bluuebunny/crossref_metadata_2025 huggingface dataset:
Leaf Elongation and Turgor Pressure in Field‐grown Soybean1
Authors: Wenkert W. , Lemon E. R. , Sinclair T. R.
Published: July 2010

Cell and leaf elongation have been reported to be highly sensitive to plant water deficit and may represent the primary mechanism of stress and yield reduction. This study was designed to determine if leaf expansion is restricted by the routine daytime water deficit experienced by field plants in moist soil. Leaf elongation in soybean [Glycine max (L.) Merrill ‘Rampage’] was monitored during several 2 to 4‐day periods in the field in conjunction with pressure bomb measurement of water and osmotic and turgor potential. Short‐term (minutes) leaf‐elongation rate was highly responsive to step changes in water deficit but gradually recovered over periods of about an hour. Length that was lost during the transient rate reduction tended to be made up by high rates following improved water status. Mean elongation rates were not limited by normal daytime water deficit (turgor pressure as low as 2 bars), except late in the season when pod‐filling occurred at nodes adjacent to the growing leaves. Elongation rate was always sensitive to temperature. We conclude that within the range of moderate, daytime water deficits we encountered, soybean leaves may adapt to the extent that turgor pressure does not limit growth.
Yield Response of Corn to Irrigation on Sandy Soils1
Authors: Follett R. F. , Benz L. C. , Doering E. J. , Reichman G. A.
Published: July 2010

Irrigation is being developed on large areas of coarse and moderately coarse‐textured soils in North Dakota. Extensive areas of similar soils, including those in adjacent States, are near areas planned for irrigation. Knowledge of crop response to water is needed to effectively use irrigation in these large areas. The objective of this study was to investigate the effects of irrigation and precipitation, and to use the Mitscherlich equation to evaluate the effect of limited water supply on crop yields and apparent water use efficiencies. Yield response of corn (Zea mays L.) to the amount of water received (irrigation and precipitation) was investigated in this 3‐year field study. The corn was grown on a Hecla loamy fine sand, a Udic Haploboral, and irrigated weekly at rates based on predicted evapotranspiration calculated using the Jensen‐Haise equation. Irrigation with more water than the amount predicted by the Jensen‐Haise equation did not significantly increase forage or grain yield for any single year, but did significantly increase average grain production over the 3‐year period. Successive, larger increments in the amount of water applied to the crop resulted in successively smaller increases in forage and grain yields. Mitscherlich equations fitted yield data for all 3‐years and predicted limiting yields of 16.48 metric tons/ha of oven‐dry forage and 10,150 kg/ha of grain at 15% moisture. For oven‐dry forage production, apparent water‐use efficiency (AWUE) was about 0.28 and 0.21 metric ton/ha‐cm of water applied (precipitation plus irrigation) between emergence and final harvest for the nonirrigated and highest irrigation rate treatments, respectively. For the corresponding treatments, the respective AWUE's for corn grain production were 323 and 167 kg/ha‐cm of water received (between 3 weeks before silking and final harvest). Yield response to irrigation treatments that considered precipitation probability at Oakes, North Dakota, were calculated. Results indicated that in 95% of the cropping seasons at least 8.9, 10.9, 12.4, or 13.4 metric ton/ha of oven‐dry forage and 6,070, 7,230, 8,060, or 8,650 kg/ha of corn grain at 15% moisture could be expected from irrigating with 20, 30, 40, or 50 cm of water, respectively. In 50% of the cropping seasons, however, only 6.3 metric ton/ha of forage and 3,770 kg/ha of grain or less could be expected with no irrigation.
Frost Heaving in Alfalfa Establishment on Soils with different Drainage Characteristics1
Authors: Russell W. E. , Olsen F. J. , Jones J. H.
Published: July 2010

The susceptibility of alfalfa (Medicago sativa L.) to frost heaving is a major problem in stand establishment in southern Illinois. This study was conducted at Carbondale, Illinois, to determine the effects of frost heaving on the establishment and production of alfalfa cultivars in relation to soil drainage characteristics. Four alfalfa cultivars (‘Cody’, ‘Spredor’, ‘Weevlchek’, and ‘WL‐307’) were seeded on three soil series, a deep well‐drained AIford (Typic Hapluadalf, fine‐silty mixed mesic), a moderately well‐drained Hosmer (Typic Fragiudalf, fine‐silty, mixed, mesic) with a fragipan starting at a depth of 60 to 70 cm, and a nearly level poorly‐drained Weir (Typic Ochraqualf, fine, montmorillonitic, mesic). Piezometers were installed in each soil to monitor the presence of perched water tables and their position to the soil surface. Small wooden dowels were used to assess soil movement in relation to alfalfa seedling heave. The higher amount of heaving as measured by the distance wooden dowels were raised above a reference point occurred when the night temperature was a few degrees below freezing and the day temperature was above freezing, with a perched water table near the soil surface. Poorly‐drained, Weir soil had the highest perched water table, most alfalfa seedling heave, greatest alfalfa seedling winterkill, and most dowel heave. In contrast, well‐drained Alford series had no perched water table, no appreciable seedling heave or winterkill, and least dowel heave. No significant differences in amount of frost heaving of seedlings were noted amonga alfalfa cultivars on any drainage site. Highest dry matter yields were obtained on the well‐drained Alford site; significant yield reductions occurred as soil drainage class became more poorly drained. Alfalfa stands were successfully established on the well‐drained Alford series and the moderately well‐drained Hosmer series. Soil drainage characteristics did influence alfalfa establishment and production in the climatic transitional zone of the central U. S. Poorly‐drained soils should not be considered for alfalfa production.
Growth and Development of Meadow Plants as Affected by Environmental Variables1
Authors: Gomm F. B.
Published: July 2010

The low production of seasonally flooded meadows is a problem in many locations throughout the world. An understanding of the effects of environmental factors on the growth and production of the meadow species will aid in developing practices to increase forage production. Controlled studies were undertaken to determine the effect of soil moisture, temperature, irradiance, and soil fertility on the phenological development and growth of slender sedge (Carex praegracilis W. Boott), beardless wildrye (Elymus triticoides Buckl.), Nevada bluegrass (Poa nevadensis Vasey ex Scribn.), and reed canarygrass (Phalaris arundinacea L.). Potted plants were grown in growth rooms under various environmental conditions: temperatures of 15 and 30 C, irradiances of 4.2 and 42.0 W/m2; soil moisture levels with amounts of moisture added approximating the volume of water that the soil would retain at 0, 0.3, and 10 bars; fertilizer‐N at rates equivalent to 0, 110, 220. and 440 kg/ha. Plant responses were evaluated by number of leaves per stem, number of stems per plant, leaf area per plant, plant height, and herbage yield at the end of three growth periods. In the controlled‐study conditions, mortality of bluegrass plants was high when grown with 4.2 W/m2. Phenological development progressed faster and plant growth‐rate increased when the irradiance received was increased to 42.0 W/m2. Canarygrass, however, continued in a vegetative stage regardless of temperature or light treatments. Increasing temperature from 15 to 30 C increased the rate of growth for plants receiving 42.0 W/m2, but the increased temperature also increased the mortality of all species receiving 4.2 W/m2. Fertilizer rates and soil‐moisture levels generally had no significant effect on plant‐growth parameters when plants, except for canarygrass, were grown at 15 C or with 4.2 W/m2. The greatest rate of growth was produced when plants were grown at 30 C with 42.0 W/m2. Under these conditions, yields tended to increase with fertilizer, and yields from canarygrass increased as fertilizer rates and soil‐moisture levels increased.
Compatibility and Phytotoxicity of Herbicide‐Fertilizer Combinations1
Authors: Martens A. R. , Burnside O. C. , Cramer G. L.
Published: July 2010

During the past decade herbicides and liquid fertilizers have been combined for joint application with increasing frequency. This practice has been labeled the “weed and feed” concept. It saves time and labor, reduces soil compaction, and reduces application expenses. Thus, the effect of compatability treatments on phytoxicity of mixture of 10 herbicides with 11 fertilizers were studied in the laboratory and greenhouse. The objective was to determine the feasibility of joint application of each herbicide with each liquid fertilizer selected. Herbicides were generally compatible with suspension‐grade fertilizers and maintained their phytotoxicity for 24 hours with agitation as determined by greenhouse bioassays. Of the clear liquid fertilizers, 11‐37‐0 was the most compatible with the 10 herbicides. Atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine], chloramben [3‐amino‐2,5‐dichlorobenzoic acid], and propachlor [2‐chloro‐N‐isopropylacetanilide] were the herbicides most compatible with the liquid fertilizers. Chloramben remained dispersed for 24 hours without agitation in most of the fertilizers. In general, separation of the herbicide‐fertilizer mixtures occurred within 1 hour after initial mixing, without agitation. Agitation was essential for maintaining phytotoxicity of most herbicide‐fertilizer mixtures. COMPEX (alcohol sulfates) at 0.25% volume/weight (v/w) of spray solution and ATTAGEL 150 (attapulgite clay) at 0.75% weight/weight (w/w) of liquid fertilizer solution were the most effective compatibility treatments added to the herbicide‐fertilizer mixtures. COMPEX retarded the formation of precipitates in fluorodifen [p‐nitrophenol‐α,α,α‐trifluoro‐2‐nitro‐p‐tolyl ether] fertilizer mixtures. Use of a 2:1 water:herbicide (w/w) dilution aided in mixing wettable powder herbicides with liquid fertilizers. Addition of SURFACTANT WK (dodecyl ether of polyethylene glycol) increased compatibility of some wettable powder herbicide‐fertilizer mixtures. However, with adequate agitation nearly all herbicide‐fertilizer mixtures were compatible and herbicide phytotoxicity was maintained without the need for the addition of compatibility agents.
Seasonal Forage Nutritive Value Variation of Coastal and Coastcross‐1 Bermudagrass1
Authors: Jolliff Gary D. , Garza A. , Hertel J. M.
Published: July 2010

Chronological age is a common basis of reference used in bermudagrass research treatments and forage production management recommendations. Plant growth and development changes due to the environment could cause a confounding of research results when assuming that forage of a given chronological age has a similar nutritive value regardless of the season or year. This field study on victoria clay soil (a Typic Pellusterts) was conducted to measure the mouth‐to‐mouth variation in quality of Coastal and Coastcross‐1 varieties of bermudagrass (Cynodon dactylon, (L.) Pers.) harvested at 4, 8, 12, 16, 20, and 24 week growth intervals through the 1975 growing season, Samples were taken from March through December. Acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), and in vitro dry matter digestibilit (IVDMD) were measured. Statistical comparisons or quality were made only within age intervals. Fifty percent of 312 month‐to‐month comparisons were significantly different. Coastcross‐1 bermudagrass was more variable than Coastal bermudagrass, because of greater declines as well as greater increases in quality due to environmental changes. The 8‐week‐old forage had the greatest variation in quality in both varieties. The most measurable variability was in crude protein content. Month‐to‐month variability of CP declined with advancing maturity in Coastal and increased in Coastcross‐1. Variation as measured by ADF and IVDMD was second and third to CP, respectively, and the grassa responded similarly. Overall variability measured by NDF was the lowest of the four methods used. Actual percentage changes in ADF, NDF, CP, and IVDMD of 8‐week‐old forage within a 30day period was as high as 9.9, 3.0, 4.6, and 12.7 percentage units, respectively, for Coastcross‐1. The impact of environmental conditions on forage quality was significant and was dependent up on the age of the grass, the specific quality component in question, and the grass variety. Therefore, care should be exercised in extrapolating research data from one season of the year to another even at the same geographical location.
Productivity and Quality of Bermudagrass and Orchardgrass‐Ladino Clover Pastures for Beef Steers1
Authors: Fribourg H. A. , McLaren J. B. , Barth K. M. , Bryan J. M. , Connell J. T.
Published: July 2010

Bermudagrass (Cynodon dactylon (L.) Pers.) has high potential summer forage production and can help fill the gap in foragebeef production systems during late summer. The productivity and quality of ‘Midland’ grown at four levels of N fertilization (0, 112, 224, 448 kg.ha) as forage systems for grazing beef steers were compared to those of common bermudagrass (C. dactylon var. dactylon) fertilized with 112 kg N/ha and of a mixture of orchardgrass (Dactylis glomerata L) and ladino clover (Trifolium repens L.) (Orc.‐Lad.). Pastures were grazed by a put‐and‐take system to maintain bermudagrass pastures at an average height ≥ 3.5 cm and ≤ 10 cm, and Orc.‐Lad. ≥ 8 cm and ≤ 15 cm. Forage growth and consumption were estimated by the cage‐and‐strip method.

Forage production and animal performance were different in all treatments for the two periods April through June (spring) and July through September (summer). Average length of grazing season (23 April to 12 September) was not affected by N fertilization. Bermudagrass production was similar in spring and summer, and was increased greatly by N in both periods. Forage production of Orc.‐Lad. was twice as large in spring as in summer. Average stocking rate ranged from 3.7 steers/ha on Midland‐0 to 9.9 on Midland448 in April through June, and from 2.7 steers/ha on 0rc.‐Lad. to 14.3 on Midland448 pastures in July through September. Animal grazing days/ha for the entire season ranged from 546 on Midland‐0 to 1,759 on Midland448 pastures.

Total beef production (kg/ha) was 162, 283, 350, 605, 308, and 561 from Midland‐0, ‐112, ‐224, ‐448, Common‐112, and Orc.‐Lad. pastures for the entire season, respectively. These values were associated with average gains (weighted for period within season) of 0.33, 0.41, 0.38, 0.44, 0.49, and 0.84 kg/steer/day and estimated forage dry matter intakes of 8.2, 8.9, 6.0, 5.7, 8.1, and 8.7 kg/steer/day, respectively. Most of the beef production occurred in spring. High stocking rates were necessary to harvest grazable forage and maintain grass in a young leafy stage in Midland224 and ‐448 pastures; thus, grazing selectivity was minimized and probably led to low intakes. Since 112 kg N/ha were not sufficient to produce acceptable quantities of forage or beef, a rate of 175 to 200 kg/ha on Midland is recommended for the future. At that N level, Midland will produce more than common which, at lower N levels, outproduced Midland.
Leaf Conductance and Leaf‐Water Potential Relationships for Two Soybean Cultivars Grown Under Controlled Irrigation1
Authors: Carlson R. E. , Momen N. N. , Arjmand O. , Shaw R. H.
Published: July 2010

Both leaf‐water potential and leaf conductance are used singly or in combination as important indicators of soil moisture stress. The relationship between these two parameters may not be unique between species or even within a species, depending upon environmental conditions.

These relationships were studied in soybeans [Glycine max (L.) Merr.] by growing plants in large potometers in the field under controlled soil moisture conditions. The potometers were previously filled with the top 15 cm of a Nicollet silt loam (Aquic Hapludolls, fine‐loamy mixed mesic). The plants were subjected to four independent drydown stress periods during critical reproductive stages of growth. Soil moisture was controlled by hand watering and the use of an automatic shelter, which covered the plots during periods of rainfall. Five levels of soil moisture were imposed during each of the four stress periods. Soil moisture was monitored with a neutron soil moisture probe, and leaf‐water potential was measured by using a pressure bomb. Leaf conductance data were collected using a diffusion porometer.

Leaf conductance was significantly correlated with leafwater potential over most days; however, a unique nonlinear relationship between these two parameters was not established. Atmospheric demand, time of day, and some type of moisture stress hardening contributed as significant sources of variation. Although not consistent over all days, these two cultivars were shown to differ significantly in their leaf‐water potential, leaf‐conductance relationships.
Plant‐Parasitic Nematode Effects on Water Use and Nutrient Uptake of a Small‐ and a Large‐rooted Tall Fescue Genotype1
Authors: Elkins C. B. , Haaland R. L. , Rodriguez‐Kabana R. , Hoveland C. S.
Published: July 2010

Plant‐parasitic nematodes often adversely affect tall fescue (Festuca arundinacea Schreb.) on sandy soils in the Southeast. Stand and yield reduction and damage to root systems by plant‐parasitic nematodes have been reported, but little is known about the effect of these nematodes on plant functions such as water use and nutrient uptake.

A controlled‐environment room experiment was conducted to determine the effect of plant‐parasitic nematodes on water use and nutrient uptake of two tall fescue genotypes with differing root systems, and to determine the feasibility of developing plants with root characteristics that would minimize the detrimental effects of nematodes. One of the genotypes (AF‐81) had many small‐diameter primary roots with a median diameter of 1.0 mm. The other genotype (AF‐7) had fewer and larger roots with a median diameter of 2.2 mm. The two genotypes were grown in Cahaba loamy sand topsoil (Typic Hapludult, fine‐loamy, siliceous, thermic) with and without a mixed population of plant‐parasitic nematodes. Measurements were made of root development, water use, forage yield, and Ca, Mg, and K content of the forage.

The small‐rooted genotype produced 30% more forage and was more efficient in water use than the large‐rooted genotype. Nematodes suppressed forage yield of the small‐ and large‐rooted genotypes by 9 and 50%, respectively, but had no effect on water use efficiency. Nematodes severely retarded root growth of the large‐rooted genotype, but had only a moderate effect on root growth of the small‐rooted genotype. The large‐rooted genotype supported twice the population of lance nematodes (Hoplolaimus galeatus [Cobb] Sher.) as did the small‐rooted genotype. Nematodes reduced forage Mg content of both genotypes to levels that could cause tetany in ruminants. Root size may be important in determining the effect of plant‐parasitic nematodes on plant performance and should be considered by plant breeders in developing nematode‐tolerant cultivars.
Nitrogen, Phosphorus, and Potassium Effects on Quality and Growth of Kentucky Bluegrass and Creeping Bentgrass1
Authors: Christians N. E. , Martin D. P. , Wilkinson J. F.
Published: July 2010

Much of the previous work involving the effects of N, P, and K on the growth and quality of turfgrasses has not involved methods by which the interactions among these nutrients, could be evaluated.

In the present investigation, a double cube, composite, statistical design was used to investigate the N, P, and K requirements of Kentucky bluegrass (Poa pratensis L. ‘Merion’) and creeping bentgrass (Agrostis palustris Huds., ‘Penncross’) under controlled environmental conditions in sand culture. Nitrogen treatments ranged from 6 to 294 ppm, P from 2 to 98 ppm, and K from 4 to 196 ppm in solution. The objectives of the investigation were to study the effects of a wide range of N, P, and K levels on turfgrass growth and quality, and to observe the nutrient interactions.

Quadratic relationships for dry tissue production of Merion in response to increasing levels of N and K were observed. Tissue production reached a maximum at 125 pprn N and 144 ppm K. Dry tissue production of Penncross in response to N was also quadratic, with a maximum at 96 ppm. Tissue dry weight increased linearly with K to the 196 ppm level. The most desirable quality characteristics for Merion occurred at the N concentration of 96 ppm, and a P concentration of less than 2 ppm. Maximum response to K was not reached at the 196 ppm treatment. Penncross attained these characteristics at a N concentration of 54 ppm and less than 2 ppm P. Again, maximum quality had not been reached at a K level of 196 ppm. Potassium may play a more important role in turfgrass fertilization than was previously realized. Penncross demonstrated maximum root production at a solution concentration of 6 ppm N and 196 ppm K. Minimum production of roots occurred at 150 ppm N and 64 ppm K. An interaction between N and K in solution was observed in the quality response of creeping bentgrass. As the level of K was increased, less N was required to attain maximum quality. It is possible that addition of higher levels of K to this species can affect its requirements for N. Additional work under field conditions will be required to evaluate the importance of this interaction.
Fescue Forage Production and Quality Response to Sequential Nitrogen Applications1
Authors: Smith A. E. , Calvert G. V.
Published: July 2010

There is a lack of formation concerning the influence of sequential applications of similar nitrogen rates on tall fescue (Festuca arundinacea Schreb. ‘Ky 31’) forage production. The purpose of this study was to determine the influence of the application of 240 kg ha−1 N, in differing annual sequences, on forage production and quality. In general, forage production was highest in plots receiving high (> 120 kg/ha) N rates just prior to the spring (April–May) and/or fall (August and September) periods of growth. Total annual production was highest (9,645 kg ha−1) in plots receiving 240 kg ha−1 N as a single application in March. Plots receiving single N applications in September and November and semiannual N applications in July and January produced in excess of 8,000 kg ha−1 forage. The IVDMD varied only six percentage units for all treatments, was highest in plots promoting highest production during March and October, and was lowest in forage from the check plots (receiving no N). Frequent applications of N increased forage production during June and August when compared to total annual application of N in March. High N rates applied in July allowed for increased vegetation composition of invaders in plot areas and the highest IVDMD.
Response of Alfalfa and Sorghum to Lime and P on Highly Weathered Soils1
Authors: Sumner M. E.
Published: July 2010

On highly weathered soils, crop response to low levels of lime is usually positive, corresponding to the neutralization of exchangeable Al and Mn, but response at high levels often becomes negative. Because the reasons for depressed yields when highly weathered soils are limed to near‐neutral pH values have not been adequately elucidated, two Oxisols (Typic, Umbriorthox) having similar properties but responding differently to lime were used to further probe the mechanisms involved. Alfalfa (Medicago sativa L.) and sorghum (Sorghum sudanense) were used as test crops in greenhouse experiments in which the levels of P and lime were varied. The depressive effect of high rates of lime appears to be linked with the presence of toxic levels of exchangeable Al before liming. Although this depressive effect can be overcome by the application of large quantities of P, it is not proposed that the effect is due primarily to exchangeable Al. Rather the level of exchangeable A1 at a given pH reflects the reactivity of the aluminous surfaces which, in turn, govern the solubility of P.
Growth Rates of Turfgrasses Propagated Vegetatively1
Authors: Busey Philip , Myers Barbara J.
Published: July 2010

Vegetative propagation is valuable as a cultural method in commercial sod production and as a tool in turfgrass research. Experiments were performed in the greenhouse and in the field in order to describe and compare growth rates in vegetative propagation of seven warm season turfgrasses. Daily growth rates were calculated as the logarithm of the quotient final/initial fresh weights, divided by the number of days between planting and harvest. By means of this criterion an elemental biological concept was demonstrated as a measure of rapidity of vegetative propagation and as a predictor of sod production time. The soil medium for most experiments was a Hallandale fine sand, a siliceous, hyperthermic, Typic Psammaquent. Maximum growth rates of turfgrass species ranged from l.8% per day for centipedegrass [Eremochloa ophiuroides (Munro) Hack.] to 9.2% for common bermudagrass [Cynodon dactylon (L.) Pers.]. These rates were larger than growth rates in commercial sod production, that were estimated to be no more than 2.6% per day. Duration of growth periods may explain the disparity between theoretical and observed growth rates. Growth periods of as long as two years are used in commercial sod production; much shorter intervals were used in our studies. A comparison of growth rates for various durations of growth periods suggested that for zoysiagrass (Zoysia japonica Steud.) and St. Augustinegrass (Stenotaphrum secundatum [Walt.] Kuntze) growth was not strictly exponential, but was sigmoidal. The levelling off of growth rates as turfgrasses become larger, or more densely sodded, may be explained by self‐inhibition through crowding. It appears possible to use frequent divisions to rapidly propagate warm season turfgrasses far initial increase of foundation blocks and experimental plantings. This and other cultural practices may be applied to improving the efficiency of commercial sod production. We propose the use of growth rate analysis as a method for describing and comparing cultural practices. Dry weight is preferred as the growth criterion, in contrast to fresh weight, coverage, or possibly other parameters. This simple model may be a powerful tool, as well, for testing genotypic response to pests and environmental stresses.
Forage Quality of Prostrate Kochia Compared with Three Browse Species1
Authors: Davis A. M.
Published: July 2010

Prostrate kochia [Kochia prostrata (L.) Schrad.], a shrub native to Asia, has received considerable attention because of its adaptation as a browse plant on western ranges. Prostrate kochia is a member of the Chenopodiaceae, the same family to which halogeton [Halogeton glomeratus (Bieb.) C. A. Mey.] and greasewood [Sarcobatus vermiculatus (Hook.) Torr.] belong. Both of these accumulate oxalates and can be toxic, depending on environmental conditions.

This report presents data comparing crude protein, crude fiber, beta carotene, tannins, and oxalates of 13 prostrate kochia introductions to winterfat [Ceratoides lanata( Pursh.) J. T. Howell], an Iranian saltbush (Atriplex verrucifera Bieb.), and fourwing saltbush [Atriplex canescens (Pursh.) Nutt.], a favored browse plant native to the western range, during the browse utilization season of August to March.

Two‐month‐old seedlings were transplanted to the field at Central Ferry, Wash. in early April. The soil was a Snake River bar alluvial classified as “Spofford” silt loam “fine‐silty, mixed, mesic typic Natrixerolls” with a pH of 6.7. Harvests were made at the end of the second and third growing seasons.

Crude protein exhibited a regular downward trend from 14.7% to 8.9% in prostrate kochia, while fourwing saltbush varied from 13.60%, to 11.40%, and winterfat from 16.8% to 10.1%. Crude fiber increased from 19% to 42% in prostrate kochia. There was little change in fourwing saltbush and winterfat (14.6% to 17.8% and 30% to 33%, respectively). The highest tannin value was 7.0 mg/g in prostrate kochia, well below the critical level of 25 mg/g reported by E. D. Donnelly and W. B. Anthony in 1969. Oxalates averaged 1.20% in prostrate kochia, 1.75% in fourwing saltbush and 1.55% in winterfat. Using the 45 g critical level for sheep reported by H. L. Morton and coworkers in 1959, it would require daily consumption in excess of 2.25 kg of 2% oxalate forage before oxalates would be toxic. In August the carotene levels were comparable, but fourwing saltbush and winterfat were clearly superior during the winter months. Carotene levels dropped from 42 mg/100 g to 6.9 mg/100 g in January in prostrate kochia, but increased to 11 mg/100 g in March due to early bud development. The average of fourwing saltbush was 50 mg/100 g in August and 13 mg/100 g in March. Winterfat contained 50.5 mg/100 g in August, dropped to 19.6 mg/100 g in January, and climbed to 30.4 mg/100 g in March.
An Analysis of N Nutrition on Yield and Yield Components for the Improvement of Rice Fertilization in Korea
Authors: Vlek P. L. G. , Hong C. W. , Youngdahl L. J.
Published: July 2010

The statistical procedure of path coefficient analysis was applied to five field experiments conducted in Korea to help set criteria for the development of new controlled‐release fertilizers and fertilizer management practices tailored to flooded rice. The yield components which are most sensitive to N nutrition and the growth stages when N uptake is most efficiently translated into yield component development were identified.

The experiments were conducted over a period of 2 years using two varieties of rice (Oryza sativa L., var. Tongil and Jinheung), two water management regimes (continuous and intermittent flooding), and three fertilizer sources (regular urea and two sulfur‐coated ureas) applied at four or five different levels of N. Continuously flooded experiments were conducted on an Aquic‐Fluventic Eutrochrept and the intermittently flooded on an Aquic‐Udipsamment. Yield response to N and apparent fertilizer N recovery varied with N source, rate, and variety, but in an inconsistent pattern. Close examination of yield component development as a function of N uptake revealed that variations in yield were mainly determined by panicle density and number of spikelets per panicle; the product of these components can serve as a potential yield index (PYI). The PYI is, to a large extent fixed by heading time and is closely related to the amount of N taken up between transplanting and heading. Path coefficient analysis was used to ascertain that N uptake during the period between 2 weeks after transplanting to maximum tillering most critically influenced PYI.
Effects of Broken Seed Coats on Field Emergence of Soybeans1
Authors: Luedders V. D. , Burris J. S.
Published: July 2010

Mechanical damage is a seed‐quality factor that may affect the worth of soybean [Glycine max (L.) Merr.] seed lots. Half soybean seeds (splits) can be sieved out of seed lots, but the relationship of splits, whole but damaged seed coats, and laboratory and field performance has not been investigated. Fifty uncleaned seed lots in each of 2 years were separated into clean seed, splits, small seed, and debris. The clean seed were tested for germination in sand and in rolled towels (RT) and also tested for emergence in four field environments. The percentage of seeds with broken seed coats was determined after imbibition for 15 min. Only data from seed lots with commercially acceptable germination (≥ 80%) were used. This reduced the sample sizes to 48 and 41 seed lots.

Average germination was higher in sand than in RT (92.4 vs. 86.8%). Average field emergence (60.6%) was lower than laboratory germination and greater from 5‐cm than 10‐cm planting depth (78.6 vs. 46.2%). Percentages of broken seed coats and abnormal seedlings were negatively correlated with germination and emergence and positively correlated with each other. Correlation coefficients between splits and broken seed coats were only 0.51 and 0.31. Percentage of broken seed coats could not be used predict relative field emergeability of the seed lots as well as did RT or sand germination. Results of the two germination tests and the four field environments were positively correlated with each other in both years. Coefficients for a multiple regression equation were obtained using laboratory tests and one field emergence and then used to predict the other seven field emergences. The prediction was somewhat better than using RT germination alone but slightly poorer than sand germination six out of seven times. Results from this and other published experiments indicate that the standard germination test may predict relative field emergeability as well as any vigor‐stress test or index.
Soybean Stand Establishment and Yield as Affected by Herbicides and Cultural Practices1
Authors: Johnson R. R. , Wax L. M.
Published: July 2010

When reduced soybean (Glycine max (L.) Merr.) stands occur, herbicides are often blamed for the problem. The object of this research was to determine if metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazin‐5 (4H)‐one] and/or vernolate (S‐propyl dipropylthiocarbamate) herbicides interact with other cultural variables to reduce stands and grain yield. Cultural variables researched in the field included soybean seed vigor, cultivar, planting depth, planting date, and surface versus incorporated herbicide application. In field experiments on a Typic Haploquoll soil herbicides were applied at slightly higher than recommended rates, and soybeans were seeded in 75‐cm row widths at a density of 350,000 seed/ha.

In all experiments visual symptoms of herbicide leaf damage occurred, but herbicide treatments had minor effects on stand establishment and grain yield. In contrast, several other variables significantly reduced stands and grain yields. Differences in seedbed condition created by different planting dates altered stand establishment. Seed lots low in seed vigor (as measured by cold test germination) resulted in reduced stands and in some situations reduced grain yields when compared with high vigor seed sources. Compared with a 1.9 cm planting depth, a 3.8 cm planting depth reduced stands in crusted seedbeds. In contrast, the shallow depth caused stand problems in a dry seedbed. Of the cultural variables affecting stand establishment and grain yield, none exhibited a significant interaction with herbicide treatment. In a greenhouse study, extremely high vernolate rates were more detrimental to emergence of low vigor than high vigor seed. Our data suggests that even when visual symptoms of herbicide injury occur, cultural variables such as seedbed conditions, seed quality, and minor differences in planting depth are often the major variables causing stand problems.
Tillage Effects on Biomass Production and Moisture Utilization by Soybeans on Coastal Plain Soils1
Authors: Kamprath E. J. , Cassel D. K. , Gross H. D. , Dibb D. W.
Published: July 2010

Many coarse‐textured surface soils in the southeastern Coastal Plain are prone to develop tillage pans which restrict root proliferation and moisture utilization in subsoils. The effect of tillage treatments on soybean [Glycine max (L.) Merr.] growth and soil moisture utilization was investigated on Norfolk sandy loam (Typic Paleudult) and Wagram loamy sand (Arenic Paleudult) soils. The three tillage treatments used were: conventional moldboard plowing and disking only before planting; or plowing and asking, followed by either chisel‐plowing; or subsoiling with bedding before planting. Measurements were made of top and root dry weight, leaf area, grain yield, soil water content and soil moisture tension.

Breaking the tillage pan by chisel‐plowing or subsoiling increased top growth and leaf area of soybeans at full bloom. The percentage of roots below 30 cm was increased by subsoiling and chisel‐plowing when rainfall was below normal during the growth period. A higher proportion of roots was in the top 10 cm of soil with conventional tillage than with chisel‐plowing or subsoiling. Chisel‐plowing and subsoiling increased the amount of soil moisture utilized below a depth of 30 cm. Grain yields were increased by chisel‐plowing or subsoiling in those years when rainfall was below normal during lateflowering and the beginning of pod development.

Subsoiling or chisel‐plowing of soils with compacted pans will increase soybean yields during years in which below‐average precipitation occurs during late‐flowering and the beginning of pod set. Yield increases are attributed to increased root proliferation below the pan and greater utilization of subsoil moisture.
Calcium Leaching to Increase Rooting Depth in a Brazilian Savannah Oxisol1
Authors: Ritchey K. Dale , Souza Djalma M. G. , Lobato Edson , Correa Osni
Published: July 2010

Root growth in subsoils of Oxisols is often precluded because the roots of many crops are sensitive to soil acidity. This increases plant stress during dry periods when available soil water in the limed surface layers is exhausted. The low soil CEC and high rainfall in Central Brazil suggest that soluble calcium salts might leach below the plow layer and reduce soil acidity. To test this possibility, soil columns, simulating field profiles, were constructed in the laboratory and various Ca salts were mixed in the 0 to 15‐cm layer. Addition of 1,200 mm water to 2,000 kg/ha Ca added as CaCl2, CaSO4, and CaCO8 caused Ca movement to 180, 75, and 25 an, respectively. Calcium sulfate decreased Al saturation and increased soil pH at depth.

Several field experiments were sampled to determine the effect of previous treatments on the movement of Ca + Mg. Three to four years after application of gypsum, in ordinary superphosphate, subsoil pH and Ca + Mg status were increased, and Al saturation decreased at depths as great as 75 to 90 cm. Zea mays L. roots growing in the improved subsoil environment were able to take up water and withstand droughts.
Increased Flowering and Yield from a Bromegrass‐Timothy Meadow by Timing of Nitrogen1
Authors: Rumburg C. B. , Ludwick A. E. , Siemer E. G.
Published: July 2010

Fall application of fertilizer to irrigated meadows in the mountain and intermountain region has both utility and agronomic advantages as compared to spring applications. The objectives of these experiments was to compare the efficacy or fall and spring applied N to determine why fall applications on a bromegrass (Bromus inermis Leyss.)‐timothy (Phleum pratense L.) meadow produced higher yields and more abundant flowering of bromegrass than spring applications. Fertilizer was broadcast on the surface of small plots in either spring of fall. Yields were sampled with a sickle‐bar mower at haying stage, or at regular intervals throughout the season to estimate uninterrupted growth rates. Small plots were clipped by hand to estimate number of shoots, relative species abundance, and flowering culms. Fall fertilization with N stimulated very early, spring growth of bromegrass, which slightly preceded spring fertilization, increased relative abundance of bromegrass inflorescence, and increased dry matter yields by 15% when harvested at customary haying time. A subsequent, more detailed experiment revealed no visible evidence of floral initiation in either bromegrass or timothy in the fall, and fall fertilization had no stimulating effect on early spring growth of timothy. Unfertilized timothy produced a relative abundance of 3% reproductive culms while both spring and fall‐fertilized plots had 33% on 22 July. Relative abundance of bromegrass reproductive culms was 2% from unfertilized and spring‐fertilized plots and 25% from fall‐fertilized lots. Nitrogen fertilization increased the total number of shoots of both bromegrass and timothy, but fall applications favored bromegrass to the detriment of numbers of timothy shoots. Dry matter accumulation rates from spring and fall‐fertilized plots were nearly identical (155 kg/ha/day). Increased bromegrass inflorescences resulting from fall fertilization with N has clear implications for increasing seed yield from bromegrass. The applicability of this practice to different environments is not clear. We recommend fall applications of N to bromegrass (compared to spring applications) for dry matter production under arid conditions because fall applications will assure N is readily available to the plant when temperatures are suitable for growth. Fall‐applied N advanced the growing season by about 8 days or (1,200 kg/ha) compared to spring‐applied N. This practice will likely be detrimental to timothy in mixed bromegrass‐timothy stands.
Light Penetration in a Row‐Crop with Random Plant Spacing1
Authors: Mann Jerry E. , Curry Guy L. , DeMichele D. W. , Baker Donald N.
Published: July 2010

The quantity of solar radiation penetrating a crop canopy and reaching the soil surface affects greatly the microenvironment beneath the canopy. The influence of this microenvironment upon soil radiation and evaporation as well as upon development and mortality rates of insect plant pests is well known. The development of adequate models of light penetration is an important problem associated with the characterization of the subcanopy microenvironment.

In this paper, an analytical model is proposed which estimates the sunlit soil area within a row crop where plants are randomly spaced along rows. Only direct beam, parallel light is considered. The model combines both individual plant geometry and row structure. for simplicity, plant canopies are assumed to be ellipsoidal in shape. The model incorporates plant sizes, row spacings and azimuthal orientation, foliage density, planting density, leaf orientation, and solar location. Available experimental data are inadequate for a complete validation of the model; however, a relative verification was made by comparing model output to real experimental measurements. Included in the paper is a critique of available data in light of the data requirements necessary for satisfactory model validation.
Physical Characteristics of Thatch as a Turfgrass Growing Medium1
Authors: Hurto K. A. , Turgeon A. J. , Spomer L. A.
Published: July 2010

Where a substantial thatch layer exists, new roots and stem growth from plant crowns occurs, at least initially, within the thatch. In some turfs, very little rooting may occur in the soil underlying the thatch. Therefore, under these conditions it appears that the thatch serves a greater role as a plant‐holding matrix and a growth medium while the soil's role decreases. The objective of this study was to determine the bulk density, total porosity, moisture characteristics, and organic matter contents of thatch and surface soils of thatched and thatch‐free Kentucky bluegrass (Poa pratensis L.) sites.

The evaluation methods included: 1) the core method for measuring bulk density; 2) air pycnometric determination of total porosity; 3) a modified pressure plate procedure utilizing Tempe cells for determining moisture extraction curves; and 4) organic matter content on the basis of weight loss upon ignition. Bulk density of thatch was significantly lower than soil, but varied between thatch samples depending on the amount of soil within the thatch. Total porosity of thatch samples was not significantly different, but was greater than soil porosity. Moisture retention of thatch at low water potentials was less than the surface soil from thatch‐free sites, indicating that most of these pores are macro‐size pores. This study suggests that cultural practices, such as irrigation, may need to be modified to sustain aesthetic turf where thatch is a predominant component of the edaphic environment.
Flag Leaf and Peduncle Area Duration in Relation to Winter Wheat Grain Yield1
Authors: Mohiuddin S. H. , Croy L. I.
Published: July 2010

Information on the photosynthetic area duration in winter wheat (Triticum aestivum L. em Thell.) is important in breeding programs for yield advancement and large numbers of data must be taken for the data to be meaningful. A 2‐year field study (1973 and 1974) was conducted at the Agricultural Experiment Station, Oklahoma State Univ., Stillwater, Okla. It was conducted to obtain information on flag leaf and peduncle area duration as selection indexes in relation to yield, tiller number, kernels/spike, and kernel weight in winter wheat and to investigate the response of five winter wheat cultivars to selected N levels and seeding rates higher than presently used for grain production. A split‐split plot design with four replications was used for the study. Nitrogen levels comprised main plots, cultivars were sub‐plots, and seeding rates were sub‐sub plots. The levels of N were 67, 134, and 202 kg N/ha, and the seeding rates were 67, 100, and 134 kg/ha. The five hard red winter wheat cultivars were ‘Tam W 101,’ ‘Palo Duro,’ ‘Danne,’ ‘Centurk,’ and ‘Caprock.’

All the traits measured differed between the two crop seasons, and a significant year by cultivar interaction suggested the presence of genotype by environment interaction. Differences among N levels were not significant probably because of the high residual amounts of available nitrogen at the experimental site, the lowest level of applied N was adequate for crop growth. The highest seeding rate (134 kg/ha) reduced grain yield, kernels per spike, and flag leaf area duration. Even though the growing conditions differed between the 2 years of the study, peduncle area duration and flag leaf area duration showed a positive correlation with grain yield, kernel weight, and a negative relationship with kernels per spike. These data suggested the use of peduncle area duration and/or flag leaf area duration as selection criteria in breeding for increased grain yield potential. These readings would be more rapid than total leaf area duration; and using selected photosynthetic leaf area indexes in a breeding program for yield, data could be obtained on many more genotypes. The data also support the use of kernel weight as a selection factor for increasing grain yield.
Drought Adaptation of Cowpea. I. Influence of Drought on Seed Yield1
Authors: Turk Kenneth J. , Hall Anthony E. , Asbell C. W.
Published: July 2010

Field studies were conducted to determine cowpea [Vigna unguiculata (L.) Walp.] response to different intensities of drought at different stages of growth to guide programs for the development of improved cultivars and improved management practices for semi‐arid zones.

Two cowpea cultivars were subjected to different levels of irrigation using a line‐source sprinkler system in the field on a coarse‐loamy, mixed, thermic Haplic Durixeralf soil during 2 years with contrasting weather patterns. Well‐watered plants were irrigated weekly. In other treatments, water was not supplied during either the vegetative, flowering, or pod filling stages.

Dry seed yields of well‐watered treatments were negatively correlated with degree days above 35 C during flowering.

Yields of both cultivars were not reduced by drought during the vegetative stage, compared with the weekly irrigated treatment, providing subsequent environmental conditions were conducive to rapid recovery of growth and efficient pod set. Drought during the flowering stage substantially reduced yields, but partial yield recovery was observed where drought caused all flowers to abscise and the subsequent environment, after irrigation was resumed, permitted a new flush of flowers to produce pods. Drought during pod filling substantially reduced yields of both cultivars in both years.

Variations in yield due to environmental stresses were mainly due to variations in number of pods/m2 except for drought during pod filling which resulted in both low pod density and small seed. Yield with abundant water or drought during pod filling appeared to be partially source limited, whereas intermediate levels of drought at other stages may have resulted in sink limitations on yield because these treatments produced the heaviest seed.