bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of Selected Forage Grasses to Herbicides
Authors: Bovey R.W. , Hussey M.A.
Published: July 2010

Early spring applications of herbicides were evaluated for weed control and phytotoxicity to kleingrass (Panicum coloratum L.) during establishment. In 1986, areas treated with MSMA (monosodium salt of methylarsonic acid) at 2.2 and 4.5 kg ha−1 or chlorsulfuron {2‐chloro‐N‐[ [(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl) amino] carbonyl] benzenesulfonamide} at 0.018 and 0.035 kg ha−1 reduced weed yield to <900 and increased kleingrass yield to >9300 kg ha−1. Untreated areas produced 5400 and 4300 kg ha−1 of weeds and kleingrass, respectively. In 1988, kleingrass yields were increased only where weeds were removed by hand or MSMA. Bensulide [O,Obis( 1‐methylethyl) S‐[2‐[(phenylsulfonyI) amino] ethyl] phosphorodithioate], butylate [S‐ethyl bis(2‐methylpropyl)carbamothioate], siduron [N‐(2‐methylcyclohexyl)‐N'‐phenylurea], and sulfometuron {2‐[[[[(4,6‐dimethyl‐2‐pyrimidinyl) amino] carbonyl] amino] sulfonyl] benzoic acid) were highly injurious to kleingrass. In 1989, no treatment increased kleingrass yields. In the greenhouse, ‘Selection 75’ kleingrass, common buffelgrass (Cenchrus ciliaris L.), ‘WW‐Spar’ and ‘WW‐Ironmaster’ old world bluestem [Bothriochloa ischaemum (L.) Keng var. ischaemum (Hack.) Celarier and Harlan], ‘Bell’ rhodesgrass (Chloris gayana Kunth), ‘Cowboy’ laurisiagrass (Penniseturn orientale L.), ‘Haskel’ sideoats grama [Bouteloua curtipendula (Michx.) Torr.], ‘Lameta’ Indiangrass (Sorghustrum nutans L.), 'Alamo' switchgrass (Panicum virgatum L.), and ‘Palar’ Wilman lovegrass (Eragrosfis superba Peyn.) were treated. Based on seedling weight, most grasses tolerated butylate, MSMA, 2,4‐D [(2,4‐dichlorophenoxy) acetic acid], chlorsulfuron, and metsulfuron {2‐[[[[(4 methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)amino] carbonyl] amino] sulfonyl] benzoic acid]. Buffelgrass, Indiangrass, and old world bluestem tolerated sulfometuron. Atrazine [6‐chloro‐N‐ethyl‐N'‐(‐methylethyl)‐ 1,3,5‐triazine‐2,4‐diamine] and propazine [6‐chloro‐N,N'‐ bis(l‐methylethyl)‐l,3,5‐triazine‐2,4diamine] were sometimes injurious, but bensulide and siduron were highly injurious to most grasses.
Functions of Crop Yield from Applied Water
Authors: Helweg Otto J.
Published: July 2010

Although there is no unique crop water production function (yield vs. applied water), curves of general functional relationships have utility and are commonly presented in the literature. Some crop production functions used in research and practice are assumed to be linear. Other functions are assumed to be quadratic, or less frequently some other non‐linear form. Though these functions may be adequate for the purpose for which they are used, they do not always produce a realistic shape. As the need to know and display the correct shape of the function becomes greater, an improved mathematical expression of the function is required. The criteria of a desirable production function includes being robust as well as accurately fitting the data. Evaluation of several popular functions showed that the Meixner functional series accurately modeled the water‐yield relationship of wheat (Triticum aestivum L.) from an experimental plot in Saudi Arabia.
Modeling Lamb Weight Changes on Wheatgrass and Wheatgrass‐Sainfoin Mixtures
Authors: Karnezos T.P. , Matches A.G.
Published: July 2010

Prediction of animal weight change (CUM) with regression models developed from grazing trials typically uses herbage parameters and CUM measured on the same day. We hypothesized that lamb (Ovis aries L.) CUM recorded at time t was a function of herbage quality and/or quantity measured at a previous harvest t − x (where x = days prior to measurement of CUM). Our objectives were (i) to determine if time series regression analysis (TSR) could be used to model CUM from three irrigated wheatgrasses, ‘Hycrest’ [Agropyron cristatum (L.) Gaertner × A. desertorum (Fischer ex Link) Shulters], ‘Luna’ [Thinopyrum intermedium subsp. barbulatum (Schur) Barkw. and D.R. Dewey], and ‘Jose’ [T. ponticum (Podp.) Barkw. and D.R. Dewey] grown alone and with ‘Renumex’ sainfoin (Onobrychis viciifolia Scop.), and (ii) to test the models. Replicated pastures grown on a fine, mixed thermic Torrertic Paleustolls were rotationally grazed by Rambouillet × Suffolk wether lambs for an average of 77 d in spring of 1987 and 1988. Herbage quality, quantity, and plant parts were estimated from pregrazing, after 2 and 4 d of grazing, and postgrazing (7 d) harvests and used as variables in TSR. For TSR models, lagged variables (t − x) were selected more (67–92% of total) than nonlagged variables (t), supporting our hypothesis. Time series regression models described CUM accurately (average R2 > 0.70), but selected variables were not consistent among treatments, time lags, or years. Model testing indicated poor predictive accuracy (r2 = 0.07−0.51), limiting the usefulness of projecting CUM across seasons and demonstrating the necessity of testing regression models.
Florigraze Rhizoma Peanut in Association with Warm‐Season Perennial Grasses
Authors: Dunavin L. S.
Published: July 2010

The rhizoma peanut (Arachis glabrata Benth.), a warm‐season perennial legume, offers enough promise to justify investigating its potential as a companion legume with various adapted perennial grasses. A field experiment was conducted on an Orangeburg sandy loam (fineloamy, siliceous, thermic Typic Paleudults) near Jay, FL, to determine the efficacy of using ‘Florigraze’ rhizoma peanut with ‘Tifton 44’ bermudagrass [Cynodon dactydon (L.) Pers.], ‘Floralta‘ limpograss [Hemarthria altissima (Poir.) Stapf and C. E. Hubb], and ‘Pensacola’ bahiagrass (Paspalum notatum Flugge) from 1981 through 1988. Volunteer grasses replaced Floralta in 1985 through 1988, and cool‐season forage crops, ‘Wrens abruzzi’ rye (Secale cereale L.), ‘Fla. 80’ ryegrass (Lolium multiflorum Lam.), and ‘Dixie’ crimson clover (Trifolium incarnatum L) were then seeded over the peanut‐grass plots in the fall. Dry matter (DM), crude protein (CP), and digestible organic matter (DOM) production of the combined grass and legume forage were determined. During the first 4 yr, the yields of DM, CP, and DOM from each grass‐peanut mixture were essentially equal; however, more DM and DOM were produced by limpograss‐peanut in 1981 and 1982. In the last 4 yr, the volunteer grass‐peanut generally produced the least DM, and less DOM, in 1986 and 1987. The peanut content decreased during the last 4 yr in all mixtures but most markedly in the bahiagrass‐peanut mixture. In general cool‐season crops performed best when seeded over bermudagrass‐peanut followed by performance over volunteer grass‐peanut and bahiagrass‐peanut, respectively. Rhizoma peanut can be successfully grown with various perennial grasses for several years but may eventually be crowded out by such thick‐sodded grasses as Pensacola bahiagrass.
Early Season Floral Bud Removal and Cotton Growth, Yield, and Fiber Quality
Authors: Pettigrew W.T. , Heitholt J.J. , Meredith W.R.
Published: July 2010

Cotton (Gossypium hirsutum L.) has a capacity to partially compensate for the loss of floral buds (squares). A 2‐yr (1989 and 1990) field study was conducted to determine how growth, yield, and fiber quality traits of different genotypes were affected by early season square removal. Early developing squares were removed by hand, or were induced to abscise by ethephon [(2‐chloroethyl)phosphonic acid] application. Genotypes used were ‘DPL 50’, a normal leaf type, and three leaf type isolines of ‘MD 65–11’ (normal, okra, and super okra). Compared to the check, the ethephon application decreased plant height by as much as 11% early after application, but the treated plants ultimately exceeded the check by 5% in height, in 1990. The seasonal maximum vegetative dry weight and leaf area index (LAI) did not differ between treatments either year, though the ethephon treatment did increase mainstem node number to 26, compared to 24 nodes for the check. Lint yields did not differ between treatments in 1989, but the ethephon treatment yielded 7% less than the check in 1990. Ethephon application reduced boll size 7% each year, compared to the check. Fiber quality traits were not affected by treatments in 1989, but in 1990 micronaire, maturity, and cell wall thickness were decreased by 6% on fiber from the ethephon plots as compared to the check. This study demonstrated that cotton has potential to compensate for early square loss but did not suggest that early square removal consistently leads to improved yields or fiber quality.
Nitrogen Fertilizer Recovery by Soybean in Monoculture and Rotation Systems
Authors: Varvel G. E. , Peterson Todd Andrews
Published: July 2010

Crop rotations including soybean [Glycine max (L.) Merr.] have increased in importance because of their potential to increase yields, reduce expenditures for pesticides and fertilizer, and increase net returns to the producer. Despite the importance of soybean in the USA, there is a lack of understanding of how N affects soybean in rotation systems. This study was conducted to determine the effects of rotation and N fertilization on N uptake and recovery by soybean. Soybean was grown under rainfed conditions on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic, Typic Argiudoll) in five cropping systems: (i) continuous soybean monoculture, (ii) a 2‐yr corn (Zea mays L.)‐soybean rotation, (iii) a 2‐yr grain sorghum [sorghum bicolor (L.) Moench]‐soybean rotation, (iv) a 4‐yr rotation of corn‐oat [Avena sativa (L.)] + clover [80% Melilotus officinalis (L.) and 20% Trifolium pratense]‐grain sorghum‐soybean, and (v) a 4‐yr rotation of grain sorghum‐oat + clover‐corn‐soybean at Mead, NE. Broadcast applications of 15N‐depleted NH4NO3 were made at 34 and 68 kg N ha−1 in 1985 and 1986 to evaluate N fertilizer recovery by soybean in each cropping system. Nitrogen recovery determined by isotope analyses was approximately 50% in all rotation systems and was not significantly affected by rotation or N rate. Large amounts of N were removed by the harvested soybean seed in all systems (150 to 200 kg N ha−1), regardless of N fertilizer applications. Soybean can act as a N sink and potentially aid in reducing the amount of soil N available for leaching. Since soybean grown in a rotation can utilize soil or fertilizer N along with the other benefits of rotations, soybean shows promise as a crop that may help reduce the leaching of nitrate‐N in to ground water.
Conservative Response and Stress‐Damage Interactions in Cotton Reproductive Development
Authors: Ungar E.D. , Kletter E. , Genizi A.
Published: July 2010

Increasing costs of inputs in upland cotton (Gossypium hirsutum L.) have highlighted the need for more sophisticated within‐season management of the crop. The objective of this study was to investigate the interaction between the timing of water stress and simulated pest damage in their effects on cotton yield and yield components. A field experiment was repeated throughout 5 yr on a Gan Shmuel vertisol (clayey, montmorillonitic, calcareous, thermic Typic Chromoxerert). Treatments comprised a control [post‐emergence irrigations at first flower (f), f+23, and f+38 d]; a delay in this sequence from the first (f+ 8, f+ 33, and f+ 47 d), second (f, f+ 32, and f+ 46 d), or third irrigation (f,f+23, and f+48 d); four irrigations (f−9,f+ 12,f+ 27, and f+ 40 d); and severe mid‐season stress (f−10, f+ 23, and f+38 d). Total irrigation amount was constant. The dates of the six irrigation schedules were repeated with pest damage simulated by the early removal of 120 floral buds meter−2. There was a significant stress‐damage interaction in flower, boll, and fiber production. In comparison with the undamaged control, boll production was reduced by damage alone and by stress alone. All stress‐damage combinations, however, restored boll production to the control level. Only severe mid‐season stress without damage, reduced seed cotton yield. Treatment effects were detected despite an underlying conservatism in crop response, whereby flower retention was inversely related to flower production. This resulted in low variability of boll number. The effect of boll number on yield was in turn buffered by boll weight. Consequently, irrigation scheduling and the control of pests that damage fruiting bodies cannot be optimized independently.
Nitrogen Release from Crimson Clover in Relation to Plant Growth Stage and Composition
Authors: Ranells N. N. , Wagger M. G.
Published: July 2010

Increased N‐use efficency and economic savings may result from a better understanding of N release patterns from legume residues. A 2‐yr field experiment was conducted on a Cecil fine sandy loam (clayey, kaolintic, thermic Typic Kanhapludult) to examine the effects of crimsom clover (Trifolium incarnatum L.) growth stage on dry matter accumulation, N concentration, and chemical composition in relation to N release under no‐tillage management. Crimson clover was harvested in the spring at four growth stages (late vegetative, early bloom, late bloom, and early seed set). Air‐dried plant material in 1‐mm mesh nylon bags was placed on the soil surface; retreived at 1−, 2−, 4−, 8−, and 16‐wk intervals; and analyzed for total N, C, cellulose, hemicellulose, and lignin concentrations. Averaged over 2 yr, dry matter production increased from 2.3 to 5.6 Mg ha−1, and N concentration declined from 30.2 to 21.2 g kg−1 as crimson clover matured from late vegetative to early seed set growth stages. Cellulose concentration increased by 66%, hemicellulose by 37%, and lignin by 87% from late vegetative to early seed set. Estimated clover N release at the 8‐wk retrieval was 28, 40, 40, and 54 kg ha−1 in 1989 and 51, 67, 73, and 55 kg ha−1 in 1990 for the late vegetative, early bloom, late bloom, and early seed set growth stages, respectively. Results indicated that allowing crimson clover to attain the late bloom stage prior to desiccation and planting of the summer crop can maximize clover top‐growth N content and subsequent N release.
Environment, Cultivar, and Ethephon Rate Interactions in Barley
Authors: Stobbe E. H. , Moes J. , Bahry R. W. , Visser R. , Iverson A.
Published: July 2010

Ethephon[(2‐chloroethyl)phosphonic acid] reduces barley (Hordeum vulgare L.) plant height and lodging potential, but variable effects on yield components and yield also have been reported, depending on ethephon rate, cultivar, and environment. This study was conducted to investigate environment– and cultivar–by‐ethephon‐rate interactions for barley grown under Manitoba conditions. ‘Argyle’, ‘Bedford’, and ‘Samson’ barley were sown on each of two dates in 1986 and 1987, and on single dates in 1988 and 1989, at Portage la Prairie, MB on Neuhorst clay loam (fine‐loamy, frigid aquic Haploboroll). Ethephon was applied at Zadoks GS45‐47 at 0, 120, 240, 360, or 480 g ha−1. Plant height, Belgian lodging index, yield components, and yield were determined at maturity. Plant height reductions due to ethephon were unaffected by environment, and the percentage height reduction was described as a quadratic function of ethephon rate with higher increments of ethephon producing smaller increments of height reduction. Lodging only occurred in 1986, and ethephon at 240 g ha−1 eliminated lodging in most cases. Environment‐by‐cultivar‐by‐ethephon treatment interactions are significant for grain yield, spikes per square meter, and kernels per spike. Grain yield was not consistently affected by ethephon. Spikes per square meter sometimes increased, but was more often unaffected by ethephon. Kernels per spike was often reduced by ethephon. Kernel mass decreased with increasing rates of ethephon for Argyle and Bedford, but remained stable for Samson. Grain yield increased for Argyle and Bedford in cases where ethephon reduced lodging and increased spikes per square meter. Grain yield tended to decrease in cases where lodging was not a factor and ethephon reduced kernels per spike and/or kernel mass. Year‐to‐year variation in rainfall amount and distribution, and temperature may explain some of the observations made. In Manitoba, a maximum rate of 240 g ha−1 of ethephon should be used only in cases where the risk of severe lodging is high.
Soybean Growth and Development Alterations caused by Helicoverpa zea (Boddie) Feeding
Authors: Eckel Craig S. , Bradley J.R. , Van Duyn John W.
Published: July 2010

Corn earworm, Helicoverpa zea (Boddie), injury to soybean, Glycine max (L.) Merr, is characterized primarily by feeding on leaves, pods, and flowers. Although soybean can withstand considerable damage to each plant part individually or in combination without yield loss, corn earworm larvae frequently cause yield reductions. To evaluate alterations in plant growth that determine if yield losses occur, the plant growth and yield response of soybean to corn earworm injury was observed at six experimental sites from 1985 to 1987. Insecticides were used to either promote or suppress corn earworm populations, and population levels were monitored during the period of infestation with ground‐cloth samples. The effect of corn earworm feeding on leaf area index, number of flowers, number of pods, and pod weight was monitored weekly from the time of infestation until harvest. Leaf area index was reduced at each site. Flower and pod feeding resulted in a delay in pod fill and a reduction in final pod number at several sites. The rate of pod fill was increased in treatments with large corn earworm populations at two sites and was decreased at one site. The number of seeds per pod was also reduced by corn earworm feeding at several sites; the weight per pod was decreased at one site and increased at other sites. At harvest, the seed number, weight per seed, percent oil and protein, and harvestable yield were sampled. Yields were reduced at all but one site, and losses were attributed primarily to reduction in pod and seed number. At one site where infestation occurred during the early flowering stage, yield loss was attributed primarily to reduced weight per seed. Since mechanisms of yield reduction were different, different thresholds may be required for soybean in early reproductive stages and soybeans in later stages.
Soil Tillage and Windbreak Effects on Millet and Cowpea: I. Wind Speed, Evaporation, and Wind Erosion
Authors: Banzhaf J. , Leihner D. E. , Buerkert A. , Serafini P. G.
Published: July 2010

Deforestation, overgrazing, and declining soil regeneration periods have resulted in increased wind erosion problems in dry areas of the West African Sahel, but little is known about the bio‐physical factors involved. This research was conducted to determine the effects of ridging and four different windbreak spacings on wind erosion, potential evaporation, and soil water reserves. A field trial was conducted from 1985 to 1987 on 12 ha of a Psammentic Paleustalf in Southern Niger. Millet, Pennisetum glaucum (L.), and cowpea, Vigna unguiculata (L.) Walp., were seeded in strips on flat and ridged soil. Windbreaks of savannah vegetation were spaced at 6, 20, 40, and 90 m. The effects of ridging on wind speed, evaporation, and wind erosion were small and mostly non‐significant. However, average wind speed at 0.3 m above ground in the center of cowpea and millet strips was significantly reduced from 2.8 to 2.1 m s—1 as windbreak distances narrowed from 90 to 6 m. As a consequence, potential evaporation declined by 15% and the amount of wind blown soil particles by 50% in ridged and by 70% in flat treatments. Despite reduced potential evaporation, average subsoil water reserves were 14 mm smaller in the 6‐ than in the 20‐m windbreak spacing indicating excessive water extraction by the windbreak vegetation. Thus, establishing windbreaks with natural savannah vegetation may require a careful consideration of the agronomic benefits and costs to competing crops.
Changes in Soluble Carbohydrate Composition of Barley, Wheat, and Rye during Winter
Authors: Olien C. R. , Clark J. L.
Published: July 2010

Significant increases in the production of winter cereals could be realized with improved hardiness. The objective of this research was to determine if overwintering cereals modify water soluble carbohydrate composition in response to naturally occurring winter freeze stress. Fields of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and rye (Secale cereals L.) were monitored throughout the winter between 1986 to 1990 for snow‐pattern development, temperature, and snowfall. Plant crowns were analyzed for freeze injury (form and intensity) and water soluble carbohydrate composition (fructan, sucrose, glucose, and fructose). Growth chamber plants were frozen and analyzed to confirm the interpretation of field plant data. In 1986, there was less fructan and more soluble sugars in the exposed than in the snow‐covered wheat plants (but no complete depletion of fructan), and no crown injury from equilibrium freezing. In 1987–1988, little injury or fructan hydrolysis occurred in barley, wheat, or rye; the plants were snow covered during cold periods. In 1989–1990, fructan hydrolysis to sugar in exposed barley, wheat, and rye plants paralleled that in the exposed wheat plants of 1986–1987. The fructan content of exposed barley plants was nearly depleted during the coldest weather. Exposed plants had typical equilibrium freeze injury. Growth chamber plants responded similarly to the exposed field plants. Plants exposed to freeze stress converted fructan to sugars which probably alleviated adhesive freeze stress. The energy of hydrolysis may be useful for placing sugar into sites within the tissue where its cryoprotective activity is most effective.
Ryegrass Companion Crops for Alfalfa Establishment: II. Forage Quality in the Seeding Year
Authors: Sulc R. M. , Albrecht K. A. , Casler M. D.
Published: July 2010

Ryegrass (Lolium spp.) use in the northcentral USA has been limited by its lack of winterhardiness. But potential exists for its use in this region as a companion crop for alfalfa (Medicago sativa L.) establishment. This study was conducted to determine nutritional value of forage from ryegrass‐alfalfa mixtures in the seeding year. Five ryegrass cultivars, representing four species, were sown at 215, 430, and 645 seeds per square meter with alfalfa at two locations in Wisconsin in April of 1988, 1989, and 1990. Alfalfa was also established alone and with oat (Avena sativa L. ‘Ensiler’). Forage from mixtures of annual ryrgrass (L. multiflorum Lam.) was usually lower in crude protein (CP) concentration and higher in fiber concentration (neutral‐and acid‐detergent fiber) than forage from intermediate ryrgrass (L. hybridum Hausskn.) or perennial ryegrass (L. perenne L. and Festulolium braunii K. A.) mixtures. A threefold increase in ryegrass seeding rate usually reduced nutritional value of the forage. At the first harvest, forage from all ryegrass‐alfalfa mixtures was higher in CP concentration and lower in fiber concentration than the oat‐alfalfa forage. At subsequent harvests, the nutritional value of ryegrass‐alfalfa forage was inferior to that of forage regrowth in the oat companion crop seeding, except in dry environments when alfalfa predominated in the ryegrass‐alfalfa mixtures. We conclude that ryegrass‐alfalfa mixtures in the northcentral USA can provide forage with higher nutritional value than oat companion crop seedings at the first harvest in the establishment year, but not at subsequent harvests, especially when adequate rainfall promotes vigorous ryegrass growth.
Spring‐Clipping Response in Snake River and Thickspike Wheatgrasses
Authors: Jones T. A. , Nielson D. C.
Published: July 2010

Grazing at the boot stage can severely damage stands of bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) A. Löve]. Snake River wheatgrass [proposed name Etymus lanceolatus ssp. wawawaiensis (Scribner & Gould) J.R. Carlson & D.R. Dewey] has recently been recognized as a taxon distinct from bluebunch wheatgrass, based on cytological data, and placed in the same species as thickspike wheatgrass [Elymus lanceolatus ssp.lanceolatus (Scribner & J.G. Smith) Gould]. Grazing tolerance of Snake River wheatgrass is unknown. This study was conducted to evaluate the effect of clipping at the boot stage on vigor of ‘Secar’ Snake River wheatgrass, ‘Elbee’ and T‐21076 thickspike wheatgrass, and hybrid populations D30 (50% Snake River wheatgrass/50% thickspike wheatgrass) and D38 (75% Snake River wheatgrass/25% thickspike wheatgrass). Plots were established at North Logan, UT (mollisol) and near Stone, ID (aridisol) in 1987, clipping treatments (clipped or unclipped at the boot stage) were applied in 1988 and 1989, and treatments were compared in 1990. Regardless of spring‐clipping treatment, all plants were clipped once in the summer at both locations and again in the fall at North Logan both in 1988 and 1989. Spring clipping reduced Secar dry weight 21%, spike number 27%, and plant basal area (above‐ground area occupied by tillers) 17% at North Logan, while the other populations were unaffected. Spring clipping reducedry weight 26 and 31%, spike number 37 and 36%, and plant basal area 24 and 33%, of Secar and D38, respectively, near Stone, while the other populations were unaffected. Spring clipping was more detrimental at the Stone aridisol than the North Logan mollisol site. Currently available germplasm of the rhizomatous thickspike wheatgrass appears to be more tolerant of spring clipping than that of the caespitose Snake River wheatgrass. It should be possible to make substantial genetic progress for spring‐clipping tolerance in hybrid populations.
Shading and Crop‐Cover Effects on Meadowfoam Oil Yield
Authors: Norberg O. S. , Fiez T. E. , Jolliff G. D. , Seddigh M. , Crane J. M.
Published: July 2010

Meadowfoam (Limnanthes alba Hartw. ex Benth. subsp. alba cv. Mermaid) seed yield and oil yield vary among years. Consistent high oil yield is needed to encourage profitable commercialization. Field experiments were conducted at Oregon State University in 1987–1988 and 1988–1989 on an Amity silt loam (fine‐silty, mixed, mesic Argiaquic Xeric Argialboll) to test the hypothesis that light and temperature effects before the beginning of rapid elongation of stems influence oil yield through alteration of phytomass (total aboveground dry matter) development. Shade‐cloth and a transparent floating crop cover were used to alter light and temperature, compared to the control. Cover early, cover early plus late, and shade treatments were applied on 22 Jan. 1988 and 24 Jan. 1989. Shade and cover early were removed 29 Mar. 1988 and 28 Mar. 1989; and cover early plus late was removed 12 April 1988 and 11 April 1989. At 2 wk after the beginning of rapid elongation of stems, shaded plants had 24% less phytomass and 28% fewer stems than the control. Shade increased open flowers 27%, seeds per square meter 30%, seed yield 35%, seed oil content 8%, and oil yield 47%. Cover early increased open flowers 23%, seeds per square meter 34%, seed yield 21%, seed oil content 9%, and oil yield 33%. Effects of cover early plus late treatment on crop growth and yield were inconsistent between years. Seed yield improvement by all treatments was associated with fewer primary stems per plant, more flowers that opened, and more seeds per square meter. Genetic manipulation and cultural practices which reduce the number of primary stems per plant and increase the number of flowers opened may lead to increases in oil yield.
Subterranean Clover Enhances Production of ‘Coastal’ Bermudagrass in the Revegetation of Lignite Mine Spoil
Authors: Harris Pamela A. , Zuberer David A.
Published: July 2010

Lignite mine spoils in Texas are commonly revegetated with ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.]. Legumes hare been overseeded in bermudagrass in reclamation programs in Texas, but information regarding establishment and persistence in mine spoil is limited. Therefore, we conducted a field study to investigate the effects of fertilization and inoculation with Rhizobium spp. on subterranean clover (Trifolium subterraneum L.; subclover) establishment and production in mine spoil and to assess the effect of subclover on a subsequent crop of Coastal bermudagrass. Subclover seed was broadcast into a 6‐mo‐old bermudagrass sod in October 1986. Individual plots were fertilized with 57‐25‐47 kg ha−1 (N‐P‐K), 0‐25‐47 kg ha−1, or left unfertilized at the beginning of each clover season (Sept.–Oct.); however, all plots were fertilized with 57‐25‐47 kg ha−1 at the start of each grass season (April‐May) to ensure grass growth. Although low numbers (0–l02 g‐1) of native rhizobia were present in plots, inoculation with a commercial, multi‐strain inoculant increased subclover forage production (100%) and total N and P yields of subclover early in the first season. Yields from inoculated and uninoculated plots were generally comparable later in the first season and in the second year. The overseeding of subclover into the bermudagrass sod increased grass production and total N and P yields later in the first year and in the second season. However, inoculation of subclover had little effect on subsequent grass production. We also demonstrated the apparent positive benefit of P fertilization on subclover and bermudagrass production. Clover forage production, as well as N and P yields, were enhanced with P fertilization. In addition, P fertilization was necessary to achieve the greatest benefit of clover enhancement of bermudagrass production. The effect of subclover on grass production was apparent by the end of the first grass season, and it became even more evident in the second year. The results showed that subclover was established and maintained for at least two seasons in a bermudagrass sod on reclaimed lignite spoil, and that the clover benefited the subsequent grass crop when fertilized with P and K, apparently by providing extra “fixed” N for grass production.
Bahiagrass Canopy Size, Soil Water, and Establishment of Aeschynomene
Authors: Kalmbacher R. S. , Martin F. G. , Hammond L. C. , Boote K. J. , Mislevy P.
Published: July 2010

Aeschynomene americana L. is a tropical pasture legume, and in Florida, where it is usually grown with bahiagrass (Paspalum notatum Flügge), there are about 5000 ha. Limited soil water is a primary reason for stand failure of this annual. Soil water in three bahiagrass canopy sizes: small (2.2 leaf area index [LAI]), medium (4.5 LAI) and large (7.7 LAI) was measured at seeding and related to aeschynomene establishment. All canopies were clipped to a 50‐mm height when aeschynomene seedlings emerged. Soil was Eau Gallie fine sand (sandy, siliceous, hyperthermic Haplaquods). Aeschynomene was drilled into sod on 17 dates between May and July in 1981 to 1985, and seedling density was determined at emergence and periodically for 21 d. Six of the 17 seedings were failures because of drought (one because of flooding), and when failure occurred, it was in all three canopy sizes. Water potential at 75‐ and 150‐mm soil depths was analyzed from 209 dates, and canopy size affected soil water potential on 41 dates. Gravimetric soil‐water was analyzed on 42 dates, and canopy size affected (P ≤ 0.05) gravimetric soil‐water on five dates. Evapotranspiration (ET) rate was measured twice and was not different among canopy sizes on 26 June 1984 (avg. 94 mg m−2 s−1). Differences (P ≤ 0.03) in ET rate were found on 16 May 1986 when the large canopy (128 mg m−2 s−1) had greater ET rate than the small canopy (100 mg m−2 s−1), with the medium canopy (117 mg m−2 s−1) intermediate. Bahiagrass canopy size before aeschynomene emergence had little effect on the amount of soil water and resulting success or failure of aeschynomene. Only rain and soil water potential were useful for predicting aeschynomene stand success. Together, rain 0 to 8 d before seeding [descriminant value (DV) ≤ 22 mm] and soil water potential at seeding (DV ≤ −15 kPa) correctly predicted 13 out of 17 seedings.
Plant Yields and Fodder Quality Related Characteristics of Millet‐Stylo Intercropping Systems in the Sahel
Authors: Kouamé C. N. , Powell J. M. , Renard C. A. , Quesenberry K. H.
Published: July 2010

The integration of forage legumes into the low‐input, cereal‐based farming system of the Sahel may be the key to sustaining soil, crop, and livestock production. The objectives of this study were to evaluate the effects of intercropping the forage legumes Stylosanthes fruticosa (Retz.) Alston or S. hamata (L.) Taub. with millet [Pennisetum glaucum (L.) R. Br.] on grain yield, fodder yield, and crude protein (CP) yield and concentration. Four field trials were conducted on a Psammentic Paleustalf (siliceous, isohyperthermic) soil from 1988 to 1990 at Sadoré, Niger. Each Stylosanthes species was grown in alternate single and triple row patterns with millet for 1 and 2 yr, with stylo regrowing from stubble during the second year. Control treatments were sole crops of millet and stylo. Intercropping either Stylosanthes species with millet for 1 yr in alternate single rows did not affect millet grain yield, because of low stylo competition. Total dry matter (DM) harvested of intercrop was similar to that of sole millet, while CP concentration of total DM increased moderately from 43 g kg−1 in sole millet crop to 75 g kg−1 in intercrop. During the second year of association, stylo was very competitive, depressing intercropped millet grain by an average of 67% in 1989 and 48% in 1990 compared with sole millet grain yield. Total DM and CP yields, and CP concentration of the harvested fodder were, respectively, 1.4, 3.0, and 2.3 times greater in intercrop than sole millet. Millet‐stylo intercrops, with each species planted at half its sole crop density, appear to have an advantage in fodder yield and CP over sole millet cropping but not in total grain yield.
Nitrogen Availability from Surface‐Applied and Soil‐Incorporated Crop Residues
Authors: Smith S. J. , Sharpley A. N.
Published: July 2010

Management systems which maintain crop residues on the soil surface have prompted a need for more detailed information regarding crop residue N availability. Such information is needed from both agronomic and environmental standpoints. Our study examined the placement effects of 15N tagged alfalfa (Medicago sativa L.), sorghum [Sorghum bicolor (L.) Moench], and wheat (Triticum aestivum L.) residues on crop residue N availability in association with eight Oklahoma surface soils representing five soil orders. The experiment was conducted under aerobic laboratory conditions, and involved 0.25‐mm crop residue materials and 2‐mm soil particles. Crop residue N availability was determined on the basis of N mineralized during short‐term (14 d) and long‐term (168 d) incubation. Mean amounts of crop residue N mineralized ranged from <18 kg N ha−1 for sorghum and wheat (<28% of residue N) to 55 kg N ha−1 for alfalfa (35% of residue N). Surface placement of crop residue reduced residue N availability compared to soil incorporation, but the differences were only equivalent to 1 to 7 kg N ha−1. Relative to residue type, the influence of soil type on crop residue N mineralization was secondary. Overall, differences in crop residue N availability associated with residue placement should have minor agronomic and environmental impact.
Broadcast Nitrogen Sources for No‐Till Continuous Corn and Corn Following Soybean
Authors: Stecker J. A. , Buchholz D. D. , Hanson R. G. , Wollenhaupt N. C. , McVay K. A.
Published: July 2010

Studies evaluating surface broadcast urea‐based N sources in no‐till corn (Zea mays L.) have been primarily conducted with continuous corn. Most corn grown in Missouri follows soybean [Glycine max (L.) Merr.]. Our objective was to evaluate no‐till, continuous corn and corn following soybean response to surface applied ammonium nitrate (AN) and urea‐based N sources. Field studies were conducted at three Missouri sites during 1988–1990. Factorial combinations of rotation (continuous corn and corn‐soybean) N source [AN, urea, urea ammonium nitrate (UAN), and UAN + ammonium thiosulfate (UAN + ATS)], and N rate (67, 135, and 202 kg ha−1) were studied in a split‐block design. Nitrogen rate and source affected grain yields each site‐year. Ammonium nitrate was superior to the urea‐based N sources in 5 of 8 site‐years. Averaged across site‐years, grain yields (Mg ha−1 were 8.22 for AN, 7.57 for urea, 7.09 for UAN + ATS, and 6.99 for UAN. Apparent fertilizer N losses were estimated at 11% for urea, 18% for UAN and 17% for UAN + ATS. Ammonium thiosulfate did not improve the performance of UAN. Grain yield responses to applied N were greater with continuous corn than corn following soybean. Continuous corn also resulted in larger yield differences between N sources. In continuous corn, AN resulted in greater grain yield than urea by 0.81 Mg ha−1, than UAN by 1.35 and Mg ha−1, and than UAN + ATS by 1.32 Mg ha−1. For corn following soybean, the yield advantage for AN was 0.42 Mg ha−1 greater than urea, 0.98 than UAN, and 0.82 than UAN + ATS. Therefore, reduced fertilizer efficiency of surface applied urea‐based N sources appears to be a problem in both continuous no‐till corn and no‐till corn following soybean.
Traversing Sensor Platform for Environmental Measurements
Authors: Ham Jay M. , Caldwell F. W.
Published: July 2010

Under conditions of high spatial variability, environmental sensors can be transported across or through the region of interest to obtain representative samples of the measured parameter. A traversing platform was designed to carry heavy sensors and instruments along a horizontal path under field conditions. The system was composed of a 0.17‐ by 0.13‐m rolling platform atop a 2.2‐m long aluminum channel. A motorized cable‐chain drive was used to move the platform at a speed of 0.035 m s−1. The system was powered with 12‐V DC deepcycle batteries and consumed ≈6 W of power when the sensor platform was in transit. On‐board circuits can be used in conjunction with a programmable datalogger to sense the platform's location or stop the platform at user‐specified locations along the traversing path. The mechanism was capable of transporting a 5‐kg sensor package at inclination angles up to 45°. The system operated without failure for a 6‐wk period under field conditions.
Dry Matter Production, Yield, and Allocation of Carbon‐14 Assimilates by Wheat as Affected by Nitrogen Source and Salinity
Authors: Botella M. A. , Cerdá A. C. , Lips S. H.
Published: July 2010

Wheat (Triticum aestivum L.) growth is affected by both salinity and the type of N fed to the plants. The objective of this research was to determine the effect of salinity applied at different stages of the life cycle of wheat plants supplied with either NH4 or NO3 on growth, yield, and translocation of photosynthates. Plants were grown in sand culture irrigated with nutrient solution until maturity. The nutrient solution contained 4 mM N, either as (NH4)2SO4 or Ca(NO3)2. Salinity (60 mM NaCl) was applied to the nutrient solution at 19, 70, and 92 d after sowing. Some of the plants received 14CO2 pulses 100 d after sowing, and 14C distribution in each plant part was determined 24 h later. Dry biomass production and grain yield were reduced when salinity was applied 19 d after sowing (beginning of the vegetative stage), whereas no effect of NaCl was observed when salinity was applied later. Ammonium‐fed plants always produced more tillers and spikes than NO3‐fed plants. Total grain yield was similar with plants growing in either N form. Nitrate‐treated plants produced fewer, but heavier, spikes due to a larger number of grains per spike than NH4‐fed plants. Ammonium‐fed plants showed a preferential allocation of 14C‐assimilates to young developing tillers. Nitrate‐fed plants, under similar conditions, allocated assimilates preferentially to grain. Salinity enhanced translocation of assimilates to the spikes when plants were grown with NO3.
One‐Row Machine for the Harvest of Corn Stover
Authors: Frerichs R. , Brentlinger R. , Shapiro C. A. , Moomaw R. S.
Published: July 2010

Many corn (Zea mays L.) experiments require total dry matter determination in addition to grain yield. Mechanized small‐plot grain harvest is a common practice, but determination of total dry matter is usually accomplished by hand harvesting. Hand harvesting is time consuming and labor intensive. Our objective was to construct a mechanized stover sampling system that would reduce the labor requirements for collecting dry matter data. A machine was assembled that cuts, chops, and delivers corn stover to a bag without hand cutting and carrying. A New Holland 707 forage harvester was modified and rear‐mounted on a Model 1910 Ford tractor to harvest a single row with a minimum width of 0.76 m. Chopped corn stover is blown through a tube over the top of the tractor to a platform on the front of the tractor where the material is collected and weighed. By using this machine, the number of people needed for data collection is reduced from eight to three, and longer rows can be harvested to increase experimental precision.
Furrow Diking Effects on Yield of Dryland Grain Sorghum and Winter Wheat
Authors: Tewolde Haile , Mulkey J. R. , Elledge Robert E.
Published: July 2010

Dryland sorghum [Sorghum bicolor (L.) Moench] and wheat (Triticum aestivum L.) production in areas where a large fraction of the annual rainfall is received during the fallow period may be improved by rain‐conserving practices. Furrow diking mainly during the growing season has been shown to improve crop production by conserving rainfall in many parts of the Southern Great Plains. The objectives of this study were to determine whether seasonal or year‐round furrow diking increases dryland yields of sorghum and wheat, to test the yield advantage of planting sorghum and wheat on a flat seedbed or on beds, and to analyze the dependence of yield on rainfall. The treatments included nonbedded (FLAT), bedded–nondiked (BND), bedded–diked during the growing season (BDG), bedded—diked during the fallow period (BDF), and bedded–diked during the fallow period and the growing season (BDFG). Relative to BND, the BDFG treatment increased yield by up to 72% in sorghum and 23% in wheat. The BDF treatment increased yield by up to 62% in sorghum and 23% in wheat. Furrow diking during the growing season alone did not significantly increase yield in sorghum or wheat. When annual rainfall exceeded the average, the FLAT treatment in sorghum yielded less than the BND treatment by 39%. Planting wheat on beds was not an improvement over the conventional flat seedbed. Dryland sorghum and wheat production in areas where a significant fraction of the annual rainfall is received during the fallow period may be improved by fallow period or year‐round furrow diking.
‘Tifgreen’ Bermudagrass Response to Late‐Season Application of Nitrogen and Potassium
Authors: Goatley J. M. , Maddox V. , Lang D. J. , Crouse K. K.
Published: July 2010

Late‐season application of N to bermudagrass (Cynodon dactylon × transvaalensis Burtt‐Davey) putting greens are often made in an attempt to extend turfgrass growth and color. Research was conducted to evaluate the physiological and morphological responses of bermudagrass to late‐season application of N and K. Application of 0, 4.9, and 9.8 g N m−2 in factorial combination with 0, 4.1, 8.2 g K m−2 were made in October of 1989, 1990, and 1991. Following fertilizer application, measurements of fall and spring turfgrass color, total nonstructural carbohydrate (TNC) concentrations, and leaf tissue concentrations of N, P, and K were made. No changes in turfgrass color or TNC levels were observed for any level of K fertilization. Application of 4.9 or 9.8 g N m−2, alone or in combination with K, improved fall turfgrass color through October for each trial, and gave significantly higher spring turfgrass color ratings. Rhizome TNC levels declined linearly in December 1989 as N levels increased from 0 to 9.8 g m−2. There was a quadratic response in TNC levels across N fertility levels in March 1990. No significant differences in TNC levels were measured for any N level for 1990 and 1991 in December or March, although N at 9.8 g m−2 tended to give lower rhizome TNC levels as compared with 0 or 4.9 g m−2 of N. Nitrogen applications provided a linear increase in N, P, and K concentrations in the leaves. Late‐season application of N improved fall and spring bermudagrass color, and generally had little effect on rhizome TNC levels when measured in December or March.
Field Response of Alfalfa to Harvest Frequency, Cultivar, Crown Pathogens, and Soil Fertility: I. Survival and Yield
Authors: Gossen B. D. , Horton P. R. , Wright S. B. M. , Duncan C .H.
Published: July 2010

Declining productivity in older alfalfa (Medicago sativa L.) stands is an important problem in the Canadian prairies. Field trials were established in 1985 at three locations in Saskatchewan to examine the interaction of (i) harvest frequency, (ii) two alfalfa cultivars, (iii) inoculation with one of three fungal pathogens (Coprinus psychromorbidus, Phoma sclerotioides, or Fusarium spp.), and (iv) K fertilization on survival and forage yield of alfalfa. Harvest and inoculation treatments were initiated in 1986 and continued each year until the tests were terminated in 1989–1990. Plants were dug in spring and fall each year, and total nonstructural carbohydrate levels in the crowns were assessed using near infrared spectroscopy. Differences in plant numbers, stand density, persistence, and vigor between ‘Nordica’ (selected for resistance to C. psychromorbidus) and ‘Beaver’ were small. Harvest at 10% bloom (2–3 cuts) did not result in consistent reductions in numbers of plants, stand density, or total nonstructural carbohydrates relative to a single‐cut treatment. Frequent harvest reduced vigor and first‐cut yield of both cultivars in the year following the treatment, but caused larger reductions for Beaver than for Nordica. Total yields for the frequent harvests over all locations and treatments were 43% higher than for the single‐cut treatment (5.3 vs. 3.7 Mg ha−1). Potassium fertility and inoculation with fungal pathogens had minimal impact on plant survival and yield. In conclusion, interactions among the factors which cause stand decline were minimal, and the reductions in plant vigor and first‐cut yield resulting from frequent harvest were more than offset by the yield from late‐season harvests.
Quadratic and Quadratic‐Plus‐Plateau Models for Predicting Optimal Nitrogen Rate of Corn: A Comparison
Authors: Bullock Donald G. , Bullock David S.
Published: July 2010

Based on quadratic response models, the University of Illinois recommends 22 kg fertilizer N Mg−1 corn (Zea mays L.) grain yield, with adjustments for cropping history, manure, and planting date. Recent work suggests recommendations based on the quadratic model are excessive. This field study evaluated the quadratic‐plus‐plateau and quadratic models and the current recommendation for a 10‐ to 12‐yr, two‐location, two‐crop‐sequence data set with 5 N fertilizer rates in Illinois. For all location‐sequences, we detected a systematic bias with the quadratic model as compared with the quadratic‐plus‐plateau model. The quadratic response model predicted a maximum grain yield of 3 to 6% larger and an optimal N fertilizer rate 5 to 60% larger than that predicted by the quadratic‐plus plateau model and decreased profit from $0.61 to $17.12 ha−1 yr−1. Current University of Illinois recommendations differed by from − 6 to + 104 kg N ha−1 from the amount predicted by the quadratic‐plus‐plateau and resulted in a profit reduction of $0.01 to $31.42 ha−1 yr−1. These analyses indicate that the quadratic‐plus‐plateau is preferable to the quadratic model for predicting N fertilizer requirements of corn. Economic analysis indicates that the consequences of using the quadratic model rather than quadratic‐plus‐plateau model can be large, but not in all cases. Furthermore, the general recommendation of 22 kg N Mg−1 of expected grain yield minus rate adjustments is not appropriate in all cases. Site‐specificity plays a large role in determining optimal N rates.