bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro Digestibility, Crude Protein, and Phosphorus Content of Straw of Winter Wheat, Spring Wheat, Barley, and Oat Cultivars in Eastern Montana1
Authors: White Larry M. , Hartman Glenn P. , Bergman Jerald W.
Published: July 2010

Straw from small grains could be an important source of feed for maintenance of ruminants if its nutritive quality could be improved. This study was conducted to determine any differences in straw digestibility among and between cultivars of winter and spring wheats (Triticum aestivum L. var. aestivum, and T. turgidum L. var. durum), barley (Hordeum vulgare L.), and oats (Avena sativa L.) grown in eastern Montana. In vitro dry matter digestibility, crude protein, and P content of straw were measured on 8 to 25 cultivars of each crop for 2 years. Heading date, plant height, lodging severity, and grain yield were also determined to detect whether selecting for higher straw digestibility would adversely affect these important traits for grain production. The average in vitro digestibility of straw of winter wheat, spring wheat, barley, and oats was 36, 36, 40, and 45% the first year, and 40, 42, 47, and 45%,, respectively, the second year. Differences in straw digestibility were greater among cultivars within a crop than between crops. Straw digestibility of winter wheat, spring wheat, and barley cultivars differed by 9 and 14 percentage units, depending on crop and year. Straw of oat cultivars differed by 8 percentage units the first year but only 4 percentage units the second year. Differences in straw digestibility among crop cultivars was as great as some researchers have achieved by chemically treating the straw to improve its digestibility. Cultivars with higher straw digestibility did not have higher lodging or lower grain yield. Neither was straw digestibility consistently associated with heading date, plant height, crude protein, or P content. The first year, the average crude protein of winter wheat, spring wheat, barley, and oat straw was 2.5, 2.7, 4.4, and 3.3%, respectively; the second year, it was 2.5, 4.0, 5.9, and 5.8%, respectively. The first year, the average P content of winter wheat, spring wheat, barley, and oat straw was 0.02, 0.06, 0.15, and 0.07%, respectively; the second year, it was 0.05, 0.05, 0.09, and 0.06%, respectively.
Germination‐Temperature Profiles for Idaho and Sheep Fescue and Canby Bluegrass1
Authors: Young J. A. , Evans R. A. , Eckert R. E. , Ensign R. D.
Published: July 2010

Sheep fescue (Festuca ovina L.), Idaho fescue (F. idahoensis Elmer), and Canby bluegrass [Poa canbyi (Scribn.) Piper] are valuable forage species native on western rangelands. The success of artificial or natural revegetation of degraded or disturbed rangeland with these native species is partially dependent on understanding their germination and seedbed ecology. Germination tests were conducted at 55 regimes of constant and alternating temperatures. Constant temperatures were at 0, 2, and 5 C degree increments from 5 through 40 C. Alternating temperature regimes consisted of 16 hours in 24 at each constant temperature and 8 hours in 24 at each higher constant temperature. The germination from these 55 temperature profiles was used to construct quadratic response surfaces giving estimated percent germination with confidence intervals for each seed source tested. A series of germination profile characteristics was generated from these response surfaces to help interpret the germination response of the seeds to temperature. There were significant (P=0.01) differences in mean germination among the seed sources tested. ‘Covar’ sheep fescue had the highest mean germination, with most of the Idaho fescue sources intermediate and ‘Canbar’ Canby bluegrass lowest in germination. Covar sheep fescue was the only source tested that germinated above 76% at many temperature regimes. Most of the sources tested had maximum germination in the 51 to 75% range. Optimum germination, defined as that not lower than the maximum and its confidence interval (P=0.01), occurred around 15/20 C (15 C for 16 hours and 20 C for 8 hours) for the Idaho fescue sources but extended to lower temperatures for Covar sheep fescue and Canbar Canby bluegrass. Synthetic varieties of Idaho fescue had higher germination at warmer and more widely fluctuating temperatures than the other two species. In relation to seedbed temperatures monitored in field studies, Covar sheep fescue had the highest germination at moderate and colder‐than‐moderate seedbed temperatures. The synthetic varieties of Idaho fescue had the highest germination at warmer‐than‐moderate seedbed temperatures.
The Influence of Available Nitrate Levels on Nitrogen Fixation in Three Cultivars of Cowpea1
Authors: Miller J. C. , Scott J. S. , Zary K. W. , O'Hair S. K.
Published: July 2010

Soil N is known to affect N2 fixation in legumes. Increased cowpea yields might be achieved by increasing N assimilation through greater symbiotic fixation, but identification of high‐fixing genotypes requires an effective screening technique. The purpose of this investigation was to determine the optimum level of supplemental N for maximum N2 fixation in cowpeas grown under greenhouse and field conditions, and the relative contributions of the measured variables on nitrogenase activity.

Three cowpea cultivars were tested for N2 fixation, N2 (C2H2), under greenhouse conditions with 0, 5, 10, and 20 ppm N applied as Ca(NO3)2, and under field conditions with 0, 11.2, 22.4, and 44.8 kg/ha N applied as Ca(NO3)2. The soil was Vertic Albaqualf, fine, Montmorillonitic thermic. Nitrogenase activity decreased with increasing rates of N. Path analysis indicated that nitrate effects on N2 fixation activity were primarily on nodule mass, with the inhibition of nodule growth rather than nodule initiation. Nodule number was not a reliable predictor of N2 fixation potential of cowpea genotypes and was negatively correlated with nitrogenase activity. The results clearly indicated no advantage of applied nitrate in promoting maximum genotypic differences for N2 fixation.
Soil Clay Mineralogies in Relation to Fertility Management: Effect of Clay Mineral Types on Ammonium Fixation under Conditions of Wetland Rice Culture1
Authors: Bajwa M. I.
Published: July 2010

To assess the influence of soil clay mineralogy on the efficiency of normally used nitrogeneous fertilizers on soils under wetland rice (Oryza sativa L.) culture, ammonium fixation studies were carried out under hydromorphic conditions on 14 soil clays with a range of mineralogical compositions. Beidellitic and vermiculitic clays fixed more than 90% of the applied ammonium, while montmorillonitic clay fixed about 50%. Clays of all other mineralogical compositions, containing chlorite, hydrous mica, halloysite, kaolinite, and amorphous material did not fix significant amounts of ammonium. There is a need to develop management practices for soils of beidellitic and vermiculitic clay mineralogies to increase efficiency of ammonium (or ammonium‐forming) fertilizers on them through minimizing fixation.
Early Induction of Floweing in Sugarbeets1
Authors: Hogaboam G. J.
Published: July 2010

Sugarbeets (Beta vulgaris L.) are biennial and under natural conditions flower during the 2nd year of growth. Early induction of flowering and maturation of seeds under controlled conditions could accelerate sugarbeet improvement through breeding. Several cultivars were grown in controlled environment chambers starting at various ages. Floral stalks developed after as little as 30 days growth from seed in a particular growth chamber (No. 3) with a 14/10 hr, 22/14 C light‐dark temperature regime. Plants in other chambers with the same light and temperature program did not respond as early. Floral induction in seedlings was also achieved in a continuously lighted growth chamber. Not all sugarbeet lines gave the early reproductive response. The response was earlier and more complete with young, rapidly growing plants. Plants that had been started 59 days before being placed in Chamber 3 did not give a reproductive response. An annual line of sugarbeets did not flower as early or completely as some of the biennial lines in Chamber 3. Further research is needed to define the conditions required for reliable control of sugarbeet floral induction in growth chambers. Rapid floral induction will permit up to five generations a year instead of the two‐generation advances presently feasible.
Cotton Cultivar Response to Plant Populations in a Short‐Season, Narrow‐Row Cultural System1
Authors: Mohamad Khalid Bin , Sappenfield W. P. , Poehlman J. M.
Published: July 2010

The need for reducing time of crop exposure to pests has given emphasis to cultural changes in row widths and plant densities for upland cotton, Gossypium hirsutum L., and this has challenged available cultivars to avoid losses in yield and fiber quality. Four genotypes, HYC72‐234/320 (very early), ‘Auburn M’ (early), MO63‐277 BR (medium early), and ‘Stoneville 213’ (medium early to full‐season) were drilled and hill‐drop seeded in rows 51 cm apart on beds 203 cm wide on Tiptonville silt loam (fine silty‐mixed‐thermic typic argiudolls). Four planting methods and rates were used to establish the average within‐row plant populations of one, five, and nine plants per 31 cm of row. Eleven agronomic characteristics of upland cotton were measured in relation to the four within‐row populations.

Lint yields, combining genotypes, were significantly reduced by 90–131 kg/ha in stands of nine or more plants compared with stands of one and five plants in 31 cm of row. The percent of barren plants increased and the numbers of open bolls for four rows 1 m long prior to harvest decreased as number of plants per 31 cm of row increased. The lint yields of Auburn M and HYC72‐234/320, early and determinate cultivars, were not influenced significantly by the within‐row plant densities. Stoneville 213, a full‐season indeterminate cultivar, produced significantly lower yields when within‐row plant population was highest.

Only minor differences were noted in lint fraction, seed size, boll size, and fiber properties due to the various within‐row plant densities.

Our findings suggest that cultivar fruiting efficiency potential and within‐row plant population should be considered when planting dates are delayed or row‐widths modified for cotton culture in the northern extremes of the Mississippi Delta.
Response of Tomatoes to N and Water Applied Via a Trickle Irrigation System. II. Water1
Authors: Bar‐Yosef B. , Sagiv B.
Published: July 2010

The objective of the study was to relate tomato fruit yield and N uptake to water application rates via a trickle irrigation system at given N rates and to total water potential in the soil root volume. This information is needed to improve tomato cropping management under point source irrigation. The experiments were conducted on sandy soils at three different locations in Israel and included combinations of several daily N and water application rates, and two irrigation intervals. Fruit yield responded linearity to increasing total irrigation rates (Qw) up to 80% of the accumulated evaporation from a U.S. Class A pan (Ep), the slope of the response line being 15 metric tons/ha for each 10% change in Qw/Ep. The optimum average N concentration in the irrigation solution was determined to be 130 ppm N, below which yields and growth were inhibited and above which the soil water potential Ψ decreased, thus increasing the dry matter content of the fruit. A decrease in Ψ from −50 to −150 centibars appreciably decreased fresh fruit yield; a further decrease in Ψ caused a slower decrease in fresh fruit yield.
Soybean Germplasm and Cultivar Aluminum Tolerance in Nutrient Solution and Bladen Clay Loam Soil1
Authors: Sapra V. T. , Mebrahtu T. , Mugwira L. M.
Published: July 2010

High Al in acid subsoils of the Southeastern States often restricts root growth and moisture utilization. Liming subsoil is difficult and expensive. An alternative or substantial approach is to select or breed plant genotypes having greater tolerance to Al. The differential Al tolerances of soybean [ Glycine max(L.) Merr.] representing Maturity Groups V, VI, and VII were determined in a growth chamber using nutrient solutions containing 0 and 8 ppm Al. Screening was also done on acid (4.2) and limed (5.8) in Bladen soil (Typic Albaquult) in the greenhouse. Aluminum sensitive ‘Chief’ and Al‐tolerant ‘Perry’ were included as standard checks.

Soybean plants injured by 8 ppm Al in nutrient solution were characterized by narrow leaf blades, leaf chlorosis, reduced plant height, stunted, blackish root tips. In unlimed soil the relative root dry weight seemed a better index of differential Al tolerance among cultivars than top dry weight. Roots of the cv. Perry yielded 20% more dry weight than Chief in unlimed soil. Liming the soil to pH 5.8, increased the yields of sensitive cv. Chief by 40% compared to the unlimed soil. On the unlimed soil, plant symptoms such as cupping and chlorosis of young leaves were observed. The most tolerant and sensitive lines tested were; PI 81042 (V), PI 159322 (VI), Missoy (VII), and PI 88490 (V), PI 85010 Pocahontas, respectively.
Forage Yield and Quality of Indigenous and Introduced Grasses at Palmer, Alaska
Authors: Mitchell W. W.
Published: July 2010

‘Manchar’ bromegrass (Bromus inermis Leyss.) and ‘Engmo’ timothy (Phleum pratense L.) are the major forage grasses in Alaska. Other grasses have been insufficiently evaluated to determine their agronomic value at northern latitudes, and current developments portend agricultural growth into areas that may be relatively unfavorable to bromegrass and timothy.

Thirty‐six accessions in 15 species, many indigenous, were compared with Manchar and Engmo to obtain yield characteristics, to make forage quality determinations relative to feeding requirements, and to assess variability within certain species. The grasses were grown on silt loam soil (Typic Cryorthent), pH ca. 6.2, and harvested twice annually for 3 years. Concentrations of N, P, K, Ca, and Mg were determined for all entries and in vitro digestibility for selected entries from certain harvests.

Indigenous Bering hairgrass (Deschampsia beringensis Hulten) IAS 19 yielded the most herbage, averaging 9.8 metric tonsha over the 3 years, not differing significantly from the 9.2 metric tons/ha for Manchar. The hairgrass produced an exceptional 14.3 metric tons/ ha in the 1st year, but harvest‐pressure injury reduced subsequent yields. The native accessions of polargrass [Arctagrostis latifolia (R. Br.) Griseb], bluejoint reedgrass Calamagrostis canadensis (Michx.) Beauv.], red fescue (Festuca rubra L.), and Bering and tufted hairgrasses [Deschampsia caespitosa (L.) Beauv.], which are adapted to cool, acid locations, often produced more forage than Engmo timothy, generally used in more moist, acid situations in Alaska. Various introduced grasses yielded more than most native grasses on this mildly acid test site.

Engmo timothy herbage was notably high in digestibility, otherwise the forage cultivars demonstrated no advantage in quality over many indigenous entries. Crude protein generally exceeded 13% up to 20.3%. Magnesium and sometimes P tended to be limiting for animal performance, while other minerals were adequate. The first‐harvest herbage of polargrass contained consistently high amounts of the assayed elements.

The quality and yield characteristics within species varied enough to indicate their possible improvement through collection and selection programs. Hairgrass, polargrass, bluejoint reedgrass, and red fescue are currently being evaluated in more comprehensive studies.
Celery Response to Type, Amount, and Method of N‐Fertilizer Application under Drip Irrigation1
Authors: Feigin A. , Letey J. , Jarrell W. M.
Published: July 2010

Optimizing N‐fertilization is important from both economical and environmental quality points of view. An experiment was conducted to evaluate celery (Apium graveolens L.) response to type, amount, and method of N‐fertilizer application under drip irrigation. The study was conducted on San Emigdio sandy loam (coarse‐loamy, mixed, thermic Typic Xerofluvent). Fertilizer types included ammonium sulphate (AS) and a slow release (SR) fertilizer applied to the soil before planting and urea ammonium nitrate (UAN) applied with the irrigation water during the growing season. Ammonium sulphate and SR were applied at 314 kg N/ha and UAN was applied at 168, 336, and 504 kg N/ha. Two irrigation variables were 400 and 500 mm of water application. Celery production tended to be higher under higher water application when fertilized with UAN but lower under high water application for AS and SR fertilizers. There was little difference between 336‐ and 504‐kg N/ha UAN treatments on most plant parameters throughout the growth period, but the 168‐kg N/ha UAN treatment was significantly lower than the higher application rates. Higher yields were obtained with 336 kg N/ha UAN than comparable AS and SR treatments. During early stages of growth the AS treatment tended to give the highest yield and N content but by harvest gave the lowest response. Results are explained on the basis of N availability and leaching over time.
The Influence of Wetting on the Composition of Alfalfa, Red Clover, and Birdsfoot Trefoil Hay1
Authors: Collins Michael
Published: July 2010

Field cured hay is subject to yield and quality loss due to leaching, mechanical loss, and respiration. The objective of this study was to measure changes in chemical composition and in vitro dry matter disappearance (IVDMD) of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and birdsfoot trefoil (Lotus corniculatus L.) in response to wetting during hay curing.

Treatments included: (1) a control collected 96 hours after clipping (96 hour), (2) wetted after 48 hours of drying and collected 48 hours later (wet 48 hour), and (3) wetted both 24 and 48 hours after clipping and collected 48 hours later. Separate samples of each species were collected and dried immediately after clipping. Each treatment was replicated five times. Plants were grown in Plano silt loam (fine‐silty, mixed, mesic Typic Argiudoll) soil. Samples were analyzed for leaf percentage, N, IVDMD, neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, total nonstructural carbohydrate (TNC), total sugars, starch, and reducing sugars.

Wetting twice reduced alfalfa leaf percentage from 54.0 to 45.6%. The same treatment increased N concentration in alfalfa and red clover by the equivalent of 2.7 and 2.9 percentage units of crude protein, respectively. Such an increase may be due to greater losses of other plant constituents. Wetting twice reduced TNC concentration by 34, 67, and 37% for alfalfa, red clover, and birdsfoot trefoil, respectively. Neutral detergent fiber concentration increased by 6.1, 10.8, and 9.8 percentage units by wetting twice compared with the unwetted control for alfalfa, red clover, and birdsfoot trefoil, respectively. The increase in forage NDF concentration due to wetting suggests that leaching might reduce the intake potential of the forage and thus reduce animal productivity. Wetting twice significantly reduced IVDMD of red clover and birdsfoot trefoil but not alfalfa. Results of this study indicate that quality losses due to wetting during hay curing are significant and that legume species differ in their response to wetting.
Quantitative Recovery by Alfalfa with Time of K Placed at Different Soil Depths for Two Soil Types1
Authors: Peterson L. A. , Smith Dale , Krueger Armand
Published: July 2010

Knowledge of the capacity of a root system of alfalfa (Medicago sativa L.) to absorb nutrients from the soil profile is needed to evaluate fertilizer practices. Also, with the extensive perennial root system and high K requirements, alfalfa and K provide a good combination to study root activity in soil with time. This study was initiated to determine nutrient uptake patterns of the alfalfa root system over several years. Quantitative measurements were made of K uptake by two alfalfa strains from different soil depths on a Plano silt loam (Typic Agriudoll) and a Plainfield loamy sand (Typic Udipsamment). One of the alfalfa strains was predominantly taprooted, while the other was predominantly branch‐rooted, especially in the surface‐soil areas. Experimental treatments included a check, a surface (S) K application, and placement of K at various profile depths. The surface (S) treatment was a broadcast application of K as KC1. An injection method was used to place a solution of K as KC1 at depths below the soil surface. Treatments were placement of K at one profile position per treatment (S, 7.5, 22.5, 37.5, 52.5, 67.5, and 82.5 cm) and at two profile positions per treatment (S/22.5, S/52.5, S/82.5,7.5/22.5, 7.5/52.5,7.5/82.5,22.5/52.5,22.5/82.5,37.5/52.5, and 37.5/82.5cm). Rate of K was 205 kg/ha/yr in the single‐placement treatments and 410 kg/ha/yr in the dual‐placement treatments. Treatment area was 1 M2. Three harvests of each individual plot‐area were made annually at first flower for 2 years on the Plano silt loam and for 3 years on the Plainfield loamy sand. The oven‐dried herbage was analyzed for yield and K concentration. First‐year recovery of added K by alfalfa for single‐placement treatments ranged from about 35% for the surface application to 15% at 82.5 cm. An increase in recovery of added K occurred in the 2nd year for the treatments down to 37.5 cm and remained relatively constant below 37.5 cm, indicating increased root activity in the soil surface and near surface layers with no further increase in activity below 37.5 cm in the 2nd year. This trend was apparent for the two alfalfa strains on both soil types. After 3 years on the loamy sand, 60% of the added K was recovered from the surface application to 25% at 82.5 cm. Quantitative similarity of K uptake from two single‐placement treatments to that for the same soil depths for a dual‐placement treatment indicated relatively uniform K uptake from each of the soil depths. These data show that alfalfa absorbed K most heavily from the surface soil area as compared to the Ap and deeper horizons. This K absorption pattern continued for 2 years on a silt loam soil and for 3 years on a loamy sand.
Acid Scarification and Protein Synthesis during Seed Germination1
Authors: McDonald Miller B. , Khan Anwar A.
Published: July 2010

Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker] seeds exhibit an intense seed coat dormancy which is relieved by acid scarification. This study examined the influence of exogenous hormonal compounds, gibberellin A3 (GA3) and abscisic acid (ABA) and acid scarification on the early protein synthesis of these seeds. Hormonal applications failed to alter 14C‐leucine incorporation or to change the levels of amino acid pool size or soluble protein during the first 72 hours of soaking of intact seeds. However, GA3 enhanced while ABA lowered the amino acid and soluble protein levels in scarified seeds. The incorporation of relatively large amounts of 14C‐leucine into proteins occurred at 24 hours after soaking in intact seeds while no increase was detected in scarified seeds until 48 hours, a period when germination had already occurred. Soluble proteins were reduced 60 % following acid scarification compared to intact seeds and seed exudates increased with increased scarification time. These results demonstrate a profound effect of acid scarification on the seed which is manifested by delayed protein synthesis, reduced protein level, and increased leaching of electrolytes.
Seeding Year Harvest Management of Alfalfa1
Authors: Sheaffer C. C.
Published: July 2010

Seeding alfalfa (Medicago sativa L.) without a companion crop and with herbicides to control weeds has become an accepted practice in the Midwest. However, harvest strategies which maximize seeding year alfalfa yield and quality have not been investigated. The objective of this research was to determine the effect of harvest schedules during the seeding year on total season yield, forage quality, and persistence of two alfalfa cultivars established without a companion crop on several spring dates. In irrigated field studies conducted on a Udic Haploborolls in north central and on a Typic Hapludoll in southeastern Minnesota, ‘Ramsey’ and ‘Saranac’ alfalfa were seeded on several spring dates in 3 years and subjected to harvest schedules with first cuttings 40,60, or 80 days following emergence. One to three additional harvests were made in the establishment year depending on location and seeding date. First harvest dry matter yields for the earliest planting dates were increased by delaying the time of first harvest. Total season dry matter and nutrient yields were greatest for a harvest schedule within the earliest seeding dates at each location. Delaying the first harvest from 40 to 80 days after emergence usually was more detrimental to total season nutrient yields for the later emergence dates. Total season crude protein and in vitro dry matter disappearance concentrations were consistently lower for harvest schedules with the initial harvest 80 compared to 40 days after emergence. Ramsey and Saranac alfalfa did not differ in their yield or quality responses to seeding date and harvest schedule variables. Seeding year dry matter and nutrient concentrations can be maximized by early seeding of alfalfa with an initial harvest 60 days after emergence (late bud to early flowering) followed by two or three harvests. Under conditions of high soil fertility, seedling alfalfa can tolerate three to four harvests (including fall harvest) without stand loss
Ammonia Volatilization from Fertilized Turfgrass Stands1
Authors: Torello W. A. , Wehner D. J. , Turgeon A. J.
Published: July 2010

Nitrogen applied to turfgrass stands can be lost through leaching, denitrification, or ammonia (NH3) volatilization. The purpose of this investigation was to evaluate the effects of N carrier and mode of application on NH3 volatilization from a Kentucky bluegrass (Poa pratensis L.) turf growing on an acidic (pH 6.4) Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil. The NH3 which volatilized after application of any of several sulfur‐coated ureas (SCU), prilled urea, spray‐applied solubilized urea, and two liquid N products was measured by passing the airstream from microecosystems, in which the treated turfs were growing, through an indicating boric acid solution to trap NH3. Ammonia‐N losses after sulfur‐coated urea fertilization ranged from 0.2% of the applied N when the fertilization rate was 98 kg N/ha to 2.3% of the applied N when the fertilization rate was 293 kg N/ha. When prilled urea was applied at a rate of 293 kg N/ha, NH3 losses averaged 10.3% of the applied N whereas 4.6 and 1.6% of the applied N was lost after turf was fertilized with 49 kg N/ha from spray‐applied solubilized urea and prilled urea, respectively. Ammonia losses from turf treated with liquid N sources ranged from 3.2 to 4.5% of the applied N. The results of this research indicate that ammonia volatilization occurs to a limited extent in turfgrass stands growing on an acidic soil.
Soybean Recovery from Plant Cutoff, Breakover, and Defoliation1
Authors: Fehr W. R. , Hicks D. R. , Hawkins S. E. , Ford J. H. , Nelson W. W.
Published: July 2010

The current procedure for assessment of hail injury to soybeans (Glycine max (L.) Merr.) assumes that plant cutoff, breakover, and defoliation cause equivalent percentages of yield loss. Our objective was to compare the yield response of soybeans to the three types of injury in field experiments. Plants were cut off at half height and defoliated below the cut, broken over at half height and defoliated below the break, or completely defoliated. The treatments were applied to 33, 66, or 100% of the plants at the V5, R2, R3, R4, and R5 stages of development at one location in Iowa and at the R2 to R5 stages at one location in Minnesota during 1981. Yield losses from the three types of injury were not the same. Removal of the top half of the main stem by the cut‐off treatment was generally more severe than breaking it over or removing the leaves, especially when 100% of the plants were treated at later stages of development. At V5 and R2, breakover tended to cause greater yield loss than defoliation; at R3, the two treatments were the same; and at R4 and R5, defoliation caused greater yield loss than breakover. Reduction in seed weight and changes in time of maturity were generally small, except when 100% of the plants were treated. The treatments did not cause changes in lodging scores of practical importance when brokenover plants were ignored. Small reductions in plant height were observed for breakover and defoliation, but substantial reductions were observed for cutoff. The three types of plant injury should be considered independently in assessing damage caused by hail.
Response of Cotton to Mepiquat Chloride with Varying N Rates and Plant Populations1
Authors: York A. C.
Published: July 2010

Excessive vegetative growth often limits any potential cotton (Gossypium hirsutum L.) yield increase to be expected from the use of higher N rates or plant populations. Mepiquat chloride (1,1‐dimethylpiperidinium chloride) is a plant growth regulator which suppresses vegetative growth in cotton. It has been speculated that higher N rates and plant populations could be used in combination with mepiquat chloride without fear of excessive vegetative growth. Experiments were conducted at eight locations during a 3‐year period to determine if the response of cotton to mepiquat chloride is affected by N rates or plant populations. Treatments consisted of three N rates, three or four plant populations on three soil types, and 0 or 49 g/ha of mepiquat chloride. Nitrogen rates were either 45, 78, and 112 kg/ha or 28, 62, and 95 kg/ha. Populations ranged from 37,000 to 235,000 plants/ha. Mepiquat chloride increased yields in four of the eight environments. The response of yield and most other agronomic properties to mepiquat chloride was usually unaffected by rates of applied N. This lack of response was found when rates of N were both below and above those necessary for optimum yield. Mepiquat chloride had no adverse effects when populations were below those necessary for optimum yield. However, the results indicated that mepiquat chloride may sometimes partially overcome the detrimental effects of above optimum populations when environmental conditions result in excessive vegetative growth and delayed maturity. In one environment with these conditions, mepiqnat chloride increased yields 10, 23, and 51 % at 37,000, 136,000, and 235,000 plants/ha, respectively. Highest yields were obtained with 37,000 plants/ha. Differential responses were observed for boll production, lint per boll, and lint percent, but most of the yield increase that resulted from the application of mepiquat chloride was due to a differential effect of the growth regulator on maturity with the varying populations. However, in all eight environments, mepiquat chloride did not alter the optimum N rate or plant population.
Soil Water and Population Influence on Hybrid Sunflower Yield and Uniformity of Stand1
Authors: Prunty Lyle
Published: July 2010

Sunflower (Helianthus annuus L.) hybrids do not respond identically to agronomic and environmental variables. The present study was conducted to quantify the influence of soil water potential and plant population on oilseed sunflower hybrids ‘Dahlgren 704’, ‘USDA 894’, and ‘Interstate 907’. Desire to refine knowledge of yield relationships was one motivation for the study, but a deeper stimulus was the need for basic knowledge of the detailed nature of sunflower stands. Hybrids were planted at four populations at two North Dakota sites in 1980. One site had Maddock (sandy, mixed Udorthentic Haploboroll) and Gardena (coarse‐silty, mixed pachic Udic Haploboroll) soils. This location received irrigation treatments limiting soil water potentials to minimums of ‐35, ‐70, and ‐105 J kg‐−1. The second site had Bearden (fine‐silty, frigid Aeric Calciaquoll) soil and was not irrigated. Yield increased with soil water potential from 201 g m−2 at – 105 J kg−11 to 284 g m−2 at ‐35 J kg−1. Dryland yields were 200, 179, and 164 g m−21 for hybrids 894,704, and 907. Population did not influence yields. However, irrigated and nonirrigated stand loss percentages increased with population at 0.8 and 2.2% per plant per square metre, respectively. Knowledge of the threshold population for stand loss provides a rationale for selection of population in the absence of yield differences because significant stand loss indicates a possibly undesirable level of intraspecific competition. Guidelines for irrigation scheduling for sunflower by use of tensiometers are now on a sounder experimental basis. Hybrids similar under irrigation yielded differently under dryland conditions.
Shrinkage of Soybean Roots1
Authors: Taylor H. M. , Willatt S. T.
Published: July 2010

It has been postulated that shrinkage and subsequent rehydration of roots growing in soil cause significant variations in root‐soil contact resistances to ion and water movements. The research reported here used neutron radiography to evaluate shrinkage of soybean (Glycine max L. Merr. cv. Bethel) roots growing in soil as hydrated plants became severely wilted. The first experiment evaluated the amount of shrinkage possible for soybean roots as their water potential decreased from 0 to −1.34 MPa. The roots were immersed in polyethylene glycol solutions (PEG 6000) of 0, −0.37, or −1.34 MPa. Root diameters were measured as functions of time and distance from the root tip. Under controlled temperature conditions, roots did not change diameter in the 0 MPa solution but shrank to 0.97 of the original diameter in 2 h when immersed in the −0.37 MPa PEG solution and to 0.7 when immersed in the −1.34 MPa solution for 2 h. The second experiment used neutron radiography to evaluate taproot diameter of three soybean plants located in an unclassified sandy loam soil as hydrated plants lost water and wilted severely. Reproducibility with time of diameter readings on each section of root in the neutron radiography technique was about ± 0.02 mm ( ± 2%) on these three plants. When three hydrated plants wilted severely but recovered overnight, their roots shrank less than 0.02 mm (2%). These results indicated that shrinkages of plant roots growing in moist soil probably cause negligible increases in root‐soil contact resistance. These results do not rule out the possibility that roots will shrink appreciably as the soil around them dries substantially.
Simple Simulation Models for Yield Prediction Applied to Alfalfa in the Northeast1
Authors: Fick Gary W.
Published: July 2010

The effect of model elaboration upon predictive accuracy has not been adequately studied for simulation models of crop production. A set of eight simple dynamic simulation models of alfalfa (Medicago sativaL.) production were formulated to determine the relative contribution of six factors to model accuracy. The six factors were production potential (maximum yields in each harvest), heat summation, nonlinear temperature effects, soil water budgets, regrowth potential (cutting management and root reserves), and a general soil production factor based on available soil water in the root zone at field capacity. The soils considered were a Glossoboric Hapludalf, an Aqueptic Fragiudalph, and a Dystric Eutrochrept. The factors were compared individually and in selected combinations by regressing field observations on model predictions. The field observations represented yields measured across three soils, 2 years, and three harvest managements in New York (n = 60). The best model included factors for production potential, heat summation, soil water holding capacity, and cutting management (r2= 0.758). Relatively simple soil water budgets contributed little to model accuracy beyond what was accounted for by a general ranking of soils by water holding capacity in the humid environments. Representing the four factors of production potential, heat summation, soil water holding capacity, and management in a simulation model appears to provide a simple basis for formulating base‐line models.
Sod‐Seeding of Ladino Clover and Alfalfa as Influenced by Seed Placement, Seeding Date, and Grass Suppression1
Authors: Mueller J. P. , Chamblee D. S.
Published: July 2010

The competition between a grass sward and a legume seedling limits legume growth when sod‐seeding legumes into perennial grass swards. The objective of this research was to evaluate the effects of time of seeding, grass suppression, and seed placement on the spring establishment of ladino clover (Trifolium repensL.) and alfalfa (Medicago sativaL.) in a tall fescue (Festuca arundinaceaSchreb.) sod. Field experiments were conducted during 4 years (1978 to 1981) on a Cecil clay loam soil (clayey, kaolinitic, thermic Typic Hapludult) in North Carolina. Seeds were drilled or placed on the soil surface with and without broadcast applied paraquat (1, 1'dimethyl‐ 4, 4′‐bipyridinium ion) at 0.28 kg a.i. ha−1on two dates (mid‐February or mid‐March) in a randomized complete block design with a 2 ✕ 2 ✕ 2 factorial arrangement. Legume stands and dry matter yields were measured. Drilling legume seeds vs. surface placement resulted in two to four times as many seedlings initially established and up to 2000 kg ha−1more legume yield during the first season. Nevertheless, satisfactory stands were eventually obtained from surface seeding ladino in late February in 3 of 4 years. Planting in February resulted in better stands and yields of clover than March plantings in 3 of 4 years. Using paraquat for sod suppression often resulted in significant advantage when clover was seeded at the later (March) date. Alfalfa produced very low yields during the first season under all treatment variables (usually one or two harvests) and did not appear to compete well with the tall fescue sod when spring seeded. The highest yields obtained during these studies ranged from 795 to 4610 kg ha−1.
Estimating Silking and Maturity Dates of Corn for Large Areas1
Authors: Daughtry C. S. T. , Cochran J. C. , Hollinger S. E.
Published: July 2010

Knowledge of when critical crop stages occur and how the environment affects them should provide useful information for crop management decisions and crop production models. This research evaluated two sources of data for predicting dates of silking and physiological maturity of corn (Zea maysL.). Initial evaluations were conducted using data of an adapted corn hybrid grown on a Typic Agriaquoll at the Purdue University Agronomy Farm from 1979 to 1981. The second phase extended the analyses to large areas using data acquired by the Statistical Reporting Service of USDA for crop reporting districts (CRD) in Indiana and Iowa from 1969 to 1980. Several thermal models were compared to calendar days for predicting dates of silking and physiological maturity. Mixed models which used a combination of thermal units to predict silking and days after silking to predict physiological maturity were also evaluated. At the Agronomy Farm the models were calibrated and tested on the same data. For each CRD the models were calibrated using 4 or 5 years of data and tested using 7 different years of data. The thermal models were significantly less biased and more accurate than calendar days for predicting dates of silking. Differences among the thermal models were small. Significant improvements in both bias and accuracy were observed when the mixed models were used to predict dates of physiological maturity. The results indicate that statistical data for CRD can be used to evaluate models developed at agricultural experiment stations.
Crop Water Stress Index, Soil Water, and Rubber Yield Relations for the Guayule Plant1
Authors: Nakayama F. S. , Bucks D. A.
Published: July 2010

Canopy temperature measurements based on remote infrared thermometric techniques and atmospheric vapor pressure deficits from meteorological parameters were used for developing crop water stress indices (CWSI) for three varieties of the drought‐tolerant guayule plant (Parthenium argentatumA. Gray). Measurements were conducted on a coarse‐loamy, mixed, hyperthermic Typic Calciorthids soil. Six irrigation levels were used to obtain relations between plant stress and soil water content, and also rubber yield. The results of the initial phase of a long‐term experiment showed that the CWSI values were related negatively to the fraction of available soil water in the 0 to 1.8 m of soil depth. The CWSI of the 510‐day‐old perennial plant taken during the actively growing period could also be inversely related to the rubber yield.
Four‐Year Response of a Kentucky Bluegrass‐Red Fescue Turf to Plant Growth Retardants1
Authors: Dernoeden Peter H.
Published: July 2010

Most research on plant growth retardants (PGR's) for turfgrasses has involved single and occasionally two annual PGR applications. The objectives of this study, however, were to evaluate longer term effects of PGR usage on turf density, quality, and canopy height by applying various rates of ethephon [(2‐chloroethyl) phosphonic acid], flurprimidol {α‐(1‐methylethyl‐α‐[4‐(trifluroro‐methoxy) phenyl]‐5‐pyrimidinemethanol}, mefluidide {N‐[2,4‐dimethyl‐5[[(trifluoro‐methyl)‐sulfonyl]amino]phenyl] acetamide}, and MBR 18337 (MBR) [N‐(2ethylthio)‐2‐(trifluromethyl)phenyl methanesulfonamide] twice annually, for 4 consecutive years to a Kentucky bluegrass (Poa pratensisL.)‐red fescue (Festuca rubrassp. rubraL.) turf grown on a Chillum silt loam soil (fine‐silty, mixed, mesic Typic Hapludult). The field data presented were combined over months and years for 1980, 1981, and 1982. Furthermore, 8 months following the final PGR application, turf plugs collected from field plots were evaluated for tiller and thatch production, leaf growth, and root recuperative potential. All PGR's reduced canopy height significantly from June to September. Mefluidide and MBR provided the most rapid growth suppression; however, flurprimidol provided a longer period of growth inhibition. Mefluidide and MBR caused leaf yellowing and necrosis shortly following application. Discoloration elicited by flurprimidol appeared several weeks following application in the form of leaf tip necrosis, but not death of entire leaves. Flurprimidol treated turf also developed an undesirable blue‐green color during periods of heat and drought stress. Ethephon treated turf generally possessed a dark green color during summer. Between September and April, however, many ethephon treated plants developed necrotic sheaths. Ethephon caused elongation of internodes, and crowns of many plants were elevated several mm above the soil surface. Crown elevation gave the turf a ‘puffy’ quality and resulted in a large reduction of verdure when mowed. Mefluidide and MBR reduced turf density, which resulted in a severe infestation of crabgrass (Digitariaspp.). Crabgrass infestation was not a problem in flurprimidol and ethephon treated turf. Mefluidide and MBR effectively suppressed seedhead production; whereas, flurprimidol (2.2 and 3.4 kg a.i. ha−1) enhanced their production. Flurprimidol treated turf had more tillers and leaves than turf treated with other PGR's. Signficantly higher root weights were associated with flurprimidol G (2.2 and 3.4 kg ha−1) treated turf; however, root weight was positively correlated (r=0.80*, significant at the 0.05 level) with tiller number. Data revealed that two annual applications of the PGR's evaluated caused adverse effects that would limit their use on intensively managed turf. There were, however, no deleterious effects of PGR usage upon tiller and root recuperative potential of the Kentucky bluegrass‐red fescue turf.
Leaf Area and Dry Matter Accumulation of Wheat Following Forage Removal1
Authors: Dunphy D. J. , Holt E. C. , McDaniel M. E.
Published: July 2010

Wheat (Triticum aestivum L. em Thell.) is commonly both grazed for forage and harvested for grain in the Southern Great Plains of the USA. Information is needed on the plant characteristics affected by forage removal and their relationships to grain yield. Leaf area index was measured at 0,1, and 2 weeks following forage removal in 3 years of field experiments. The soil type was a member of the fine, montmorillonitic thermic family of Vertic Albaqualfs. Leaf area and dry matter present at anthesis were also recorded. Treatments consisted of taking the final forage harvest for two cultivars at the early joint, mid‐joint, or late joint stage of development but without removing terminal meristems. All treatments were harvested for grain at maturity, including a check that was not harvested for forage. Total LAI at anthesis averaged over varieties for the first 2 years, decreased from 1.40 to 0.79 when the final forage harvest was delayed from early to late joint. Total dry matter present at anthesis averaged over all years and varieties decreased from 491 to 326 g m−2. Leaf area duration from jointing to anthesis, the product of the average leaf area present and the number of days in the sampling period, averaged 42.9 days m2m−2 for the early joint treatment, compared to 15.8 days m2m−2 for the plants harvested at late joint. These factors were highly correlated (r = 0.64 to 0.88) with grain yield in all 3 years for both cultivars. The data indicate that when the leaf area produced during the vegetative and jointing stages was harvested as forage, grain yield was limited by the potential of the plant to rapidly produce new leaf area and prevent tiller senescence during the period between jointing and anthesis.
Effects of Salinity on Seashore Paspalum Turfgrasses1
Authors: Dudeck A. E. , Peacock C. H.
Published: July 2010

Increased need for salt tolerant grasses continues due to increased restrictions on limited water resources and to salt water intrusion into groundwater. Seashore paspalum (Paspalum vaginatum Swartz.) is used in Australia as a salt tolerant turfgrass, and cultivars are commercially available in the USA. The purpose of this investigation was to document the glasshouse response of four Seashore paspalum turfgrasses to solution cultures differentially salinized with synthetic sea water. A sea salt mixture was added to half‐strength Hoagland's number 2 nutrient solution to provide six salinity treatments ranging from 0.9 to 39.7 dS m−1. A split‐plot design with five replications was utilized to study salinity as the main plot effect and grass as the sub‐plot effect. Turfgrasses differed markedly in salt tolerance. Based on inverse regression analyses, the most salt tolerant experimental selection was FSP‐1 with 50% of its top growth reduced at 28.6 dS m−1; FSP‐2 and ‘Futurf’ were intermediate in salt tolerance with 50% top growth reductions at 21.9 dS m−1; whereas ‘Adalayd’ (‘Excaliber’) was the most sensitive cultivar with 50% top growth reduction at 18.4 dS m−1. The FSP‐1 selection was 3.1 times more salt tolerant than the other grasses when top growth was reduced only 5% at low salt concentrations. Salinity differentially affected tissue content of Ca, C1, K, Mg, and Na between grasses but had no affect on N which averaged 37.3 g kg−1. Maximum tissue content of 22.3 g kg−1 of CI and 16.4 g kg−1 of Na were at a salt concentration of 31 dS m−1 in FSP‐1. However, concentrations of Cl and Na in the other grasses increased linearly 0.4 and 0.5 g kg−1, respectively, with each increase in salinity concentration. Maximum accumulation in this group was at the highest salt treatment of 39.7 dS m−1 where Cl varied between grasses from 24 to 31 g kg−1 and Na varied from 20 to 24 g kg1. Tissue content of Ca, K, and Mg decreased with increased salinity and differed between grasses. No mortality was observed although top growth of all grasses was severely reduced at the highest salt level.