bluuebunny/crossref_metadata_2025 huggingface dataset:
FORTRAN Graphics Library for PC‐Based Crop Simulation Models
Authors: Hodges Tom
Published: July 2010

A graphics library is presented for PC‐based crop growth simulation models written in the FORTRAN programming language. The library can be incorporated into simulation models with only minor programming. It allows the user to graphically plot simulated variables and measured values on the computer screen while a model is running. Graphs can also be sent to an output device such as a plotter, printer, or slide maker. Procedures for installing the library in a simulation model are described with the SIMPOTATO potato model as an example. The library is a module that can be quickly and easily added to FORTRAN simulation models by even relatively inexperienced programmers.
Reproductive Morphology of Five Kentucky Bluegrass Cultivars
Authors: Rhoads J. L. , Dunn J. H. , Minner D. D. , Hunt K. L.
Published: July 2010

A problem associated with plant growth retardant applications in Kentucky bluegrass, Poa pratensis L., is the application window for effective seedhead and vegetative growth suppression. Theoretically, the optimum timing for growth retardant applications would be just prior to the peak growth period in spring and before the inflorescence becomes visible above the youngest leaf. The objective of this field study was to determine if time of primordia initiation as an indicator of inflorescence development is consistent in selected Kentucky bluegrass cultivars in successive growing seasons. Initiation of inflorescence primordia was determined by randomly sampling and dissecting primary tillers of each cultivar during the late winter‐early spring and observing under a dissecting microscope. Our research showed that dates marking a transition from vegetative toward a predominately reproductive growth habit varied significantly among Kentucky bluegrass cultivars in both years. Also, one of the six cultivars, Kenblue “low maintenance” was not in a similar reproductive condition on several observation dates occuring in the same calendar week of 1986 compared with 1987. These results, based on our 2‐yr study, show that reproductive variation exists among Kentucky bluegrass cultivars, and that some cultivars may not develop inflorescences annually within calendar date application windows for growth retardants with much predictability.
Third‐Year Forage Yield Testing in Tall Fescue is Not Cost Effective
Authors: Nepal Pratima , van Santen Edzard
Published: July 2010

Small plot cultivar testing is an integral part of the decision‐making process in agronomic research relating to release and production recommendation of cultivars. The objective was to evaluate duration of tall fescue (Festuca arundinacea Schreb.) cultivar trials with respect to the information obtained. Tall fescue performance data from 12 states were obtained from eight different sources. Coefficients of determination were obtained from regressing three single‐year and two 2‐yr yields on 3‐yr yield for each trial. First‐year yields explained from 14 to 90% of the variation among cultivars after 3 yr of testing. Single‐year trials or single‐year data from multi‐year trials are inadequate because of many low coefficients. Two‐year yields explained from 0 to 100% of the differences among cultivars after 3 yr of testing. Twelve percent of the trials had coefficients ≤0.80 when the first two production years were used in the analysis compared to 38% when the last two years of a 3‐yr trial were used. Therefore, a trial duration of two production years is the better alternative to taking data during the last two production years of a 3‐yr trial. It is concluded that a trial duration of more than 2 yr is an ineffective use of scarce resources if total dry matter production is the only factor considered.
Nitrogen Fertilization of Tall Fescue‐Birdsfoot Trefoil Mixtures
Authors: Hoveland C. S. , Richardson M. D.
Published: July 2010

In mixtures with birdsfoot trefoil (Lotus corniculatus L.), tall fescue (Festuca arundinacea Schreb.) growth during early spring and autumn in north Georgia is limited. A study was conducted to determine if supplemental N fertilizer could extend the productive season of tall fescue‐birdsfoot trefoil mixtures. Field experiments were conducted for 3 yr in the Mountain and Piedmont regions of Georgia. Mixtures grown included ‘AU Triumph’ tall fescue with ‘Fergus’ or ‘AU Dewey’ birdsfoot trefoil and tall fescue alone, all with N rates of 0, 56, or 112 kg ha−1 in February, or 56 kg ha−1 in February and September. The grass‐legume mixture at 0 N had total forage yields similar to tall fescue + 112 kg N ha−1. Spring production of tall fescue‐birdsfoot trefoil mixtures was increased 50 to 114% with 56 kg N ha−1. Autumn production was increased 80 to 200% with 56 kg N ha−1 in September. The N concentration of non‐N‐fertilized tall fescue increased 24% when grown with birdsfoot trefoil. Apparent N2 fixation of birdsfoot trefoil grown with tall fescue ranged from 79 to 137 kg N ha−1 during a good rainfall year. Birdsfoot trefoil apparently did not fix sufficient N for cool season growth of tall fescue, so that application of N in February and again in September extended the productive season of tall fescue‐birdsfoot trefoil mixtures.
Corn Motion in the Wind during Senescence: II. Effect of Dynamic Plant Characteristics
Authors: Flesch T.K. , Grant R.H.
Published: July 2010

Lodging in corn (Zea mays L.) is often the result of wind‐induced motion, which creates a strain on the stalk and root system. In elastic theory, motion is defined by static characteristics (stiffness) and dynamic characteristics (damping coefficient [ζ] and natural frequency [fn]). A study was conducted to determine the relationship of plant ζ, fn, and stiffness (K) to total plant motion in the wind. The ζ,fn and K were calculated from stalk motion measured on 23 plants in the field during October, 1988, at West Lafayette, IN. Interrow contact was eliminated, and plants were grouped according to whether the ear was upright or had fallen to a hanging position. With the ear upright, ζ,fn, and K averaged 0.11, 1.54 Hz, and 2.44 N m deg−, respectively. Plant resonant oscillations corresponded with fn. The fn was well above the frequencies of highest wind energy. In theory, total plant motion will decrease as ζ and fn, increase. Field measurements showed that with the ear upright, and fn were uncorrelated with total motion, but when the ear dropped to a hanging position, there was a 54% increase in ζ accompanied by by a 15% reduction in motion. The results indicate that dynamic plant characteristics do affect the characteristics of plant motion. However, the plant motion was relatively insensitive to the range of ζ and fn we observed because fn, was well above the frequencies of high wind energy.
Supplemental Calcium Application on Yield, Grade, and Seed Quality of Runner Peanut
Authors: Adams James F. , Hartzog Dallas L. , Nelson Donald B.
Published: July 2010

The need for supplemental Ca continues to be the most likely nutritional problem of peanut (Arachis hypogaea L.) production on acid, sandy, and low cation exchange capacity (CEC) soils. The need for supplemental Ca from gypsum for improved yield, quality, and seed germination of four runner‐type cultivars was evaluated on 14 sites with a range in available soil Ca of 48 to 242 mg kg−1 during 1987 to 1989. Yields of all four cultivars were increased by addition of gypsum at the five sites with the lowest Mehlich‐1 extractable Ca (< 158 mg kg−1), although the magnitude of response varied among cultivars. Increases in sound mature kernal occurred for GK 7 and Southern Runner at soil Ca levels higher than that required for maximum yield. Calcium composition of nuts also was affected more by supplemental gypsum than was either yield or SMK. Germination percentage and seedling survival were both highly correlated with seed‐Ca concentration. Minimum seed Ca needed for maximum germination ranged between 368 and 414 mg kg−1 for the four cultivars. Comparable Ca values for seedling survival ranged between 361 and 445 mg kg −1. The correlations between soil Ca and either germination or seedling vigor were less than those between seed Ca and germination or seedling vigor. All correlations involving Ca and germination suggest that soils used to produce seed, probably need a higher level of available Ca than those used for general production.
Plant Growth Regulator Effects on Growth and Forage Quality of Tall Fescue
Authors: Reynolds J. H. , Krueger W. A. , Walker C. L. , Waller J. C.
Published: July 2010

Forage quality of tall fescue (Festuca arundinacea Schreb.) is low in the spring after heading. Plant growth regulators (PGRs) have been shown to improve forage quality through inhibition of seedhead development. The objective of this study was to compare the effect of fall or spring application of six PGRs on heading, yield, and forage quality of tall fescue. The soil was an Etowah silt loam (fine‐loamy, siliceous, thermic Typic Paleudults). Precipitation was more favorable in the second year of the experiment than in the first. Sethoxydim (2‐[1‐(ethoxyimino)butyl]‐5‐[2‐(ethylthio)propyl]‐3‐hydroxy‐2‐cyclohexen‐1‐one) at 70 g ha−1, haloxyfop methyl (methyl 2‐[4‐[[3‐chloro‐5‐trifluoromethyl)‐2‐pyridinyl]oxy]phenoxy]propanoic acid) at 45 g ha−1, and mefluidide (N‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)‐sulfonyl]amino]phenyl]acetamide) at 280 g ha−1 were the most consistent in reducing head density, forage yield, and neutral detergent fiber (NDF) and increasing crude protein (CP) of the May harvest. The PGRs were more effective in reducing yield, head density, and NDF and increasing CP of the May harvest when applied in April than when applied in December of the second year. Responses to the PGRs in the May harvest were fewer in the first year when precipitation was less favorable. Only one PGR increased in vitro dry matter digestibility (IVDMD) in the second year and none increased it in the first year. Four April‐applied PGRs decreased NDF in the first year's regrowth and April‐applied sethoxydim and December‐applied mefluidide increased CP in both years' regrowth. Forage quality was not consistently improved by the use of PGRs on tall fescue. An effective PGR may be more useful in turf areas than on forage because it reduces yield substantially.
Development of Double‐Crop Soybean under Different Soil Water Regimes
Authors: Pearce R. C. , Grabau L. J. , Grove J. H. , Lin H.
Published: July 2010

Double‐crop soybean [Glycine max (L.) Merr.] comprises nearly one‐third of the total soybean hectarage in the southeastern USA. This study was initiated to investigate the water relations of soybean following winter wheat [Triticum aestivum (L.) emend. Thell], with emphasis on the role of stored soil water. A treatment scheme was devised in which wheat was killed at heading, mid‐grain fill, and maturity, resulting in three different levels of stored soil water at soybean planting. In 1986, soil water levels at planting were 26.0, 23.1 and 21.4 cm of water in the 0.9‐m profile, respectively. A relatively dry early summer resulted in poor soybean stands and slow early growth; however, rainfall was well distributed during the latter half of the growing season. Soybean yields in 1986 were 2.76, 1.60, and 0.44 Mg ha−1, respectively. Initial soil water levels in 1987 were 31.1, 27.5, and 25.1 cm of water in the 0.9‐m profile. A wet early summer resulted in good stands and vigorous early growth, but a late summer drought caused severe stress during the reproductive growth period. Soybean yields recorded in 1987 were 0.97, 0.54, and 0.30 Mg ha−1, respectively. In 1989, soil water levels at planting were 33.1, 34.3, and 31.6 cm and associated yields were 1.51, 1.81, and 1.11 Mg ha−1. Rainfall was above average and well distributed during the 1989 season. Within each of the years there was a positive relationship between soil water level at planting and yield of double‐crop soybean; however, between years the amount and distribution of rainfall had a more dominant influence on yield than did soil water level at planting.
Application Placement and Timing of Nitrogen Solution for No‐Till Corn
Authors: Stecker J. A. , Buchholz D. D. , Hanson R. G. , Wollenhaupt N. C. , McVay K. A.
Published: July 2010

Fertilizing no‐till corn (Zea mays L.) with urea‐based N sources requires managing for N losses such as immobilization and NH3 volatilization. In this study the interactive effects of fertilizer N application time and placement method were evaluated by applying urea ammonium nitrate (UAN) solution to no‐till corn. Eight site‐years of data were collected from sites in central, northeast, and northwest Missouri on Ochraqualf, Albaqualf, and Udifluvent soils, respectively. Experimental design was a complete factorial of N application time (preplant and sidedress), placement method (knife, dribble and broadcast) and rate (67, 135, and 202 kg N ha−1). Knife injected N increased yields relative to broadcast and dribbled N in five of eight site‐years. Yields from knife injected N ranged from 4 to 20% more than dribble and 5 to 40% more than broadcast. Ear‐leaf N concentration and grain N uptake were increased from knife injected N in six of the eight site‐years. Dribbled and broadcast UAN performed similarly in most site‐years for grain yield, ear‐leaf N and grain N uptake. Except for two site‐years in which sidedress resulted in lower grain yields, application time had no effect on grain yield. No interaction of application time and placement method was apparent, as knife injection was superior to broadcast and dribble at both application times. This suggests that N losses associated with surface application of urea‐based N sources were similar for preplant and sidedress application times.
Nitrogen Nutrition of Rainfed Winter Wheat in Tilled and No‐Till Sorghum and Wheat Residues
Authors: Knowles T. C. , Hipp B. W. , Graff P. S. , Marshall D. S.
Published: July 2010

Decomposition of sorghum [Sorghum bicolor (L.) Moench] and wheat (Triticum aestivum L.) plant residues can immobilize enough surface‐applied N to cause a deficiency in successive winter wheat crops. This experiment examined the effects of conventional and no‐till grain sorghum and wheat residues on N requirements of dryland winter wheat. Field experiments conducted from 1987–1991 on an Austin silty clay (fine‐silty, carbonatic, thermic Udorthentic Haplustoll) soil included sorghum and wheat residue treatments with conventional till (CT), no‐till (NT), and residue removal (RR). All residue plots received four preplant N rates (0, 45, 90, and 135 kg N ha−1), with subplots planted to three winter wheat cultivars in 1988 and 1989, and two cultivars in 1990 and 1991. Grain and stover yields were significantly lower when wheat followed sorghum than under continuous wheat. Wheat grain yields at N application rates < 90 kg ha−1 were 39% lower in NT plots vs. CT plots, 5% lower in CT plots compared with yields in RR plots, and 39% lower in sorghum‐wheat rotation compared with continuous wheat. Wheat N uptake at N application rates <90 kg ha−1 was 41% lower in NT plots vs. N uptake in CT plots, 10% lower in CT plots vs. N uptake in RR plots, and 36% lower in sorghum‐wheat rotation vs. continuous wheat. Grain yield and N uptake of wheat at the 135 kg N ha−1 rate were not significantly different in NT and CT plots. Preplant soil NO3‐N analysis indicated a need for the application of N fertilizer at planting in CT and NT sorghum residues, and basal stem NO3‐N analysis showed wheat growing in NT residues and sorghum‐wheat rotations; had higher N fertilizer requirements than continuous CT wheat. Microbial immobilization of surface‐applied N was responsible for N deficiencies observed in NT winter wheat, while a decrease in fallow time between sorghum harvest and wheat planting dates was the primary cause for reduced mineralization rates of residue‐derived and indigenous soil N in sorghum‐wheat rotations. A fallow period following grain sorghum and/or band application of fertilizer N could alleviate N deficiencies observed in this study.
Grain Protein Response of Spring Barley to High Rates and Post‐Anthesis Application of Fertilizer Nitrogen
Authors: Bulman Patrick , Smith Donald L.
Published: July 2010

Barley (Hordeum vulgare L.) is an important feed crop in eastern Canada. Although the grain is used mainly as a source of energy for monogastric animals, high grain protein concentration (GPC) is desirable. Commencing in 1987, a 4‐yr field trial was conducted at the E.A. Lods Agronomy Research Centre of McGill University to evaluate the effects of N application on the GPC of spring barley. Cadette and Leger, which are adapted feed cultivars, and Argyle, an unadapted malting type, were grown with N rates of 0, 50, 100, 150, and 200 kg N ha−1 broadcast at seeding as NH4NO3. Two other treatments consisted of applying 100 kg N ha−1 at seeding and 50 kg N ha−1 as NH4NO3 (broadcast) or urea (foliar solution) 6 to 10 d after awn emergence. Increasingly higher rates of N applied at seeding increased the amount of protein per grain, thereby increasing GPC. The amount of nonprotein dry matter (DM) per grain was consistent among treatments within seasons. In only one instance did fertilizer N increase GPC by reducing nonprotein DM per grain. Split N treatments increased GPC significantly more than a single application of equivalent N at seeding in only two seasons. A foliar‐applied urea topdressing generally increased GPC more effectively than broadcast NH4NO3. With individual cultivars, the GPC response to N treatments could be explained in terms of protein per grain. Cultivar differences in GPC were not always related to protein per grain. Argyle had the highest GPC values (129.1–160.6 g kg−1), but only because of poor nonprotein DM accumulation per grain.
Oat Cultivar Response to Potassium Chloride on Soils Testing High in Potassium
Authors: Gaspar P. E. , Reeves D. L. , Schumacher T. E. , Fixen P. E.
Published: July 2010

Yield responses of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) to additions of KCl fertilizer on high‐K soils have been documented. One of the principal effects of KCl on high‐K soils is a reduction in foliar disease. Little research has been conducted on the effects on oat (Avena sativa L.) production of KCl on high‐K soils. The objective of this study was to evaluate the effects of adding KCl to high‐K‐test soils on grain yield, quality, plant water relations, crown rust (Puccinia coronata Corda) incidence, and lodging of commonly grown oat cultivars. The experiments were conducted at four locations in eastern South Dakota. Fertilization with KCl increased oat grain yields by 4% at two locations. Although the increase in grain yield was significant, it was too small to be profitable under current economic conditions. A significant increase in 1000‐kernel weight (4–7% relative to the control) occurred at locations with a yield response. Additions of KCl did not affect crown rust infection, protein, or oil content, relative water content, or stomatal conductance; however, KCl addition decreased solute potential adjusted for full turgor during the boot stage at two locations by 0.07 MPa. The decrease in adjusted solute potential was not consistently associated with a grain yield response.
Yield Component Compensation in Uniculm Barley Lines
Authors: Dofing S. M. , Knight C. W.
Published: July 2010

Asynchronous spike maturation in barley (Hordeum vulgare L.) grown at northern latitudes, caused by late‐developing tillers, frequently results in harvest delay, reduced grain quality, and increased drying costs. The uniculm trait has been suggested to promote uniform spike maturation and increased grain yield; however, the literature contains no information on the field performance of genetic uniculm lines. The purpose of this study was to assess the performance and yield component compensation of uniculm barley lines having the uc2 gene. Five spring barley lines were grown at seeding rates of 35, 90, 145, and 200 kg ha−1 at Palmer and Fairbanks, AK in both 1991 and 1992. Higher seeding rates resulted in shorter plants, earlier maturity, increased spikes per square meter, and reductions in kernels per spike and kernel weight. Results from path analysis demonstrated that spikes per square meter was the primary determinant of grain yield, followed by kernels per spike, with kernel weight of only minor importance. Increasing spikes per square meter caused relatively large reductions in kernels per spike and kernel weight, while increasing kernels per spike caused only minor reductions in kernel weight. Maximum grain yield was attained at the 200 kg ha−1 seeding rate in Fairbanks and at the 90 or 145 kg ha−1 seeding rate at Palmer. The relatively low grain yield of uniculm lines appears to be due to a low number of kernels per spike at higher spike densities.
Warm‐Season Grass Productivity and Growth Rate as Influenced by Canopy Management
Authors: Belesky David P. , Fedders James M.
Published: July 2010

Warm‐season grasses adapted to cool‐temperate environments can improve the seasonal distribution and supplement the productivity of forage systems in the northeastern USA. Management practices concerning clipping regimes for warm‐season grasses grown in the region, are not well understood. A 2‐yr field study was conducted to determine productivity and growth rates of flaccidgrass (Pennisetum flaccidum Griseb.), switchgrass (Panicum virgatum L.), bermudagrass (Cynodon dactylon L.), and Caucasian bluestem [Bothriochloa bladhii (Retz.) S.T. Blake] clipped according to sward height criteria. Treatments were replicated three times and included; first clipped at full heading; or 50% removal of short canopy and 50% and 75% removal of tall canopies at vegetative stages. Cumulative yields of warm‐season grasses were influenced by a complex clipping treatment, species, and year interaction. When first cut was made at a mature stage, 1990 and 1991 yields were similar, but were greater in 1991 than 1990 when cut early. Cumulative herbage yield of bermudagrass and Caucasian bluestem exceeded that of switchgrass and flaccidgrass when clipping was begun early in the growing season (species ✕ treatment interaction; P ≤ 0.01). Mean growth rates were greatest when canopies were managed as hay or when 75% of a tall canopy was removed, and were greater in 1991 than in 1990. Instantaneous growth rates suggest that bermudagrass and Caucasian bluestem appear to be better adapted to repeated defoliation than the tall‐growing species. Switchgrass and flaccidgrass may be best used in limited‐defoliation or conserved forage situations.
Reducing the Cost of Estimating Root Turnover with Horizontally Installed Minirhizotrons
Authors: Dubach Markus , Russelle Michael P.
Published: July 2010

Growth and decay of individual roots (i.e., root turnover) is difficult to quantify because the processes occur simultaneously in a root system. Minirhizotrons are promising tools for assessing root turnover in natural and managed ecosystems. We investigated methodological problems and improvements in using minirhizotrons to estimate root turnover. Root images were collected in field plots of alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus carniculatus L.) through minirhizotrons installed horizontally before planting at six depths, from 7 to 70 cm, parallel to and directly below the crop rows. Forty video images (13 by 17 mm) were recorded at weekly intervals at 90° from vertical along both sides of the tubes. Images were edited into time‐lapse sequences and cumulative numbers of roots that appeared and disappeared at each location were determined manually over an entire growing season. This required ≈ 29 h of labor for each replicate of each depth (a total of 80 images in one tube), with the biggest share spent on editing. Accuracy and precision of results were not decreased by using only every second image along both sides of the tube (40 images), but declined when either only one side of the tube or only 20 consecutive images on both sides were used. Reducing the recording frequency further reduced labor requirements: depending on date of root appearance and observation depth, recording intervals could be lengthened to 2 wk for the 12‐cm depth and longer for greater depths without losing either accuracy or precision. Analyzing every second image and increasing the time interval between recordings resulted in projected labor savings of ≥70%, while maintaining data integrity.
Rooting Characteristics and Associated Drought Resistance of Zoysiagrasses
Authors: Marcum Kenneth B. , Engelke M. C. , Morton Sharon J. , White Richard H.
Published: July 2010

Declining availability of water for landscape irrigation has increased the need for drought‐resistant turfgrasses. Though drought‐resistance mechanisms are known to include deep rooting in some plants, little is known concerning zoysiagrass rooting characteristics. This study was conducted to determine if differences in rooting parameters exist among zoysiagrasses, and if they are associated with drought resistance. Twentyfive zoysiagrasses cultivars and species [Zoysia japonica Steud., Z. matrella (L.) Merr., and Z. japonica Steud. ✕ Z. tenuifolia Willd. ex Trin.] were studied in polyethylene tubes in a glasshouse. Differences were observed for average maximum root depth (AMRD), total root weight, and root numbers and weights at increasing 100‐mm depth increments. Average maximum root depth was positively correlated with total root weight and root number and weight at increasing 100–ram depth increments. Grasses with superior AMRD, total root weight, and root numbers at deeper profile depths (300–500 mm) included QT2047, El Toro, DALZ8512, TC5018, Meyer, DALZ8514, and DALZ8516. In a previously reported field experiment, 11 of the 25 zoysiagrasses were rated for percent of plot area covered by green turfgrass (an indicator of drought resistance) under three levels of irrigation (0, 35, and 100% of turfgrass evapotranspiration [ET]). Average maximum root depth, total root weight, and root numbers at 200‐, 300‐, and 400‐mm depths in polyethylene root tubes were positively correlated with percent green plot cover in the field under deficit irrigation (0 and 35% ET), indicating that rooting depth, weight, and branching at lower depths are important droughtresistance mechanisms in zoysiagrasses.
Performance of Commercial Cotton Cultivars under Elevated Densities of Tobacco Budworm
Authors: McCarty Jack C. , Jenkins Johnie N.
Published: July 2010

The development of improved cultivars is essential for continued economic production of cotton, Gossypium hirsutum L. Information is limited on how different cotton cultivars compare under elevated densities of tobacco budworm, Heliothis virescens (F.), an economically important cotton pest. Seven field tests were conducted between 1988 and 1992 to evaluate cotton cultivars grown under elevated densities of tobacco budworm (TBW). Cultivars were grown under two regimes: (i) artificial elevated infestation, w/TBW, and (ii) elimination of tobacco budworm, w/o TBW. Elevated densities of TBW (w/TBW) significantly reduced yields compared with w/o TBW, but reduction varied among years and tests. The regression equation for lint yield w/TBW on lint yield w/o TBW was Y = −111.0 + 0.6X. Thus, for every 1.0 kg of lint yield increase per hectare due to cultivar improvement, the corresponding increase under artificial TBW infestation was only 0.6 kg. The regression coefficient for lint percentage on lint yield w/o TBW was Y = 30.85 + 0.006X. These data show that cotton breeders have developed high‐yielding cultivars, but that progress is still needed in the development of resistance to the tobacco budworm injury. They also show that, as cultivars with higher yield potential were developed, these cultivars were better able to tolerate damage by the tobacco budworm. The parity between yield increase per se and yield under elevated densities of tobacco budworm is not 1.0:1.0, but rather 1.0:0.6. This is a useful and practical level of parity.
Soil‐Plant Buffering of Inorganic Nitrogen in Continuous Winter Wheat
Authors: Raun William R. , Johnson Gordon V.
Published: July 2010

The soil‐plant system can limit soil profile inorganic N accumulation when N fertilizers are applied at rates greater than needed for maximum yield. Nitrogen rates that maximized grain yield and increased soil profile inorganic N accumulation under continuous dryland winter wheat (Triticum aestivum L.) were evaluated in four long‐term experiments. Soil cores (0‐210 cm) were taken in 1988 and again in 1993 from N rate treatments where wheat had been grown for more than 23 yr. Soil cores were split into 15‐ to 30‐cm increments and analyzed for NH4‐N, NO3‐N, total N, and organic C. Critical N fertilization rates were determined from linear‐plateau models of wheat grain yield on annual N applied. Plateau‐linear models were established for soil profile inorganic N accumulation (sum of NH4‐N + NO3‐N, converted to kg ha−1) on annual N applied. Maximum yields were observed at N rates less than that required to increase soil profile inorganic N accumulation. Annual N fertilization rates that increased inorganic N accumulation exceeded the N requirement for maximum yields by more than 23.3 kg N ha−1 in all experiments. Increased plant N volatilization and grain N uptake have been found when N rates exceed yield maximums. High N rates can also increase straw yield and straw N, subsequently increasing surface soil organic C and N and the potential for denitrification when wheat straw residues are incorporated. In dryland production systems, soil‐plant buffering (considering the processes discussed) implies that the system buffers against (resist) soil accumulation of inorganic N, even when N rates exceed that required for maximum grain yield.
Forage Production, Grain Yield, and Protein Content in Dual‐Purpose Triticale Grown for Both Grain and Forage
Authors: García del Moral L. F. , Boujenna A. , Yañez J. A. , Ramos J. M.
Published: July 2010

The use of cereal crops for both forage and grain production is practiced in many parts of the world. Quantity and quality of forage and grain with this dual use is strongly influenced by seeding date, cutting frequency and growth stage. The effect of two seeding dates and three cutting frequencies on forage production, grain yield, forage and grain protein content, and several associated characteristics of triticale (✕ Triticosecale Wilt.) was determined in 1990 and 1991 at three field locations in southern Spain. Seeding date was less influential on forage and grain production than cutting treatments. Forage harvest significantly reduced grain yield 19.1 to 54.7% with one cutting and 46.6 to 76.2% with two cuttings. Plant height was reduced 5.6 to 18.8% with one cutting and 16.4 to 43.3% with two cuttings. Grain protein yield was reduced 18.6 to 53.7% with one cutting and 47.9 to 72.8% with two cuttings. Grain protein content increased 5.6 to 23.3% with one cutting and 8.0 to 32.0% with two cuttings at the rainfed sites, but not under irrigated conditions. Forage protein content was negatively related to forage yield both in rainfed (r = −0.824) and irrigated (r = −0.952) environments, probably due to a dilution effect. An inverse linear relationship was found between grain yield and protein content (r = −0.901) in the four rainfed experiments, probably from differences in accumulation of starch. Under irrigated conditions and high soil fertility, cuttings did not affect the final percentage of protein in the grain, although grain yield decreased. An inverse relationship was found between the rainfall measured during the triticale growing season and the mean protein content in the grain (r = −0.911) under rainfed conditions.
Soybean Reproductive Development: Adapting a Model for European Cultivars
Authors: Colson Josiane , Bouniols Andrée , Jones James W.
Published: July 2010

The objective of this study was to simulate reproductive development and yield potential of new soybean [Glycine max (L.) Merr.] lines that might be grown in different European locations. The SOYGRO model was adapted to European crop conditions with respect to genetic parameters for pod set, pod growth, seed set, and seed enlargement. The structure of reproductive development in the model takes into account the hierarchy in assimilate partitioning for pod addition, shell growth, and seed initiation. This aspect was described in relationship with canopy photosynthesis, temperature, and photoperiod. A sensitivity analysis was conducted on yield variations with 11 parameters representing phenological traits, characteristics of pod and seed development, and foliage growth in order to identify the main genetic parameters. Field determinations of pod numbers computed from R5 to R7 on current cultivars and new lines belonging to indeterminate and determinate types showed two kinds of fruiting processes, which appear to be independent of growth habit and maturity group. Based on the comparison of the dynamics of observed pod addition for the reference cultivars, a simple procedure was proposed to calibrate the genetic parameters for new cultivars. This new procedure allowed validation of pod production and yield and provided good agreement with field data collected in several locations in Europe.
Role of Warm‐Season Weeds in Spotted Wilt Epidemiology in the Southeastern Coastal Plain
Authors: Johnson W. Carroll , Todd James W. , Culbreath Albert K. , Mullinix Benjamin G.
Published: July 2010

The role of endemic weeds in the epidemiology of spotted wilt must be determined in order to develop an integrated system to manage the disease. Field studies were conducted from 1990 through 1992 to determine concurrently the incidence of spotted wilt and population dynamics of thrips (Thysanoptera: Thripidae) on seven warm season weeds and three crop species planted in microplots. Weeds examined were Senna obtusifolia (L.) H. Irwin & Barneby (syn. Cassia obtusifolia L.] (sicklepod), C. occidentalis L. [syn. S. occidentalis (L.) Link.] (coffee senna), Jacquemontia tamnifolia (L.) Griseb. (smallflower morningglory), Ipomoea lacunosa L. (pitted morningglory), Sida spinosa L. (prickly sida), Desmodium tortuosum (Sw.) DC. (Florida beggarweed), and Xanthium strumarium L. (common cocklebur). Crops evaluated were Arachis hypogaea L. (peanut), Nicotiana tabacum L. (tobacco), and Capsicum annuum L. (bell pepper). All of the weed species were endemic to the southeastern Coastal Plain and all crops were commercially produced in the vicinity of the test site. Most of the weeds were closely related to species identified as hosts of tomato spotted wilt tospovirus (TSWV). TSWV was rarely detected in any of the weed species, while incidence in all crops increased at a linear rate throughout the growing season. Order of spotted wilt incidence in crops was peanut > tobacco > bell pepper. Thrips species diversity differed among weeds and crops. Thrips vectors were highly attracted to susceptible crops, especially peanut. While the weed species we studied were susceptible to spotted wilt, they were not preferred hosts for the thrips vectors. Any occurrence of spotted wilt in weeds is probably due to random feeding by the vector. The warm‐season weeds studied did not contribute significantly to the epidemiology of spotted wilt.
Nitrogen Fertilizer Management to Improve Crop Tolerance to Corn Rootworm Larval Feeding Damage
Authors: Riedell Walter E. , Schumacher Thomas E. , Evenson Paul D.
Published: July 2010

Widespread use of crop management practices that reduce the effect of corn rootworm (Diabrotica spp.) larval feeding damage on maize (Zea mays L.) plant lodging or grain yield production would reduce grower reliance on chemical pesticides. Nitrogen fertilizer placement can affect root system morphology and distribution within the soil profile. This study was conducted to determine if N fertilizer placement can be used as a tool to improve maize tolerance to rootworm infestation. The effects of planting time broadcast or split‐applied (planting‐cultivation) banded N (UAN; 28‐0‐0 N‐P‐K) treatments on root larval feeding damage, root pull resistance, lodging, grain yield, and survival of larvae to adult stage under different levels of controlled rootworm larval infestation were investigated. Results of the 3‐yr field experiment suggest that root systems were generally larger (greater root pull resistance) under banded N (85 kg plant−1) than under broadcast N (68 kg plant−1) at the time when rootworm larval feeding had ceased. Lodging (stem greater than 30° from vertical) in broadcast N plots (51%) was greater than that seen in banded N plots (41%). If tolerance to rootworm larval feeding damage is defined by the presence of a large root system and by the ability of the stem to stand erect, then banded N fertilizer placement can help improve tolerance to corn rootworm larval feeding damage.
Concentrations and Ruminal Degradabilities of Amino Acids from Wheat and Triticale Forage and Grain
Authors: Miller Grady L. , Bunting L. Dwain , Joost Richard E. , Ward Terry L.
Published: July 2010

A study was conducted to provide comparative data on amino acid (AA) concentrations in forage and grain of wheat (Triticum aestivum L.) and triticale (✕Triticosecale Wittmack), before and after ruminal degradation, while assessing forage and grain yield potential. Forage samples of Terral ‘817’ wheat, ‘Jenkins’ triticale, and ‘Morrison’ triticale were harvested at growth stages 5.0, 6.5, and 8.0 and AA concentrations and yield determined. Wheat and triticale forage samples were incubated in Dacron bags for 24 h in the rumen of cows to determine the comparative ruminal degradability of their EAA. Forage production among the three cultivars in 1987‐1988 was similar, but in 1988‐1989, Jenkins produced 15% more forage than Terral 817, which produced 14% more forage than Morrison. Essential amino acid concentrations in Jenkins triticale forage were equal to or greater than Terral 817 wheat or Morrison triticale; however, Morrison grain had a greater concentration of all EAA, except lysine, than did grain of Terral 817 or Jenkins. The EAA in Terral 817 forage averaged 25% higher in potential degradability in the rumen than EAA in Jenkins. Terral 817 and Morrison maintained a higher grain yield response to forage removal in contrast to Jenkins. Differences in forage yield, grain yield, and EAA concentration could not always be separated by species. The data suggest that triticale may produce forage and grain yields equal or greater than that of winter wheat while providing a better source of ruminally undegradable EAA.
A Proposed Method for Measuring the Effect of Soil Quality on Productivity
Authors: Olson Barry M. , Janzen H. Henry , Larney Francis J. , Selinger Lorna J.
Published: July 2010

The evaluation of soil quality requires definitive, measurable criteria. Our objective was to develop a field assay for identifying the specific soil attributes that govern the quality of soil for biomass production. The technique involved the removal of surface soil and subsequent deposition of soils with diverse attributes. As an initial evaluation of this approach, 36 diverse soils were deposited in a replicated design at each of two sites (dryland and irrigated), and the soils were seeded to cereals for three subsequent years. Crop growth was highly responsive to variation in soil properties. Dry matter yields on dryland in the year after establishment, for example, ranged from 5.4 to 9.4 Mg ha−1 (excluding two subsurface soils). These findings demonstrate that variation in soil quality has a quantifiable influence on productivity, and suggest a useful supplementary role for the proposed approach in identifying soil quality criteria.
Winter Wheat Responses to Surface and Deep Tillage on the Southeastern Coastal Plain
Authors: Frederick James R. , Bauer Philip J.
Published: July 2010

Conservation tillage practices have seldom been used to produce winter wheat (Triticum aestivum L.) on the U.S. southeastern Coastal Plain, primarily because of inadequate planting equipment and the need for deep tillage. Despite improved equipment, little is known about the effects of surface and deep tillage (ST and DT) systems on winter wheat development and grain yield on the Coastal Plain. Objectives of this 2‐yr study were to (i) determine whether ST affects the grain yield response of winter wheat to DT and (ii) examine the effects of ST and DT on winter wheat development. The soil was a Goldsboro loamy sand (fine‐loamy, siliceous, thermic Aquic Kandiudult). Treatments were ST (disked twice or no surface tillage) and DT (deep tilled using a ParaTill or no deep tillage). Averaged over years and levels of DT, the number of emerged seedlings was 16% less with no ST than with disking. With DT, the number of heads per square meter was similar for the two levels of ST treatment, indicating that wheat grown with no ST produced more heads per plant than with disking. Soil water contents were usually lower in 1995 than in 1994 for all treatments (<2 g kg−1 prior to inflorescence emergence in 1995). Aboveground dry weights near inflorescence emergence, kernel no. m−2, and grain yields averaged 39, 26, and 22% less, respectively, in 1995 than in 1994. Deep tillage increased aboveground dry weight, kernel no. m−2, and grain yield more for wheat in no‐surface‐tillage plots than in disked plots. When deep tilled, ST had no effect on grain yield in 1994, but yields were 25% greater for wheat grown with no ST in the drier year of 1995. There may be no need to disk the soil if DT is performed and proper planting equipment is used to produce winter wheat on the southeastern Coastal Plain. Yield increases due to DT in this region should be greater with no ST than with disking.
Comparison of Residue Decomposition Models Used in Erosion Prediction
Authors: Schomberg Harry H. , Steiner Jean L.
Published: July 2010

Crop residues protect soil from water and wind erosion. How long the residues remain effective depends on their decomposition rate. The crop residue decomposition submodels developed for the Revised Wind Erosion Equation (RWEQ) and Revised Universal Soil Loss Equation (RUSLE), which are used to determine the effectiveness of conservation practices, use different approaches to account for water and temperature effects on decomposition. Because of these differences, residue losses may not agree between the two models for a given location. We compared the climatic indices used in RWEQ and RUSLE to determine the similarity of results for simulated climatic scenarios, as well as for field data. Simulated climatic regimes were used to evaluate the relative responsiveness of the temperature and water functions. The two models estimated different numbers of decomposition days (DD) when water and temperature were not limiting. RUSLE usually predicted more DDs than RWEQ. Under water‐limiting conditions, the estimation of DD was similar for the two models. In comparisons with field decomposition data, mass loss predictions by RWEQ were as good as or better than those by RUSLE for locations in Texas, Oregon, and Georgia. RUSLE overpredicted decomposition by 20 to 50% when residues were irrigated. RWEQ underpredicted decomposition by 20 to 50% in the Pacific Northwest. Interactions between the climatic indices (CF) and decomposition coefficients influenced the differences between measured and predicted values. Differences in the CF were related to the method of calculating the water coefficient (WC) and interpretation of the interaction between the temperature coefficient and WC. The models could be improved by developing water and temperature functions that give results closer to those produced with daily time‐step functions.
Spatial Variation Affects Precision of Perennial Cool‐Season Forage Grass Trials
Authors: Casler Michael D.
Published: July 2010

Randomized complete block (RCB) designs, although commonly used in testing forage grass cultivars, often are inefficient. The objective of this study was to evaluate the RCB design, the lattice design, trend analysis, and nearest‐neighbor analysis (NNA) for their ability to account for spatial variability in 27 perennial cool‐season forage grass cultivar evaluation trials conducted over a 15‐yr period at Arlington, WI. Each trial was made up of cultivars or experimental populations of one of six species or groups of species: orchardgrass (Dactylis glomerata L.), ryegrasses [a group comprising perennial ryegrass, Lolium perenne L.; intermediate ryegrass, L. hybridum Hausskn.; and festulolium, ✕ Festulolium braunii (K. Richt.) A. Camus], smooth bromegrass (Bromus inermis Leyss.), reed canarygrass (Phalaris arundinacea L.), tall fescue (Festuca arundinacea Schreb.), and timothy (Phleum pratense L.). Dry matter forage yield was determined for 3 yr on each trial and expressed, for each plot, as mean annual yield. Yield data for each trial were analyzed by the RCB or lattice model, trend analysis, and two NNA models (one or two covariates). Three incremental improvements in precision of entry means were observed: an average of 15% due to the RCB design, an additional average of 17% due to the lattice design, and an additional average of 22 to 30% due to trend analysis or NNA. Trials were highly variable in the relative efficiency of both their experimental design and the spatial analyses, but this variability was not related to species, planting years, or plot size. The only useful predictor of trial efficiency was number of entries: three of five trials with eight or fewer entries failed to show significant differences among entries, regardless of the analysis. Spatial analysis methods cannot overcome lack of true differences among entries or failure to detect differences due to low degrees of freedom. Trend analysis or NNA appear to be useful mechanisms to account for intrablock variability in fields where it is impossible or uneconomical to predict proper blocking patterns.
Evaluation of Fine Root Length and Diameter Measurements Obtained Using RHIZO Image Analysis
Authors: Bauhus Jürgen , Messier Christian
Published: July 2010

Image analysis systems facilitate rapid measurement of root length and diameter, but their accuracy is not easily determined. The objective of this study was to develop a set of simple experiments for evaluating the accuracy of fine root measurements obtained using image analysis. Using the system RHIZO (trademark of Régent Instruments, Québec), we tested the accuracy of (i) length measurements made over a range of root lengths per unit area, (ii) average diameter measurements and length per diameter distributions in string, wire, and fine root samples of varying diameter, and (iii) diameter measurements on short segments of diagonally oriented objects. Our results suggest that preliminary testing of image analysis systems is absolutely necessary for producing reliable root measurements. Total length was accurately determined for typically encountered length per unit areas of <1.5 cm cm−2. For samples with higher values, however, the method underestimated total length by >5%. It is therefore recommended that users of image analysis systems determine this maximum length per unit area for accurate delerminations of total root length. In samples that contained different string diameters, the total sample length and average string diameter could accurately be measured. However, the length per diameter class was underestimated by >20% when the string diameter was less than one pixel smaller than the upper limit of the diameter class. Adjustment of diameter intervals and increasing the scanner resolution are required to reduce this underestimation. Both the length and the angle of the short segments analyzed were found to influence diameter measurements. Similar sets of experiments are proposed for a rigorous evaluation of the performance of other image analysis systems on root measurements.