bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of Rehydration in Leaf Disks1
Authors: Molz Fred J. , Truelove Bryan , Peterson Curt M.
Published: July 2010

The time course of rehydration by living tissue appears to occur in two distinct phases. Phase I is associated with passive recovery from a water deficit while phase II is associated with the resumption of growth‐related water uptake. However, experimental efforts have been unable to clearly separate the two water absorption mechanisms, and much controversy exists concerning when phase II begins, when phase I ends, and the relative contribution of each phase to the total water uptake. The latter is particularly important in relative turgidity determinations where phase II uptake leads to errors.

In order to help answer some of the above questions it was decided to apply the water transport theory of Molz and Ikenberry to water uptake by floating leaf disks of sunflower (Helianthus annuus L.). The theory can be used to predict quantitatively the time course of phases I and II separately and together. From computer solutions of the governing equations, it is concluded that water uptake by a dehydrated disk is initially a passive rehydration process which becomes progressively more complicated by growth‐related water uptake (phase II) as the tissue water potential rises above −4 bars. Because of the operation of phase II, which begins initially at the cut edge of the disk and progresses inward with time, the interiors of leaf disks are prevented from attaining a water potential of zero. Instead, they are maintained at −0.2 to −3 or −4 bars, a factor that could lead to significant errors in relative turgidity determinations. Phase II neither starts immediately at a steady rate (Yemm and Willis hypothesis) nor waits for phase I completion before beginning (Barrs and Weatherley hypothesis). Rather, is predicted to begin immediately at a very slow rate and to increase monotonically until a steady, maximum rate is reached at the same time phase I is completed. For a 0.5‐cm radius disk and a tissue diffusivity around 10−5 cm2sec−1, phase II water uptake accounted for about 10 to 20% of the total water uptake after a floating time of 3 to 4 hours.
Sugarbeet Yield and Quality as Affected by Nitrogen Level1
Authors: Carter J. N. , Westermann D. T. , Jensen M. E.
Published: July 2010

This study was conducted, under several climatic and soil conditions, to determine the effect of N level on sugarbeet yield and quality and to further develop and refine both soil and tissue test methods for predicting N fertilizer needs for efficient refined sucrose production. Previous studies indicate that N fertilizer needs for maximum sucrose production may be predicted by considering yield potential and all N sources.

Sugarbeets (Beta vulgaris L.) were grown under field conditions at N fertilizer levels varying from 0 to 448 kg N/ha on six sites throughout southern Idaho to determine root yield, sucrose percentages, sucrose yield, impurity index, and plant N uptake in relation to the residual NO3‐N, mineralizable N, fertilizer N, and petiole NO3‐N. These experiments demonstrated that the N fertilizer needs of sugarbeets can be determined by relating the root yield potential to the measured residual NO3‐N plus a measured or estimated mineralizable N level for an area. Optimum N level from all available soil and fertilizer sources has been found to vary between 5 to 6 kg/metric ton of beet roots produced. Using data from the current experiment and a previous study, N fertilzer could be predicted within 56 kg N/ha of that needed for maximum sucrose yield in 83% of the sites using measured NO3‐N and mineralizable N levels, 67% using measured NO3‐N and average mineralizable N levels, and only 12.5% using recommendations by fieldmen. Linear correlations were found between the total available N, total plant N uptake, other plant N variables, and root quality factors, like percentage sucrose and impurity index. These relationships confirm previous findings and will be useful for predicting root quality, optimum harvest date, and for verifying recommended fertilization practices. The use of the proposed soil and tissue test will improve root quality and sucrose production, as well as production efficiency, that will economically benefit the consumer, producer, and manufacturer.
Time and Rate of Fertilizer Application for Seeded Warm‐season and Bluegrass Pastures. I. Yield and Botanical Composition1
Authors: Rehm G. W. , Sorensen R. C. , Moline W. J.
Published: July 2010

Field studies were initiated in 1971 and continued through 1974 to evaluate the influence of time and rate of fertilizer application for both seeded warm‐season and bluegrass (Poa pratensis L.) pastures. The warm‐season pastures consisted of a mixture of big bluestem (Andropogon gerardi Vitman), switchgrass (Panicum virgatum L.), indiangrass (Sorghastrum nutans L.) and sideoats grama (Bouteloua curtipendula L.). Prior studies had shown that fertilization would increase production of several forage species. Yet results were often conflicting and influence of time of fertilizer application had not been investigated. Rates of fertilization ranged from 0 to 180 kg N/ha and from 0 to 34 kg P/ha. Fertilizer was broadcast in both early and late spring on established stands on Crofton silt loam, a Typic Usthorthert. Applications were repeated each year. The relationship between yields of the bluegrass to rate of applied N and P was linear in each year of the study. Higher yields were recorded when fertilizer was applied in early (15 April) compared to late (30 May) spring.

For the warm‐season grasses, the relationship of yields to rate of N application was linear in 1971 and 1972 but was curvilinear in 1973 and 1974. Yields were linearly related to rate of P applied in all years except 1972. Botanical composition of the warm‐season grass mixture was influenced by time of fertilization. Early spring application encouraged encroachment by cool‐season species, intermediate wheatgrass (Agropyron intermedium Host.), which dominated the stand after 2 years of fertilization. Application of N rates less than 90 kg/ha in late spring did not result in encroachment. At the lower N rates, higher yields of warm‐season grasses were observed when fertilizer was applied in late spring.
Differential Response of Wheat Cultivars to Al1
Authors: Lafever H. N. , Campbell L. G. , Foy C. D.
Published: July 2010

Previous observations indicate that the adaptability of certain wheat (Triticum aestivum L. em Thell) cultivars to strongly acid conditions is due to their ability to tolerate high levels of free aluminum. Studies were conducted to determine the differential response of cultivars to high levels of exchangeable Al in soil and to correlate these data to nutrient solution screening techniques. Field plots were located on a naturally low pH (4.5) Wooster silt loam soil (fine, loamy, mixed, mesic Typic Fragiudalf) in which pH levels, and, thus, available Al were controlled by liming. Data on yield, height, maturity, and winter survival of 43 wheat cultivars and experimental lines and two barley (Hordeum vulgare L. emend.) cultivars were obtained in 1973, 1974, and 1975. Field results were related to measurements of root length, weight, and number, leaf length and top weight of plants grown for 10 days in nutrient solutions containing 0 and 8 ppm Al. Many cultivars developed in the eastern USA appeared to have been selected unconsciously for Al tolerance. ‘Fultz’, ‘Trumbull’, ‘Fulcaster’, ‘Thorne’, ‘Seneca’, ‘Lucas’, ‘Butler’, ‘Fulton’, ‘Atlas 66’, ‘Blueboy’, and ‘Pennoll’ were classified as tolerant; whereas, most Indiana developed varieties such as ‘Abe’, ‘Arthur’, ‘Arthur 71’, ‘Redcoat’, ‘Reed’, and ‘Riley’ tended to lack aluminum tolerance. ‘Logan’, ‘Fairfield’, ‘Ruler’, and many of the experimental lines exhibited intermediate degrees of tolerance, indicating that this trait was not simply inherited. Root length in nutrient solutions containing Al was a good indicator of varietal response to the high acid conditions of the field. Nutrient solution techniques provide an efficient nondestructive screening method for use in the development of Al‐tolerant wheat cultivars.
Phytotoxicity and Efficacy of Nematicide Seed Treatment on Wheat, Rye, Oats, and Ryegrass1
Authors: Hoveland C. S. , Rodriguez‐Kabana R. , Haaland R. L.
Published: July 2010

Root‐pruning nematodes can restrict roots of winter annual forage grasses (seeded in autumn) and prevent utilization of water at greater than normal depths during autumn droughts in the southeastern U.S. The efficacy of seed treatment as an inexpensive method for precise delivery of the nematicide in the seedling root zone was studied in the greenhouse. Seed of ‘Maton’ rye (Secale cereale L.), ‘Coker 68‐15’ wheat (Triticum aestivum L.), ‘Florida 501’ oats (Avena sativa L.), and ‘Gulf’ ryegrass (Lolium multiflorum Lam.) were treated in acetone solutions of oxamyl (methyl N′, N′‐dimethyl‐N {(methylcarbamoyl) oxy}‐1‐thiooxamiimidate), carbofuran (2, 3‐dihydro‐ 2, 2‐dimethyl‐7‐benzofuranyl methylcarbamate) or phenamiphos (ethyl‐3‐methyl‐4‐(methyl thio) phenyl (1‐ methylethyl) phosphoramidate) containing 0, 0.25, 0.50, 1.25, 2.5, or 5.0% (w/v) nematicide. Seeds were planted in sterilized soil or soil naturally infested with lance (Hoplolaimus galeatus (Cobb) Sher.) and stunt (Tylen‐ chorhynchus claytonii Steiner) nematodes. Both oxamyl and carbofuran were relatively non‐toxic to germinating seed while phenamiphos was quite phytotoxic. Relative tolerances of the grass species to nematicide seed treatment were rye>wheat>ryegrass>oats. Seed treatment at 1.25% w/v with all nematicides reduced the soil population of stunt nematodes, although the effect was greatest on wheat and oats. Stunt nematodes on wheat declined 65% or more with treatment concentrations of 1.25% w/v. Oxamyl was most effective in reducing populations of lance nematodes. These results indicate that seed treatment is a promising economical method of applying nematicide to control plant parasitic nematodes.
Yield and Quality Trends of Tall Fescue Grazed with Different Subdivisions of Pasture1
Authors: Vartha E. W. , Matches A. G. , Thompson G. B.
Published: July 2010

Subsequent to a grazing experiment which showed average daily gains of growing cattle on N‐fertilized tall rescue (Festuca arundinacea, Schreb.) to be similar whether grazed continuously or in a two‐paddock grazing round baled hay aftermath system, a study was done to determine short‐term changes in the quantity and quality of herbage‐on‐offer for pastures with 0, 2, or 4 subdivisions of grazing. The objective of this experiment was to provide possible explanations for the lack of differences in rate of gain in the on‐going grazing trial. Six groups of three weaner calves grazed replicated pastures of N‐fertilized tall rescue (0.256 ha/group) for 80 days in spring‐summer and 40 days in fall. Cattle were used as defoliators, and animal performance data are not presented. During each grazing cycle, cattle were continuously grazed on pastures with no subdivisions, rotated every 20 days with 2 subdivisions and every 10 days on pastures with 4‐subdivisions. At 5‐day intervals, herbage samples (10 × 0.26 m2) were cut to ground level from each subdivision under grazing. These samples were later analyzed for in vitro dry matter disappearance (IVDMD), N, and mineral composition. Residual herbage samples were also obtained following the completion of the second and third grazing cycles.

In the spring and summer (20 May to 7 August), subdivision treatments did not differ in average amount of herbage‐on‐offer/ha. On removal of cattle on 7 August when the no‐subdivision treatment was fully grazed, amount of residual herbage among treatments was nearly the same. Percent IVDMD declined curvilinearly in all treatments from an average of 64% in May to 49% in mid‐July, followed by a 2.5 percentage unit increase in August.

In the fall (17 September to 27 October), average amount of herbage‐on‐offer/ha ranged from 800 to 1,000 kg/ha higher with 4 subdivisions than with the other treatments. Fall digestibilities ranged from 62 to 43% IVDMD. Low values occurred at the end of the grazing cycle, especially in the 4 subdivision treatment where the most residue (trampled herbage) was observed.

Composited herbage samples from the no‐ and 4‐subdivision treatments showed little difference between the spring‐summer and fall grazing cycles in range of concentrations for N and eight minerals.

The results indicate that subdividing pastures for rotational grazing did not have a marked effect on average quantity and quality of tall rescue during the spring and summer. However, pastures with 4 subdivisions did provide more herbage growth in the fall. These findings may partially explain why cattle daily gains in another on‐going grazing trial have not been different.
Changes in Water Potential During Pressure Bomb Measurement1
Authors: Wenkert W. , Lemon E. R. , Sinclair T. R.
Published: July 2010

Potential errors in the pressure bomb measurement of water potential are important to a wide range of users. We report here specifically on changes in water potential within the chamber associated with measurement technique. Individual soybean leaves (Glycine max L..) were measured repetitively while left in the chamber for varying amounts of time, both with and without a plastic covering. Thermocouples were used to monitor leaf and air temperature during compression. For uncovered leaves, initially at −3 to −5 bars, water potential decreased as much as 1 bar during a single measurement due to drying associated with high tissue temperatures during the compression. Passing the entering air through water in the bottom of the chamber did not limit either the temperature increase or desiccation. When the leaves were wrapped in more than one layer of plastic, they were effectively insulated from the temperature increase in the chamber and decreases in water potential were reduced to 0.1 to 0.2 bars per measurement. Changes in water potential with time were negligible when desiccation was prevented. We conclude that the pressure bomb can yield highly reproducible measurements if the leaves are covered to prevent desiccation.
Concentration, Composition, and in vitro Disappearance of Hemicellulose in Tall Fescue and Orchardgrass1
Authors: Daughtry C. S. T. , Holt D. A. , Lechtenberg V. L.
Published: July 2010

Hemicelluloses are complex groups of cell wall polysaccharides which comprise significant proportions of the dry matter of many forages. Factors affecting hemicellulose concentration in grasses could influence efficient utilization of fibrous feeds by ruminants. The purpose of this research was to evaluate the effects of N‐fertilization, maturity, and plant tissue on the disappearance of cell wall constituents (CWC), hemicellulose, and the components of hemicellulose in two forage grasses during in vitro rumen fermentation.

Tall fescue (Festuca arundinacea Schreb.) and orchardgrass (Dactylis glomerata L.) plots on a Chalmers silty clay loam (fine silty typic argiaquolls) were fertilized with either 0 or 112 kg/ha of N as urea. The grasses were labeled with 14CO2 on 21 May 1975 (heading stage) and were sampled on the 1st, 7th, and 19th days after labeling. Cell wall constituents were prepared by neutral detergent extraction of lyophilized, ground tissue before and after the tissue had been incubated in buffered rumen fluid for 48 hours. Hemicellulose was hydrolyzed in situ with 1.0 N H2SO4. Sugar residues of hemicellulose were separated and identified by paper chromatography and the radioactivity was measured by liquid scintillation counting.

The concentrations of each cell wall component of tall rescue and orchardgrass generally were not significantly different (P = 0.10). Leaves of N‐fertilized grass contained 51.1% CWC and 29.5% hemicellulose compared to 58.1% CWC and 24.0% hemicellulose in leaves of non‐fertilized grass. Concentrations of CWC and hemicellulose in stems were 10 and 5 percentage units, respectively, higher than in leaves. Xylose and arabinose were the major components of hemicellulose, accounting for 37.8 and 23.6%, respectively, of the hemicellulose. Glucose, galactose, and uronic acids formed the remainder. The relative proportion of xylose in the hemicellulose of leaves declined an average of 14% during the sampling period.

Disappearance of CWC and hemicellulose was 52.6 and 69.1%, respectively, during in vitro tureen fermentation. All of the hemicellulose components were not fermented equally. The ratio of xylose:arabinose increased from 1.6 in the original leaf tissue to 3.0 after rumen fermentation. Arabinose in vitro disappearance was 74.7% compared to 53.7% for xylose. 14C‐Xylose accounted for 50% of the radioactivity in hemicellulose before rumen fermentation and more than 70% of the radioactivity in hemicellulose after fermentation. Greater than 96% of 14C‐arabinose and nearly all of the radioactivity in glucose and galactose were lost during fermentation, further indicating that the constituents of hemicellulose are not equally available to rumen microorganisms. An inverse relationship between hemicellulose in vitro disappearance and the xylose: arabinose ratio suggests possible selection criteria for improving forage utilization by ruminants.
Metabolic Changes in Indian Ricegrass Seeds in Relation to Coat‐imposed and Embryonal Dormancy1
Authors: McDonald M. B. , Khan A. A.
Published: July 2010

Indian ricegrass, Oryzopsis hymenoides (Roem & Shult.) Ricker, seeds are dormant at harvest and show a coat‐imposed as well as an embryo dormancy. In this investigation we report on the relationship of the two types of dormancy to changes in certain enzymes implicated in seed germination and seedling growth. Scarification with concentrated sulfuric acid followed by hormonal treatments released both types of dormancy. The removal of seed coat was essential for germination and for the induction of peroxidase, α‐amylase, and ribonuclease activities. Marked quantitative differences were found in cathodic isoperoxidases from intact and scarified seeds as early as 24 hours after imbibition suggesting their involvement in pregermination processes. Hormones had little effect on peroxidases. Inhibitor studies indicated that all isoperoxidases with the exception of one might be synthesized de novo. The enhancement of α‐amylase and ribonuclease by gibberellic acid and kinetin in scarified seeds occurred only after 24 hours. This result suggests, that gibberellin or cytokinin modulation of these enzymes might be post‐germination events and that seeds are presumably deficient in these hormones. Qualitative and quantitative changes were not detected in isoribonucleases of intact seeds. The differences in isoribonucleases between hormone treated and untreated scarified seeds appeared only after 24 hours. The enhancement of RNA polymerase activity by chilling in intact seeds at zero time and in scarified seeds at 24 hours may be due to gene derepression directly related to the release of embryonal dormancy.
Alkaloid Levels in Phalaris aquatica L. as Affected by Environment1
Authors: Ball Donald M. , Hoveland Carl S.
Published: July 2010

Phalaris aquatica L. (also referred to as P. tuberosa L.), a species widely grown in Australia, may have forage potential in the southeastern U.S. and, therefore, has been made the subject of an Auburn University breeding program. In Australia, however, livestock toxicities have been reported from alkaloids in the forage. Field, greenhouse, and environmental chamber experiments were conducted to determine the effect of N fertilization, radiation density, and drought stress on alkaloid concentration of Phalaris aquatica lines. Nitrogen applications up to 336 kg/ha had no effect on alkaloid concentrations in the field on a Cahaba fine sandy loam (Typic hapldult, fine‐loamy, siliceous, thermic) soil, and 224 kg/ha had only a slight effect in an environmental chamber study. Shading to 30 or 55% of full sun caused slight alkaloid increases in the field, but decreased radiation had no effect in an environmental chamber. The order of alkaloid concentration in aerial portions of individual plants of two genotypes was: upper one‐half of leaves>leaf sheaths>stems. Drought stress caused greater alkaloid increases both in field and environmental chamber studies than did any other factor. In Australia, toxicity frequently occurs after severe drought, while in the southeastern U.S. drought is less frequent and severe. Also, pasture composition in the southeastern USA is more diverse, a factor known to lessen toxicity potential probably by dilution. In addition, cattle (which are less susceptible to toxicity than sheep) predominate on pastures in this region, and the chronic form of toxicity occurs only in Co deficient areas, a condition not prevalent here. It is concluded from comparisons to conditions in Australia that the probability of toxicity to grazing animals due to high alkaloid concentrations in P. aquatica in the southeastern U.S. is low, and that selection for low alkaloid types is presently unnecessary.
Influence of Percent NO3−/NH4+ on Growth, N Absorption, and Assimilation by Lima Beans in Solution Culture1
Authors: McElhannon William S. , Mills Harry A.
Published: July 2010

Application of the appropriate quantity and form of N in proportion to the rate of plant uptake and assimilation could significantly increase the utilization of applied N fertilizers. The objective of this study was to determine the influence of various percentages of NO3− to NH4+ and N concentration on N absorption, assimilation, growth, and yield for lima beans (Phaseolus lunatus L.) when grown in solution culture. Nitrogen was supplied as Ca(NO3)2 and/or (NH4)2SO4 at three N concentrations and five percentages of NO3− to NH4+. Peak absorption periods for NO3− and NH4+ were observed when NH4+ supplied 50% of the N. Two peak absorption periods for NO3− occurred, the first at the initiation of inflorescence and the second during pod filling. Peak periods of NH4+ absorption occurred during initiation of the inflorescence, pod development, and pod filling.

Dry weights of all plant parts were consistently higher when NO3− was 75% or more of the N. Lima bean root morphology was altered at all N concentrations when NH4+ was more than 50% of the N. Plant N content was highly influenced by the form and level of N available for assimilation and may not be an accurate indicator of the N available for pod development.
Effect of Thatch on Residual Activity of Nonselective Herbicides Used in Turfgrass Renovation1
Authors: Hurto K. A. , Turgeon A. J.
Published: July 2010

Paraquat (1,1′‐dimethyl4,4′‐bipyridinium ion) and glyphosate (N‐[phosphonomethyl]glycine) are used for controlling existing vegetation in turfgrass renovation programs. While these nonselective herbicides are rapidly inactivated in many soils, the effect of a thatch layer at the soil surface on the residual activity of these herbicides has not been reported. The purpose of this study was to determine the effect of thatch on the residual activity of paraquat and glyphosate as it affects the establishment of perennial ryegrass (Lolium perenne L.) from seed.

Paraquat and glyphosate were applied to Kentucky bluegrass (Poa pratensis L.) turf growing on an Aquic Arquidoll (Flanagan silt loam) at thatchy and thatchfree sites. Establishment of perennial ryegrass on paraquat‐treated thatchy sites was inhibited due to herbicide residues in the thatch. Modification of the thatch by soil incorporation following core cultivation, or removal of the thatch layer by vertical mowing, significantly improved the percent cover of ryegrass on these sites. Glyphosate showed no adverse affects on perennial ryegrass development. Placement of clipping debris containing paraquat residues onto the soil surface inhibited emergence of perennial ryegrass and Kentucky bluegrass in greenhouse studies. Adsorption of paraquat by thatch was rapid, but the tenacity with which it was adsorbed appears to differ from soil as evidenced by field and laboratory studies.
Selection for Aluminum Tolerance in Soybeans Based on Seedling‐Root Growth1
Authors: Hanson W. D. , Kamprath E. J.
Published: July 2010

Laboratory techniques for screening soybean (Glycine max (L.) Merrill) genotypes for tolerance to Al would facilitate breeding programs for areas where AI toxicity limits soybean production. Genotypes from a broad‐base soybean population were screened For Al tolerance based on root growth rate of 5‐day‐old seedlings grown in solutions containing 0.4 ppm Al and 10 ppm Ca (pH 4.6). The selections were intermated to produce a second cycle. Three cycles of divergent selection were completed. The changes associated with selection were evaluated in laboratory studies and in greenhouse studies using Lynchburg sandy loam soil (Aeric Paleaquult).

Tolerance to Al as measured by root growth rates proved to be heritable (0.67) with responses in each cycle of selection; however selections completely tolerant to 0.4 ppm Al in solution were not obtained. When high quality seed was used, genetic differences for tolerance were not affected by the environment used for seed production. Selection based on seedlings from individual plants was feasible. Genotypes selected for Al tolerance had less reduction in growth in soils with high exchangeable Al saturation than non‐tolerant selections; however, the differences were not as distinct as that found for the seedling root‐growth studies. Divergent selections had similar levels of metabolic intermediates in the root tips when seedlings were grown in 0 ppm Al, but pyruvate and ATP levels increased significantly under Al stress for the tolerant but not the non‐tolerant selections. Selection for Al tolerance based on growth of 5‐day‐old soybean seedlings in 0.4 ppm Al apparently identified genetic differences for tolerance in established plants as well as tolerance which appeared unique to the seedling stage.
Field Evaluations of the Herbicidal Effects of Fluridone on Two Soils1
Authors: Banks P. A. , Merkle M. G.
Published: July 2010

The selective control of perennial weeds in cotton (Gossypium hirsutum L.) with soil applied herbicides has been difficult to achieve with currently available chemicals. Also, the long‐term use of the dinitroaniline herbicides in cotton has resulted in a shifting of the weed spectrum to species which are resistant to these herbicides. New herbicides are needed to control these weed problems. The purpose of this study was to evaluate fluridone {l‐methyl‐3‐phenyl‐5‐[3‐trifluoromethyl)phenyl] ‐4(lH)‐pyridinone}, a newly developed soil applied herbicide, for effectiveness in the control of various annual and perennial weeds found in cotton. Fluridone, at several rates, was applied preplant incorporated or preemergence to Miller clay, a fine, mixed thermic vertic Haplustolls, and Lufkin fine sandy loam, a fine montmorillonitic, thermic vertic Albaqualfs, in the springs of 1976, 1977, and 1978 and in the fall of 1977. Weed control evaluations in cotton were made periodically after application. Spring applications of 0.45 kg/ha or higher effectively controlled broadleaf weeds for the growing season. Fluridone at 0.45 and 0.90 kg/ha effectively controlled rhizome johnsongrass [Sorghum halepense (L.) Pers.] 2 of 3 years evaluated. Season‐long control of yellow nutsedge (Cyperus esculentus L.) in a sandy loam soil was observed with preplant incorporated and preemergence rates of 0.90 kg/ha. Phytotoxic effects of fluridone residue were noted in a sandy loam soil one year after treatment but these effects were not as evident in the clay soil. Fluridone applied in the fall provided variable weed control the following spring depending upon soil type, weed density, and weed species present. Incorporation of the fall treatments increased the effectiveness of fluridone on annual grasses in the sandy loam soil. These experiments determined that fluridone could effectively control yellow nutsedge, rhizome johnsongrass, and many annual weeds in cotton at rates above 0.45 kg/ha but the residue of this treatment may limit the use of rotational crops the following year.
Forage Production and N Contents, and Soil Changes During 25 Years of Continuous White Clover‐Pensacola Bahiagrass Growth on a Florida Spodosol1
Authors: Blue W. G.
Published: July 2010

This experiment was established in 1952 with white clover (Trifolium repens L.) and Pensacola bahiagrass (Paspalum notatum Flugge) on virgin Myakka fine sand (sandy, siliceous, hyperthermic Aeric Haplaquod) at the Beef Research Unit near Gainesville, Fla., to evaluate the effects of lime and micronutrients on white clover‐grass production and N fixation, the persistence of this combination of plants under good management, and their effects on the soil. Initial treatments consisted of one without lime and nine with calcitic lime at 5 metric tons/ha incorporated into the soil to a depth of 15 cm. Two of the limed treatments were without micronutrients; the remaining seven included a variety of B sources and experimental frit materials. The experimental area was seeded to Pensacola bahiagrass in July and overseeded with white clover in October. Nitrogen, P, and K were uniformly applied to all plot areas through 1957; subsequently only P and K were applied. Micronutrients were reapplied periodically to plots which received them initially and lime was surface applied as needed. All forage was removed from the experimental area.

Oven‐dry forage was increased by lime from 3,870 to 9,660 kg/ha per year. The percentage increase in forage N was similar even though N was applied to all treatments during the first 5 years. Forage yield and N content were increased additionally by micronutrient treatments.

Soil organic matter was approximately twice as high in 1977 as in 1953. Total soil N increased from 1,180 to 2,560 kg/ha where lime was applied. Where lime was omitted and white clover did not grow, soil N still increased by approximately 800 kg/ha. Exchangeable A1 was eliminated by liming, but was reduced only slightly by phosphate additions. Cation exchange capacity determined by NH4,OAc (pH 7.0) was 2 meq/100 g for each percent of organic matter in soils collected in 1953. In 1977, it was 1.36 and 1.68 meq/100 g for each percent organic matter in unlimed and limed soils, respectively. Very little K accumulated even in unlimed soil where removal by plants was small.
Cotton Cultivar Response to Propazine and Atrazine1
Authors: Abernathy J. R. , Keeling J. W. , Ray L. L.
Published: July 2010

Forty‐eight cotton (Gossypium hirsutum L.) cultivars were evaluated in field studies over a 2‐year period to determine tolerance to phytotoxic soil residue levels of propazine [2‐chloro‐4,6‐bis (isopropylamine)‐s‐triazine] and atrazine [2‐chloro‐4‐(ethylamino)‐6‐isopropylami)‐s‐triazine] present after use in rotational grain crops. After planting, preemergence, broadcast applications of atrazine and propazine at 0.56 kg/ha were applied to an Amarillo sandy clay loam soil (a member of the fine‐loamy, mixed thermic family of Aridic Paleustalfs). Cotton cultivars injury ratings were obtained 6 to 8 weeks after planting, In another study, propazine rates of 0.56 and 1.12 kg/ha were applied preemergence to test yield differences between tolerant and susceptible cotton cultivars.

Injury ranged from 8 to 80%, and 3 to 53% among varieties subjected to atrazine and propazine, respectively. In the propazine yield test, where a tolerant cotton cultivar (‘Paymaster 303’), was compared to a sensitive cotton cultivar (‘Paymaster lllA’), the tolerant cultivar produced 210 kg/ha more than the sensitive cultivar. In the absence of the herbicide, there were no differences in the yield of the two cultivars. This research indicates that choice of cultivar can significantly limit injury to cotton and the likelihood of reduced yields.
Root Elongation and Plant Growth in a Basal Till Compact Soil Treated with 3,5‐Diiodo‐4‐Hydroxybenzoic Acid and Gibberellic Acid1
Authors: Saini G. R.
Published: July 2010

Soils developed on basal till have very dense compact subsoil, which may extend many meters below the topsoil. To improve their moisture storage and other physical conditions, deep subsoiling is usually practiced. In most instances, the beneficial effect of subsoiling is short‐lived and the operation has to be repeated every few years. The spiralling costs of fossil fuel may make repeated subsoiling operations prohibitive. Therefore, as an alternative management technique, the use of small quantities of 3,5‐diiodo‐4‐hydroxybenzoic acid (DIHB) and gibberellic acid (GA3) in the top‐soil to promote root elongation and enhance crop yields was compared with loosening the sub‐soil and also with incorporating limestone in the subsoil after loosening.

A growth chamber study showed that roots of alfalfa (Medicago saliva L.) ‘Saranac’ penetrated the dense subsoil, bulk density 1.9 g cm−3, of a poorly drained basal till soil (Fera Luvic Gleysol) when 1,700 g topsoil was treated with 200 ml of 10−2M DIHB or with GA3. However, the roots in loosened subsoil and to which limestone at 11.2 metric ton/ha had been added and incorporated went deeper. The treatments in order of their superiority were: loosened sub‐soil plus limestone > loosened sub‐soil > top‐soil treated with DIHB > topsoil treated with GA3 > control. Mean root lengths of the alfalfa plants in the various treatments were 66.3, 61.0, 51.2, 49.0, and 33.2 cm, respectively. Corresponding mean dry weight yields of shoots in each treatment were 7.05, 6.08, 5.59, 4.65, and 3.08 g.

Should the spiraling costs of energy make periodic subsoiling operations uneconomical, the use of small quantities of DIHB in the topsoil may provide an alternate management technique for agricultural lands with dense subsoil.
Foliage Injury, Nutrient Intake, and Yield of Soybeans as Influenced by Foliar Fertilization1
Authors: Parker M. B. , Boswell F. C.
Published: July 2010

Yield response to foliar fertilization (N, P, K, S, solution) of soybeans [Glycine max (L.) Merr.] in Iowa has stimulated interest in the use of the same or similar materials in other soybean production areas. Inconsistent yield increases were obtained in Iowa, and it is unknown whether foliar fertilization is feasible where environmental conditions, type of soybeans, and other factors are different from those in Iowa. Field experiments were conducted on a Tifton sl (fine‐loamy, siliceous, thermic, Plinthic Paleudult) and on a Norfolk sl (siliceous, thermic, Typic Paleudult) in the Coastal Plain region of Georgia. Urea K‐polyphosphate mix (urea, K‐polyphosphate, and K2SO4) and NH4‐polyphosphate mix (urea, NH4‐polyphosphate, KCl, and K2SO4) treatments were foliar sprayed on soybeans during the seed filling period. All spray treatments damaged the foliage and suppressed yields with the greatest damage to foliage occurring with repeated application of foliar fertilizer. Three sprayings of a mixture containing 28, 2.9, 9.5, and 1.7 kg N, P, K, and S/ha resulted in an average (two sites) yield decrease of 10.9% for the K‐polyphosphate mix and 17.6% for the NH4‐polyphosphate mix. Weight of pods, whole plants, or seeds, and seed quality were not affected by spray treatments. Absorption of applied nutrients into leaf tissue and translocation to reproductive tissue were detected only in a few instances. Increased N levels were detected only in seeds, and P levels increased only in leaves, while K levels were not changed. Under the conditions of this study, foliar N, P, K, and S fertilization of soybeans does not appear practicable for increasing yields.
Soybean Nodulation as Influenced by Seedling Vigor1
Authors: Smith R. S. , Ellis M. A.
Published: July 2010

abstract

Nodulation in soybeans [Glycine max (L.) Merr.] is influenced by environmental, rhizobial, and host symbiont factors. This investigation was conducted to determine the effects of seedling vigor on early soybean nodulation. Seed quality of three soybean cultivars was adjusted using the accelerated aging technique in order to provide seed lots with a high degree of variation in seedling vigor. Seedling vigor was defined as the number of days from planting to emergence. Aged seeds planted in both a sandbench and the field were uniformly inoculated in the furrow with a Rhizobium japonicum liquid inoculum. Days to seedling emergence was negatively correlated with plant top weight, number of tap root nodules, total number of nodules, and nodule dry weight per plant. Significant decreases in the number of tap root nodules and total number of nodules were observed in a sandbench trial between each of the three earliest emerging treatments (4, 5, and 6 days after planting). In all cases, the first plants to emerge had significantly more tap root nodules than the last plants to emerge. Significance in number of nodules/plant and nodule weight/plant between these two treatments was observed in six of the eight instances.

The results suggest that soybean nodulation may be influenced by seedling vigor and that seedlings with uniform vigor should be utilized when conducting nodulation evaluations.
Yield Variability in Proso Millet Due to Plot Size1
Authors: Nelson L. A.
Published: July 2010

Field experimentation with a new crop requires determination of optimum plot size to minimize variability and obtain an unbiased yield estimate. Plot size influences the planting and harvesting equipment, and the amount of land needed to conduct a research trial. Variability in proso millet (Panicum miliaceum L.) yields due to number of rows planted and harvested in field experimentation was compared using four cultivars for 4 years on Typic argiustoll soils. Plot size combinations selected were: plant one row, harvest one row; plant two rows, harvest two rows; plant three rows, harvest one row; plant four rows, harvest two rows; plant six rows, harvest two rows; plant six rows harvest four rows.

The results of this experiment indicated: 1) three harvest rows were optimum to minimize variance based on the best quadratic fit, 2) the number of rows harvested had a greater effect on variance than the number of rows planted, 3) plots having one border row of their own genotype on each side produced higher yields than plots with either zero or two border rows on each side, and 4) adding border rows of the same cultivar on each side of the harvested row did not decrease variance. The optimum plot size combinations for testing proso cultivars in field experiments appears to be planting five rows and harvesting the center three rows.
Use of Computer Graphics in the Development and Evaluation of Response Surfaces1
Authors: Schoney Richard A. , Bay Ted F. , Moncrief John F.
Published: July 2010

Various statistical measures and prior knowledge of functional relationships have traditionally been the main guides in developing crop response equations. Computer graphics provide a valuable addition to this developmental process. Through graphics, the distribution, physical response, and interaction characteristics of a large volume of data can be visually analyzed. In addition, the physical characteristics of alternative functional forms can more easily be compared to the original data. This paper demonstrates the use of computer graphics in the analysis of field data and the comparison of three alternative functional forms developed from the data.
Corn Physiology in Short Season and Low Temperature Environments1
Authors: Lee S. S. , Estes G. O.
Published: July 2010

Northern areas seeking to expand corn (Zea mays L.) production and thereby reduce feed costs for livestock require early plantings of short season hybrids with good seedling vigor. The association between physiological behavior of corn to low temperature and its field performance could be important in selecting hybrids adaptable to such areas.

Twenty corn hybrids of commercial importance in New Hampshire which varied in maturity were planted 21 April and 19 May at the Univ. of New Hampshire Agronomy Research Station, Madhury, NH; nine selections from the above were also grown at three other locations in the state with widely differing growing conditions. The effect of controlled temperature on chloroplast structure and photosynthetic activity was also determined using the earliest and one of the latest maturing hybrids which differed in early development under field conditions.

Low temperatures following the early planting of 21 April did not adversely affect stand density of hybrids; seedling growth of the two earliest maturing hybrids was superior to all other selections. At the normal planting date of 19 May seedling growth of the 20 hybrids was negatively correlated with their maturity rank; seedling growth was greatest in the earliest hybrids.

Yield of total dry matter (TDM) at maturity was not related to seedling growth. In field studies in the southern and middle part of New Hampshire with a growing degree days (GDD) range of 1,100 to 1,300, TDM yields of the earliest corn hybrids were lower than yields of the later maturing corn. At the northern locations, with GDD < 1,100, yield of TDM was not significantly different among hybrids although % DM was higher in early maturing corn. A greater decline in photosynthesis and altered chloroplast ultrastructure in the leaves of a late‐maturing corn following exposure to controlled day/night temperatures of 15/10 C in the greenhouse was observed; no such changes occurred at 15/10 C either in the earliest hybrid, which had shown superior seedling performance under field conditions, or in either hybrid when grown at 10/15 C.
Deleterious Effects on Yield of Drilling Fertilizer into Established Alfalfa Stands1
Authors: Leyshon A. J.
Published: July 2010

Drilling fertilizer into an established forage crop has been suggested as a means of increasing fertilizer availability. Experiments were conducted at Swift Current, Saskatchewan on an orthic Brown chernozem (aridic haploboroll) to investigate the effects of fertilizer rate and placement depth on the yield of an established dryland alfalfa (Medicago ✕ vuriu Martyn) stand. In one experiment phosphorus fertilizer at rates of up to 64 kg P/ha was drilled‐in to depths of 0, 5, and 10 cm and in a second experiment, N fertilizer at rates of up to 200 kg N/ha was drilled‐in to the same depths. Fertilizer rate did not affect yields in either experiment and there were no interactions between depth of placement and fertilizer rate. However, in both experiments, increasing the depth of placement decreased yields between 12 and 20% in the first year and in both experiments the yield decreases persisted for 2 or more years. In a third experiment the soil 30 cm from the row of an old established stand of alfalfa was disturbed at four depths (0, 2.5, 5 and 10 cm) with a tractor‐drawn spike to simulate a fertilizer drill. A 20% decrease in yield was observed when the soil was disturbed below 2.5 cm. It is suggested that the reduced yields were a result of mechanical damage to roots and that the persistence of the effect was due to an inability of the root to regrow in the dry topsoil common to southwest Saskatchewan. It is recommended that for established alfalfa stands all fertilizer be surface applied.
Drought Response of Sorghum Hybrids under a Sprinkler Irrigation Gradient System1
Authors: O'Neill M. K. , Hofmann W. , Dobrenz A. K. , Marcarian V.
Published: July 2010

Reliable techniques for identification of drought‐resistant germplasm are essential if new lines and hybrids are to be developed for arid and semiarid areas of the world. This experiment was designed to evaluate the irrigation gradient system as a mechanism for evaluating drought tolerance in sorghum [Sorghum bicolor (L.) Moencb.] in the field. Fifty sorghum hybrids which were developed with A‐lines ‘CK‐60’ and ‘Redlan’ were planted perpendicular to the mainline of the sprinkler irrigation gradient system at Yuma, Ariz. in 1979 and 1980. The soil was a superstition sand (sandy, mixed, hyperthermic Typic Calciorthid) with an average available soil moisture of 3.6 % . Characteristics including panicle rank, anthesis date, plant height, panicle and peduncle length, crown diameter, and plant weight were measured on plants of each hybrid grown in the high and low water areas of the gradient system. The distance from the line source to the last grain‐producing panicle in the low water area of the gradient was also measured on each hybrid. Hybrids developed with CK‐60 were able to produce seed‐producing panicles in drier areas of the gradient compared to hybrids developed with Redlan. The average distance from the sprinkler Line source was 14.4 m for CK‐60 hybrids and 11.3 m for Redlan hybrids over both years. Days to anthesis, panicle and peduncle length of plants in the stressed area of the gradient may be potential indicators of drought resistance. The irrigation gradient system is a useful tool for evaluating drought resistance and the selection of parental lines over a wide range of available soil moisture conditions.
Weed Control in a Winter Wheat – Corn – Ecofarming Rotation1
Authors: Vorst P. B. Vander , Wicks G. A. , Burnside O. C.
Published: July 2010

Adequate information is not available regarding the influence of row spacing, seeding rate of winter wheat (Triticum aestivum L.), and time of herbicide application on weed control following wheat harvest and in the succeeding corn (Zea Mays L.) crop. Field experiments, conducted during 1977 through 1980 on a Holdrege silt loam (fine‐silty, mixed, mesic Typic Argiustoll) at North Platte, Nebr. determined that narrow‐row spacing (17 vs. 35 cm) and seeding rates of 67 or 100 kg/ha vs. 33 kg/ha of winter wheat significantly improved weed control in a wheat – Corn – fallow rotation. Wheat grain yield did not differ between row spacings. Wheat yielded 15% more grain when seeded at 67 or 100 kg/ha than at 33 kg/ha in 1978. Weed yield and grass weed panicle production in wheat stuhhle increased as atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] + paraquat (1,1'‐dimethyl‐4,4'‐bipyridinium ion) application was delayed from 5 to 25, 45, or 260 days after harvest, but atrazine persistence was not sufficient to maintain better weed control when planted to corn the following year. Atrazine applied 260 days after wheat harvest provided the best weed control in the following corn crop. However, corn yield was reduced 22% in 1978, because weed growth between wheat harvest and herbicide spraying used soil water needed for the corn. Narrow‐row spacing and high seeding rate of wheat the year prior to corn reduced weed populations during the fallow period the year following corn. Reduction of weed seed production is essential during the entire rotational sequence in order to prevent the buildup of weed populations.