bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectral Reflectance Measurements of Alfalfa under Sheep Grazing
Authors: Mitchell A. R. , Pinter P. J. , Guerrero J. N. , Hernandez C. B. , Marble V. L. 
Published: July 2010

AbstractLamb grazing experiments conducted on alfalfa (Medicago sativa L.) fields require numerous measurements of phytomass in order to identify optimum conditions for lamb weight gain. Our objective was to test the ability of spectral reflectance measurements with a portable hand‐held radiometer to predict alfalfa phytomass. We used vegetative indices consisting of linear combinations of the near infrared (NIR) and red wavelength intervals, such as the NIR/Red ratio and normalized difference (ND). Reflectance measurements were taken during two grazing trials where alfalfa phytomass ranged from 200 g m−2 initially to negligible phytomass after 15 d of intensive grazing. A portion of the alfalfa was desiccated due to frost damage during the second trial. The ND and NIR/Red were well correlated with alfalfa phytomass (r = 0.87−0.97). Measurements taken at solar zenith angles (57 and 69°) were found to produce similar ND/phytomass regression coefficients. The desiccated alfalfa increased red reflectance, which consequently lowered the ND and NIR/Red values. The ND was preferable to NIR/Red because it was more sensitive to low phytomass levels that are characteristic of grazing studies. An ND of 0.55 identified a threshold phytomass level, below which continued grazing caused a decrease in lamb weight gain. Handheld radiometric measurements are a quick, accurate, nondestructive means of estimating alfalfa phytomass in pasture grazing experiments.
Tracing the vertical Distribution of Simulated Shattered Seeds as Related to Tillage
Authors: Staricka J. A. , Burford P. M. , Allmaras R. R. , Nelson W. W. 
Published: July 2010

AbstractWeed control in conservation tillage requires a knowledge of weed seed ecology, but germination and loss of viability make it difficult to trace seed movement during tillage. Ceramic spheres were evaluated as tracers to determine the effects of chisel and moldboard tillage on the vertical distribution of shattered seeds. Tracers and seeds of foxtail millet (Setaria italica [L.] Beauv.) were applied to the soil surface [Ves loam (a fine‐loamy, mixed, mesic Udic Haplustoll)] before fall primary tillage with a chisel or moldboard plow. Soybean (Glycine max [L.] Merr.) and oat (Avena sativa L.) were grown in a strip‐plot design. Soil cores (18 mm diam.; 60 cm deep) were taken midsummer, sectioned into 2‐cm increments, and composited (12‐15 cores per sample) by depth. Soil bulk density, seed counts, and tracer counts were recorded for each sample. Seeds and tracers were found to depths of 12 cm in the chisel plots and 32 cm in the moldboard plots. In the chisel plots, 51 and 48% of the seeds and tracers, respectively, were found within 4 cm of the surface compared to 11 and 4% for the moldboard plots. Germination of applied seeds was greater in the chisel plots whereas germination of indigenous seeds (previously buried by tillage) was greater in the moldboard plots. An abrupt increase in the soil bulk density occurred at the penetration depth of the primary tillage operation and coincided with the maximum burial depth of seeds and tracers. These observations verify the differences in working depth and associated seed placement by the two implements. Ceramic spheres can trace the vertical distribution of shattered seeds related to tillage.
Using Upper‐Bound Slope Through Origin to Estimate Genetic Harvest Index
Authors: Prihar S. S. , Stewart B. A. 
Published: July 2010

AbstractHarvest index (HI), the ratio of grain to abovegronnd dry matter, is reported to be a species‐related parameter and is recommended for screening cultivars. But the fact that it is affected by environmental stress limits its use for intercrop or intercultivar comparisons. Fair comparisons should be based on estimated genetic HI for a given environment, but a procedure to determine the same is lacking. We propose that the slope of an upper‐bound in the grain yield vs. dry matter plot passing through the origin approximates the genetic HI because the highest grain yields against given dry matter represent the least‐stressed and/or stress‐adapted plants and passage of the line through the origin is necessary to satisfy the definition of HI. This HI also provides a useful reference for interpreting agronomic data with respect to stress effects associated with management practices. The HIs of sorghum [Sorghum bicolor (L.) Moench], corn (Zea mays L.), and wheat (Triticum aestivum L.) were estimated by the upper‐bounds of grain yield (corrected to dry weight) vs. dry matter yield taken from existing reports in the literature. Harvest index of sorghum and irrigated corn ranged between narrow limits of 0.48 to 0.53 and 0.58 to 0.60, respectively. Harvest index of irrigated wheat ranged from 0.38 to 0.47. Stress effects on HI are illustrated in plots of published and unpublished (dry) grain yields vs. dry matter yields and reasons for the same are discussed.
Long‐Term Ecological Research in Temperate and Boreal Forest Ecosystems
Authors: Powers Robert F. , Van Cleve Keith 
Published: July 2010

AbstractForest ecosystems are distinguished by their complexity and diversity, their progressive nature of development, and the constant risk of random catastrophes. These systems develop relatively slowly, and research conducted on them requires years or decades to yield meaningful findings with broad extension. Prolonged development, coupled with uncertainty about disruption, work against long‐term commitment to fund and maintain study sites. Alternative research strategies (chronosequence and retrospective studies) produce rapid results, but are marred by limited application and uncertainty about past events. With notable exceptions, most long‐term studies have centered on relatively undisturbed natural ecosystems. While such studies are useful, they lack the flexibility needed to gauge the long‐term impacts of manipulation. New programs, such as the National Science Foundation's network of Long‐Term Ecological Research sites, and the USDA Forest Service's Long‐Term Soil Productivity studies, encompass and support a wider range of objectives and variables than was possible in earlier studies.
Potential for Using Long‐Term Field Research Data to Develop and Validate Crop Simulators
Authors: Acock Basil , Acock Mary C. 
Published: July 2010

AbstractAt the time when many long‐term field experiments were initiated, the principal method of analyzing crop yield data was to use multiple regression analysis. This technique is based on the assumption that the interacting effects of environmental factors on plants can be described with empirical additive or multiplicative models. We now know that such models do not adequately describe the interactions between factors. In the early days of agricultural experimentation, when gross nutrient deficiencies in soils were being corrected, the exact form of the model did not matter much. Now, with soil nutrient levels near optimum, additional (plant and weather) factors have to be considered in our analysis and our models must deal with the interaction between all factors realistically. The most realistic way of considering how a large number of factors affect plants is to use a limiting factor model. This enables us to develop mechanistic crop models (simulators) that simulate many of the processes going on in the plant, soil, and atmosphere. However, the validation of crop simulators requires more types of data than does the development of empirical models. Many of the data used to develop crop simulators come from studies in controlled‐environment plant growth chambers, where environmental factors can be manipulated independently. However, it is widely recognized that plants grown in chambers differ from those in the field, and model parameters often have to be adjusted to fit field data. Thus, field data are essential to the final stages of model development and validation. Long‐term field research is especially useful because: (i) it provides data in which some environmental factors are constant over time, and observed effects can be attributed to uncontrolled factors, and (ii) it provides data in which the unknown effects of previous treatments have been minimized. Despite these advantages, long‐term field data have rarely, if ever, been used in the development and validation of crop simulators. Modelers would benefit from working more closely with scientists running long‐term field experiments, showing then what additional types of data are needed and how existing crop simulators can be used to interpret results.
Soybean Yield Responses and Intraspecific Competition from Simulated Seedcorn Maggot Injury
Authors: Higley Leon G. , Pedigo Larry P. 
Published: July 2010

AbstractThe reproductive and competitive responses of plants to early season stresses are not well known. In field experiments from 1983 to 1986 we examined these effects for one system; simulated seedcorn maggot (SCM), Delia platura (Diptera: Anthomyiidae) injury to soybean, Glycine max (L.) Merr. Injury included different plant densities (simulating stand reductions) and different ratios of plumule‐injured to uninjured plants (simulating different levels of plumule destruction). Our objectives were to describe (i) how simulated SCM injury affected total yield, yield components, and intraspecific competition between injured and uninjured plants, and (ii) to determine the value of the replacement series experimental design for examining intraspecific competition from injury. Plant density did not influence plot yields but did affect yield components of injured and uninjured plants. The proportion of injured to uninjured plants influenced plot yields in 1983 and 1984 but not in 1985 or 1986. Uninjured soybean were much stronger competitors than injured soybean. Yield reductions of injured plants were attributable to competition from uninjured plants. Specifically, competition seemed to increase shading and reduce assimilate availability of injured plants. The replacement series design was a powerful technique for describing intraspecific competition arising from insect injury.
Germination of Twenty Forage Legumes as Influenced by Temperature
Authors: Brar G. S. , Gomez J. F. , McMichael B. L. , Matches A. G. , Taylor H. M. 
Published: July 2010

AbstractMany studies have shown that water potential at planting will affect germination rate and final germination. Much less is known, however, about the effects of different temperatures at planting on seed germination. Our objectives were to compare the influence of different temperatures on the germination percentage and germination rate index of 20 forage legumes. Legume seedlings were grown for 10 d in polyethylene growth pouches placed in germination chambers and held in the dark at constant temperatures of 10, 15, 20, 25, or 30 °C. There were major effects of temperature on germination rate and germination percentage for all 20 legume entries. If we define satisfactory germination as 80% germination at 10 d after planting, 18 of the 20 entries had satisfactory germination at some temperature between 10 and 30 °C. There were no significant effects of temperatures between 10 and 30 °C on germination percentage at 10 d for ‘Arlington’ red clover (Trifolium pratense L.) and ‘Maxidor’ alfalfa (Medicago sativa L.) entries. Since temperature had a strong influence on germination, seeding time for some legumes should be selected to match expected temperatures for particular locations.
Organic Matter, Nutrient, and pH Distribution in No‐ and Conventional‐Tillage Semiarid Soils
Authors: Unger Paul W. 
Published: July 2010

AbstractThere is widespread interest concerning whether the influence of conservation tillage systems on soil conditions is beneficial or detrimental to crop production. Objectives of this study were to evaluate the distribution with depth of organic matter (OM), total N, NO3‐ N, P, K, Ca, and pH on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). The crop rotation used was dryland winter wheat (Triticum aestivum L.)‐grain sorghum [Sorghum bicolor (I,.) Moench]‐fallow (WSF) involving stubble mulch (SM) tillage arid no‐tillage (NT). The SM field and an adjacent NT field had been used for the WSF rotation since 1956. No‐tillage was started on the adjacent field in 1981 (NT‐81), continuing the same rotation. On another field, the NT‐WSF rotation was started in 1979 (NT‐79) on land previously used for irrigated crops. Sampling was in August 1988 at depths of 0 to 1, 1 to 2, 2 to 4, 4 to 6, 6 to 8, 8 to 10, 10 to 15, and 15 to 20 cm. On the SM field, there were few differences, except for pH, throughout the tillage zone (0‐8 cm). There were differences at depths below 8 cm in some cases relative to those above 8 cm. The NT fields tended to have higher mean OM, N, NO3−N, P, and K values at the surface than the SM field, but all differences were not significant. In general, more differences with depth were significant on NT fields than on the SM field. Although NT is changing the distribution of OM and some plant nutrients in the soil, the changes are relatively small and NT appears to be a viable cropping practice for conserving soil and water and maintaining crop productivity on dryland in the southern Great Plains.
Effects of Furrow Diking and Tillage on Corn Grain Yield and Nitrogen Accumulation
Authors: McFarland M. L. , Hons F. M. , Saladino V. A. 
Published: July 2010

AbstractCultural practices that conserve soil and water while maintaining or improving crop yield and quality are needed. Furrow diking and reduced tillage may constitute two such practices. The effects of furrow diking in combination with reduced (ridge tillage) or conventional disk tillage on soil‐water content, grain yield, and N accumulation of corn (Zea mays L.) were evaluated on a Weswood silt loam/Ships clay intergrade (fine‐silty, mixed thermic Fluventic Ustochrept/ very‐fine mixed thermic Udic Chromustert) near College Station, TX in 1987 and 1988. Five N rates (0, 75, 150, 225, and 300 kg N ha−1) as NH4NO3 were preplant subsurface banded into plots representing all combinations of tillage (reduced or conventional) and diking (all furrows diked or all furrows open). Neither diking nor tillage significantly increased soil‐water content in the above average rainfall year of 1987. In contrast, furrow diking with conventional tillage, and reduced tillage, with or without diking, significantly increased soil‐water content in the surface 150 cm compared to nondiked, conventional tillage treatments in the below average rainfall year of 1988. Diking significantly decreased or tended to reduce grain yields in 1987 at most fertilizer‐N rates, but had no effect on grain yield in 1988. Diking significantly increased grain‐N accumulation at the 150 kg N ha−1 rate in 1987, but had no effect at higher or lower N rates. Leaf‐N concentration was not affected by diking in 1987, and diking had no significant effects on grain‐N uptake or leaf‐N concentration in 1988. Effects of N fertilization on grain yield, grain‐N accumulation, and leaf‐N concentration were generally similar for reduced and conventional tillage treatments.
Heteroscedasticity in Whole Plant Growth Curves Developed from Nonreplicated Data
Authors: Meek D. W. , Hutmacher R. B. , Mackey B. E. , Davis K. R. 
Published: July 2010

AbstractAgronomic researchers usually neglect heteroscedasticity in crop growth formulae and analysis. When they consider it they are not consistent in the methods they use. This study was conducted to: (i) find a method of testing for heteroscedasticity in nonreplicated whole plant growth data and (ii) determine the best weighting for such crop growth data. We developed seven different crop growth models with yield data collected during the growing season of five different crops (14 sets total, six with replicates). Next we performed tests for heteroscedasticity on model residuals and heterogeneity of variance tests on replicated data. Finally we conducted simulations to assess the confidence interval coverage of various weighted predictions based on one model fit to two of the replicated crop sets. Five of the models usually exhibited realistic growth responses throughout the growing season. All heterogeneity of variance tests were significant (P < 0.05) and most suggested a logarithmic weighting. In contrast, tests devised from groups of sequential residuals usually indicated a square root weighting but were generally not significant (P ≥ 0.05). Simulations revealed that weighting was needed but that none of the variance models always adequately characterized the true variance. While not a good variance model, a linear trend in a model's squared residuals (P < 0.10) proved to be a sound test for heteroscedasticity in growth curves developed from nonreplicated data. Crop growth curves need to be weighted with an exact Box‐Cox variance model when replicates are available and one intermediate between the logarithmic and square root model when replicates are unavailable.
Seasonal Forage Production and Regrowth of Hard and Soft Red Winter Wheat
Authors: Carver Brett F. , Krenzer Eugene G. , Whitmore Wayne E. 
Published: July 2010

AbstractThe dual use of winter wheat (Triticum aestivum L.) for forage and grain throughout the southern Great Plains of the USA demands that breeding programs consider forage characteristics during cultivar development. This study was conducted to determine if the present pool of adapted cultivars provides enough variability in seasonal forage production and regrowth to allow future genetic improvement. Eighteen cultivars from two market classes, soft (SRW) and hard red winter (HRW), were evaluated in three environments. Long‐term (seasonal) and short‐term forage harvests (weekly regrowth following the long‐term harvest) were scheduled in the fall and late winter to correspond to maximum forage growth. Soft and hard wheat classes did not differ in average long‐term or short‐term production in the fall. The SRW cultivars produced 30% more winter forage, but the HRW cultivars produced 26% more late winter regrowth than the SRW cultivars. Within‐class differences were detected in both seasons, except for fall regrowth. Long‐term winter production was not correlated with long‐term fall production. Short‐term forage regrowth was a linear function of accumulated growing degree‐days. No significant relationship was found between long‐term production and regrowth rate in the fall. In contrast, an inverse rank‐order relationship (r = −0.53, df = 16, P ≤ 0.05) was found in the winter, where differences in regrowth rate were likely influenced by ontogeny. Soft and hard red winter cultivars appear equally suited as germplasm sources for genetic improvement of wheat forage capacity.
Silage Characteristics of Elephantgrass as Affected by Harvest Frequency and Genotype
Authors: Woodard K. R. , Prine G. M. , Bates D. B. 
Published: July 2010

AbstractElephantgrass (Pennisetum purpureum Schum.) was evaluated in the colder subtropics of Florida as a potential forage source for ruminants. Our objective was to determine if this thick‐stemmed bunchgrass could be stored as silage. A dwarf (‘Mott’) and two tall (PI 300086 and ‘Merkeron’) elephantgrasses were harvested one, two, and three times per season and ensiled (direct‐cut) during 1986 and 1987. Dry matter (DM) recoveries for all silages ranged from 861 to 984 g kg−1 of DM ensiled. Mean pH values ranged from 3.8 to 4.0 for tall elephantgrass silages made from plants	harvested at the different frequencies. Highest pH values were obtained from silages made from immature dwarf elephantgrass plants harvested three times per year (2‐yr mean was 4.3). Lactic acid was the major end‐product of fermentation in most silages with the exception of those made from immature dwarf elephantgrass where lactic and acetic acids were both major fermentation components. Butyric acid levels were negligible in all silages. In vitro digestible organic matter (IVDOM) concentration of silage was mainly dependent on that of initial forage at the time of harvest. Water soluble carbohydrate concentrations in fresh herbage (range: 26.2–83.7 g kg−1 DM) increased with more frequent harvesting. Buffering capacities of fresh PI 300086 herbage were exceptionally low and increased with more frequent harvesting. The ease with which elephantgrass was preserved as silage was attributed to adequate levels of water soluble carbohydrate concentrations and inherently low buffering capacities in standing forages.
Yield and Quality of Forage Maize as Influenced by Hybrid, Planting Date, and Plant Density
Authors: Graybill J. S. , Cox W. J. , Otis D. J. 
Published: July 2010

AbstractAlthough forage maize (Zea mays L.) is grown extensively on livestock operations, most management studies in the USA focus on grain production. Field studies were conducted in New York to evaluate dry matter (DM) yield and forage quality responses of commercial hybrids to planting dates and densities. Six hybrids were planted on 25 April, 9 May, and 23 May and thinned to 5.0, 6.5, and 8.0 plants m−2 in 1988 and 1989. A significant year ✕ planting date interaction was observed for DM yield because dry early‐season conditions in 1988 negated the advantage of early planting in northern latitudes (13.4, 13.9, and 14.6 Mg ha−1 for planting dates 25 April, 9 May, and 23 May, respectively). When averaged across years, high plant densities increased DM yields (15.7, 16.5, and 17.5 Mg ha−1 at 5.0, 6.5, and 8.0 plants m−2, respectively) with no significant effect on harvest index (524, 523, and 526 g kg−1 at 5.0, 6.5, and 8.0 plants m−2, respectively). A hybrid ✕ density interaction was observed for DM yield that suggests that some hybrids in this study performed better at higher densities. Plant density had little effect on acid detergent fiber (ADF) and neutral detergent fiber (NDF) concentrations indicating that forage quality can be maintained at high densities. Hybrids showed distinct variation for ADF (186‐217 g kg−1), NDF (414‐434 g kg−1), and crude protein (CP) (72‐77 g kg−1) concentrations. The forage quality differences among hybrids may be of sufficient magnitude to be of value to the forage producer.
Growth and Nutrient Composition of Maize Genotypes in Acid Nutrient Solutions
Authors: Jariel D. M. , Wallace S. U. , Jones U. S. , Samonte H. P. 
Published: July 2010

AbstractCrop production in acid soils may be limited by several factors, including low pH. Development of acid‐tolerant cultivars requires information about differences in tolerance to low pH among crop genotypes. To determine whether differential responses to nutrient solution pH occurred among seven maize (Zea mays L.) genotypes, seedlings were grown in a growth chamber in flowing solutions at pH levels ranging from 3.3 to 6.7. Top weights, root lengths and weights, and concentrations of Ca, Mg, Fe, Zn, and Mn in plant tops were determined after 12 d. All genotypes grew well with pH of 4.0 to 5.5, with maximum dry weights of plant tops at pH 4.6 for most of the genotypes. However, all genotypes had necrotic root tips and decreased root lengths at pH 3.3, with relative root lengths (length at pH 3.3/maximum length) ranging from 0.26 to 0.55. Root weights were relatively unaffected by solution pH, but top weights decreased markedly at both pH extremes. Iron concentrations of all genotypes were decreased at pH 6.7, and interveinal chlorosis, resembling Fe deficiency, appeared in the younger leaves. Relative top weights (weight at pH 3.3/maximum weight) averaged 0.79 for Trinidad Grpl&2 and ‘PDMR Comp 1’ and 0.58 for ‘UPCA Varl’, ‘PDMR3’, Kalimpos, and Dikit at pH 3.3, and relative top weights among genotypes were positively correlated (r = 0.85) with Mn concentrations in tops. Based on relative top weight at pH 3.3, the former two genotypes were relatively more tolerant of extremely low pH than those in the latter group.