bluuebunny/crossref_metadata_2025 huggingface dataset:
Air Pollution Oxidant Effects on Cool‐Season and Warm‐Season Turfgrasses1
Authors: Youngner V. B. , Nudge F. J.
Published: July 2010

Although turfgrasses are grown extensively in urban areas where air pollution is a problem, little is known about their reaction to air pollutant oxidants. Cultivars of common turfgrass species were started in a greenhouse with charcoal‐filtered air. One lot of each was fumigated with 0.50 ppm ozone and another with 0.50 ppb peroxyacetyl nitrate (PAN) for 3 hours. A third lot was retained in the greenhouse as a control. Significant variations in leaf injury were noted among the species and cultivars. Injuries to a cultivar from ozone and PAN were often of different magnitudes. All Lulium perenne L. cultivars showed severe injury while Poa pratensis L. cultivars ranged in sensitivity between the extremes for both pollutants. Agrostis tenuis Sibth. and Festuca rubra L. cultivars had moderate injury. Warm‐season grasses, in general, were less sensitive than the cool‐season; only ‘Emerald’ Zoysiagrass and ‘Tifgreen’ bermudagrass showed injury.
Characteristics of the Occurrence and Some Factors Associated with Reduced Palatability of Pearl Millet1
Authors: Rouquette F. M. , Keisling T. C. , Camp B. J. , Smith K. L.
Published: July 2010

During the prolonged drought conditions of 1978, cattle throughout the East Texas area abruptly refused to graze many fields of commercial pearl millet hybrids [Pennisetum americanum (L) K. Schum.]. This study was undertaken to characterize the occurrence of the lack of palatability, investigate some plant factors associated with reduced palatability, and verify that drought was involved in the development of the palatability problem. Forage was sampled from a pasture on an upland site where plants exhibited visual drought stress, and from a bottomland site where plants did not show drought stress symptoms. Analyses were conducted for total alkaloids and nitrate. Two management treatments, shredding and irrigation, were used in an effort to increase palatability of the drought stressed pearl millet. Total alkaloid concentration of non‐drought stressed forage, which was readily consumed, ranged from 10 to 20 mg/kg throughout the August sampling period. Drought stressed forage, which was not consumed, had total alkaloid contents of 180 to 460 mg/kg. The total alkaloid concentration in the drought stressed plants was reduced to 20 mg/kg 4 days after a 1.8 cm rain. Re‐growth forage from previously shredded areas in the drought stressed pasture was not consumed. Forage taken within the drought stressed pasture which was irrigated was readily consumed. The total alkaloid concentration of irrigated forage ranged from 10.0 to 16.7 mg/kg. Drought‐stressed plants contained 3% nitrate and non‐drought stressed plants contained 1% nitrate. Under extreme drought stress conditions, there appeared to be a negative relationship between both total alkaloids and % NO3, and palatability and total consumption.
Nitrogen Fertilization of Maize on an Oxisol of the Cerrado of Brazil1
Authors: Grove Thurman L. , Ritchey K. Dale , Naderman George C.
Published: July 2010

Information about N management for crop production on the highly weathered, tropical Oxisols is limited. Six crops of ‘Cargill 111’ maize (Zea mays L.) were planted on an Oxisol (Typic Haplustox, fine, kaolinitic, isohyperthermic) of the Cerrado of Brazil to 1) define the N fertilizer response curve; 2) estimate increase in N content of aboveground dry matter per unit fertilizer; 3) estimate soil N supply; 4) determine the effects of timing of application on yield and N recovery; and 5) compare conventional and S‐coated urea. Treatments included sidedressed urea at 0, 60, 80, 100, and 140 kg/ha with 20 kg/ha applied at planting and the remainder 30 days later, sidedressed urea at 100, 140, and 220 kg/ha with 20 kg/ha applied at planting and the remainder equally split and applied 20 and 60 days later, 100 kg/ha lime‐coated NH4NO3 and 140 kg/ha sulfur‐coated urea. Grain and stover yields were measured for each crop and subsamples collected for N analysis. Soil samples were collected throughout the experiment and analyzed for organic N. Yield increased significantly with N fertilization. Average maximum grain yield of 6.1 metric tons/ ha resulted from application of 203 kg/ha N. Recovery of fertilizer N varied with application rate from 60% at 60 kg/ha to 35% at 220 kg/ha. A single application of fertilizer 30 days after planting produced the same yield and N recovery as split applications at 20 and 60 days. Neither Scoated urea nor lime‐coated NH4NO3 produced greater yield or N recovery than conventional urea. Average N content of above‐ground dry matter at maximum yield was 1.18%. Average uptake of soil N was 70 kg/ha/crop. There appears to be no fundamental difference in response of maize to N fertilizer between Oxisols and soils of the temperate regions.
Photosynthesis, Transpiration, and Ribulose Bisphosphate Carboxylase of Selected Crested Wheatgrass Plants1
Authors: Frank A. B.
Published: July 2010

Information on rates of physiological processes is needed to identify genotypes differing in physiological characteristics for use in varietal improvement programs. Apparent photosynthesis (AP), transpiration (E), stomatal conductance (rc), ribulose bisphosphate Carboxylase (RuBPc), specific leaf weight (SLW), and stoma frequency were measured in diploid, tetraploid, and hexaploid crested wheatgrass [Agropyron cristatum (L.) Gaertn.] plants from Iran to determine rates for these physiological processes in this species. Two named varieties of crested wheatgrass, A. desertorum (Fisch. ex Link) Schult. ‘Nordan’ and A. cristatum ‘Ruff’ were also evaluated.

Mean AP rates were 22.0, 12.5, and 12.2 mg CO2 dm‐2 hour‐1 and mean E rates were 2.7, 1.4, and 1.6 g H2O dm‐2 hour‐1 for greenhouse‐grown tetraploid, hexaploid, and diploid plants, respectively. Field‐grown (natural water stress) hexaploid plants had higher AP rates (18.1 and 10.4 mg CO2 dm‐2 hour‐1 in 1976 and 1977, respectively) than did tetraploid plants (13.1 and 8.3). Activity of RuBPc averaged 12.1, 6.9, and 11.0 µmoles CO2/(mg protein)‐1 hour‐1 for greenhouse‐grown hexaploids, tetraploids, and diploid plants, respectively, and 8.7, 7.6, and 7.4 for field‐grown plants. The field soil was a Parshall fine sandy loam (Pachic haploborolls). The fact that tetraploid plants had the higher AP rates and dry matter production under non‐water stress growing conditions in the greenhouse may indicate a greater potential for increased growth and yield as compared with the other plants evaluated in this study. Hexaploids had the higher SLW with the tetraploids and diploids having similar and lower SLW. Stomate frequency was greater for the tetraploids as compared with hexaploid plants.

In the greenhouse, the tetraploid plants fixed more CO2 per unit of RuBPc than either the diploid or hexaploid plants. Both greenhouse and field hexaploid plants had high RuBPc activity, but with less range in AP rates than greenhouse (nonstressed) and field (stressed) tetraploid plants which indicated that either stomatal response is sluggish in the hexaploids or that these plants are capable of fixing greater amounts of CO2 under waterstress conditions. The latter quality may indicate greater drought tolerance.
Soil Moisture Requirements for Germination of Sorghum, Millet, Tomato, and Celosia1
Authors: Fawusi M. O. A. , Agboola A. A.
Published: July 2010

In most tropical countries, tomatoes (Lycopersicon esculentum Mill.) are first started in nursery flats and transplanted to the field 4 to 6 weeks later to ensure good establishment. Seed of Celosia argentea (Amaranthaceae L.) usually fail to germinate under the slightest droughty condition. While sorghum (Sorghum vulgare L.) seeds germinate well in arid zones, field establishment and seedling growth are poor under very low soil moisture condition. It is suspected that if adequate soil moisture is maintained, good emergence and field establishment are possible by direct seeding of these crops into well‐prepared seed beds. A greenhouse study was carried out to investigate the optimum soil moisture required for the germination of these crop seeds. Two temperatures, 25 to 28 and 34 C and four moisture regimes, 25, 50, 75, and 100% of field capacity were used. The soil was a sandy loam belonding to Iwo series, derived from coarse‐grained granites, gnesses, and pegmatites.

A 2 ✕ 4 ✕ 4 factorial arrangement in a randomized, complete‐block design was employed. Germination and early seedling growth of tomatoes were best at soil moisture between 50 and 75% of field capacity while Celosia seeds germinated best at 75% soil moisture regime. The optimum moisture requirement for the germination of sorghum and millet (Pennisetum americanum L.) ranged between 25 and 50% of field capacity. Celosia seeds seemed to have a narrower soil moisture tolerance than tomato, while tomato seeds seemed to be more temperature sensitive than Celosia. Both sorghum and millet seed germination were adversely affected by soil moisture in excess of 50% of field capacity, but were less temperatures sensitive than tomato. The observation that sorghum and millet performed well at low soil moisture regime partly explains their ability to survive in dry ecological zones. The moisture requirements of Celosia and tomato seeds suggest supplementation of natural precipitation with irrigation to maintain the required soil moisture for best seedling emergence and growth.
Prediction and Control of Porosity and Water Retention in Sand‐Soil Mixtures for Drained Turf Sites1
Authors: Spomer L. Art
Published: July 2010

Sand‐soil mixtures are commonly used in drained turf sites such as golf greens and athletic fields to ensure proper water retention. The objective of this study was to develop a physical model useful in developing mixture recommendations based on a few simple laboratory measurements on the components and which eliminates extensive field testing. A simple physical model which predicts the total porosity, water retention porosity, and aeration porosity of bidisperse sand‐soil mixtures from the bulk or mixing volumes of each fraction and their individual total porosities was developed and laboratory tested. The porosities of each of a series of compacted sand‐soil mixtures were measured and compared to those predicted by the model. Actual porosities were within 3% of predicted values. This model apparently accurately predicts the porosity and water retention of sand‐soil mixtures and should prove useful in developing recommendations for using such mixtures on golf greens.
Relationship Between Maize Single Crosses and Their Parent Inbred Lines for N Content in the Grain1
Authors: Russell W. A. , Pierre W. H.
Published: July 2010

The main objectives of this investigation were: a) to determine the N content of maize (Zea mays L.) parental inbred lines and their single‐cross progenies when grown at high levels of N sufficiency; and b) to determine the relationship between the N content of inbreds and of their single‐cross progenies. Such information is basic to the characterization of hybrids with respect to their N content at maximum yields relative to N and to the possible use of the N content of maize grain in N‐sufficiency diagnoses. Also, such information is useful to breeders who are interested in developing inbred lines and hybrids that have high protein content. There have been few investigations of the relationship between the N or crude protein content of grain of maize inbred lines and their hybrid progenies.

The average N content in the grain of 29 inbred lines grown at Ames, Iowa, for 3 years (1974‐1976) ranged from 1.45% N for B73 to 2.27% N for W64A, and the average for all lines was 1.80%. For 52 single crosses grown near Martinsburg, Iowa, in 1976, involving 15 inbred lines, N content ranged from 1.35% to 1.80% and averaged 1.53%, whereas for 49 single crosses grown near Grundy Center, Iowa, in 1976, involving 52 hybrids and 17 inbred lines, N content ranged from 1.39% to 1.85% and averaged 1.63%. The simple correlation coefficients between the hybrids and the means of the two parents for N content were 0.84** for the Martinsburg experiment and 0.65** for the Grundy Center experiment. There was no evidence of dominance in the inheritance of crude protein content in either experiment, and the r‐values indicated that gene action was primarily additive for N content. This means the proximate values for N or crude protein content of single crosses can be predicted reasonably well from the mean percent N of the two parents.

A classification of hybrids according to N content of the inbreds showed consistent average differences in N content between types. It can, therefore, be considered a useful way for the general characterization of hybrids until more information is obtained for more specific characterization.
Ionic Balance in Coastal Bermudagrass Influenced by Nitrogen Fertilization and Soil Salinity1
Authors: Thomas J. R. , Langdale G. W.
Published: July 2010

A stimulus in yields of coastal bermudagrass [Cynodon dactylon (L.)] with N on moderately saline soils previously reported may be due to cation‐anion balance. Other investigators have shown that a normal organic anion (C‐A) concentration was one of the conditions necessary for maximum growth, and they have postulated that yield response to N fertilization of saline soils was due to the substitution of NO3 for Cl and an increase in (C‐A) concentration of the grass. The objective of this study was to compare the relation between yield and (C‐A) concentration of coastal bermudagrass under several N fertilizer‐soil salinity regimes.

The grass was grown in pots in a greenhouse on Brennan fine sandy loam (Aridic Haplustalfs). The soil was salinized by treatment with saline water to develop four salinity treatments (S0, S1, S2, and S3) with electrical conductivities (EC) of 1.2, 4.8, 9.6, and 14.4 mmho/cm, respectively. Fertilizer treatments were applied in a factorial arrangement with N rates of 0, 67, 133, and 200 mg/kg of soil and P rates of 0, 20, 40, and 60 mg/kg. The concentration of organic anions in the grass was determined as the difference between the concentration of cations (Na, K, Ca, Mg) and of inorganic anions (Cl, NO3, H2PO4, SO4).

Nitrogen fertilization increased the (C‐A) concentration of the grass at all salinity levels. The increase in Cl concentration with increasing salinity decreased (C‐A) concentrations. An increase in growth was associated with an increase in the (C‐A) concentration. However, SO4 deficiency apparently controlled growth on the adequately N fertilized nonsaline soil, and cation accumulation in the salinized soils depressed growth.
Drought Adaptation of Cowpea. III. Influence of Drought on Plant Growth and Relations with Seed Yield1
Authors: Turk Kenneth J. , Hall Anthony E.
Published: July 2010

Concurrent studies described drought effects on seed yield, plant water status, and water use of cowpea (Vigna unguiculata L. Walp.). In the present studies, drought effects on the growth of cowpea were determined to analyze possible relationships between seed yield, plant growth, and drought, and to evaluate possible mechanisms for the extreme drought avoidance exhibited by cowpea.

Two cowpea cultivars were subjected to different intensities of drought at the vegetative, flowering, and pod filling stages in the field during 2 years having contrasting weather patterns. Plant growth analyses were conducted at the end of the vegetative and flowering stages.

Increase in percent ground cover with time during the vegetative and flowering stages was either slowed down or delayed by drought. Increasing levels of drought, as determined by cumulative xylem pressure chamber values, resulted in progressively less leaf area, shoot dry matter, number of leaflets, and average leaflet area with total leaf area having the greatest sensitivity, and leaflet size the least sensitivity to drought. These responses were partially responsible for the extreme drought avoidance by this crop, but they also may have caused yield reductions. Seed yields were correlated with the leaf area index at the end of flowering and with the percent cover duration from the beginning of flowering to pod filling, but they were not correlated with the amount of leaf area present during the vegetative stage. Earliness, determined by the dry weight in pods at the end of flowering, increased with moderate drought and decreased with more severe drought.

Specific leaf weight increased with increasing levels of drought and may provide a measure of the long term water status experience of plants due to its correlation with cumulative pressure chamber values. A multiple correlation of seed yield with specific leaf weight and degree days above 35 C at flowering accounted for most of the variation in seed yield due to progressive drought and for three growing seasons with contrasting temperature regimes.
Comparison of Cottonseed Delinting Methods in Evaluating Seed‐treatment Fungicides1
Authors: Minton Earl B. , Quisenberry J. E.
Published: July 2010

Evaluating fungicides used to treat planting seed of cotton (Gossypium hirsutum L.) had traditionally been made with acid‐delinted seed and repeated on machine‐delinted seed under the assumption that the treatment response may depend upon the delinting method used. Machine and acid‐delinted cottonseed from the same seed lot were treated with different fungicides. The seed were planted in replicated field tests at eight locations for 3 years. Stand counts were recorded about 30 days after planting. Our primary concern was to determine the effects of methods of delinting cottonseed so seedling survival, but the effects of seed treatments, locations, and years and their interactions were determined. There were no differences in mean percentages of survived seedlings between acid and machine‐delinted cottonseed and there were no significant interactions of delinting method and any of the other variables except those noted below. Differences in seedling survival among years and locations were not significant, but the first‐order interaction between these components was significant, indicating a need to test fungicides each year at as many locations as is feasible. The results should be the same for acid‐delinted as for machine‐delinted cottonseed. There were stand differences among the seed treatments, but most of these differences were between fungicide‐treated seed and the untreated seed. Small differences occurred in percentage of seedling survival among the fungicide seed treatments. Either acid or machine‐delinted cottonseed can be usd to evaluate fungicide seed treatments for their effect on plant stands. Acid‐delinted seed should be used in these tests since most of the planting seed are acid‐delinted.
Herbicide Antidotes With Triallate1
Authors: Miller S. D. , Nalewaja John D.
Published: July 2010

Triallate [S ‐ (2, 3, 3‐trichloroallyl) diisopropylthiocar‐bamate] must be applied and incorporated shallowly (2 to 3 cm) postplant to prevent wheat (Triticum aestivum L.) injury; however, deeper incorporation (6 to 10 cm) has given more consistent wild oat (Avena fatua L.) control. Antidotes which would increase the tolerance of wheat to triallate would allow preplant applications with deep soil incorporation for more consistent wild oat control. Research was conducted in the glasshouse with greenhouse potting soil (2:1:1 v/v/v Fargo silty clay, sand, and compost) or in the field on a Fargo silty clay (fine montmorillonitic, frigid, vertic Haplaquolls) to determine the effectiveness of several antidotes for increasing wheat tolerance to triallate. Treatment of the wheat seed with N, N‐diallyl‐2, 2‐dichloroacetanilide (R25788), 1, 8, napthalic anhydride (NA) or carboxin (5, 6‐dihydro‐2‐methyl‐1, 4‐oxathin‐3‐carboxanilide) increased tolerance of wheat to triallate in both the glasshouse and the field. R‐25788 and carboxin were more effective antidotes than NA with triallate. Applications of R‐25788 and 2, 2‐dimethyl 3‐dichloroacetyl‐oxazolidine (R‐28725) in combination with triallate and seed treatment with 4‐chloro‐2‐hydroxyminoacetanilide (S‐449) or R‐28725 were ineffective antidotes against triallate injury to wheat. This research indicates that R‐25788 or carboxin as seed treatments increased wheat tolerance sufficiently to allow preplant applications of 0.8 kg/ha triallate without injury.
Laboratory Analyses for Predicting Digestibility and Intake of Corn Silage1
Authors: Collins Michael , Ferreira Armando M. , Rohweder Dwayne A. , Jorgensen Neal A.
Published: July 2010

High starch samples are difficult to filter using the neutral detergent fiber (NDF) method. Additional research is also required to identify the best in vitro dry matter disappearance (IVDMD) technique for prediction of in vivo digestibility of whole‐plant corn (Zea mays L.) forage. We designed experiments to compare methods of NDF and IVDMD determination for predicting in vivo intake and digestibility, respectively. In Experiment I, normal corn (105‐day maturity) harvested at five maturity stages (75% silk and 12, 24, 36, and 48 days later) was analyzed for NDF with and without amylase addition during refluxing. The standard deviation among triplicate samples was ±1.08 and ±0.56 for the unmodified and modified procedures, respectively. In Experiment II, normal and brown midrib corn of three maturity stages (75% silk and 24 and 60 days later) and mature (60 days) waxy and male sterile corn were analyzed using the treatments outlined above. In vivo digestibility was regressed on IVDMD dtermined by four methods (IVDMD, IVDMD + amylase, IVDMD + nitrogen, and IVDMD + NDF) and in vivo intake on NDF and NDF + amylase values. A greater percentage of variation in in vivo dry matter intake was explained when amylase was added (R2 = 96.0%) than when not (R2 = 52.0%). The addition of amylase to the in vitro fermentation vessel improved the prediction of in vivo dry matter digestibility (R3 = 67.2%) compared with the unmodified procedure (R2 = 53.3%).
Drought Sensitivity at Various Growth Stages of Barley in Relation to Relative Evapotranspiration and Water Stress1
Authors: Mogensen V. Overgaard
Published: July 2010

Previous investigations into the influence of drought on yield of barley (Hordeum distichurn L.) have been related to either the intensity of water stress or the duration of drought periods. Little attention has been given to the combination of intensity and duration of water stress. In this investigation drought sensitivity (F), calculated as relative grain yield reduction (1 — u/U) of barley at various growth stages, was related to the number of stress days (SD). The number of stress days was calculated as the product of relative evapotranspiration deficit (1 — Ea/Er) and the duration of drought periods (days). Barley (‘Zita’), grown in loamy sand (mixed mesic Typic Udipsamment) in lysimeters, was exposed to drought at different development stages. The lysimeters were automatically protected from rain by a mobile glass roof. Each drought treatment consisted of a single period without irrigation. Watering resumed when all available soil water was used. The first drought occurred during jointing and the final one during ripening. Relative evapotranspiration (Ea/Er) was found to be a more sensitive expression for crop water stress than leaf water potential. Relative evapotranspiration began to decrease when two‐thirds of available soil water had been used. The length of drought periods is defined from that time until irrigation was resumed. Drought sensitivity per stress day (F/SD) was decreased from 0.14 during jointing to 0.08 during booting. For drought after heading F/SD was 0.038 corresponding to a 3.8% grain yield reduction per stress day. This means that one stress day corresponds to one day without grain growth.
A Retractable, Neutron‐Probe Access Tube1
Authors: Glenn D. M. , Henderson R. L. , Bolton F. E.
Published: July 2010

Soil moisture measurements with a neutron‐probe moisture meter provide a rapid and non‐destructive means for measuring soil water in long‐term studies. The inability of farm machinery to pass over the extended access tube limits its use in some situations. A retractable, neutronprobe access tube was designed to allow implement passage at the normal speed and tillage depth without contacting the access tube.

This design has been used for soil‐moisture studies in a fallow‐crop rotation in which 6 to 10 tillage operations, including planting, have been performed over the access tubes. It has worked well with disks, sweeps, harrows, chisels, and deep‐furrow planters.
Soil Contamination of Forage Samples by Forage Plot Harvesters1
Authors: Stringer W. C. , Peiffer R. A.
Published: July 2010

Soil contamination of herbage samples during harvesting may inflate forage yields and render samples unfit for chemical analysis. Observations of soil in herbage samples led to these experiments to quantify soil contamination of herbage samples by various plot harvesting methods. Three harvester designs were compared: the Carter flail harvester; a Penn State‐designed flail harvester with a blower to provide lift to the forage stream; and the conventional sicklebar and rake method. Soil contamination by harvesting was determined by comparing ash content of harvested samples with that of handharvested samples. The flail harvesters resulted in considerable soil contamination of samples. The Carter harvester consistently introduced more soil (5.1 to 9.1% by weight) into the herbage than the sicklebar and rake (0.1 to 1.0% by weight). However, the flail‐with‐fan did not always exceed the sicklebar‐and‐rake in soil introduction. It appears that significant soil contamination and yield inflation is possible with flail‐type forage harvesters.
Modeling Soybean Leaf‐Water Potentials Under Nonlimiting Soil Water Conditions1
Authors: Stanley C. D. , Kaspar T. C. , Taylor H. M.
Published: July 2010

Leaf‐water potential measurements for plants can be valuable in evaluating plant water status because they integrate effects of crop species, plant age, soil moisture conditions, and atmospheric demand on plant water status. When soil moisture is nonlimiting, atmospheric demand controls leaf‐water potential responses. If these responses can be predicted on the basis of key atmospheric demand components, these predictions can be useful in evaluating water‐stressed studies.

This study investigated the possibility of using commonly measured meteorological data (solar radiation, air temperature, pan evaporation, relative humidity, and wind speed) to statistically model diurnal leaf‐water potential response of soybeans [Glycine max (L.) Merr.] grown under nonlimiting soil moisture conditions. It also evaluated the relative contribution to the models of each of the meteorological parameters measured. Coefficients of determination for regression models for five soybean cultivars ranged from 0.86 to 0.88 when leaf‐water potentials were predicted by using solar radiation and air temperature only as input variables. No significant differences were detected among the five cultivars, so a combined overall model was developed. Model verification data were collected from a separate location. These findings provide a tool in irrigation research to test check treatments as true “no stress” treatments.
A Device for Rapid Measurement of Rate of Flow from Gated Irrigation Pipe1
Authors: Regier Cecil
Published: July 2010

When irrigating with gated pipe it is desirable to adjust each gate so that all gates have equal rate of flow. Visual estimates are inaccurate, and other methods currently used are cumbersome and time consuming. A simple, accurate device (“Ettergate”) is described that gives rapid measurement of flow rate from gated irrigation pipe. The device is made from a 3.8 liter rectangular can and a 0.45 kg coffee can.
Legume Growth and Nitrogen Fixation as Affected by Plant Competition for Light and for Soil Nitrogen1
Authors: Kitamura Y. , Whitney A. S. , Guevarra A. B.
Published: July 2010

Since the legume responses to environmental factors may be different in grass mixtures than in pure stands, a pot experiment was conducted to evaluate the effects of plant top and root competition on the growth and N fixation of Desmodium intortum, cv. ‘Greenleaf’ grown in association with Setaria anceps, cv. ‘Nandi.’ The plants were grown in deep, narrow pots which provided for ± top competition (set close together or far apart) and ± root competition (roots in same or different half sections of the pot). All treatments were grown with and without an initial application of 60 kg N/ha.

Greenleaf was a better competitor for light than Nandi in spite of the taller height of Nandi. However in contrast with Nandi, Greenleaf yields and leaf areas were reduced by root competition, especially in the minus‐N treatments. There were no significant differences in acetylene reduction activity due to either N levels or competition treatment. Nodule numbers were depressed by both top and root competition at both N levels, but the plants were able to compensate to various degrees by increases in nodule size and to a greater extent by increases in acetylene reduction activity per unit of nodule weight.
Soil Acidity Tolerance of Symbiotic and Nitrogen‐Fertilized Soybeans1
Authors: Munns D. N. , Hohenberg J. S. , Righetti T. L. , Lauter D. J.
Published: July 2010

In soybean (Glycine max L.), unlike other legumes, poor growth in acid soil might not be due to nodulation failure. This possibility was tested by observing lime effects on nodulation, early growth, and N concentrations in symbiotic (N2‐dependent) plants as compared with control plants fertilized with NH4NO3. There were two lime ✕ N factorial trials with acid soils: a greenhouse trial in a Typic Haploxerult, with two cultivars and 13 single‐strain rhizobial inoculants; and an outdoor container trial in a Typic Hapludult, with nine cultivars and three rates of inoculation that produced large differences in nodule weight and number. The soils were high in exchangeable and soluble Al. In both trials, liming from pH 4.4 to 6.0 (aqueous paste) doubled growth, regardless of N‐source, cultivar, or Rhizobium strain or numbers; and inoculated plants were nodulated, green, and high in N even when their growth was severely acid‐affected.

Symptomatic indications that soybean growth in the acid soils was limited by Al toxicity to the host plant were confirmed in solution culture experiments with pH, Al, and Ca controlled at levels resembling those found in extracts of the soil solutions. Growth was unaffected by low Ca (200 µM) or low pH (4.5), but was depressed at 30 and 65 µM Al.

The data suggest that efforts to improve acid tolerance in soybean should center on plants, not rhizobia.
Cultivar and Rhizobium Strain Effects on Nitrogen Fixation and Remobilization by Soybeans1
Authors: Israel D. W.
Published: July 2010

Maximum utilization of the N2‐fixation capability of leguminous plants such as soybean (Glycine max L. Merr.) in crop production requires an understanding of factors that control seasonal expression of N2‐fixation activity. The purposes of this investigation were to determine the seasonal N2‐fixation pattern for a determinate soybean cultivar nodulated by an efficient Rhizobium strain and the influence of determinate soybean cultivar and Rhizobium strain on the relationship between N2‐fixation capability and reproductive tissue N demand. Greenhouse experiments were conducted in a nil‐N culture system that was sterile until inoculated with the appropriate Rhizobium strain.

The seasonal N2‐fixation pattern for the ‘Ransom’ cultivar nodulated by R. japonicum strain USDA 3I1b110, revealed that 65% of the total seasonal N2 fixation occurred after N began to accumulate in reproductive tissue and that N2 fixation during reproductive development and remobilization of vegetative tissue N met 83% and 17%, respectively, of the reproductive tissue N requirement.

In a second experiment, ‘Davis’ and Ransom soybeans fixed over 100% more N2 during the growing season when nodulated by strain USDA 3I1b110 than when nodulated by strain USDA 3I1b31. When Ransom and Davis soybeans were nodulated by strain USDA 3I1b110, they achieved essentially the same yields of seed dry matter and seed N by expression of N2‐fixation capability at different times in the growth cycle. High N2‐fixation capability before reproductive development coupled with remobilization of vegetative tissue N was associated with the yield potential of Davis soybeans while high N2‐fixation capability during reproductive growth was associated with the yield potential of Ransom soybeans. With either cultivar, nodulation by strain 3I1b31 restricted the amount of N stored in vegetative tissue for remobilization to developing seed.
Sod‐Seeded Soybeans for Forage1
Authors: Ocumpaugh W. R. , Matches A. G. , Luedders V. D.
Published: July 2010

The availability of quality forage in the mid‐summer often limits livestock production in the southern U.S. Corn Belt. Soybeans [Glycine max (L.) Merr.] sod‐seeded into grass pastures may give farmers a chance to improve the quantity and quality of forage available for grazing. The objectives of this study were to examine the growth and development patterns of four soybean cultivars grown in grass sod and to determine the potential of sod‐seeded soybeans for forage. The cultivars PI 89003‐1 (Group II), ‘Williams’ (Group III), ‘Bobwhite’ (Group V), and ‘Hill’ (Group V) were seeded on 18 June into a tall fescue (Festuca arundinacea Schreb.) sod with and without paraquat (1,1'‐dimethyl‐4,4'‐bipyridinium ion) at 0.57 kg(ai)/ha. Paraquat was used in this research to suppress the tall fescue sod.

Total forage (soybeans plus grass) yields ranged from 6,700 kg/ha for Hill, sprayed with paraquat, to 4,500 kg/ha for Williams unsprayed. The crude protein (CP) content at frost ranged from 15 to 18%, and the in vitro dry matter disappearance (IVDMD) averaged about 60%. Tall fescue grown alone produced 2,800 kg/ha dry matter with 50% IVDMD and 8 to 10% CP.

Dry matter accumulation of soybeans was affected by paraquat and the duration of constant growth rate. During the constant growth rate phase, plots sprayed with paraquat produced about 75 kg/ha·day of dry matter, whereas unsprayed plots produced about 50 kg/ha·day. Duration of constant growth rate increased with time to maturity except for the viney‐type Bobwhite, which had a shorter constant growth rate phase than expected.

Late‐maturing soybean cultivars appear better for use as a forage because they offer greater flexibility as to time of harvest, maintain higher forage quality, and generally produce more forage than early‐maturing soybeans. These results, based on a single season, indicate that soybeans can add to the quantity and quality of the forage available in tall fescue pastures.
Delayed Emergence and Temperature Influences on Cotton Seedling Vigor1
Authors: Wanjura D. F. , Minton E. B.
Published: July 2010

Quantitative information relating the effects of delayed emergence caused by soil crusting to cotton (Gossypium hirsutum L.) seedling vigor are needed to improve the technology for stand establishment. A greenhouse study measured the effect of crusted soil (Amarillo fine sandy loam, Aridic Paleustalfs) in delaying emergence for 50, 100, and 150% of normal emergence time for constant soil temperatures of 20, 25, and 30 C. Measurements of maximum emergence, seedling survival, hypocotyl diameter, and root disease rating were used as indicators of seedling vigor. Regression analysis indicated that seedling survival and hypocotyl diameter were minimal at 26 and 24 C, respectively, and root disease rating had a maximum value at 24 C. Seedling emergence and survival were significantly reduced when emergence was delayed between 50 and 100% of the normal emergence period, but almost all increase in hypocotyl diameter occurred in the first 50% delay. Estimates of reductions in vigor for seedlings emerging through crusted soil should be possible by measuring the degree of emergence delay and/ or hypocotyl diameter
Nitrogen Fertilization Effects on Seasonal Ca, Mg, P, and K Levels of Western Wheatgrass and Green Needlegrass1
Authors: Halvorson A. D. , White L. M.
Published: July 2010

Nitrogen fertilization has been found to increase forage production of range grasses in the northern Great Plains; however, little information is available as to how N fertilization may affect the mineral composition of the forage. Our objective was to determine the effects of N fertilization on the levels of P, K, Ca, and Mg, and the grass tetany proneness of the vegetative and floral tillers of western wheatgrass (Agropyron smithii) and green needlegrass (Stipa viridula) throughout the growing season. Nitrogen fertilizer (0, 40, 80, 160, 320, and 640 kg N/ha) was applied in a completely randomized design to each grass species in a calcareous silt loam (Typic Haploboroll). Plant samples were collected on 10 and 11 sampling dates in 1973 and 1974, respectively. Nitrogen fertilization generally increased Ca, Mg, K, and ash alkalinity and generally had little effect on the P levels of the forage; however, the absolute changes caused by N fertilization were very small and of little practical significance. Except for K and P, the level of each nutrient generally increased significantly in each grass as the growing season progressed from April to October. Season or growth stage had more effect than did N fertilization on forage nutrient content. Floral tillers had lower levels of each nutrient than did the vegetative tillers. The Mg and P contents of both the floral and vegetative tillers of both grasses were often < 0.2%. Therefore, supplementation of Mg and P to grazing livestock may be required. The potential for grass tetany, according to the K/(Ca + Mg) ratio of the forage and blood serum Mg estimates, was highest during April and May for both grasses. Western wheatgrass tended to have a greater potential for causing tetany than green needlegrass early in the growing season. Time of harvest and percentage of vegetative and floral tillers can greatly affect the concentration of K, P, Mg, and Ca in the forage. In general, the earlier the harvest, the higher the nutritional value of the forage.
Weed Control in Production of Okra in Trinidad1
Authors: Brathwaite Richard A. I.
Published: July 2010

Weed control is frequently a severe limiting factor in okra [Abelmoschus esculentus (L.) Moench] production in the Caribbean. The objective of this field investigation was to further evaluate the effectiveness of selected herbicide treatments to control weeds in okra and to determine their effects on the yield and quality of okra under rainfed conditions. The research was conducted for 3 consecutive years on River Estate loam, a fluventic eutropept, in Trinidad. Preplant herbicide treatments of benefin (N‐butyl‐N‐ethyl‐ά, ά, ά‐trifluoro‐2, 6‐dinitro‐p‐toluidine), butralin [4‐(1, 1‐dimethylethyl)‐N‐(1‐methylpropyl)‐2, 6‐dinitrobenzenamine], and trifluralin (ά, ά, ά‐trifluoro‐2, 6‐dinitro‐N, N‐dipropyl‐p‐toluidine) and preemergence herbicide treatments of benefin, butralin, DCPA (dimethyl tetrachloroterephthalate) + diphenamid (N, N‐dimethyl‐2, 2‐diphenyl‐acetamide), DCPA, diphenamid, nitrofen (2,4‐dichlorophenyl‐p‐nitrophenyl ether), and prometryn [2, 4‐bis (isopropylamino)‐6‐(methylthio)‐s‐triazine] were applied to ‘Dwarf Long Green Pod’ okra. All herbicide treatments controlled weeds during the first 28 days after treatment. At 42 days after treatment good weed control was obtained with prometryn, trifluralin, preplant benefin, and diphenamid; and acceptable weed control was obtained with preemergence benefin and DCPA. Preplant benefin and trifluralin, and premergence benefin, prometryn, and diphenamid gave fruit yields (i.e. weight and numbers) that were equivalent to those of the handweeded check and superior to those of the other treatments. None of the herbicide treatments significantly affected the grading quality, total carbohydrate, protein, fat, or moisture content of the okra fruit. Slight initial injury to okra plants was caused by prometryn, diphenamid, and DCPA + diphenamid. The DCPA alone caused some leaf distortion which later disappeared. With the exception of nitrofen, which reduced stands, no other symptoms of injury were observed. Results of this study indicate that preplant or preemergence herbicide treatments can be used effectively in okra production.
Forage Yield and Quality of Quaker Comfrey, Alfalfa, and Orchardgrass1
Authors: Hart R. H. , Thompson A. J. , Elgin J. H. , McMurtrey J. E.
Published: July 2010

Quaker comfrey (Symphytum ✕ uplandicum Nym.) has been promoted for years as a high‐yielding proteinrich forage crop. Although considerable research has been done in other countries, almost none has been reported from the United States. Therefore, we established field trials on a Codorus silt loam (Fluvaquentic Dystrochrept) at Beltsville, Maryland and on an Archerson sandy clay loam (Aridic Argiustoll) at Cheyenne, Wyoming. At Beltsvill, three cultivars of comfrey under two cutting schedules were compared to orchardgrass (Dactylis glomerata L.) at three N rates, and to three cultivars of alfalfa ( Medicago saliva L.) alone and in mixture with orchardgrass. At Cheyenne, two cultivars of comfrey at three N rates were compared with alfalfa. Forage dry matter yield was determined at both locations; protein concentration and in vitro dry matter digestibility were determined at Beltsville, and vitamin B12 concentration was determined at Cheyenne. Comfrey yields at both locations were about half those of alfalfa or orchardgrass at the same N rate. Closer spacing of comfrey probably would have increased yield. Protein concentration of comfrey was less than that of alfalfa or orchardgrass except at very high N rates. In vitro dry matter digestibilities of comfrey, alfalfa, and orchardgrass were 37, 62, and 61%, respectively. Contrary to some reports, comfrey forage did not contain detectable amounts of vitamin B12. Moisture content of fresh comfrey averaged 85% and was consistently higher than that of alfalfa or orchardgrass. In view of its low yield and digestibility in these tests, high cost of establishment and weed control, and low palatability to some animal species, Quaker comfrey is not recommended as a forage crop.
Prediction of Boll Opening in a Cotton Crop1
Authors: Wallach Daniel , Kletter Elazar
Published: July 2010

A number of management decisions in cotton (Gossypium hirsutum L.) production rely heavily on estimated dates of boll opening. A simple, quantitative method to predict the timing of boll opening is presented here. The algorithm is based on the assumption that all large bolls will become open bolls after a fixed number of degree‐days. The rate of large boll accumulation and the number of degree‐days from large to open boll are taken from field counts of large and open bolls if possible. Otherwise, default values are used. The algorithm was tested with data from 13 commercial, irrigated cotton fields in Israel. Predictions of subsequent boll opening, made shortly after boll opening began, gave an average error of 4.5 open bolls/m‐row. This method of predicting boll opening is practical for individual growers, since the requirements in terms of data and computing time are small.
Seasonal Drought Response of Selected Wheat Cultivars1
Authors: Sojka R. E. , Stolzy L. H. , Fischer R. A.
Published: July 2010

The relationship between seasonal plant water status and final yield as affected by cultivar is not well documented in wheat. In a 2‐year field experiment, plant water status measurements were used to compare the drought response of selected wheat cultivars. Yield, xylem pressure potential (ψx), adaxial leaf diffusive resistance (R5), and soil water content (θ) were monitored. Twelve cultivars of Triticum aestivum L. em Thell and T. durum Desf., and two of Tritosecale wittmack were used. Genotypes with lower seasonal ψx generally had higher percent yield reduction, when yield was expressed as a percent of irrigated controls. Water use during the observation period in the second season was similar for all droughted treatments and cultivars (about 17 cm H2O) which was less than half that of the irrigated controls (44 cm H2O). Late in the second season, ψx, decreased to as low as −47 bars in some treatments. Correlation between midday ψx and yield (absolute or percent of control) for individual cultivars were highly significant. The importance of full night ψx recovery to near zero was apparent since for three cultivars studied intensively, 80% of the yield difference between nonstressed controls and stressed treatments had already accrued when pre‐sunrise ψx decreased to −7 bars. Further reduction of predawn ψx to −38 bars was associated with only an additional 20% of the yield loss. Observations of R, proved relatively insensitive to cultivar differences in these severely arid conditions.
Germination of Kochia prostrata Seed1
Authors: Young James A. , Evans Raymond A. , Stevens Richard , Everett Richard L.
Published: July 2010

Kochia prostrata (L.) Schrad. has shown potential as a valuable forage species for Artemisia rangelands in the western United States. Stands are relatively difficult to establish by direct seeding, while transplanted plants persist and have proved adapted on numerous Sites. The effects of temperature on the germination of K. prostrata seeds was studied by determining the influence of 55 constant and alternating temperature regimes on seed germination. The constant temperatures were 0, 2, and 5‐degree increments, 5 through 40 C. Alternating temperature regimes consisted of 16 hours at each constant temperature and 8 hours daily at each higher constant temperature. The phenology of germination in relation to incubation temperature and time was studied, and three criteria for germination were developed: (a) root tip uncoiled, (b) hypocotyl arch raised, and (c) cotyledons spread. Quadratic response surfaces and estimated percent germination with confidence limits were developed for each germination criterion. Kochia prostrata seeds readily uncoiled at a wide range of moist incubation temperatures, but seedling development was very slow at low temperatures (0 to 5 C) and seedling mortality occurred at high temperatures (40 to 50 C). Raising of the hypocotyl arch was determined to be a more appropriate criterion by which to judge germination of this species because it could be recognized as actual growth rather than an indication of imbibition. By this criterion, K. prostrata seeds attained 42% germination at temperatures considered, based on field monitoring on Artemisia rangelands, to be moderate seedbed temperatures.