bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Alfalfa Plant and Soil Extracts on Germination and Growth of Alfalfa
Authors: Chung Ill‐Min , Miller Darrell A. 
Published: July 2010

AbstractAlfalfa (Medicago sativa L.) plants contain water‐soluble substances that inhibit the germination and seedling growth of alfalfa. Determining where allelochemicals may be found in alfalfa in the greatest concentration would aid in trying to isolate the compound or compounds responsible for autotoxicity. This study investigated the allelopathic effects of various alfalfa plant parts, and the soil in which alfalfa had been grown, on alfalfa germination and seedling growth. Aqueous extracts of alfalfa leaf, stem, flower, seed, and root plant parts were made to determine their effects on germination and dry weights of hypocotyl, radicle and total length of 5‐d‐old alfalfa seedlings over a range of extract concentrations. Soil samples (Flanagan series: fine, montmorillonitic, mesic Aquic Argiudolls) from around alfalfa plants at the vegetative and reproductive stages were compared with sterilized and nonsterilized soil formerly seeded with alfalfa, hairy vetch (Vicia villosa Roth), and winter rye (Secale cereale L.) Increasing the aqueous extracts concentrations of separated alfalfa plant parts significantly inhibited alfalfa germination, seedling length and weight. Radicle length was more sensitive to extract source than seed germination or hypocotyl length. Based on 5‐d‐old alfalfa radicle length growth, and averaged across all extract concentrations, the degree of toxicity of different alfalfa plant parts and soil from around alfalfa can be classified in order of decreasing inhibition as follows: leaf, seed, complete plant mixture, soil, root, flower, and stem. Leaf extracts (12 g kg−1) caused a 48% decrease in water uptake by alfalfa seed. Soil in which alfalfa had previously grown was the most inhibitory to alfalfa growth after 25 d of growth compared with soil where winter rye or hairy vetch had previously grown. Inhibitory effects were greater for soil collected around alfalfa grown at the reproductive than the vegetative growth stage. These data indicate that alfalfa autotoxicity may result from a release of one or more water‐soluble compounds from alfalfa leaf tissue.
PC‐SAS Program for Estimating Hühn's Nonparametric Stability Statistics
Authors: Lu Hsui Ying 
Published: July 2010

AbstractA program written in the SAS language for personal computers to estimate Hühn's two nonparametric stability statistics is presented. Nonparametric methods proposed by Hühn in the 1970s are based on the ranks of genotypes in each environment and use the idea of homeostasis as a measure of stability. A stable genotype shows similar rankings across environments. Nonparametric stability statistics provide a viable alternative to existing parametric measures based on absolute data. They require no statistical assumptions about the distribution of the phenotypic values and are easy to use. Addition or deletion of one or a few observations is not as likely to cause great variation in the estimates as would be the case for parametric stability measures. For many applications (e.g., selection in breeding and testing programs), the rank orders of genotypes are the most essential information. The program deals with a two‐way table with K genotypes and N environments. The output contains two main features: (i) corrected values and their ranks of genotypes within each environment, and (ii) two nonparametric stability estimates and their test of significance. From the output, one may examine the rankings of genotypes in each environment and look for stability differences among genotypes. This program should make practical the more frequent use of nonparametric stability statistics to investigate genotype ✕ environment interactions in agricultural research.
Timing and Rate of Ethephon Application to Two‐Row and Six‐Row Spring Barley
Authors: Bridger Gregory M. , Klinck Harold R. , Smith Donald L. 
Published: July 2010

AbstractEthephon (2‐chloroethyl phosphonic acid) reduces lodging in barley (Hordeum vulgare L.) by shortening straw, but the optimal rate and growth stage of application, both of which may interact with cultivar and environment, are unclear, especially for two‐row barley in North America. Field studies in Quebec in 1985 and 1986 evaluated the response of ‘Leger’ six‐row and ‘Birka’ two‐row barley to ethephon applied at varying rates, growth stages, and times of day. The two‐row cultivars Rodeo and Micmac were also included in one experiment. Lodging was slight or absent in all experiments. The taller Leger was usually shortened more than Birka, largely due to greater shortening of the peduncle. Late boot applications of ethephon consistently shortened straw, but the window of effective application began at the flag leaf stage and extended for more than 1 wk for Birka, while for Leger it was about 4 d, but differed phenologically between years. Heading was delayed by ethephon. In Rodeo and Birka, ethephon often reduced the degree of spike emergence from the flag leaf sheath. Incomplete spike emergence may have contributed to reduced kernel and test weights, particularly with applications from the flag leaf until the late boot stage. Ethephon increased Leger yield by up to 15% in one experiment under the favorable conditions of 1985. In 1986, a wet year, yield in one experiment was reduced by 11% by the higher ethephon rate (480 g a.i. ha−1), due to reduced spikes per square meter. Birka yield was reduced (P = 0.06) by 6% by the higher rate (480 g a.i. ha−1) in the 1986 application date study. Harvest index of Rodeo and Birka was reduced due to reduced tiller survival following application of ethephon at 480 to 500 g a.i. ha−1. Yield component compensation usually occurred between spikes per square meter and kernel weight, particularly for two‐row cultivars. Height was reduced more by applications at 0400 h and 0600 h than later in the day. Birka kernel weight was reduced with morning or evening applications, while Leger kernel weight was little affected by application time of day. In the absence of lodging and under conditions of environmental stress, ethephon applied at rates over 240 g a.i. ha−1 may reduce yields, particularly of two‐row barley, for which spike emergence may be severely reduced.
Dry Matter Partitioning in a True vs. Facultative Annual Forage Legume
Authors: Williams M. J. , Chambliss C. G. , Brolmann J. B. 
Published: July 2010

AbstractDifferential partitioning of photosynthate has been suggested as the reason for low early‐season (8 to 12 wk post planting) dry matter (DM) yield of ‘Savanna’ stylo [Stylosanthes guianensis (Aubl.) Sw.], a facultative annual over much of its Florida range. In a 3‐yr field study (1991–1993), the effect of planting date (April vs. June) on root‐to‐shoot ratio (g g−1), leaf‐to‐stem ratio (g g−1), and total plant weight (g) of Savanna stylo was compared with common alyceclover [Alysicarpus vaginalis (L.) DC.], a true annual, for 16 wk post planting. Only time post planting consistently affected root‐to‐shoot ratio, which declined as time post planting increased. Within years, leaf‐to‐stem ratio also declined with increasing time post planting, but, on average, Savanna stylo had a higher leaf‐to‐stem ratio than alyceclover. There was a planting date × legume × year × time post planting interaction for total plant weight. This was because total plant weights, although similar regardless of planting date or legume in 1991 and 1993, differed in 1992, when April‐planted Savanna stylo plants had greater total plant DM than June‐planted Savanna stylo or either planting date of alyceclover. Across the 16‐wk post‐planting period, there was a consistent legume × planting date interaction each year for total plant weight. This was because both Aprilplanted legumes were vegetative for the full 16‐wk post‐planting period (April–August) and total plant weight remained similar, but only Savanna stylo remained vegetative for the full 16‐wk post June‐planting period (June–October). Total plant weight of June‐planted alyceclover was lower due to flowering and leaf loss in the later part of the 16‐wk post‐planting period. These data indicate that the lower early‐season DM yield of Savanna stylo compared with alyceclover is not due to physiological differences associated with perennial and annual growth habits.
An Inexpensive Silver‐Silver Chloride Reference Electrode
Authors: Shuman Larry M. , Wander Michelle M. , Pitts Ray B. 
Published: July 2010

AbstractSimple, inexpensive, and rugged reference electrodes are essential for field applications. The objective of this study was to develop an inexpensive, field‐worthy reference electrode. The electrode developed consists of a silver wire coated with AgCl held in a small glass tube filled with 4 M KCl gelled with agar. The glass tube assembly is fitted inside a larger polyvinyl chloride (PVC) tube filled with gelled (NH4)2SO4 solution and capped with a fritted soil‐contacting membrane. The millivolt output compared well (R2 = 0.999) with predicted values and values from commercial reference electrodes when paired with pH and nitratesensing electrodes. Comparisons of commercial and fabricated electrodes in two soils showed that the outputs were statistically the same, and that they were operational within a moisture range from saturation to 0.7 to 0/1 kg kg−1, depending on the soil texture. The fabricated electrodes are low cost, rugged, and stable for months when kept wet.
Windbreak Effect on Biomass and Grain Mass Accumulation of Corn: A Modeling Approach
Authors: Zhang Hehui , Brandle James R. 
Published: July 2010

AbstractWhile numerous studies have indicated that field windbreaks both improve crop growing conditions and generally enhance crop growth and yield, especially under less favorable conditions, the relationship between the two is not clearly understood. A simple model is proposed to simulate biomass and grain mass accumulation of corn (Zea mays L.) with a windbreak shelter or without (exposed condition). The model is based on the positive relationship between intercepted solar radiation and biomass accumulation and requires plant population and hourly inputs of solar radiation and air temperature. Using published data, radiation use efficiency (RUE) was related to plant population, and a temperature function was established between the relative corn growth and temperature for pre‐silking stages. Biomass and grain mass simulated by the model agreed well with those measured for both sheltered and unsheltered plants from 1990 to 1992. Windbreaks did not significantly increase biomass or grain mass of corn for this study, even though air temperature was greater with than without shelter, probably indicating that the microclimatic changes induced by windbreaks were not physiologically significant for the 3‐yr period studied. The model has potential use in future studies to relate windbreak effects to crop yield and to evaluate windbreak designs for maximum benefits.
Pasture Soil Surface Temperature Response to Drought
Authors: Feldhake Charles M. , Glenn David M. , Peterson Donald L. 
Published: July 2010

AbstractForage persistence during severe drought is dependent on the plant's ability to maintain, at the soil surface, a viable crown from which growth regenerates upon renewed availability of water. The objective of this study was to evaluate the surface soil temperature under a tall fescue canopy during the progression into severe drought. A 2.5‐ by 2.5‐ by 2.0‐m weighing lysimeter was shielded from precipitation during rainy weather from the summer solstice through the fall equinox of 1992 at Kearneysville, WV. As evapotranspiration decreased to 23% of the calculated potential rate, there was no increase in midday soil heat flux relative to net radiation but a 2.3‐fold increase in surface soil temperature relative to levels of net radiation. During severe water stress, daytime surface soil temperatures remained from 0 to 3°C cooler than canopy temperature; however, nighttime surface soil temperatures were typically around 5°C warmer than canopy temperature, suggesting that surface soil temperature was poorly coupled to canopy temperature. Surface soil temperature under complete canopy cover may be useful for quantifying forage water stress by evaluating the magnitude of daytime changes relative to net radiation. The forage canopy provides shielding for the crown from daytime radiation and high temperatures during water stress; however, this is in part offset by the insulation provided and the resultant higher nighttime temperatures.
Influence of Soil Moisture Regimes on Subsequent Soil Manganese Availability and Toxicity in Two Cotton Genotypes
Authors: Weil Ray R. , Foy Charles D , Coradetti Carol A. 
Published: July 2010

AbstractDifferential plant tolerance to high levels of Mn and effects of changing soil aeration on Mn availability and are major factors in the problem of Mn toxicity in acid soils. A pot study was conducted to evaluate the effects of temporary flooding or drying on Mn forms and toxicity during subsequent cotton (Gossypium hirsutum L.) growth. Two acid, high‐Mn Hapludalfs were incubated for 16 d in flooded, air‐dry, or moist conditions, then restored to field moisture content and planted with two cotton genotypes: C‐310,73‐307 (307, Mn‐tolerant) and C‐Sgl,70‐517 (517, Mn‐sensitive). After the incubation period, levels of exchangeable Mn in the Jackland soil (pH 4.8) were 9.0, 2.6, and 0.3 mmol kg2212;1, respectively, for flooded, air‐dry, and moist pretreatments. Corresponding values for the Myersville soil (pH 5.2) were only 4.4, 0.6, and 0.1 mmol kg2212;1. Three days after seedling emergence in the flooded pretreatment, exchangeable Mn declined to 4.4 mmol Mn kg2212;1 in the Jackland soil and 0.2 mmol Mn kg2212;1 in the Myersville soil. Manganese toxicity symptoms (crinkle leaf) for both cotton genotypes developed only on the Jackland soil, with severity of symptoms following the order: flood > air dry > moist. With both soils, flooding pretreatment decreased dry matter production; generally more for 517 than for 307. Tissue Mn concentrations were 20 to 50 times higher in leaves from Jackland soil compared to those from Myersville soil. Where flooding caused toxicity symptoms in both genotypes, lower exchangeable Mn was measured in pots growing Mn‐tolerant cotton. Differential Mn tolerance of cotton genotypes was not associated with differential Mn uptake or tissue concentration.
Root Heave of Alfalfa Cultivars with Differing Levels of Resistance to Aphanomyces Root Rot
Authors: Wiersma Daniel W. , Undersander Daniel J. , Grau Craig R. 
Published: July 2010

AbstractAphanomyces root rot (ARR) (caused by Aphanomyces euteiches Drechs.) and phytophthora root rot (PRR) (caused by Phytophthora sojae M.J. Kaufmann & J.W. Gerdemann) are important diseases of alfalfa (Medicago sativa L.) grown in wet soil, but few studies have quantified the effects of ARR on alfalfa performance. An alfalfa cultivar trial of 82 cultivars with differing levels of ARR resistance was seeded in July 1993 in a naturally infested soil at Marshfield, WI. Excessive precipitation in 1993 and 1994 led to widespread expression of ARR and PRR, and large cultivar yield differences were measured. There was differential root heaving among cultivars in the 1993–1994 winter. Fall 1993 forage yield was low, but cultivars with high ARR resistance yielded >400% more than did susceptible cultivars. Root heaving in 1994 was inversely correlated with level of resistance to ARR (r = −0.68), 1993 forage yield (r = −0.72), and 1994 forage yield (r = − 0.81). Resistant and highly resistant cultivars produced 2 Mg ha−1 more forage than susceptible or low resistance cultivars. Forage yields in 1995 (a relatively dry year) did not differ with ARR resistance level. Under wet soil conditions, ARR‐resistant alfalfa cultivars can produce higher forage yields than susceptible cultivars. In addition, resistance to ARR reduces damage due to root heaving.
Increase of CO2 and Climate Change Effects on Iowa Soybean Yield, Simulated Using GLYCIM
Authors: Haskett Jonathan D. , Pachepsky Yakov A. , Acock Basil 
Published: July 2010

AbstractIncreases in atmospheric CO2 concentration are likely to have a significant impact on the climate and to affect the growth and development of crops. The effect of climate change on crops has to be assessed for large areas to provide information for global estimates and regional strategy development. In this study, computer simulations were done using the soybean [Glycine max (L.) Merr.] crop model GLYCIM to assess the effects of these changes on soybean yields in the state of Iowa. The ability of the model to accurately predict the effect of changes in atmospheric CO2 concentration was tested by comparing model results with a curve fit of CO2 concentration yield response derived from measured data. To simulate the effects of climate change, we used projected monthly weather variables for ambient and increased CO2 from three general circulation models (GCMs): Goddard Institute for Space Studies (GISS), Geophysical Fluid Dynamics Laboratory (GFDL), and United Kingdom Meteorological Office (UKMO). The monthly weather variables were converted to the daily weather to simulate soybean crop yields in nine crop reporting districts (CRDs) of Iowa, with and without increases in atmospheric CO2. When climate change was simulated with increasing levels of CO2 (baseline 350, 450, 550, and 650 µL L−1), yields increased. Without increases in atmospheric CO2, yields remained essentially constant in the GFDL and GISS scenarios, while decreasing by 2 to 10% in the UKMO scenario. The variability in yields among nine CRDs increased for all scenarios as climate changed and levels of CO2 increased. Overall, projected climate changes did not substantially alter simulated soybean yields. The increase in CO2 concentration in the atmosphere was the primary determinant of yield response.
Yield and Nitrogen Uptake of Rotated Corn in a Ridge Tillage System
Authors: Iragavarapu Tammiraj K. , Randall Gyles W. , Russelle Michael P. 
Published: July 2010

AbstractInformation is scant on the response of corn (Zea mays L.) following legumes seeded with small grains in reduced tillage systems in the upper Midwest. Our objective was to determine yield and N uptake response of ridge‐tilled corn planted after soybean [Glycine max (L.) Merr.], wheat (Triticum aestivu L.) alone, wheat with alfalfa (Medicago sativa L.), or wheat with hairy vetch (Vicia villosa Roth), compared with continuous corn. Field studies were conducted from 1991 through 1994 at two southern Minnesota locations on a poorly drained Webster clay loam (fine‐loamy, mixed, mesic Typic Endoaquoll) soil. At Freeborn, corn grown in rotation with soybean yielded highest (6.8 Mg ha−1) in 2 of 3 yr, while continuous corn usually yielded less than corn grown after other crops. Corn grown after other crops accumulated 23 to 36 kg ha−1 more N than continuous corn in 2 of 3 yr at all fertilizer‐N rates up to 135 kg N ha−1. At Waseca, corn grain yields and N uptake were generally similar among rotations, except that yields were 1.5 to 1.9 Mg ha−1 lower and total N uptake was 16 to 18 kg ha−1 less following wheat alone in 2 of 3 yr, compared with other rotations at fertilizer‐N rates up to 135 kg N ha−1. Regression analysis indicated that significant, positive, non‐N‐related rotation effects were present at Freeborn, but not at Waseca, where there was a negative effect of wheat alone on subsequent corn yield. The potential fertilizer‐N savings due to including annual alfalfa or hairy vetch could not be calculated because the N rates used in this study were insufficient to determine the economically optimum N rate. However, neither the alfalfa nor hairy vetch provided a consistent source of available N for the subsequent corn crop in this study.
Yield‐Independent Variation in Grain Nitrogen and Phosphorus Concentration among Ethiopian Wheats
Authors: Schulthess Urs , Feil Boy , Jutzi Samuel C. 
Published: July 2010

AbstractNew semidwarf wheat (Triticum aestivum L.) cultivars and new land management practices for Vertisols are being introduced in Ethiopia. Our objectives were to (i) determine the variation of N and P content and concentration in the grain and whether these are related to grain yield, (ii) test cultivar response to different fertility levels, and (iii) assess component traits of N and P yield. Five bread wheat cultivars and three durum wheat (Triticum durum Desf.) cultivars were sown in Exp. 1 at three locations in Ethiopia on two dates. In Exp. 2, seven of these cultivars were grown on a P‐deficient soil at four N levels (0, 20.5, 41, 61.5 kg N ha−1) and four P levels (0, 10, 20, 30 kg P ha−1); in Exp. 3, two cultivars were grown in all possible combinations of the same four N and P levels. Grain yields did not differ among cultivars, but significant variations were found for total shoot N and P, grain N and P yield, and grain N and P concentration. Cultivar differences in these traits were fairly consistent across the treatments and were corroborated by Exp. 3. The N and P concentrations in the grain were not related to grain yield (r = 0.36 NS for N; r = 0.28 NS for P). There was a positive association between grain N and P concentrations in Exp. 1 (r = 0.66; P = 0.07) and in Exp. 2 (r = 0.92; P < 0.01). The N and P grain yields were related to total shoot N and P at maturity (r = 0.99; P < 0.001). However, postanthesis accumulation of N was more closely related to postanthesis dry matter accumulation (r = 0.84; P < 0.05) than to the postanthesis accumulation of P (r = 0.56 NS). Total shoot P varied by as much as 50%. Thus, cultivar choice is an important factor determining removal of P from the soil.
Measures of Validity in Cultivar Performance Trials
Authors: Bowman Daryl T. , Watson Clarence E. 
Published: July 2010

AbstractThe coefficient of variation (CV) has been used for many years by researchers to determine the validity of performance trials. The premise behind the CV, that the standard deviation is proportional to the mean, compromises one of the assumptions of a normal distribution (i.e., that the sample mean and sample variance are independent). If there is a nonnormal distribution, then the data may need to be transformed, which in turn may invalidate the use of the CV. A constant CV across trials implies a relationship between the error variance and the mean such that the slope = 2.0 in the regression of In error variance on ln mean. The purpose of this paper is to stress the relationship between the error variance and mean in the CV, review this relationship in actual yield data, and examine the effects of various transformations on CVs and coefficient of determination (R2). The ln error variance regressed on In mean for several agronomic crops ranged from −0.11 for full‐season corn (Zea mays L.) to 1.31 for oat (Avena sativa L.). Although some crops had a nonzero regression coefficient for this relationship, none approached 2.0, the level that supports the hypothesis that the CV is a viable tool for comparing the relative variation of different trials. Data transformations (e.g., square root, logarithmic, angular, inverse, reverse, and addition of a constant) tend to lower CV values in most cases, but can cause dramatic increases, depending on the nature of the variance and the specific transformation. On the other hand, R2, which is a measure of the amount of variability accounted for in the model, remains relatively unaffected by most transformations. Reasonable R2 values for determining validity of performance trials may vary by location and crop species. Examination of North Carolina data revealed that discarded trials generally had R2 values less than 50%. The R2 may be affected by the size of the dataset, and so adjusted R2 maybe more useful for comparing trials of varying sizes; however, adjusted R2 will tend to be larger where there are larger differences among entries. There is no one perfect measure of the validity of trial data, but the R2 and the adjusted R2 are reasonable alternatives to the CV and should be examined along with other statistical measures when evaluating crop performance data.