bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Liquid‐Applied Nitrogen Fertilizers on Kentucky Bluegrass Turf1
Authors: Spangenberg B. G. , Fermanian T. W. , Wehner D. J.
Published: July 2010

Solution and suspension N sources have been developed as substitutes for urea in spray solutions used by lawn‐care professionals. A field study was conducted to evaluate the response of Kentucky bluegrass (Poa pratensis L.) growing on a Catlin silt loam (Typic Argiudoll), to applications of the new solution and suspension N sources, alone or combined with urea, by comparison to turf response from application of the traditional fertilizer materials ammonium nitrate (AN), Nitroform (ureaform), sulfur‐coated urea (SCU), ammonium sulfate (AS), granular urea, spray‐applied urea (US), and urea‐ammonium nitrate (UAN) solution. Also, urea and AS treated with dicyandiamide (DCD) were compared to the untreated sources. Fertilization rate was 195 kg N ha−1 yr−1 split into four applications except SCU which was applied twice. Turfgrass color and clipping production were monitored along with thatch accumulation and soil pH. In a second field experiment, foliar burn potentials of the new N sources were evaluated by comparison to burn potentials from US, UAN, and a liquid 12‐1.8‐3.3 fertilizer. Turf response to Formolene (solution N source) paralleled that due to US. Turf treated with US received higher color ratings than did that treated with Nitroform or FLUF (suspension N source) during the early growing season but this trend was reversed by late summer. Turf fertilized with FLUF resembled turf fertilized with Nitroform but was inferior to turf fertilized with SCU. There was no benefit from the inclusion of DCD with either AS or urea. Soil pH after 2 yr ranged from 5.3 to 6.4 and was lowest with AS treatment; thatch depth ranged from 7.0 to 19.3 mm and was greatest with AS treatment. Formolene and FLUF caused less foliar injury than did US, UAN, or the 12‐1.8‐3.3 fertilizer. Results from the two experiments indicated that the major advantage of using Formolene or FLUF was the reduced potential for foliar fertilizer burn.
Effects of Water Deficits on Yield, Yield Components, and Water Use Efficiency of Irrigated Corn1
Authors: Eck Harold V.
Published: July 2010

Irrigated corn (Zea mays L.) is an important feed grain crop on the Southern High Plains where the supply of water for irrigation is declining. Limited irrigation‐applying less water than is required to meet potential evapotranspiration‐is extensively practiced on the drought tolerant crops of grain sorghum [Sorghum bicolor (L.) Moench], wheat (Triticum aestivum L.), and cotton (Gossypium hirsutum L.). The purpose of this paper is (i) to report the effects of timing and duration of water deficit periods on growth and yield components of corn, (ii) to evaluate the seasonal evapotranspiration requirements of corn, and (iii) to give further information regarding the adaptation of corn for limited irrigation in a region of normally high evaporative demand climate. In a 4‐yr study, corn was grown under five irrigation treatments: adequate water, 2‐ and 4‐week water deficit periods during vegetative growth, and 2‐ and 4‐week water deficit periods during grain filling. Water deficits imposed 41 days after planting reduced leaf, stalk, and ear yields, while those imposed 55 days after planting reduced only stalk and ear yields. Deficits during vegetative growth reduced kernel numbers but had little effect on weight per kernel. Deficits during grain filling did not affect leaf and stalk yields but reduced ear yields. Kernel numbers were not affected by water deficits during grain filling unless severe deficits were imposed early in the period; thus, grain yield reductions were proportional to reductions in weight per kernel. With adequate water, seasonal water use averaged 964 mm on graded furrows and 834 mm in level borders. Although water use efficiency (WUE) was sometimes increased slightly when plants were subjected to water deficits, the data indicate that limited irrigation of corn would not be feasible on the Southern High Plains.
Comparison of Nitrogen Fertilizer Methods for Irrigated Barley in the Northern Great Plains1
Authors: Kucey R. M. N. , Schaalje G. B.
Published: July 2010

Yield response curves that consider differences in the effectiveness of fertilization practices are necessary to increase the accuracy of yield response predictions. Such curves are lacking for the northern regions of the Great Plains. A comparison of three commonly used N fertilization practices (broadcasting urea, broadcasting ammonium nitrate, and banding anhydrous ammonia) was conducted to determine their relative efficacies for irrigated barley (Hordeum vulgare L. ‘Gait’) production and to develop N response curves. Spring and late‐fall applications were also compared. Field plots were established on Aridic Haploboroll (Brown Chernozemic) and Typic Cryoboroll (Dark Brown Chernozemic) soils in southern Alberta between 1981 and 1984. Fertilizers were added in late fall or early spring at rates of 30,60,90, and 120 kg N ha−1. Broadcast fertilizers were incorporated into the top 20 mm of surface soil. Anhydrous ammonia resulted in significantly greater barley grain yield responses to N than the addition of urea. Yield responses to ammonium nitrate were intermediate between those for anhydrous ammonia and urea. The fertilizers did not differentially affect grain and straw N concentrations. Application of N fertilizers in the fall, after soil temperatures fell below 5°C, did not result in yields lower than those obtained by equivalent spring‐applied treatments. Yield response equations were developed for the combinations of fertilizer and time of addition.
Area‐×‐Time Equivalency Ratio: A Method For Evaluating The Productivity Of Intercrops1
Authors: Hiebsch C. K. , McCollum R. E.
Published: July 2010

Production systems involving interplanted food crops are widespread in tropical latitudes, and interest in quantifying the productive potential of intercrops is high. Published data often suggest a sizable gain in land‐use efficiency by growing such crops in mixtures. Our thesis is that many of the large intercrop advantages reported in the literature are misleading because the conceptual basis on which the monoculture‐vs.‐intercrop comparisons were made is incomplete. In this paper, we review the various methods for estimating intercrop productivity, propose a concept which we believe will remove the principal limitation in conventional methodology, and test the new concept with intercrop data from the literature. The land equivalency ratio (LER) is the most‐used convention for intercrop‐vs.‐monoculture comparisons, but LER is frequently inappropriate because cropping‐system duration, i.e., time, is not included in its calculation. Duration of land occupancy by an intercrop is often longer than production‐cycle duration for one or more of the interplanted species. We propose an area‐×‐time equivalency ratio (ATER) and suggest that it will correct this conceptual inadequacy in LER. When published intercrop data were reevaluated via the ATER concept, large land‐use advantages ascribed to growing food crops in mixtures disappeared. We conclude that most crop mixtures utilize land area and time (area·time) at about the same efficiency as pure stands of the mixture's components.
Soil‐Dependent Spectral Response in a Developing Plant Canopy1
Authors: Huete A. R.
Published: July 2010

A major problem in the use of remote sensing techniques to assess plant biomass and condition over incomplete canopies concerns the soil background contribution toward measured spectral response. An understanding of this soil signal is essential to better relate canopy spectra with plant properties. An interactive, plant‐soil radiant flux model was developed to separate spectral variations associated with soil background from those attributable to vegetation. Field measured spectra taken over n developing cotton (Gossypium hirsutum L.) canopy with four soil types (Cumulic Cryoboroll, Typic Torrifluvent, Ustollic Haplargid, and Typic Calciorthid) alternately inserted underneath were decomposed into soil and vegetation spectra by utilizing the model in a principal component analysis. The soil component included all radiation penetrating the canopy and interacting with the underlying soil. The vegetation component represented all radiation reflected directly from the plant cover with no soil interaction. The soil component was found to resemble the spectral response of green vegetation due to the scattering and transmittance properties of the overlying plant canopy. Results show how the soil signal mixes into various vegetation indices inhibiting reliable vegetation discrimination. The potential improvements in vegetation analysis that can result from filtering soil background response from plant‐canopy spectra are also discussed.
Nitrogen Contribution to Succeeding Corn from Alfalfa and Red Clover1
Authors: Bruulsema T. W. , Christie B. R.
Published: July 2010

The use of leguminous crops as plowdown has stimulated interest in their contribution to soil fertility. The contribution of N from single‐year plowdown to a succeeding corn (Zea mays L.) crop was evaluated in two field experiments located at Elora, Ontario, on a Guelph‐London loam series Grey‐Brown Luvisolic (Typic Hapludalf) soil. In Experiment 1, 20 cultivars of alfalfa (Medicago sativa L.) and 10 cultivars of red clover (Trifolium pratense L.) were compared. Experiment 2 included two cultivars each of alfalfa and red clover under three management treatments. Nitrogen yield of plowdown legumes was considered in relation to the yield and wholeplant N concentration of the succeeding corn crop. In both experiments, whole‐plant N concentration of corn was significantly higher following alfalfa than following red clover. This suggested that alfalfa N was more readily mineralized than that of red clover, as predicted by a decomposability index based on the C/N ratio and lignin concentration of the plowdown material. However, corn yield following alfalfa plowdown was not always greater than that following red clover. Factors other than N‐supply may have influenced corn yield response to legume plowdown. Although significant cultivar variation in plowdown N yield was observed, there appeared to be no association with succeeding corn yield and N concentration. In general, legume plowdown supported corn yields equivalent to those achieved with 90 to 125 kg ha−1 of fertilizer N.
Growth and Yield of Ethephon Treated Maize1
Authors: Langan T. D. , Oplinger E. S.
Published: July 2010

Ethephon (2‐chloroethylphosphonic acid) has well‐known effects on many horticultural crops and is effective as an antilodging agent for small grains. However, very few studies have tested its effects on maize (Zea mays L.). Field experiments were conducted during 1983 and 1984 on a Plano silt loam (fine‐silty, mixed, mesic Typic Argiudoll) to study the effects of ethephon on maize. Ethephon was applied at rates from 0 to 840 g ha−1 at growth stage V10. Other treatments included populations from 64 200 to 133 330 plants ha−1 and row spacings of 0.38 and 0.76 m. Hybrids included Pioneer hybrids 3901 and 3780. Ethephon had highly significant effects on grain yield, plant height, ear height, and brace root development. Yield of hybrid 3901 generally decreased with increasing ethephon rate, while the lowest rate (140 g ha−1) increased yield of hybrid 3780 by as much as 0.7 Mg ha−1. Yield response of hybrid 3901 to ethephon was linear while that of hybrid 3780 was quadratic. Increasing ethephon rate decreased plant and ear height and promoted brace root development of both hybrids. Response of hybrid 3901 was greater than that of hybrid 3780. Low rates of ethephon can increase grain yield of maize.
Fertilizer Effects on Yield, Grain Composition, and Foliar Disease of Doublecrop Soft Red Winter Wheat1
Authors: Boquet Donald J. , Johnson Catherine C.
Published: July 2010

Improvements in cultivars and management technology have increased the yield potential of soft red winter wheat (SRWW) (Triticum aestivum L.). Field experiments were conducted for 3 yr to define fertilizer requirements for doublecrop SRWW grown on Sharkey clay soil (Vertic Haplaquent). Nitrogen rates were 0, 34,56,78, and 101 kg ha−1 applied as both a single February topdress application (growth stage 5, Feeke's scale) and as a fall‐February split with 17 kg of the total N applied preplant. The effects of application of P (20 kg ha−1) and K (24 kg ha−1) were evaluated singly and in combination at a February applied N rate of 56 kg ha−1 and fall + February split N application rates of 17 + 39 and 17 + 62 kg N ha−1. Significant yield increases were obtained from applied N up to the maximum rate of 101 kg ha−1. The best estimate of yield (
Y) plotted against N rate (X) was the linear equation Y = 3002 + 9.9 × (R2=0.98). Kernels per spike increased and specific kernel weight decreased slightly with N application. There was no yield benefit from splitting the total applied N. Leaf rust (Puccinia recondita Rab. ex Desm.) and powdery mildew (Erysiphe graminis D.C.) infection showed a positive linear association with increasing N rate (R2=0.77 and 0.42, respectively). Phosphorus fertilization decreased the incidence of both leaf rust and powdery mildew. Nitrogen, at the rates applied in this study, did not affect grain protein content but did increase total protein per hectare by increasing yield. Nitrogen fertilization increased the S content of grain and tended to decrease P and K content. Phosphorus and K had no effect on grain protein or mineral composition.
Germination and Emergence Response of Common and Tepary Beans to Controlled Temperature1
Authors: Scully B. , Waines J. G.
Published: July 2010

Soil temperature strongly influences the germination and emergence of common beans (Phaseolus vulgaris L.) and tepary beans (Phaseolus acutifolius A. Gray). The purpose of this investigation was to identify accessions of both species that could potentially germinate and emerge under cool soil conditions, and to determine an optimum germination temperature for tepary beans. Germination of 129 common and 18 tepary bean accessions was initially evaluated at 10°C. The 10 earliest common and the five earliest tepary beans to germinate were entered into an emergence test at three temperatures (12, 14, and 16°C). The common beans emerged 1 day earlier than the teparies at 12 and 14°C, while the teparies emerged 1 day earlier at 16°C. The most cold‐tolerant common bean at emergence was PI 165‐426, while accessions G40034 and PI 319‐443 displayed the highest cold tolerance among the tepary beans. Subsequently, tepary beans were compared to common beans for germination response over six temperatures from 10 to 35°C. In general, tepary and common beans took approximately the same time to germinate except at 35°C where teparies germinated faster. A scarification experiment was undertaken with the same six temperatures as above to determine any effects of the seedcoat on tepary bean germination. Scarification generally resulted in an earlier germination response, but the effect was small. Both germination experiments indicate that the optimum temperature range for teparies is 25 to 35°C, whereas it is lower, 20 to 30°C, for common beans.
Induction of Tobacco Seed Germination Synchrony through Dark Preincubation1
Authors: Mohapatra S. C. , Arcila J. , Johnson W. H. , Nelson L. A.
Published: July 2010

Nicotiana tabacum cv. Speight G‐28, a popular cultivar of bright leaf tobacco, has a high percentage of seed germination but it takes a long time (nearly a week under laboratory conditions and several weeks under field conditions) to give maximum germination. This study was undertaken to develop a laboratory seed treatment to improve germination synchrony. Twenty‐three seed treatments, including the control, were developed through the use of dark‐preincubation (DPI), polyethylene glycol (PEG) or chilling alone, or in various combinations thereof. An index of synchrony (IS) was calculated from the formula,

urn:x-wiley:00021962:agj2agronj198700021962007900030012x:equation:agj2agronj198700021962007900030012x-math-0001 The theoretical highest value of the IS for a given seed lot would be 1.0. In absence of an absolute synchrony, the practical objective of a given seed treatment would be to raise the IS as close to 1.0 as possible. All the 23 seed treatments tested were ranked on the basis of this consideration. Treatments giving 0.8 or greater IS are, indecreasing order: DPI at 23°C for 1 week followed by DPI for 1 week under chilling (0.95); DPI under chilling for 1 week followed by DPI at 23°C for 1 week (0.93); DPI at 23°C for 1 week followed by chilling under light for 1 week (0.90); and DPI at 23°C for 1 week (0.81). As compared to these treatments, the IS of the control was 0.52. Possible physiological mechanisms involved in DPI‐induced germination synchrony and the potential for practical application of this treatment are discussed.
Potassium, Boron, Nitrogen, and Lime Effects on Corn Yield and Earleaf Nutrient Concentrations1
Authors: Woodruff J. R. , Moore F. W. , Musen H. L.
Published: July 2010

Intensified production practices have included irrigation and higher‐than‐traditional rates of N and K to reach high yield goals for corn (Zea mays L.). Previous studies have shown that B is low in southeastern Coastal Plain soils and that additions of high rates of N, K, and lime to soils low in B may decrease B availability. This 3‐yr factorial experiment was conducted on a Dothan loamy sand (Plinthic Paleudults) to examine the effects and interactions of B, K, N, and lime on corn yield and earleaf nutrient concentrations with the objective of better defining B needs of intensive corn production. Two levels of B (0 and 2.24 kg ha−1), K (131 and 317 kg ha−1), N (202 and 426 kg ha−1), and lime (0 and 1120 kg ha−1) were employed. Corn yields showed a positive response to N in 1982, a negative response to lime in 1983, and no response to individual factors in 1984. There was a trend in 1982 and 1984 toward less yield (average 18.2% less) where high K was added with no B, compared to where low K was added with no B. There was a significant B ✕ K interaction effect (P≤0.05) on yield in 1984, and the same effect (P≤0.01) appeared for the 3‐yr combined analysis of variance. Earleaf B was influenced by N ✕ B interaction in 1982 and lime ✕ K interaction in 1984. The results showed that B fertilization was necessary to prevent yield reduction where high K fertilization was used.
Purpling in Maize Hybrids as Influenced by Temperature and Soil Phosphorus1
Authors: Cobbina J. , Miller M. H.
Published: July 2010

Purpling in maize (Zea mays L.), which has been prevalent in Ontario in recent years, has been attributed to combinations of P deficiency, low temperature, and genotype. The intensity of purpling in maize hybrid seedlings grown in growth rooms in an Aqnic Hapludalf soil at three P levels (4,22,100 mg L−1 NaHCO3‐extractable P) and two air temperatures (15/10 and 25/20°C, light/dark) was studied to determine the extent to which differential purpling at low temperature could be attributed to variable shoot P concentration. All hybrids tested (Pioneer 3720, 3732, 3780A, 3949, PAG SX111, Pride 1169) showed some purpling at very low soil P and 15/10°C temperatures. At 25/20°C and very low soil P, Pioneer 3732 and Pride 1169 were severely purpled, Pioneer 3780A and PAG SX111 were intermediate, and Pioneer 3720 and 3949 had the least purpling. Although intensity of purpling decreased with increasing P concentration in shoots, at 15/10°C some hybrids showed purpling even with 5 g P kg−1 DM in shoot. Hybrids differed markedly in intensity of purpling at similar P concentration. Anthocyanin content decreased with increasing shoot P concentration, but there were marked differences among hybrids in anthocyanin content at a given shoot P concentration. There were also marked differences in degree of purpling among hybrids with similar anthocyanin contents. The effects of genotype and temperature on degree of purpling may be due to: (i) reduced shoot P concentration; (ii) higher anthocyanin content regardless of shoot P concentration; or (iii) greater purpling at similar anthocyanin contents. The appearance of purple color in maize seedlings is not necessarily due to inadequate P concentration in the plant.
Root Growth Rate of Soybean as Affected by Drought Stress1
Authors: Hoogenboom Gerrit , Huck M. G. , Peterson Curt M.
Published: July 2010

Roots play an important role in plant survival during periods of drought. A 3‐yr study was performed to investigate the effect of drought stress on daily root growth rates of soybean [Glycine max (L.) Merr. ‘Braxton’] plants grown in a Marvyn loamy sand (fineloamy, siliceous, thermic Plinthic Paleudult) at the Auburn rhizotron. During each growing season, plants received either rainfall (NI) or rainfall and supplemental irrigation (IR) controlled by tensiometers installed at a 0.4‐m depth. Root growth was estimated by measuring the length of new roots visible at the glass viewing surface at regular intervals throughout the growing season. Bins were excavated at the end of the 1983 growing season to estimate total root biomass. Roots of both IR and NI plants grew in the upper soil regions (above 0.4 m) during early vegetative growth (V1–V4) and then gradually penetrated into deeper layers, at a rate of 0.5 to 1 m/(m2 day). A large increase in root growth [up to 6 m/(m2 day)] was observed when drought stress occurred during later stages of vegetative growth or early reproductive development (R1–R2). Root growth was less affected by drought [<1 m/(m2 day)] after plants had reached the pod development stage (R4) and finally ceased during seed fill (R5). The IR plants mainly produced roots in soil layers above 0.6 m, while roots of NI plants penetrated deeper soil layers (>0.6 m), especially during drought periods. After rainfall, root growth rates decreased in both treatments. At the end of the season, NI plants had significantly larger root systems (total root length) than IR plants, but total root mass (tap roots and secondary roots) between the two treatments was similar
Midseason Soil Water Recharge for Corn in the Northwestern Corn Belt1
Authors: Johnson Bradley S. , Blake George R. , Nelson Wallace W.
Published: July 2010

Incomplete soil water recharge between fall harvest and spring planting, and insufficient growing‐season precipitation limit plant growth in southwestern Minnesota. Our objectives in this study were to test the hypotheses that (i) corn (Zea mays L.) production on a fine‐textured soil of high water‐holding capacity may be increased with irrigation, and (ii) that a single application of water at midseason to partially recharge the soil water reservoir would be as beneficial to the crop as more frequent, smaller additions. Treatments consisting of irrigation timing and amounts were established in field studies conducted from 1979 to 1983 on Nicollet clay loam (Aquic Hapludoll). Soil water depletion to 0.9 m was evident during only 2 yr (1980 and 1981). A shallow water table was present in 1979 and 1980 but was not detected within 2.0 m of the soil surface from 1981 to 1983. Despite wet soil conditions and above‐normal precipitation, positive and significant grain yield responses to the addition of supplemental water were observed each year except 1982. Grain yields with a single application of 76 mm at midseason exceeded those with natural precipitation by 1.57, 2.73, and 0.72 Mg ha−1 in 1979, 1980, and 1983, respectively. No difference in grain production was noted between single midseason applications of 76 mm of water and optimum irrigation (application of 38 mm at 50% depletion of plant‐available water to a soil depth of 0.9 m). The economic feasibility of irrigation on Nicollet clay loam appears to be questionable based on yield responses to supplemental water from 1979 to 1983.
No‐Tillage Intercropped Corn Production in Tall Fescue Sod as Affected by Sod‐Control and Nitrogen Fertilization1
Authors: Wilkinson S. R. , Devine O. J. , Belesky D. P. , Dobson J. W. , Dawson R. N.
Published: July 2010

Conservation tillage methods are needed for grain production on the sloping, erodible soils of the southern Appalachian mountains. The purpose of this study was to determine rainfed no‐till corn (Zea mays L.) production in viable tall fescue (Festuca arundinacea Schreb.) sods relative to conventional tillage and complete kill no‐tillage systems. Main plot treatments were: (i) conventional tillage of fescue sod in the first year followed by no‐till planted rye in the second and third years (CT); (ii) no‐till planting in completely killed tall fescue, then in killed no‐till planted rye (NT100); (iii) no‐till planting in a 0.41‐m wide killed strip of tall fescue (NT40); and (iv) no‐till planting in a 0.20‐m wide killed strip of tall fescue (NT20). Subplot treatments consisted of 145 or 290 kg N ha−1yr−1. Adequacy of mineral nutrition for corn was evaluated by plant analysis. The experiment was conducted on a Tate loam soil (fine‐loamy, mixed, mesic Typic Hapludult) with a 5 to 15% slope. No‐till corn production (NT100) was highly successful at both N levels and yielded comparable to conventional tillage. Winter‐spring forage production was comparable whether the forage was no‐till planted rye or the remaining viable tall fescue. Competitive effects of a corn crop at 290 kg N ha−1 resulted in less summer forage for fall utilization. NT40 resulted in slightly reduced corn and forage production and soil erosion control at 290 kg N ha−1yr−1. Competition for water, N, and K limited the effectiveness of the NT20 treatment for no‐till corn production under southern Appalachian conditions.
Effects of Vegetation on Spectral Irradiance at the Soil Surface1
Authors: Heilman J. L. , Kress M. R.
Published: July 2010

Spectral discrimination of vegetation is affected by changes in irradiance at the soil surface produced by the overlying canopy. This study was conducted to quantify effects of vegetation on spectral and spatial variations of irradiance at the soil surface. Direct and diffuse spectral irradiance were measured beneath cotton (Gossypium hirsutum L.) with a spectroradiometer for three soils differing in reflectance. At intermediate and high canopy cover, the cotton altered the spectral composition of diffuse irradiance at the soil surface in a manner that reflected the optical properties of the canopy. At shaded locations, irradiance at visible wavelengths was low due to the high absorptance of the canopy, while the near infrared irradiance was high (nearly 40% of that measured above the canopy) because of the high degree of transmission and scattering by the canopy. At sunlit locations between rows, the total irradiance (direct beam and diffuse) was lower in visible wavelengths and higher in the near infrared than that incident at the top of the canopy. Midway between rows, visible diffuse irradiance was higher and the near infrared diffuse irradiance was lower than beneath the plants. At less than 40% cover, insufficient vegetation was present to significantly affect soil irradiance. The results demonstrate that at intermediate and high canopy cover, irradiance at the soil surface contains spectral contributions from the overlying canopy. The canopy produces significant spectral and spatial variations in diffuse irradiance that should be considered in the analysis of spectral measurements.
Genotypic Variability in Response of Oat to Delayed Sowing1
Authors: Baltenberger D. C. Colville , Frey K. J.
Published: July 2010

A classification of oat (Avena sativa L.) genotypes for reaction to delayed sowing could be used for developing cultivars that either escape the effects of or tolerate high temperatures. The effects of delayed sowing on duration of growth of nine genotypes of oat were studied in field experiments grown on a Coland loam (Cumulic Haplaquoll) soil at the Hinds Experiment Farm near Ames, IA. Sowing dates were 18 March, 2 April, 17 April, and 30 April in 1981; and 14 April, 28 April and 11 May in 1982. Number of growing degree days (GDD) and number of days to reach emergence, tiller initiation, fourth‐, fifth‐, and flag‐leaf stages, heading, and 80% panicle ripe were recorded. Plant height, biological and grain yields, and test weight were measured, and straw yield was calculated. Days and GDD required to reach each developmental stage varied significantly among genotypes. Genotypic differences occurred for plant height, biological and grain yields, harvest index, and test weight, but the differences were not associated with maturity differences. Significant variation occurred across sowing dates for plant height, grain yield, and test weight for most genotypes. Number of GDD required to reach any developmental stage across sowing dates generally was less variable than was number of days for all genotypes, indicating that GDD is a better predictor of oat cultivar development than is number of days. Thus, GDD for oat would be used much as corn heat units (CHU) are used in maize (Zea mays L.).
Aerial Parts of Hard Red Spring Wheat. II. Nitrogen and Phosphorus Concentration and Content by Plant Development Stage1
Authors: Bauer Armand , Frank A. B. , Black A. L.
Published: July 2010

Information is lacking on N and P concentration and content in the aerial components of hard red spring wheat (Triticum aestivum L.) at definitive development stages over its life cycle. Such information would enhance nutrient management strategies and provide algorithms for crop development/yield modelers. The concentration and content of N and P were measured in aerial components of three cultivars field‐grown 2 yr on a Williams loam (fine‐loamy, mixed Typic ArgiboroIIs) under three water and three fertilizer N levels, sampled weekly from about the three‐leaf to kernel‐hard stage.

From a maximum of about 70 g kg−1, leaf N decreased linearly about 2.93 g kg−1 with each development stage, while stem N decreased curvilinearly, most rapidly between the three‐leaf and flag leaf extension stage, to a minimum of 5.0 g kg−1 at kernel‐hard stage. Spike N concentration increased linearly about 3 g kg−1 from anthesis to kernel‐hard stage. Maximum leaf and stem P concentrations were about 12 and 14 g kg−1, respectively, then decreased curvilinearly to about 2.0 and 0.5 g ka−1, respectively, at kernel‐hard stage. Spike P concentration increased linearly about 0.5 g kg−1 from anthesis to kernel‐hard stage. Leaf peak N content occurred at flag‐leaf‐extension through boot stage and in stems at anthesis. Leaf peak P content occurred at flag leaf through heading and in stems at anthesis. About 71% of the N and 57% of the P in spikes at kernel‐hard stage was translocated from leaves and stems.
Vesicular‐Arbuscular Mycorrhizal Fungus Infestation and Phosphorus Fertigation to Overcome Pepper Stunting after Methyl Bromide Fumigation1
Authors: Haas Jerry H. , Bar‐Yosef B. , Krikun James , Barak R. , Markovitz T. , Kramer S.
Published: July 2010

Fumigation with methyl bromide (MB) is practiced to control pepper (Capsicum annuum L.) collapse disease, but in P‐sorbing soils the plants grow poorly after fumigation. A field trial was conducted on a high P‐sorbing soil (fossiliferous Typic Torriorthents) to compare P‐fertigation effects on plants grown on fumigated soil subsequently inoculated with Glomus macrocarpum Tul. & Tul. [MB plus vesicular‐arbuscular mycorrhizal fungus (MB+VAMF)] and not inoculated (MB), and on nonfumigated soil (NF). Pepper plants in MB+VAMF were most mycorrhizal, and MB plants the least. Both VAMF inoculation and P fertigation controlled early season stunting. Plants fertigated with 1.3 mmol P L−1 weighed the most 9 weeks after seeding, and among them the MB+VAMF plants were the heaviest. After 9 weeks, all plots were fertigated with 0.6 mmol P L−1. Yields were high (61 to 65 Mg ha−1) where 0.4 mmol P L−1 and more was supplied early in the season, and highest (73 to 74 Mg ha−1) where both P fertigation and VAMF inoculation were used. The presence of significant quantities of mycorrhiza early in the growth season induced the highest percentage of large‐size fruit, thus making P fertilization with VAMF inoculation most beneficial. Phosphorus fertilization recommendations may have to be adjusted when used in conjunction with soil treatments that significantly reduce VAMF populations in the soil. High sorption made it impossible to raise the P concentration in the soil solution to a level that would support maximum nonmycorrhizal‐pepper growth, unless large quantities of P were supplied frequently in the irrigation water.
Phomopsis Seed Decay and Nutrient Accumulation in Soybean under Two Soil Moisture Levels1
Authors: Thomison P. R. , Jeffers D. L. , Schmitthenner A. F.
Published: July 2010

Infection of soybean [Glycine max (L.) Merr.] by Phomopsis longicolla Hobbs is associated with physiological changes that occur during senescence. The purpose of this research was to determine the relationship of carbohydrate and mineral nutrient composition of pod tissue to seed infection by P. longicolla during senescence and maturity. Soybean pod nutrient levels were altered by N deficiency and water stress by growing nodulating and non‐nodulating isolines of soybean on a Typic Fragiudalf soil at high and low soil moisture (approximately 100 and 1500 kPa tension, respectively) and with high and low N (75 kg ha−1 and 0 kg ha−1, respectively). Nitrogen fertilizer‐isoline treatments affected plant growth and yield but not seed infection by P. longicolla or seed quality. Physiological maturity occurred 1 to 2 weeks earlier in plants grown under low compared to high soil moisture. Seed produced under low soil moisture exhibited less infection by P. longicolla (18 vs. 58% maximum) and greater germinability (66 vs. 47% minimum) than seed from high moisture soil. Total nonstructural carbohydrates (TNC), N, and P were greater in pod walls from plants grown on high compared to low moisture soil. A lower incidence of P. longicolla in upper nodes (3–32%) compared to lower nodes (13–58%) of plants was associated with higher germination levels, lower K, and greater Ca and TNC levels in pod walls. Decreases in seed germination of 14%, 20 weeks after harvest maturity in 1981, and 7%, 8 weeks after harvest maturity in 1982, were only associated with increased seed infection by P. longicolla (10–15%) in 1982. This difference in P. longicolla between years due to harvest delay was associated with higher levels of TNC in pod walls from high soil moisture treatments in 1982 (86–145 vs. 55–58 g kg−1 dry weight). Reducing seed infection by P. longicolla might be achieved by preventing pod wall accumulation of TNC, N, and P, increasing pod wall accumulation of Ca, and shortening the time from physiological maturity to harvest maturity.
Periodic Shading and the Location and Timing of Branches in Soybean1
Authors: Acock Basil , Acock Mary C.
Published: July 2010

An understanding of the environmental influences on branch initiation and growth is essential for developing mechanistic models that simulate crop behavior. In this study shading was used to determine how limited C availability affects the timing and location of branches in soybean [Glycine max (L.) Merr.] plants grown outdoors. Carbon availability was limited by covering the plants with 66% shade cloth (34% light transmittance) for up to 3 weeks at various times during the seedling stage. Treatments were designated as 000, 100, 110, 111, 011, and 001, where 0 indicates the absence and 1 the presence of shade during each of the 3 weeks from the VC to the V6 stages. The number of branches and the number of nodes on branches were counted at each mainstem node on three observation dates. The total number of nodes on the branches was inversely proportional to the number of weeks in shade. In addition, both timing and location of branch growth on the plant were affected by when the shade treatments were imposed. The cotyledonary node was the preferred site for branch initiation prior to the V2 stage. The unifoliolate node was the preferred site between the V2 and the V6 stages. The number of nodes on trifoliolate branches was affected by the number of branch nodes already present at the cotyledonary and unifoliolate sites. Active branch growth at the lower nodes tended to suppress branch growth at the trifoliolate nodes.
Plant Water Relations, Photosynthesis, and Rubber Content of Young Guayule Plants during Water Stress1
Authors: Allen S. G. , Nakayama F. S. , Dierig D. A. , Rasnick B. A.
Published: July 2010

Guayule (Parthenium argentatum Gray, cv. N565 II), a drought tolerant, rubber‐producing shrub native to the desert Southwest, was grown in field plots at Phoenix, AZ, in an Avondale loam soil [fine, loamy, mixed (calcareous), hyperthermic Typic Torrifluvent] in well‐watered and drought conditions. The purpose of the investigation was to characterize the relationships between plant water relations, photosynthesis, and rubber content during drought stress to improve water management practices. The drought treatment lasted 70 days (29 May–5 Aug. 1986) during which the soil moisture content gradually declined from 340 to 165 mm in the top 1.1 m of soil. The well‐watered plots were maintained at greater than 260 mm soil moisture per 1.1 m of soil. Values for psychrometric measurement of water potential of the stressed plants declined to −3.0 MPa, 1.2 MPa less than the well‐watered plants, while maintaining approximately equal and positive pressure potential. This suggests an important role for osmotic adjustment in the drought tolerance of guayule. Net photosynthesis in both treatments steadily declined from about 10.0 to 3.5 µMol m−2 s−1 during the experiment, but with no apparent inhibition due to drought stress. Rubber content increased over fivefold in the stressed plants (from 0.4 to 2.1%) and doubled in the well‐watered plants (from 0.4 to 0.8%) over the course of the experiment. However, the stress treatment reduced final plant size, based on plant height and width measurements, by approximately one‐third compared to the well‐watered treatment. Controlled periods of stress should be investigated as a potential management tool to increase rubber content as well as reduce irrigation water requirements.
Tolerance of Perennial Ryegrass and Tall Fescue Seedlings to Fenoxaprop1
Authors: Dernoeden Peter H.
Published: July 2010

Summer annual grass weed competition can limit successful spring or summer establishment of cool‐season grasses. Fenoxaprop [(±)‐ethyl 2‐{4‐[(6‐chloro‐2‐benzoxazolyl) oxy]phenoxy}propanoate] is an effective postemergence summer annual graminicide that is safe to use on mature stands of perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.). Field studies were conducted to determine the tolerance of perennial ryegrass and tall fescue seedlings to fenoxaprop and to assess fall turfgrass cover of the aforementioned species grown in competition with smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl.]. Separate areas of ‘Citation’ and ‘Palmer’ perennial ryegrass and ‘Olympic’ and ‘Houndog’ tall fescue were seeded on either a Chillum silt loam (fine‐silty, mixed, mesic Typic Hapludults) or a Beltsville silt loam (fine‐loamy, mixed mesic Typic Fragiudults). Fenoxaprop caused seedling yellowing of both species on one of six application dates over a 2‐yr period. No stand reduction or other adverse visual effects from any fenoxaprop treatment (0.09–0.28 kg ha−1) were observed. Fenoxaprop applied at 0.09 kg ha−1 effectively controlled (>90%) one‐ to 3‐leaf stage smooth crabgrass, but 0.28 kg ha−1 were required to effectively control two‐ to four‐tiller stage smooth crabgrass. Single applications of fenoxaprop at all rates and dates of application were sufficient to reduce smooth crabgrass competition and insure good (89%) to excellent (99%) turfgrass cover.
Root Morphology and Vigor Effects on Winter Heaving of Established Alfalfa1
Authors: Perfect E. , Miller R. D. , Burton B.
Published: July 2010

There has been considerable speculation regarding the influence of root system morphology on the susceptibility of alfalfa (Medicago sativa L.) to frost heaving injury. This field study represents a first attempt at quantification of that relationship. A tagging technique was developed for monitoring heave of established alfalfa plants during winter. Measurements were made on a Collamer silt loam (Glossoboric Hapludalf) intergrading to a Niagara silt loam (Aeric Ochraqualf) near Ithaca, NY. Final (net) crown displacement above the soil surface was positively correlated with plant upheaval in midwinter, although maximal uplift was partially reversed as the soil thawed. Plants were retrieved after the winter and evaluated for differences in vigor and taproot architecture. Under comparable soil heaving conditions, 2‐yr‐old plants with the creeping root trait experienced a mean net uplift of 5.5±1.1 mm compared to 8.5±1.2 mm for plants with a pronounced taproot; this difference was significant at P < 0.06. In contrast, spatial variation in maximum soil heave was more important than root morphological parameters in determining uplift of 3‐yr‐old plants from a single taprooted cultivar. Only 45% of the total variance in maximal crown displacement could be explained by multiple regression analysis, suggesting that undefined variables, such as root anchorage and tissue elasticity, may be involved. Approximately 60% of the taproots appeared to have heave related lesions. The vigor of these mature plants was generally unrelated to frost heaving; net upheaval was correlated with the degree of crown rot, but not with root rot, number of crown buds, or curculio (Sitona hispidula F.) scarring.
Indeterminate and Determinate Soybean Responses to Planting Date1
Authors: Wilcox J. R. , Frankenberger E. M.
Published: July 2010

Determinate and indeterminate soybean [Glycine max (L.) Merr.] strains respond differently to planting date in the northern United States. The objectives of this study were to compare performance of closely related determinate and indeterminate strains in response to planting date. Five pairs of determinate and indeterminate isolines or related cultivars were evaluated at three planting dates for 1 yr, and five planting dates for two succeeding years at West Lafayette, IN. Dates were recorded when plants reached stages V1 to V5 and all reproductive stages. Additional data were recorded on agronomic characteristics of the isolines. Planting delays resulted in fewer days between stages V1 to V5 in 2 of the 3 yr and in stages R2 through R8 in all 3 yr. Determinate and indeterminate strains responded the same to planting delays in the vegetative stages V1 to V5 but not in the reproductive stages. Indeterminate strains were shorter and had fewer nodes with planting dates after May 24. Determinate strains either increased or were the same in plant height and number of nodes with successive planting dates after May 24. When lodging was moderate to severe, strains of both types lodged more severely when planted in June than in May. In general, determinate strains yielded more when planted late May or early June; indeterminate strains produced maximum yields when planted from early to late May. Determinate strains responded similarly to planting date regardless of the source of the dt1 gene.
Effects of Nitrogen Fertilization on a Chinese Cabbage Hybrid
Authors: Guillard K. , Allinson D. W.
Published: July 2010

Brassica spp. may be used advantageously during forage‐deficit periods, particularly for late‐season grazing in the northern USA. This study evaluated the influence of N fertilization on the yield and N metabolism and distribution in ‘Tyfon’ [B. rapa L. × B. pekinensis (Lour.) Rupr.], a Chinese cabbage hybrid. Field experiments were conducted in August through November of 1983 and 1984 on a Woodbridge fine sandy loam soil (coarse‐loamy, mixed, mesic Aquic Dystrochrept). Tyfon was no‐till seeded into a herbicide‐suppressed sod, followed by broadcast N at rates of 0, 56,112,168, and 224 kg ha−1. Foliage yields, N uptake, and concentrations of total N and NO3−N increased with applied N. Root yields, concentrations of dry matter, and N use efficiencies were reduced as N rate increased. The amount of N partitioned into the foliage was much greater than in the roots. Once total N uptake reached approximately 100 kg ha−1, no significant increases in yield were observed. Total N recovery, averaged over years, exceeded 75% at the 56 to 168 kg N ha−1 treatments. These data suggest that N fertilization of Tyfon is beneficial only when the amount of N available to plants results in N uptakes of less than 100 kg ha−1. Excessive N fertilization is accompanied by accumulation of NO3–N in the plant.
Timing and Intensity of Water Deficits During Flowering and Grain‐Filling in Pearl Millet
Authors: Mahalakshmi V. , Bidinger F. R. , Rao G. D. P.
Published: July 2010

Yields of pearl millet [Pennisetum americanum (L.) Leeke]–a rainfed crop grown mainly on light soils in the semiarid and arid regions–are often reduced by water deficit when rains end early. The comparative response of this crop to varying intensity and timing of water deficit during flowering and grain‐filling was investigated in field experiments using a line‐source sprinkler system. The soil was an Alfisol (Udic Rhodustalf) with approximately 60 mm of plantextractable moisture. Genotypes differing in maturity were used to simulate differing timings of terminal stress. Grain yields were linearly reduced with increasing intensity of stress in all genotypes. Yield reduction rate was dependent on the time of stress onset in relation to time of flowering, as earlier‐flowering genotypes partially escaped stress. Grain number per unit area and grain size were reduced by intensity of water deficit. Grain yield and grain number, but not grain size, were affected by the time of stress onset at all intensities. Across the entire data set, stress intensity and timing accounted for 75% of the variation in measured grain yield. An advance in time of onset of stress by a day caused a 0.9% reduction in relative grain yield, compared to a 0.7% reduction in relative grain yield for each 1% additional irrigation deficit. Effects of timing of stress increased significantly with increase in stress intensity. The results emphasize the importance of timing and intensity of stress when comparing genotypes of different maturity groups using linesource gradient system, or when selecting genotypes for droughtprone environments
Short‐Term Crop Rotation Systems for Soybean Production
Authors: Dabney S. M. , McGawley E. C. , Boethel D. J. , Berger D. A.
Published: July 2010

Continuous monocrop soybean [Glycine max (L.) Merr.] production has been common in Louisiana for 20 yr. This field study was undertaken to determine if, and how, short‐term crop rotations could increase soybean yield on a Providence silt loam (fine‐silty, mixed, thermic Typic Fragiudalfs) in southeast Louisiana. Eight 2‐yr rotations were evaluated in a field following 15 yr of continuous soybean production. Rotations investigated were: continuous soybean; soybean rotated with grain sorghum (Sorghum bicolor L.); soybean rotated with fallow; soybean doublecropped with winter wheat (Triticum aestivum L.); soybean alternated with winter wheat underseeded with alfalfa (Medicago sativa L.); and three additional rotations, identical to the first three listed with the addition of a winter ryegrass (Lolium multiflorum L.) cover crop. Two soybean cultivars, Centennial and Davis, with different plant parasitic nematode susceptibility, were evaluated in each rotation. Over four complete rotation cycles, Centennial consistently out‐yielded Davis. Soybean grown after either grain sorghum or fallow consistently out‐yielded soybean grown following soybean. This difference existed during favorable and unfavorable growing seasons and was greater for Davis than for Centennial. Insect populations were not high at the study site and did not have a major impact on crop yields. Soybean cyst nematode (Heterodera glycines Inchinohe) populations were higher under Davis than Centennial soybean, increased each year, and were greater with continuous soybean than with rotation. Control of cyst nematode populations appeared to be the main reason for the beneficial rotation effect observed in this study.