bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Empirical Model of Diurnal Temperature Patterns
Authors: Sadler E. John , Schroll Ronald W. 
Published: July 2010

AbstractAir temperature is a key driving factor in many crop growth models. Hourly air temperature data required for input are often not available and must be estimated from daily extremes. Several methods to model diurnal patterns exist; all are arbitrary functions of time during the day, chosen to match the daily pattern. Of all possible mathematical shapes, it would be preferable to use the one generated by the data themselves. Thus, our objective was to develop an empirical model to reconstruct the diurnal air temperature curve from measured daily extremes. As usual, temperature was normalized to range from 0 to 1 at the daily extremes. However, we also normalized time, to reduce seasonal variation in the shape of the temperature pattern. Calibration consisted of developing the cumulative distribution function of normalized temperature for a year's data, fitting a beta distribution to the data, and evaluating the 50th percentile, all as a function of time. The resulting vectors of normalized time and air temperature were used to generate diurnal patterns from daily extremes. The model was calibrated with one year's data for each of 14 sites across the USA, and tested for additional years at each site. For the total 32 site‐years, annual mean r1 ranged from 0.47 to 0.87, with values highest for Arizona sites, intermediate for South Carolina, and lowest for mountainous Idaho sites. Model performance was better than or equal to that of the next‐best model in 16 of 32 site‐years, and also overall. Normalization of both time and temperature produced diurnal air temperature patterns that were sufficiently general to apply with minimal loss of predictive accuracy at widely separate sites in the USA.
Analysis of Amino and Fatty Acid Composition in Soybean Seed, Using Near Infrared Reflectance Spectroscopy
Authors: Pazdernik David L. , Killam Arthur S. , Orf James H. 
Published: July 2010

AbstractSoybean [Glycine max (L.) Merr.] is an important animal and human food source, mainly because of its high protein and oil concentrations. However, there is a need to improve the quality of soybean protein and oil. The objectives of this study were to (i) determine the potential use of near infrared reflectance spectroscopy (NIRS) for amino and fatty acid analysis in soybean seed and (ii) compare NIRS amino and fatty acid equations developed with ground‐seed and whole‐seed soybean samples. A total of 90 NIRS calibration samples and 26 NIRS validation samples were used for NIRS equation development and validation, respectively. All 116 soybean samples were grown at St. Paul and Rosemount, MN, in 1994 and 1995. Seventeen amino acid and five fatty acid NIRS equations for both groundseed and whole‐seed soybean samples were developed using the calibration samples. Validation of these NIRS equations showed a wide range for bias (−1.7 to 3.2 g kg−1), standard error of prediction corrected for bias [SEP(C)] (1.4 to 13.1 g kg−1), and coefficient of determination (R2) (0.38 to 0.85) for all ground‐seed NIRS equations, and a broad range for bias (−3.1 to 4.2), SEP(C) (2.6 to 17.8), and R2 (0.06 to 0.83) for all whole‐seed NIRS equations. It was concluded that NIRS could be used as a gross screening method for many amino and fatty acids contained in soybean seed. Additionally, NIRS was more accurate for amino and fatty acid analysis of ground‐seed than wholeseed soybean samples.
Cattle Grazing Preference among Eight Endophyte‐Free Tall Fescue Cultivars
Authors: Shewmaker Glenn E. , Mayland Henry F. , Hansen Susie B. 
Published: July 2010

Abstract‘HiMag’ tall fescue (Festuca arundinacea Schreb.) was selected for high Mg concentration to reduce grass tetany risk to ruminants, but neither animal preference nor consumption of HiMag were known. The objectives were to evaluate methods of quantifying preference and to determine intake and preference by cattle (Bos taurus L.) of HiMag relative to seven other tall fescues. All entries were free of a fungal endophyte [Neotyphodium coenophialum (Morgan‐Jones & Gams) Glen, Bacon & Hanlin] that reduces cattle performance. The experimental design was a randomized complete block with three replications of eight cultivars nested within each of three test pastures. Six heifers grazed the vegetative to boot‐stage pastures for 48 h in May, June, August, and September of 1993 and 1994. The pastures, located at 1200 m elevation, were furrow irrigated. Pre‐ and postgrazed forage were clipped and weighed to determine yield and utilization (48‐h utilization< 50%) Preferencsec oringo f 0 to 10 (0 to 100% of forage eaten) was done by four trained observers at 24, 30, and 48 h. The heifers quickly learned to distinguish between cultivars, and their order of preference was Kenhy > KY 31 > HiMa=g Barcel= C1= Stargrazer > MO96 = Mozark. The cultivar × trial(year) interaction for preference indicated that cultivars responded differently to weather conditions, which in turn affected animal preference. Preference scoring had high repeatability and ranked cultivars similarly to the clip‐and‐weigh method of measuring utilization. Preference scoring was accomplished with 27% of the experimental error and only 6% of the time required for clip‐and‐weigh. Only 44% of the variation in preference score(PS) was explained by the model: PS = 8.8 ‐ 1.1(Mg DM yield ha−1). Estimated dry matter (DM) intake of HiMag was 6.4 kg (animal unit day)−1. Consumption and preference HiMag by cattle are satisfactory relative to other tall fescue cultivars.
Phosphorus Soil Test Calibration for Lowland Rice on an Inceptisol
Authors: Fageria Nand K. , Santos A. B. , Baligar Virupax C. 
Published: July 2010

AbstractEfficient use of an adequate level of P in crop production on high‐P‐fixing acid soils is essential, due to high crop response to P fertilization and the high cost of P fertilizers. Soil‐test‐based P fertilization recommendations are not available for lowland rice (Oryza sativa L.) grown on Inceptisols. The objective of this study was to calibrate P soil testing for the response of lowland rice (cv. Javae) to added P. Two field experiments were conducted in two years at two locations in central Brazil on Haplaquept Inceptisols. In the first year, the broadcast P levels used in both experiments were 0, 87, 175, 262, 350, and 437 kg P ha−1, applied as triple superphosphate. In the second year, each residual broadcast P level from the previous year received band application of 0, 22, 44, and 66 kg P ha−1. Soil test levels of Mehlich‐1 extractable P were categorized, based on relative grain yield from the first year, as very low (0‐2.6 mg P kg−1 soil), low (2.6–8.8), medium (8.8–13.0), or high (>13.0). The amount of broadcast P needed to build up soil P test concentrations at very low, low, medium, and high soil test categories was 80, 220, 292, and >444 kg P ha−1, respectively. The rice crop produced 0 to 70%, 70 to 95%, 95 to 100%, and 100% of relative yield at the very low, low, medium, and high P levels, respectively. The amount of banded fertilizer P required to obtain maximum yield at both locations was 66 kg P ha−1 for the very low and low soil P levels, 44 kg P ha−1 for the medium soil P level, and 22 kg P ha−1 for the high soil P level.
Predicting Developmental Morphology in Switchgrass and Big Bluestem
Authors: Mitchell Rob B. , Moore Kenneth J. , Moser Lowell E. , Fritz John O. , Redfearn Daren D. 
Published: July 2010

AbstractSwitchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) are important warm‐season grasses in livestock production systems in the central and eastern USA. The objectives of this study were to quantify the morphological development of ‘Trailblazer’ switchgrass and ‘Pawnee’ big bluestem and to evaluate day of the year (DOY) and growing degree day (GDD) as predictors of switchgrass and big bluestem morphological stage. Pure stands of each species were sampled at weekly intervals in 1990 and 1991 at Mead, NE, and classified as to mean stage count (MSC) and mean stage weight (MSW). Prediction equations for MSC and MSW were developed based on DOY and GDD. The validation study was harvested at 2‐wk intervals in 1992 and 1993 at Mead, NE, and Manhattan, KS, and classified as to MSC and MSW. Switchgrass and big bluestem MSC and MSW were related linearly in all environments. Linear DOY calibration equations accounted for 96% of the variation in switchgrass MSC across four environments, which indicates that switchgrass development was related to photoperiod and that general management recommendations could be based on DOY in the central Great Plains. Quadratic GDD calibration equations accounted for 83% of the variation in big bluestem MSC across four environments, which indicates that big bluestem development is more difficult to predict and management recommendations in the central Great Plains should be based on morphological development (which is best predicted by GDD). The comprehensive growth staging system gave repeatable results for quantifying the morphological development of switchgrass and big bluestem. The morphological development of switchgrass and big bluestem can be reliably predicted for adapted cultivars in the central Great Plains during years with near‐normal precipitation using DOY and GDD because of the determinate growth habit of these grasses.
Morphological Development of Switchgrass as Affected by Planting Date
Authors: Smart Alexander J. , Moser Lowell E. 
Published: July 2010

AbstractLate‐spring and early‐summer plantings of warm‐season grasses often fail, due to dry soil conditions and competition from annual grass and broadleaf weeds. The objective of this study was to compare the morphological development of switchgrass (Panicum virgatum L.) planted in early, mid, and late spring in eastern Nebraska. This study was conducted in 1994 and 1995 at Lincoln, NE, on a Kennebec silt loam (fine‐silty, mixed, mesic Cumulic Hapludolls). ‘Blackwell’ and ‘Trailblazer’ switchgrass were planted in mid‐March, late April, and late May using a single‐row, precision grass‐seed cone planter to a depth of 0.6 to 1.3 cm at 98 pure live seed per linear meter of row in a split‐plot design. Twenty seedlings from each plot were excavated to a depth of 20 cm with a spade. Seedling morphological parameters measured were mean stage count root (MSCR) and shoot (MSCS), leaf area, shoot weight, and primary and adventitious root weight. Plots were sampled every 10 d following the first sample date. In 1994, seedlings from the March planting date were more advanced morphologically in MSCR and MSCS, had accumulated 2.5 times more leaf area, and about 3 times more shoot and adventitious root mass than the April planting date when sampled from late May to late June. In 1995, seedlings from the March planting date generally were more advanced morphologically in root and shoot development, had accumulated 2 to 12 times more leaf area, had 2 to 10 times more shoot mass, and had 2 to 33 times more adventitious root mass than the April or May planting dates at the sample periods from early June to mid‐July. We suggest that switchgrass should be planted in early spring instead of in late April and May, as suggested by previous research.
Nitrogen and Defoliation Management: Effects on Yield and Nutritive Value of Flaccidgrass
Authors: Burns Joseph C. , Chamblee Douglas S. , Belesky David P. , Fisher Dwight S. , Timothy David H. 
Published: July 2010

Abstract‘Carostan’ flaccidgrass (Pennisetum flaccidum Griseb.), a C4 perennial grass, has shown high quality potential in animal trials. Its yield response to defoliation frequency and N fertilization, however, has not been reported. We examined the influence of stubble height and of a range of N applications in two defoliation experiments over 4 yr. Experiment 1 (Raleigh, NC) combined two harvest heights, 76 and 38 cm, with two stubble heights, 25 and 15 cm (76–25, 76–15, 38–25, 38–15); all treatments received 380 kg N ha−1 yr−1. After Year 1, the 76–15 defoliation produced higher yields than 76–25 (Year 2: 11 330 vs. 7930 kg ha−1, P < 0.001; Year 3:8950 vs. 6270 g kg−1, P < 0.001), while in vitro dry matter disappearance (IVDMD) was similar (Year 3) (mean = 582 g kg−1). Compared with 38–15, the 38–8 defoliation resulted in lower yields (Year 2: 8638 vs. 9344 kg ha−1, P = 0.001; Year 3, 6173 vs. 8090 kg ha−1, P = 0.07) but higher IVDMD (Year 3, 651 vs. 635 g kg−1, P < 0.01). Experiment 2 (Raleigh, NC, and Watkinsville, GA) had four defoliations: clipping to 5 cm at 20 and 51 cm (vegetative) and to 8 cm at boot and anthesis stages (20–5, 51–5, Boot—8, Anthesis—8). All defoliation treatments were topdressed with 291 kg N ha−1, and 51–5 and Boot—8 were also evaluated with 179 and 403 kg N ha−1 (eight N—defoliation treatments in all). At both locations, highest yields were obtained with Anthesis—8, averaging 19 010 kg ha−1 at Raleigh and 12 390 kg ha−1 at Watkinsville. The 20–5 defoliation resulted in lowest yields at both locations, averaging 7648 kg ha−1 at Raleigh and 5100 kg ha−1 at Watkinsville. Defoliation frequency altered IVDMD (range = 550 to 789 g kg−1), but N application did not; however, increasing N application increased N concentrations linearly (P = 0.05). Flaccidgrass had high yield potential and high nutritive value at the Raleigh location, and warrants further evaluation in the upper South.
Tracing Nitrogen Movement in Corn Production Systems in the North Carolina Piedmont: A Nitrogen‐15 Study
Authors: Crozier Carl R. , King Larry D. , Volk Richard J. 
Published: July 2010

AbstractLegume cover crops have been studied in the southeastern USA, but there have been no 15N tracer studies comparing movement of legume N and fertilizer N for this region. Our study used l5N‐enriched crimson clover (Trifolium incarnatum L.) (135 kg N ha−1) and either 15NH4NO3 or NH154NO3 (70 kg total N ha−1) to quantify N movement through soil inorganic and organic N pools and into corn (Zea mays L.). Clover N mineralized rapidly, with 45% of the initially applied N detectable as inorganic N at 18 d following incorporation. Rapid nitrification of enriched NH+4 occurred, but, since the soil NO‐3 pool was larger in this treatment than in the enriched NO‐3 treatment (presumably due to chance), the relative enrichment of the soil NO‐3 pool was less than with the application of enriched NO‐3. At anthesis, 25% of the N in corn had been derived from the NO‐3 source, while only 11% had been derived from the NH+4 source (P < 0.05). At physiological maturity in 1990, the first growing season, 38 to 44% of each enriched source could be accounted for. By physiological maturity in 1991, 60% of the clover source but only 28 to 36% of the fertilizer sources could be accounted for. This study demonstrates the substantial amounts of endogenous soil N mineralization, inorganic N immobilization, and legume N persistence in these cropping systems.
Production Practices Improve Grain Sorghum and Pearl Millet Competitiveness with Weeds
Authors: Limon‐Ortega Augustin , Mason Stephen C. , Martin Alex R. 
Published: July 2010

AbstractPearl Millet [Pennisetum glaucum (L.) R. Br.] is a new grain crop adapted to many grain sorghum [Sorghum bicolor (L.) Moench] production regions, but weed control is often difficult, due to slow initial crop growth and limited herbicide options. An experiment was conducted in 1994 and 1995 to compare the competitiveness of pearl millet topcross hybrid 79‐2068A/NPM‐1 and grain sorghum singlecross hybrid DK28 with velvetleaf (A butilon theophrasti Medik.) and foxtail (Setaria spp.) as influenced by crop row spacing and N fertilizer application. The experiment was conducted on a Sharpsburg silty clay loam (fine, smectitic, mesic, Typic Argiudoll) near Mead, NE. Crops were planted in rows 38 and 76 cm apart, and N rates were 0 and 78 kg ha−1. Weed levels were obtained by differential herbicide applications at 7 d after emergence and by hand weeding. Yield losses of grain sorghum in 1994 and 1995, and pearl millet in 1995, were described by a nonlinear model based on a rectangular hyperbola. As velvetleaf and foxtail biomass approached zero, grain yield reduction of both crops was similar. In 1994, as weed pressure increased, grain sorghum yield loss was less in 38‐cm than in 76‐cm row spacing. In 1995, row spacing had no effect on grain yield. In contrast, pearl millet grain yield loss was greater in 38‐cm than in 76‐cm row spacings as weed level increased in 1995. All yield components of both crops were affected by weed level: number of kernels per head was influenced the most. Nitrogen fertilizer application enhanced yield of both crops by an average of 1.15 Mg ha‐1 in the 1994 season, but did not increase yield in the dry 1995 season. Narrowing row spacings from 76 to 38 cm increased grain yield of both crops by an average of 1.06 Mg ha−1 in 1994 and 0.83 Mg ha−1 in 1995. Grain yields of both crops were enhanced by weed control, narrow row spacing, and N application with adequate seasonal precipitation.
A Standardized Plate Meter for Estimating Pasture Mass in On‐Farm Research Trials
Authors: Rayburn Edward B. , Rayburn Susan B. 
Published: July 2010

AbstractA plate meter for estimating pasture mass (PM) was constructed of 5.6‐mm‐thick acrylic plastic cut into a 46‐cm square and fitted with a 3.8‐cm center hole. (The acrylic is stable under varying humidity, readily available, inexpensive, and easy to work.) A meter stick through the center hole measures the plate height (PH) resting on the pasture canopy. The meter was tested on six rotationally grazed pastures (0.2‐2.4 ha), measured before eight grazing events. Each pasture was double‐sampled for PH and clipped PM at 10 to 30 locations. The calibration regression slope was 452 kg (ha cm)−1, with a residual standard deviation (RSD) of 753 kg ha−1 and an r2 of 0.52. The high RSD is typical of forage stands, which vary widely in forage bulk density. The relatively low r2 was probably due to the uniform height of these rotationally grazed (as opposed to continuously grazed) pastures resulting in a small range in PH. The validation regression had a slope of 0.72 and a RSD of 808 for individual samples and a slope of 1.11 and RSD of 155 for means of 20 samples. The reduction in RSD with increasing sample size points to the need to take 15 to 30 measurements when calibrating the plate meter or sampling rotationally grazed pastures, to have an estimate within 10% of the mean PM. This simple plate meter provides as accurate a measure of PH and PM as the more sophisticated metal plate meters, is practical for carrying in the field, and in 1996 cost $12.
Soybean Leaf Water Potential Responses to Carbon Dioxide and Drought
Authors: Allen Leon H. , Valle Raul R. , Jones James W. , Jones Pierce H. 
Published: July 2010

AbstractRising CO2 can have direct effects on crop water relations and indirect effects on water available for growth. We studied the effects of elevated CO2 and drought on leaf water relations of soybean [Glycine max (L.) Merr. cv. Bragg] and considered the hypothesis of osmotic adjustment mediated by increased photosynthesis (Hypothesis 1) vs. the hypothesis of water conservation mediated by decreased stomatal conductance (Hypothesis 2) to explain improved water relations of plants growing under elevated CO2. In Exp. 1, soybean was grown at 330, 450, 660, and 800 μmol mol−1 CO2 in sunlit, closed‐circulation, controlled‐environment chambers under well‐watered conditions. Leaf total water potential (WP), osmotic potential (OP), and turgor potential (TP) were measured at midday during V4 to R6 stages of development. In Exp. 2 (well‐watered, R1‐R3) and Exp. 3 (13‐d drying cycle, R6 seed filling), soybean was grown at 330 and 660 μmol mol−1 CO2, and WP, OP, and TP were measured five times per day on sunlit and shaded leaves. In Exp. 3, stomatal conductance (gs) and transpiration rate (TR) of leaves were also measured. Experiments 1 and 2 showed that elevated CO2 increased TP and decreased OP, but did not affect leaf WP, thus favoring Hypothesis 1. In Exp. 3, leaf WP was higher in elevated than ambient CO2. Diurnal TP was higher in elevated than ambient CO2 at the beginning of drought, and was maintained longer each day as drought progressed. At the end of drought, TP and WP was higher in elevated than ambient CO2. Elevated CO2 leaves had lower TR because of lower gs than ambient CO2 counterparts. Thus, Exp. 3 supported Hypothesis 2, that both stressed and nonstressed plants in elevated CO2 have a better water status (e.g., higher TP) than plants in ambient CO2 due to water conservation mediated by decreased gs. Remobilization of leaf nutrients during seed filling may limit the capability for osmotic adjustment. Regardless of the mechanisms, growth of plants in elevated CO2 should be less affected by drought than plants in ambient CO2.
Corn Response to Cover Crop Species, Spring Desiccation Time, and Residue Management
Authors: Vaughan Jeffrey D. , Evanylo Gregory K. 
Published: July 2010

AbstractCover crops are integral parts of whole farm systems that include corn (Zea mays L.), but there is a lack of synchrony between cover crop N release and corn N uptake. This synchrony may be enhanced by varying the cover crop spring desiccation time and subsequent residue management. A field study was established to determine (i) the effect of rye (Secale cereale L.), hairy vetch (Vicia villosa Roth), and rye + hairy vetch spring desiccation timing on cover crop biomass, N content, and C:N ratio and (ii) the effect of the cover crop species, spring desiccation timing, and residue management on soil moisture content, soil mineral N concentration, corn tissue N concentration, and corn grain yield. Chemical desiccation times were either the boot stage of rye (approximately 3 wk prior to corn planting) or the early flowering stage of hairy vetch (several days prior to corn planting) for all three cover crop treatments. Three cover crop residue management treatments were implemented several days after each chemical desiccation: no further treatment (control), cover crop residue mowed (mow), or cover crop residue mowed and disked (mow + disk). All cover crops increased in biomass accumulation, but only hairy vetch increased in N content between desiccation times. Cover crop N availability was more important for corn yield potential than cover crop soil moisture conservation. Corn yields were higher following hairy vetch than following rye and rye + hairy vetch, due to greater N availability from hairy vetch residue. Corn N concentrations and yields were not influenced by desiccation time following hairy vetch, indicating that hairy vetch should be allowed to grow until immediately prior to corn planting, to permit maximum N accumulation. However, corn N concentrations and yields were higher with early desiccation than late desiccation following rye and rye + hairy vetch, indicating that cover crops including rye should be desiccated several weeks before corn planting. Mowing may be an alternative cover crop management technique that enhances the synchrony of cover crop N release with corn N need and uptake while maintaining a moisture conserving mulch.