Leaf growth at 35.5 °C was only approximately 60% of that at 31.3 °C. Leaves required about 40% longer to expand at 18.9 °C than at 31.3 °C. All leaves required the same length of time to expand when grown at the same temperature, regardless of position on the mainstem. Since leaves varied greatly in mature leaf size, depending on leaf position, rates of expansion also varied similarly. Maximum leaf growth rates occurred during the 28‐to‐64‐days‐after‐emergence period compared with earlier growth periods, apparently reflecting greater light interception during that period. Biomass accumulation and growth rates were very temperature sensitive and closely related to leaf growth.
Scales: a Computer Program to Convert among Three Developmental Stage Scales for Wheat
Authors: Harrell D. M. , Wilhelm W. W. , McMaster G. S.
Published: July 2010

The Haun, Feekes, and Zadoks‐Chang‐Konzak developmental stage scales are often used to report phenological information for wheat (Triticum aestivum L.) development. Agronomists familiar with one of these scales may have only a passing acquaintance with developmental scales other than the one they consider most appropriate for their purposes. This makes review and interpretation of the literature more difficult. Although wheat development models often report phenological results, they generally use no more than one scale. For these reasons, and because there is not a simple numeric correspondence among the three scales, a computer program to convert among them is a useful tool. SCALES is a three‐module FORTRAN program that relates the three scales based on published descriptions. The interactive user interface module requests an input scale value and minimal additional information, which the conversion module uses to determine values for the remaining two scales via a dichotomous key. The output module writes the conversion results to the monitor. SCALES may be used independently for comparing phenological data based on different developmental scales, or the conversion module may be incorporated into computer models to provide output of developmental stage information for the simulation.
Validation of Salinity Crop Production Functions Obtained with the Triple Line Source Sprinkler System
Authors: Royo A. , Aragüés R.
Published: July 2010

Traditional methods of screening crops under field conditions for salt tolerance produce low selection efficiencies at a relatively high cost; consequently, more practical and reliable methods need to be developed. We evaluated the reliability of salinity crop production functions obtained with a triple line source (TLS) sprinkler system, the reproducibility of the results from different years and site locations within the TLS, and the minimum plot size per cultivar that allows for consistent results. Ninety‐six percent of the 154 ECaw (electrical conductivity of the applied water)‐grain yield response functions obtained from 6 yr of field experiments with the TLS had significant correlation coefficients (P < 0.05), and 77% of the standard errors (SE) of the estimated EC50 (EC of the applied water that reduces yield by 50%) values were <2.0 dS m‐1. The EC50 and SE values of four barley (Hordeum vulgare L.) cultivars sown at the center and at the far end of the TLS plot indicate that the response functions were independent of location within the TLS. The EC50 and SE values of eight barley cultivars grown in different years indicate nonsignificant differences (P > 0.05) in 79% of the 29 comparisons performed. The EC50 values of four barley cultivars grown in hill plots and in two‐row, three‐row, and six‐row plots did not differ statistically (P > 0.05). With a typical 30‐ by 60‐m TLS system, elemental two‐row 1.2‐m‐long plots, and 10 saline treatments, 120 salinity crop production functions can be developed. Hence, this system is a reliable and practical field method for developing salinity‐crop production functions and screening for salt tolerance.
Nitrogen Fertilization Effects on Planting Stock Characteristics and Establishment Performance of Dwarf Elephantgrass
Authors: Rusland G. A. , Sollenberger L. E. , Jones C. S.
Published: July 2010

‘Mott’ elephantgrass (Pennisetum purpureum Schum.) is a high‐quality tropical forage that is vegetatively propagated using stems or stem cuttings. Mott is more difficult to establish than tall elephantgrass, and a better understanding is needed of management factors that affect its establishment. During 1987 through 1989, field studies were conducted on an Adamsville fine sand (hyperthermic, uncoated, Aquic Quartzipsamment). Objectives were to determine the effect of N fertilization of planting stock nurseries on chemical and physical characteristics and establishment performance of Mott stems, and to determine if relationships exist between planting stock characteristics and establishment performance. Nitrogen rates were 0, 50, 100, 200, 300, and 400 kg ha−1, and treatments were replicated twice for measurement of stem characteristics and three times for establishment performance. Stem length (31.0–40.5 cm), mass (10.4–14.8 g per stem), N concentration (8.9–16.0 g kg−1), N content (0.09–0.24 g per stem), and total nonstructural carbohydrate (TNC) content (0.97–1.33 g per stem) increased linearly with increasing N rate. Measures of establishment performance generally increased with increasing N rate in 1987 and 1989, years for which rainfall was near or above normal during the time when planting stock was growing. Drought during this period in 1988 resulted in lower values for most stem characteristics and for measures of establishment performance. Highest correlation coefficients (0.53–0.60) were observed between number of emerged shoots per row and the stem characteristics, length, mass, and TNC concentration and content. These data indicate that N fertilization of Mott nurseries (≥200 kg ha−1) and soil moisture during growth of planting stock are critical to subsequent establishment performance of planted stems, and that stem characteristics are correlated with establishment performance.
Deriving Fertilizer Recommendations with a Flexible Functional Form
Authors: Sain Gustavo E. , Jauregui Mario A.
Published: July 2010

General fertilizer response models are useful to derive robust recommendations for farmers who face different circumstances. This paper shows that a flexible functional form such as the transcendental can be applied to develop both agronomically and economically sound recommendation tables using a set of soil test, climate, and management variables. Data from thirty‐eight experiments on wheat response to N and P in the Humid Pampa, Argentina, were used to build a general response model that incorporates the initial levels of soil test measures (NO3‐N and Bray‐1 P), rainfall from sowing to maturity, and previous crop. The economic analysis was performed for relevant nutrient/grain price ratios ro = 8.0 and rp = 18.3 for N and P, respectively. A table of fertilizer recommendations for wheat was derived for different combinations of rainfall expectations, previous crop, and soil test values. The following results were obtained: (i) the estimated model not only accounted for a significant percentage of the total variability in the dependent variable (InY), with R2 =0.56, P = 0.01, but it also gave coefficients with signs in conformity with agronomic expectations; (ii) the economic optima for N (N*) and P (P*) are compatible with the range of optima computed with per‐site economic analyses; (iii) N* and P* increased as rainfall increased; (iv) N* was lower for wheat after soybeans than for wheat after maize; (v) N* was higher for smaller values of soil N, while P* was practically unaffected by soil N; and (vi) P* was higher for smaller values of soil P, while N* was affected by soil P, with a pattern that depended on both previous crop and rainfall. Similar tables can be derived for groups of farmers under different economic circumstances (i.e., different input/output price ratios).
Timing of Furrow Irrigation Termination for Determinate Soybean on Clay Soil
Authors: Heatherly Larry G. , Spurlock Stan R.
Published: July 2010

Irrigation commencing at or near beginning bloom (R1) and continuing during reproductive development of determinate soybean [Glycine max (L.) Merr.] grown in the southern USA in dry years increases seed yield. The number of irrigations between the first and last irrigation event can influence the direct costs of irrigation; however, the optimum time to stop irrigation in relation to crop maturity has not been identified. ‘Leflore’ (1987–1990) and ‘A5980’ (1988–1990) determinate cultivars were grown on Sharkey clay (very‐fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) at Stoneville, MS, to determine the effect of timing of last furrow irrigation on seed yield, yield components, yield increase, and net returns. All irrigation treatments within a cultivar were started at R1 (beginning bloom) or later. One treatment was dropped from the sequence with each successive furrow irrigation event through R6 (full seed). Irrigation applied through mid‐R5 (seed‐filling period) during a dry year produced the greatest seed yield increase of 1855 kg ha−1, which was 610 kg ha−1 greater than the yield of the treatment terminated at R4 (full pod), and equal to the yield of the treatment terminated at R6. Yield increases due to irrigation during wet years were smaller or nonexistent. In all cases, increased number of seeds was the sole contributor to increased yield. In the dry years, irrigation terminated at either mid‐ to late‐R2 or mid‐R5 produced the greatest yield increase per unit of irrigation water, but irrigation continued into the seedfill period and then terminated produced the highest net return. These results indicate that furrow irrigation of soybean grown on a cracking clay soil in dry years should be continued through mid‐R5 to achieve maximum seed yield and net returns.
Timing of the First Irrigation in Corn and Water Stress Conditioning
Authors: Jama Ahmed Omar , Ottman Michael J.
Published: July 2010

Delaying the first irrigation is thought to encourage root growth and to condition crop plants for stress later in the growing season. We tested this common practice for corn (Zea mays L.) grown under arid conditions in Tucson, AZ, in 1989 and 1990. In field studies conducted on an Agua sandy clay loam (coarse‐loamy over sandy, mixed, thermic Typic Torrifluvent), the first irrigation was applied at the 2‐leaf, 4‐leaf, or 6‐ to 8‐leaf stages, followed by irrigation or water stress at anthesis. Delaying the first irrigation did not encourage root growth but actually restricted it in 1989. Seasonal water use was decreased from an average of 796 mm to 705 or 652 mm if the first irrigation was delayed from the 2‐leaf to the 4‐leaf or 6‐ to 8‐ leaf stages, respectively. Timing of the first irrigation did not affect yield in 1989, or in 1990 if irrigations were withheld at anthesis. However, grain yield was decreased from 830 to 693 g m−2 and total plant yield was decreased from 2490 to 2185 g m−2 when the first irrigation was delayed past the 2‐leaf stage in 1990 and the crop was well‐watered at anthesis. Delaying the first irrigation of corn, with 148 mm (1989) and 170 mm (1990) plant available water in the top 1.5 m of soil at the beginning of the season, did not appear to condition the crop for water stress later in the season in an arid environment, but may substantially decrease yield if adequate water is available for the remainder of the growing season.
Errors in Measuring Absorbed Radiation and Computing Crop Radiation Use Efficiency
Authors: Gallo Kevin P. , Daughtry Craig S. T. , Wiegand Craig L.
Published: July 2010

Radiation use efficiency (RUE) is often a crucial component of crop growth models that relate dry matter production to energy received by the crop. RUE is a ratio that has units g J−1, if defined as phytomass per unit of energy received, and units J J−1, if defined as the energy content of phytomass per unit of energy received. Both the numerator and denominator in computation of RUE can vary with experimental assumptions and methodologies. The objectives of this study were to examine the effect that different methods of measuring the numerator and denominator have on the RUE of corn (Zea mays L.) and to illustrate this variation with experimental data. Computational methods examined included (i) direct measurements of the fraction of photosynthetically active radiation absorbed (ƒA), (ii) estimates of ƒA derived from leaf area index (LAI), and (iii) estimates ƒA derived from spectral vegetation indices. Direct measurements of absorbed PAR from planting to physiological maturity of corn were consistently greater than the indirect estimates based on green LAI or the spectral vegetation indices. Consequently, the RUE calculated using directly measured absorbed PAR was lower than the RUE calculated using the indirect measures of absorbed PAR. For crops that contain senesced vegetation, green LAI and the spectral vegetation indices provide appropriate estimates of the fraction of PAR absorbed by a crop canopy and, thus, accurate estimates of crop radiation use efficiency.
Manual and Digital Line‐Intercept Methods of Measuring Root Length: A Comparison
Authors: Farrell Richard E. , Walley Frances L. , Lukey Adele P. , Germida James J
Published: July 2010

The manual line‐intercept (MLI) method is widely accepted as the standard method of estimating root length. Recently, however, semiautomated systems employing a digital line‐intercept (DLI) method have been developed. Although the DLI method is said to represent a significant time savings over the MLI method, comparisons between the two methods are relatively scarce. This study was conducted to determine and compare root length estimates obtained using manual and digital line‐intercept methods and to evaluate different methods of preparing root subsamples for analysis. Roots were collected from spring wheat (Triticum aestivum L.) inoculated with three different plant growth‐promoting rhizobacteria and a vesicular‐arbuscular mycorrhizal fungus. Subsamples were cut from bulk root systems before or after they had been dried, and root lengths were estimated using both the MLI and DLI methods. Although the DLI and MLI methods yielded highly correlated results (r2 = 0.880***) when the subsamples were dried before being cut, the DLI method consistently underestimated root lengths and could not distinguish between inoculant effects. This was attributed to the inability of the imaging system to resolve small pieces of shattered root. When subsamples were prepared from fresh root material, the number of small root fragments was minimized; the two methods yielded highly correlated results (r2 = 0.943***) and both methods were equally adept at distinguishing significant differences between inoculant effects. Accurate root length estimates can be obtained using the DLI method with subsamples prepared from fresh roots in one‐ to two‐thirds less time than can be achieved with the MLI method.
Modeling the Occurrence of Reproductive Stages after Flowering for Four Soybean Cultivars
Authors: Grimm Sadi S. , Jones James W. , Boote Kenneth J. , Herzog D. C.
Published: July 2010

Soybean growth and yield models require good predictions of vegetative and reproductive development stages, as a function of specific environmental variables. Parameters for predicting R5 (beginning of seed growth) and R7 (physiological maturity) dates of four soybean cultivars were estimated for a development rate model. R5 is predicted by accumulating a daily rate of development, which depends on night length and temperature, starting at Rl (flowering) until a threshold is reached. Daily development rate is computed by a multiplicative relationship containing two linear‐plateau functions: one for describing the variation in development rate with night length under optimal temperature and the other describing variation with temperature under optimal night length. The downhill simplex method was used to estimate phenological parameters for each cultivar, minimizing the error sum of squares between observed and simulated dates of R5 occurrence. The same type of model and methodology was used to estimate parameters for R7 prediction, but beginning at R5 until a threshold is reached. The results indicate that as plants develop from V1 (first true leaf) to R7 they become more responsive to photoperiod and less sensitive to temperature. Differences among cultivars with respect to optimal night length tend to diminish as the plants approach physiological maturity; with respect to temperature, the reverse happens. The optimal temperature for reproductive development varied between 25 and 29 °C, without great differences among cultivars of differing maturity, but with a slight increasing trend from V1 toward R7.
Performance Comparisons of Conventional and Laboratory‐Scale Alfalfa Hay Bales in Small Haystacks
Authors: Coblentz Wayne K. , Fritz John O. , Bolsen Keith K.
Published: July 2010

Field trials designed to study the storage of moist hay have often been plagued by uncontrollable factors such as weather. A system for making laboratory‐scale (10.3 by 10.8 by 13.4 cm) hay bales was evaluated in two trials. In the first experiment, three conventional small square bales of alfalfa (Medicago sativa L.) were prepared in the field at each of seven different combinations of moisture and density. One bale was randomly selected to be used as the forage source for laboratory‐scale bales of the same density. Laboratory bales were incubated between the two remaining conventional bales. Bale types were compared for maximum temperature, 30‐d average temperature, degree days > 30 °C, visual mold, dry matter (DM) recovery, total nitrogen (N), acid‐detergent fiber (ADF), neutral‐detergent fiber (NDF), and acid‐detergent‐insoluble nitrogen (ADIN). Laboratory bales generally remained different (P < 0.05) from parent conventional bales for most temperature‐related traits. Agreement between bale types was better for most quality analyses. In an effort to improve relative performance between bale types, a second experiment was conducted, in which the laboratory bales were prepared at 1.0, 1.3, 1.6, and 2.0 times the density of the conventional bales. Results showed improved agreement between laboratory bales of elevated densities and conventional bales for most temperature traits. Acid‐detergent‐insoluble N levels for laboratory bales were greatly affected by bale density. High‐density laboratory bales had significantly greater ADIN fractions than conventional bales, particularly in the high moisture treatment. These results implicate bale density as an important factor in damage to alfalfa proteins by the Maillard reaction.
Sensitivity of Winter Wheat Phyllochron to Environmental Changes
Authors: Cao Weixing , Moss Dale N.
Published: July 2010

The effect of environmental changes on the rate of leaf emergence in wheat (Triticum aestivum L .) must be understood to accurately simulate the development of the crop canopy. We determined the phyllochron for ‘Stephens’ winter wheat plants in growth chambers at two constant temperatures (10 and 18 °C) at a daylength of 14 h and at two constant daylengths (8 and 18 h) at a temperature of 20 °C, and for plants transferred between the two temperatures and between the two daylengths at the first‐, second‐, third‐, and fourth‐ leaf stages. The phyllochron of all plants transferred from low to high temperature increased to that of plants kept continually at the high temperature. The phyllochron of plants transferred from high to low temperature at the one‐leaf stage was identical with the phyllochron of plants kept continually at the low temperature, but was intermediate between that of the high and low temperatures for transfers at the second‐, third‐, or fourth‐leaf stage. The phyllochron of plants transferred from short to long days decreased to values identical to those plants kept continually at the long daylength. The phyllochron of all plants transferred from long to short daylengths increased to values equal to or greater than that of plants kept continually at the short daylengths. Thus, plants adapted to either temperature or daylengths environments that favor rapid leaf emergence in real time had less capacity to utilize a less favorable environment for leaf growth than plants that were kept continually in the less favorable environment. The results help explain why the phyllochron is often constant for a particular field planting where plants are subject to seasonal changes in temperature and daylength.
DIALLEL: A Microcomputer Program for the Simulation and Analysis of Diallel Crosses
Authors: Burow Mark D. , Coors James G.
Published: July 2010

A microcomputer program has been developed to be used as a teaching tool in quantitative genetics classes and as a means of analyzing real data from diallel crosses. The first part of the program, the simulation module, is of use as a teaching tool, offering students the opportunity to examine the ramifications of the underlying genetic and statistical assumptions of diallel mating designs. In particular, the program illustrates the difficulty in obtaining reliable estimates of genetic components of variance when employing a restricted number of parents. Using user‐entered values for the population mean, the number of parents, and genetic, environmental, and error variances, the program generates and analyzes multiple sets of data. The user can experiment by altering the parameters to test different strategies to cope with the difficulties inherent in the diallel mating design. The second module allows the analysis of real‐world experiments made in any of four diallel mating designs. The user may enter and correct data in the program itself, or import data as ASCII files from other programs. The program prints an analysis of variance table, and tables of means by variety and cross, heterosis, general and specific combining abilities, and genetic components of variance and their standard errors.
Seedling Growth as Affected by Seed Weight in Common Vetch
Authors: Qiu J. , Mosjidis J. A. , Williams J. C.
Published: July 2010

Growth pattern of seedlings is important for any species to achieve successful establishment. Growth chamber experiments were conducted to study the relationships between seed weight and usage of cotyledonary reserves and growth rates of major seedling components and to determine the changes in relative importance of cotyledonary reserves and newly developed photosynthetic tissues on seedling growth in common vetch (Vicia sativa L.). Seedlings from three seed‐weight groups of ‘Warrior’, PI 284563, and ‘Cahaba White’ were grown in growth chambers at a temperature of 28/12°C under complete darkness and light–dark cycle (13/11 h) conditions. Seedlings from heavier seeds utilized cotyledonary reserves (UCR) at a faster rate; however, conversion efficiency of cotyledonary reserves (CECR) into plant tissue was the same regardless of seed weight. Hence, the advantage of heavy seeds lies in their higher content of cotyledonary reserves and on their ability to provide energy more rapidly to the growing seedlings. Seedlings from heavier seeds had greater rates of elongation, accumulation of leaf area and shoot, leaf, and root dry weights than those from light seeds. Thus, heavier seeds produce seedlings with a higher growth capacity in common vetch. Cotyledonary reserves supported heterotrophic seedling growth for ≈7 d after emergence (DAE) under dark conditions. However, cotyledonary reserves had little importance in subsequent growth once the first tetrafoliolate leaf emerged at 5 DAE for light‐grown seedlings. Thus, the emergence of the first tetrafoliolate leaf marks the transition between heterotrophic and autotrophic seedling growth.
Matric Priming Increases Germination Rate of Great Basin Native Perennial Grasses
Authors: Hardegree Stuart P.
Published: July 2010

Cheatgrass (Bromus tectorum L.) is an undesirable nonnative annual that germinates at relatively low temperatures in the spring and fall and can establish a root system more quickly than Great Basin native perennial grasses. The purpose of this study was to determine whether seed priming could be used to enhance low‐temperature germination rate of native perennial grasses so that they can better compete with cheatgrass. A matric‐priming technique was used to increase low‐temperature germination rate of seven native perennial grasses: blue‐bunch wheatgrass [Pseudoroegneria spicata (Pursh) Löve], thickspike wheatgrass [Elymus lanceolatus (Scribn. & J.G. Smith) Gould; syn. Agropyron dasystachyum (Hook.) Scribn.], basin wildrye [Leymus cinereus (Scribn. and Merr.) A. Löve], sheep fescue (Festuca ovina L.), canby bluegrass (Poa canbyi Scribn.), sandberg bluegrass (Poa sandbergii Vasey), and bottlebrush squirreltail [Sitanion hystrix (Nutt.) J.G. Smith]. Seeds primed at both 10 and 25°C were evaluated for germination response at both 10 and 25°C. Days to 50% germination (D50) was ≈ 4 d for cheatgrass germinated at 10°C. Native grass seeds in control treatments germinated between about 4 and 11 d later than cheatgrass at 10°C. Priming reduced D50 by between 4 and 8 d for all native species when germinated at 10°C. Germination rate at 10°C was generally higher when the seeds were primed at 25°C, except for basin wildrye. Priming increased cold temperature germination rate of bluebunch wheatgrass, thickspike wheatgrass, and sheep fescue to a level comparable to cheatgrass.
Grain Sorghum Yield Response to Nonuniform Stand Reductions
Authors: Larson E. J. , Vanderlip R. L.
Published: July 2010

Nonuniform stand reductions caused by poor emergence, insect damage, or other factors, occur frequently in grain sorghum [Sorghum bicolor (L.) Moench] fields. This research was conducted to determine the effect of within‐row skip patterns on grain yield and yield component compensation, particularly for hybrids differing in tillering ability. Dryland field studies were conducted at Manhattan (Reading silt loam, fine‐silty, mixed, mesic Typic Argiudoll) and St. John (Naron fine sandy loam, fine‐loamy, mixed, thermic Udic Argiustoll), KS, during 1988 and 1989. Two medium‐maturity hybrids, DeKalb DK‐46 and Pioneer 8500, were selected based on low and high tillering ability. Plots were three rows, with the middle row containing a within‐row skip pattern. Results were analyzed separately by skip row, adjacent row, and average for the three rows. Skip lengths within a 7.6‐m row were 0.9 m, 0.9 m repeated three times, and 2.7 m within the skip row, and the 0.9 m × 3 pattern in all three rows. Yield of the skip row was reduced by every configuration bordered by control stand adjacent rows. Yield compensation from adjacent rows and within the skip row compensated for reduced stands, except for a 2.7−m skip resulting in 5.1% yield reduction, 64% uniformly spaced stand in all three rows with 6.9% yield reduction, and three 0.9 m within‐row skips in all three rows with 10.9% yield reduction. Compensation was primarily in number of heads per plant and seeds per head. Difference in hybrid tillering response did not influence grain yield. Thus, yield reduction is likely only where skips result in severe plant spacing nonuniformity.
Plant Development, Water Relations, and Carbon Allocation of Heart‐Podded Hoary Cress
Authors: Miller Richard F. , Svejcar Tony J. , Rose Jeffrey A. , McInnis Michael L.
Published: July 2010

Attempts to control the noxious weed heart‐podded hoary cress [Cardaria draba (L.) Desv.] in the Pacific Northwest have been relatively ineffective, and this species has expanded its distribution from irrigated hayland onto adjacent semiarid rangelands. The objective of this study was to define the seasonal pattern of development and biological activity of heart‐podded hoary cress growing on semiarid rangeland. The study was conducted in the field over a 2‐yr period on a terrace site that has deep Cumulic Haploxeroll soil and an adjacent upland site that has a shallow Lithic Argixeroll soil. Soil water content, phenology, xylem pressure potential and leaf conductance were measured at both sites. Aboveand belowground biomass and spring C allocation pattern, determined by labeling plants with 13C, were measured at the terrace location. Regardless of location, no heart‐podded hoary cress seedlings were found; all shoots developed from rhizome buds. The majority (76%) of heartpodded hoary cress biomass was located belowground. Although drought occurred earlier on the upland than the terrace site, phenology was similar on the two sites. Carbon was translocated to belowground tissues within 1 h of labeling and reached peak accumulation within 24 h. The greatest 13C enrichment of roots and rhizomes occurred during the flowering stage. The peak in belowground C allocation occurred at a stage when leaf conductance was declining rapidly. The short period of maximum C allocation to belowground tissue, the large proportion of belowground tissue, and the wide variation of phenology among plants at a given time may account for the difficulty in chemically controlling this species.
Responses of Kura Clover to Sheep Grazing and Clipping: I. Yield and Forage Quality
Authors: Peterson Paul R. , Sheaffer Craig C. , Jordan Robert M. , Christians Charles J.
Published: July 2010

Few perennial legumes have dependable long‐term productivity under grazing in the northern USA. Our objective was to determine the effects of frequent clipping and sheep(Ovis spp.) grazing on forage yield and quality of kura clover (Trifolium ambiguum. Bieb.), a rhizomatous perennial legume. Clipping and grazing trials were initiated on a 5‐yr‐old stand of ‘Rhizo’ kura clover on a Waukegan silt loam and conducted for 3 yr. Total season yield (mean of 8.6 Mg ha‐1) was unaffected by clipping frequency until the third year, when five and six cuttings per season produced 80 and 70% as much forage, respectively, as either three or four cuttings. In the second and third years of sheep grazing treatments, kura clover rotationally stocked with 14‐d rest periods produced 28 and 16% less forage, respectively, than that under rotational stocking with 28‐d rest periods. In contrast to total season forage yield, spring yield following 3 yr of clipping and grazing did not differ among clipping frequency increased from three to six cuttings per year, (Missing Data.) (CP) and in vitro digestible dry matter (IVDDM) concentrations increased from 222 to 254 and from 854 to 880 g kg ‘1 DM, respectively, and neutral‐detergent fiber (NDF) concentration decreased from 326 to 295 g kg‐1 DM. Forage was of high quality, because leaf concentration always exceeded 850 g kg‐1 of forage dry matter. Established kura clover is tolerant of frequent and close defoliation and warrants pasture use because of its long‐term productivity and high forage quality.
Growth Characteristics of Rhizoma Peanut and Nitrogen‐Fertilized Bahiagrass Swards
Authors: Williams M. J.
Published: July 2010

The interaction of plant sensitivity to drought with N deficiency has been suggested as the reason grasses fail to persist under grazing when grown in association with rhizoma peanut (Arachis glabrata Benth.). To test this assumption, aboveground dry matter (DM) accumulation and relative growth rate (RGR) of ‘Florigraze‘ rhizoma peanut and ‘Pensacola’ bahiagrass (Paspalum notatum Flügge) fertilized with 0, 56, and 112 kg N ha−1 were measured from March to November in 1990 and 1991. Rhizoma peanut aboveground DM accumulation was greater both years (4950 and 6100 kg ha−1 1990 and 1991, respectively) in July at the start of the summer rainy season than any N‐fertilized bahiagrass treatment (640 and 1530, 1240 and 2330, and 1570 and 4490 kg ha−1 in 1990 and 1991 for 0‐N, 56‐N, and 112‐N treatments, respectively), due to higher RGR. Although the RGR of rhizoma peanut was similar to or less than that of the bahiagrass treatments for the remainder of the growing season in both years, by August 1991 only the 112‐N bahiagrass treatment (5260 kg ha−1) had total DM accumulation similar to rhizoma peanut (5110 kg ha−1). Rhizoma peanut RGR appeared to be more sensitive to rainfall, and was positively correlated (r = 0.71) with rainfall for as long as 8 wk prior to the sample dates in the dry spring of 1990. Bahiagrass RGR showed no correlation with rainfall either year. This suggests that lack of persistence of bahiagrass in mixed swards is due to severe competition for light with rhizoma peanut in springs when moisture is adequate and to potentially increased stress due to grazing in springs when drought restricts growth of rhizoma peanut.
Evaluation of LEACHM: II. Simulation of Nitrate Leaching from Nitrogen‐Fertilized and Manured Corn
Authors: Jemison John M. , Jabro Jalal D. , Fox Richard H.
Published: July 2010

High NO3‐N concentrations in groundwater resulting from agricultural production have increased the need for mathematical models to predict the concentration and mass of NO3‐N leached from agricultural soils. Study objectives included evaluating the N version of LEACHM (LEACHMN) to predict mass of NO3‐N leached from nonmanured and manured corn (Zea mays L.), and to test two methods of model validation. Four treatments (no manure with 0 and 200 kg N ha−1 and a manure treatment with 0 and 100 kg N ha−1) from a NO3 leaching experiment were modeled for 1988, 1989, and 1990. Model calibration involved adjusting nitrification, denitrification, and volatilization rate constants to minimize differences between predicted and observed data. When calibrated for each year, LEACHMN produced reasonably accurate predictions of NO3‐N mass leached; however, LEACHMN tended to overestimate summer and underestimate spring leaching losses. The lack of a provision in LEACHM to allow solute diffusion out of water flow channels, and underpredicted corn N uptake early in the season probably created conditions conducive for high leaching losses early; following harvest, insufficient NO3‐N in the soil profile resulted in the model underestimating leaching in the spring. Validating LEACHMN using 1988 rate constants for the 1989 and 1990 years was unsuccessful. When 3‐yr average rate constants were used, simulation accuracy improved somewhat; most accurate simulations were found if 3‐yr average values were close to the calibrated rate constant for that year. The model's predictive capability would probably improve if it contained a more complex corn N uptake routine and a dual‐pore water flow component.
Accumulation and Partitioning of Dry Matter in Water Yam
Authors: Goenaga Ricardo J. , Irizarry Heber
Published: July 2010

There is a scarcity of field‐growth data from which a yam (Dioscorea alata L.) growth model could be developed to promote agrotechnology transfer of the crop in the tropics. A 2‐yr field study was conducted on Corozal soil (clayey mixed isohyperthermic Aquic Tropudults) in an initial effort to collect data on patterns of leaf area development and dry matter accumulation and partitioning among various plant parts during growth and development of yam plants. In the first year of the study, plants of D. alata cv. Gunung were subjected to fertilizer rates of 0, 667, 1333, 2000, and 2667 kg ha−1 of a 15‐2.2‐12.4‐3% (N‐P‐K‐Mg) commercial mixture at 5O d after planting (DAP). Biomass harvests were conducted at 60, 90, 120, 150, 180, and 210 DAP. For all plant parts studied, dry matter content was not significantly affected by fertilizer treatment. Even after excluding application of fertilizer during the second year, there were no statistical differences in total and tuber dry matter content between years. Maximum leaf area index values (LAI ≈ 8) were attained by 140 DAP. During this period, leaves and vines accounted for at least 80% of the total plant dry matter; thereafter, their dry matter content declined. After 140 DAP, increases in total dry matter were the result of rapid increases in tuber dry matter accumulation. The lack of response to fertilizer treatment and high tuber dry matter production suggest that the preplanting soil nutrient status was adequate to support optimum growth of the yam cultivar used during both years of this study, even without the application of fertilizer.
Simulated Hail Damage to Rice: II. Effects during Four Reproductive Growth Stages
Authors: Counce Paul A. , Wells Bobby R. , Norman Richard J. , Leong Jeff
Published: July 2010

Knowledge of grain yield responses to simulated hail damage is useful in assessing hail damage, assessing similar types of damage, and better understanding crop biology. In previous experiments, we determined that reproductive stages of rice (Oryza sativa L.) development were most sensitive to damage. Objectives of this study were to delineate grain yield effects of simulated hail damage during critical reproductive growth stages at which various components of yield are set. Field experiments were conducted on a Crowley silt loam soil (fine, montmorillonitic, thermic Typic Albaqualfs) in 1985 and 1986 using the cultivar Lebonnet. At four reproductive growth stages, yield loss was determined from these three treatments: (i) removal of the top 1, 2, and 3 fully expanded leaves, (ii) bending of 10, 20, or 40% of culms, and (iii) severing of 10, 20, or 40% of culms. All three types of damage were significant at some level of intensity at all four growth stages. The largest yield reductions resulted from leaf removal. Leaf removal resulted in the greatest amount of yield reduction at booting and heading, with less damage from leaf removal 14 d after heading and least damage from leaf removal at panicle initiation (PI). Yields were reduced as more leaves were removed. Culm severing caused less yield reduction than leaf removal and the least yield reductions resulted from culm bending. Culm severing was progressively more damaging to yield as the rice developed through the season and reductions were similar to those found for leaf removal at 14 d after heading. Culm bending was found to be significantly damaging to yield except at the 10% treatment levels at heading and 14 d after heading. Despite apparently extreme damage treatments, rice yields were reduced by <15% in response to most of the treatments imposed. Consequently, the rice crop has considerable ability to compensate for physical damage due in part to the unique biology of the rice plant.