bluuebunny/crossref_metadata_2025 huggingface dataset:
Wheat Canopy Resistance Determined by Energy Balance Techniques1
Authors: Hatfield J. L.
Published: July 2010

Canopy resistances are important to evaluate plant environmental responses and difficult to measure in situ. This study was designed to evaluate a residual energy balance method for obtaining canopy resistances. A field study was conducted under natural rainfall conditions at Davis, CA during 1980 to 1981 on the Yolo silt loam soil (fine‐silty, mixed, nonacid, thermic Typic Xerorthent) with Anza wheat (Triticum aestivum L.) seeded at 120 kg ha−1 with 80 kg ha−1 N supplied prior to planting. One‐half of the plots received unobstructed solar radiation, the other half had solar radiation reduced by a 55% shadecloth. From shortly after emergence to maturity, net radiation, air temperature, canopy temperature, incoming solar radiation, vapor pressure deficit, and windspeed were continually recorded. Canopy resistances were calculated from a residual of the energy balance. Canopy resistances obtained under optimal available soil water for both radiation treatments exhibited exponential decline with increasing solar radiation. Midday values of canopy resistance in the unshaded area were typically 20 to 25 s m−1 and 40 to 50 s m−1 in the shaded plot. Canopy resistance was 20 s m−1 under conditions which would be considered near potential evapotranspiration and, increased linearly with decreasing available soil water with a change in canopy resistance of 0.4 and 2.1 s m−1/% available soil water for the unshaded and shaded, respectively. These were normalized by computing the ratio of canopy resistance under non‐optimal soil water contents to the canopy resistance influenced only by solar radiation. This allowed both solar radiation treatments to fit the same relationship and revealed that canopy resistance was not affected until 20% of the available soil water was removed. The residual energy balance method provides a valuable tool to quantify canopy resistance and will be useful to compare genotypes or management practices.
Deficit Sprinkler Irrigation of Sunflower and Safflower1
Authors: Hang A. N. , Evans D. W.
Published: July 2010

Increasing competition for water supplies and rising costs of applying water make efficient irrigation increasingly important. Yield and water use of sunflower (Helianthus annuusL.) and safflower (Carthanus tinctoriusL.) were evaluated on silt loam soil. Deficit irrigation treatments using the line source method were initiated near the time of canopy closure and continued until maturity. Moisture stress on sunflower and safflower caused shortened plant height, early blooming, early maturity, and decreased seed yield. In 1980 sunflower yields ranged from 2.41 to 4.50 Mg ha−1for 2.5 to 35.0 cm irrigation. In 1981 sunflower yields ranged from 1.56 to 3.37 Mg ha−1for 2.5 to 45.0 cm irrigation. Safflower yields in 1981 ranged from 1.84 to 5.15 Mg ha−1for the same irrigation rates. In 1981, sunflower and safflower received the same total amount of water to produce maximum seed yield. Increased irrigation water results in increased yield for both sunflower and safflower; however, yield per unit applied water decreases with increased irrigation rates so that at some point, the expected increase in yield would not cover the cost of additional water application. Increased irrigation increased oil concentration of sunflower except for cv. 894 in 1980. Oil concentration of safflower did not respond to increased irrigation rates. It was concluded that limiting irrigation on sunflower and safflower to ≤ 30 cm permits utilization of residual soil water on silt loam soil with consequent savings in irrigation water supplies and costs of application. Soil moisture is then recharged by winter rainfall.
Timing of Foliar Manganese Application for Correction of Manganese Deficiency in Soybean1
Authors: Gettier S. W. , Martens D. C. , Brumback T. B.
Published: July 2010

A consensus has not been reached on how often and at what growth stage to apply foliar Mn for alleviation of Mn deficiency in soybean [Glycine max(L.) Merr.]. Three field experiments were conducted to determine soybean response to a 1.12 kg Mn ha−1foliar application at the V6 (early), the R1 (late) and at both the V6 and R1 growth stages. Determinate ‘Essex’ soybeans were grown at two locations on Dragston fsl (Aeric Ochraquults) soils and ‘York’ on a Myatt fsl (Typic Ochraquults). The Ap horizon of the soils had pH levels from 6.3 to 6.8 and had low Mehlich 1‐extractable Mn levels from 0.8 to 1.6 mg kg−1. Foliar application of MnSO4increased soybean seed yields up to 2518 kg ha−1over the control. Yield increases were due to increases in seed weight and seed numbers. The average control Mn concentrations in the leaflets, trifoliolate leaves and seeds were 11.4, 9.3, and 8.5 mg kg−1, respectively. More Mn was translocated to the seed from the late than from the early foliar Mn treatment. Seed yields were higher from plants that received a single early spray than a single late spray. Soybean plants that received 1.12 kg Mn ha−1early and again late had higher yields than plants that received a single early spray. Full correction of soybean Mn deficiency by foliar Mn technique required multiple foliar Mn applications.
Defoliation Effects on Two Corn Inbreds and their Single‐Cross Hybrid1
Authors: Vasilas B. L. , Seif R. D.
Published: July 2010

Hail damage to corn (Zea maysL.) is assessed with the use of loss charts derived primarily from research conducted with hybrids. Little data are available on the relative responses of inbreds vs. hybrids to defoliation. Therefore, field experiments were conducted at the University of Illinois on a Drummer silty clay loam (Typic Haplaquoll) in 1982 and a Flanagan silt loam (Aquic Argiudoll) in 1983 to compare the response to defoliation of two corn inbred lines, FRMol7rhmand FR27rhm, and their single‐cross hybrid. Defoliation treatments of 0,50, and 100% were conducted by hand at the 7‐leaf, 14‐leaf, anthesis, late‐milk, and soft‐dough stages in 1982 and the 7‐leaf, 14‐leaf, anthesis, milk, and dent stages in 1983. Data were taken on grain yield, kernel size, kernel number, and percentage barrens, doubles, and nubbins. The response of the inbreds was quite different than that of the hybrid and showed greater yearly variation because of differences in the growing seasons. Complete defoliation at anthesis reduced grain yield 100% in all cases. The greatest genetic variability was observed with 100% defoliation at the 14‐leaf stage, which reduced FRMol7rhmand FR27rhm✕ FRMo17rhmgrain yields by 90 and 40%, respectively, and increased FR27rhmgrain yields by 2%. In many cases, defoliation increased grain yields by decreasing transpiration or delaying flowering until irrigation water was applied. Yield reductions were due to decreases in kernel size and kernel number. Kernel size was affected most by defoliation at the milk and late‐milk stages. Kernel number was affected most by defoliation at anthesis and the 14‐leaf stage.
Effects of Sod‐Seeding Legumes on Hill Land Pasture Productivity and Composition1
Authors: Bryan W. B.
Published: July 2010

Production and quality of hill land pasture may be improved by introducing a legume. Sod‐seeding is used extensively to introduce legumes into grassland, but little work has been reported for hill land pasture. Two identical experiments were conducted to determine the productivity and composition of hill land pasture when sod‐seeded with red clover (Trifolium pratenseL.) and birdsfoot trefoil (Lotus corniculatusL.). The effects of sod‐seeding date (spring or fall), soil amendment (lime and P), herbicides, and insecticide on hill land herbage dry matter (DM) accumulation and botanical composition were examined. The experiments were carried out in permanent hill land pastures consisting mostly of Kentucky bluegrass (Poa pratensisL.), meadow fescue (Festuca elatiorL.), redtop (Agrostis albaL.), white clover (Trifolium repensL.), and herbaceous broadleaf plants. The soil (fine‐loamy, mixed, mesic Typic Fragiudalfs) had an initial pH of 4.8 (Experiment 1) and 5.3 (Experiment II) with medium P and high K. Experiment I started in 1978 and experiment II in 1979. Both continued for 4 yr. Pasture composition and herbage accumulation were estimated in mid‐June, late July, and late September each year. In Experiment I herbage accumulation increased in the order: no amendment < legumes and P = lime and P < legumes, lime, and P < lime, P, and N. Pasture with no amendment was 50% as productive as sod‐seeded pasture (legumes, lime, and P). Nitrogen at 168 kg ha−1yr−1increased yearly herbage accumulation 20 to 120% compared to sod‐seeding. Results in Experiment II were similar except in the first year when sod‐seeded pasture produced 30% less than control pasture because paraquat (l,l‐dimethyl‐4,4'‐bipyridinium ion) application resulted in a herbage loss in June. Pasture sod‐seeded with red clover (RC) produced 20 to 25% more than pasture sod‐seeded with birdsfoot trefoil (BFT) only in year 1 (Experiment I) and year 2 (Experiment II). Spring was the best time to sod‐seed RC and fall for BFT. In Experiment II, lime had no effect on percentage total legume in the pasture, but in experiment I lime increased percentage total legume. Herbicide, method of herbicide application, and insecticide had small and transitory effects on pasture production and percentage total legume.
Wetting Effects on the Yield and Quality of Legume and Legume‐Grass Hays1
Authors: Collins Michael
Published: July 2010

Information is needed on rain effects on yield and quality of legume and legume‐grass hays. A field study was conducted on a Piano silt loam soil (fine‐silty, mixed, mesic, Typic Argiudoll) to evaluate rain effects on the yield and chemical composition of hays from pure swards of alfalfa (Medicago sativaL.), red clover (Trifolium pratenseL.), and birdsfoot trefoil (Lotus corniculatusL.) and mixtures with smooth bromegrass (Bromus inermisLeyss.). Plots for the factorial experiment (each 1.1 by 7.6 m) were arranged in a split plot design with legume species and pure or mixed sward type combinations as main plots and wetting treatments as the sub plots with four replicates. Wetting treatments consisted of field drying to 750 g dry matter (DM)/kg of total mass (TM) or more without rain or exposure to rain or artificial wetting during drying. Samples were collected just after cutting and after hay curing for quality analysis. Rain reduced the proportion of leaf by 109 and 151 g/kg for alfalfa and birdsfoot trefoil, respectively, but did not affect red clover leaf content. Rain increased DM loss by as much as 154 g/kg (pure alfalfa) but did not affect DM loss for the birdsfoot trefoil‐grass mixture. Legume‐grass hays generally had more neutral detergent fiber (NDF) and lower N and in vitro dry matter disappearance (IVDMD) concentrations than pure legume hay. Rain or wetting reduced IVDMD by from 13 g/kg (birdsfoot trefoil‐grass) to 64 g/kg (alfalfa). Except for Ca, which was reduced in some cases, rain or wetting did not affect mineral concentrations in dry hay. The presence of grass in the sward provided consistent advantage in hay drying only for red clover. Rainfall increased DM losses during hay curing except for the grass‐dominated birdsfoot trefoil mixture. Rain or wetting reduced hay quality by reducing IVDMD and increasing NDF concentration. Nitrogen, P, K, and Mg concentrations were not greatly affected by rain or wetting.
Growth and Yield of Sunflower and Soybean under Soil Water Deficits1
Authors: Cox W. J. , Jolliff G. D.
Published: July 2010

Quantitative data are needed to support the thesis that sunflower (Helianthus annuusL.) is more drought resistant than soybean [Glycine max(L.) Merr.]. In 1980 and 1981 a comparative study of crop growth, seed yield, and soil water extraction patterns was conducted on a Woodburn silt loam soil (fine‐silty, mixed mesic Aquultic Argixeroll) to characterize the crop responses under moderate and severe soil water deficits. Line source sprinkler designs were used on both crops to generate well‐irrigated, deficit‐irrigated, and dryland treatments. Crop growth and soil water measurements were taken at 7‐ to 10‐day intervals on both crops in 1980 and 1981, respectively. In the well‐irrigated treatments, sunflower and soybean produced comparable total dry matter (1400 and 1350 g m−2, respectively) with seed yields of 4.10 and 3.29 Mg ha−1, respectively. Soil water deficits reduced dry matter production in the deficit and dryland treatments by 22 and 50% in sunflower and by 18 and 70% in soybean; and reduced seed yield by 20 and 51% in sunflower and by 27 and 87% in soybean, respectively. Leaf area index (LAI) was the vegetative growth characteristic of sunflower most sensitive to soil water deficits, and seeds per plant was the yield component most affected. Soil water deficits did not affect the harvest index (HI) of sunflower. In soybean LAI and net assimilation rate (NAR) were reduced under severe soil water deficits. Pod number was the yield component most sensitive to soil water deficits in soybean. Dryland sunflower extracted soil water to a 1.8‐m depth and thus avoided severe water stress during its reproductive period. In contrast, dryland soybean depleted considerably less soil water from the 0.9‐ to 1.8‐m depth. As a result, dryland soybean suffered severe water stress during its reproductive period, which dramatically lowered HI and seed yield. This study confirms that sunflower may avoid prolonged drought better than soybean by extracting water from deeper in the soil profile.
Yield and Physiological Responses of Potatoes to Deficit, High Frequency Sprinkler Irrigation1
Authors: Hang A. N. , Miller D. E.
Published: July 2010

Potatoes (Solanum tuberosumL.) of high yield and quality can be produced on sandy soil only with adequate irrigation. It is important to know the minimum water requirement and how the crop responds to water stress. The present study was conducted in 1979 and 1980 to determine the effect of irrigation rate on potato performance. Treatments were initiated at full canopy on a sandy soil (mixed, mesic, Xeric Torripsamments) using the line source technique. Daily sprinkler irrigation near the line source was equivalent to 1.15 times estimated evapotranspiration (Et). Water stress symptoms were first observed in plants receiving the least irrigation water (18% Et in 1979 and 21% Et in 1980) 2 weeks after treatments were initiated. These symptoms included reduced plant size, fewer leaves, more dead leaves, and increased specific leaf weight, compared with nonstressed plants. Tuber and top growth rates increased with increasing irrigation, ranging from 2.62 and 17.63 g m 2day 1and −0.90 (apparent negative value) to 10.01 g m −2day −1, respectively, for the lowest to the highest water application. Partitioning of assimilate to tuber growth decreased with increased irrigation. Results indicate that potatoes grown on sandy soil require irrigation at rates approaching estimated Et if reductions in yield and quality are to be avoided. Increasing irrigation water beyond 100% Et did not increase yields.
Yield Loss Due to Simulated Hail Damage on Corn: A Comparison of Actual and Predicted Values1
Authors: Shapiro C. A. , Peterson T. A. , Flowerday A. D.
Published: July 2010

Three simulated hail damage experiments were conducted to compare realized grain yields with those predicted by current hail adjustment procedures. Treatments included reductions in plant density and defoliation. Population density reduction was studied for 3 yr. An initial population of 6.4 plants m−2 was reduced to 5.9, 4.9, 4.0, and 3.0 plants m−2 at the 6‐, 9‐, 12‐, and 15‐leaf stages. Leaf stage did not affect grain yield, but yield decreased −2, 2, 6, and 19%, respectively, with each reduction in population. Yield losses due to population density reduction were less than those predicted by hail insurance procedures, especially for losses after the 10‐leaf stage. One‐hundred percent defoliation at the 4‐, 5‐ and 6‐leaf stages did not significantly reduce grain yield. One‐hundred percent defoliation from the sixth through the ninth leaf stages showed a linear decrease (regression coef. = −1.15) in grain yield with later leaf stage. The effects of early season complete defoliation varied with year. These results generally agree with the hail loss charts for very early season, 100% defoliation. Defoliation of 0, 33, 66, and 100% at the 6‐, 12‐, tassel, and blister stages was performed over four environments. Grain yield was reduced with increasing severity of defoliation, and with growth stages near the tassel stage. Five treatments produced a greater yield reduction than predicted by the hail adjustment procedures, while one treatment showed less yield reduction than predicted. Later treatments tended to show greater yield loss than predicted.
Effects of Temperature on Leaf Appearance in Spring and Winter Wheat Cultivars1
Authors: Baker J. T. , Pinter P. J. , Reginato R. J. , Kanemasu E. T.
Published: July 2010

An understanding of the genetic and environmental factors affecting the leaf area of a cereal crop is needed for accurate yield predictions by crop models. Field trials were conducted with three cultivars of winter wheat (Triticum aestivum L. em. Thell) at Manhattan, KS, under dryland and irrigated conditions and with six cultivars of spring wheat at Phoenix, AZ, in 1982 and 1983, respectively. Because leaf growth is strongly influenced by temperature, the rate of leaf appearance was expressed as leaves/thermal unit (Tu=[(TMAX+TMIN)/2]−Tb);w where Tu is thermal units, TMAX and TMIN are maximum and minimum daily temperatures, respectively, and Tb is the base temperature below which growth essentially ceases. The Tb, determined for three winter wheat cultivars, was not significantly different from 0°C (P≤0.05). Phyllochron interval (PI), the inverse of leaf appearance rate, was determined from the inverse of the slope of the regression of Haun scale growth units against accumulated Tu. The R2 values for these regressions were not less than 0.97 and 0.99 for spring and winter wheat cultivars, respectively. The PI was shorter for nonirrigated than irrigated winter wheat leaves (P≤0.01) and for spring wheat leaves formed prior to double ridges than those formed later (P≤0.01). Differences in PI were found among both spring and winter wheat cultivars (P≤0.05). These results illustrate the importance of determining PI for quantifying growth characteristics that determine the leaf area of a cereal crop.
Influence of Weather on Year‐to‐Year Yield Response of Corn to Ammonia Fertilization1
Authors: Hollinger S. E. , Hoeft R. G.
Published: July 2010

Multi‐year N studies have shown large year‐to‐year variation in the yield response of corn (Zea mays L.) to N fertilization. The objectives of this study were to (i) determine which normally predicted and measured weather variables account for this year‐to‐year variability; and (ii) to suggest a climate forecast design that will provide the most flexibility in planning N fertilization programs. Relative yield responses to N treatments were obtained from 6 yr of field research on a fine, silty, mixed mesic Typic Haplaquolls. Relative yields and spring N treatments were transformed using natural logarithms (In). The transformed N treatments accounted for more than 95% of the transformed yield responses in 5 of the 6 yr. The only year the regression failed to fit accurately was a very hot, dry year when there was a negative response to N. The analog of the equation was used to obtain α and β coefficients, where α is the fraction of maximum yield expected if no N is applied, and β is the rate of yield increase with each additional unit of applied fertilizer. The α and β values were then related to the ratio of precipitation/evaporation (P/E) from the 11 June to 15 July period in each of the 6 yr. The quadratic relationship explained 99% of the variation in α and 95% of the variation in β. When P/E is less than optimum, water is limiting and the plant is unable to use the applied nitrogen efficiently. When P/E is greater than optimum, N may be lost through denitrification and/or leaching and is thus, unavailable to the plant.
The Effect of the Fungal Endophyte Acremonium Coenophialum in Tall Fescue on Animal Performance, Toxicity, and Stand Maintenance1
Authors: Read J. C. , Camp B. J.
Published: July 2010

Weight gains have been inconsistent and numerous health problems have been associated with animals grazing tall fescue (Festuca arundinacea Schreb.). This study was undertaken to determine the effect of the fungal endophyte, Acremonium coenophialum Morgan‐Jones and Gams [syn. Epichloe typhina (Fries) Tulasne], on weight gains and symptoms of tall fescue toxicity of cattle. Grazing studies were started in the spring of 1982 and continued through the 1982–1983 and 1983–1984 grazing periods, on ‘Kenhy’ tall fescue having high and low levels of endophyte infection, at Dallas, TX, on Houston black clay soil (fine, montmorillonic, thermic Udic Pellusterts). Average daily gains were 0.46 kg and 0.97 kg for the high‐ and low‐infested pastures, respectively. Animals on the high‐infested pastures had elevated temperatures and rougher hair coats than those grazing the low‐infested pastures. During the 1983–1984 grazing period, 5 of the 6 tester animals grazing on the high‐infested pastures, had symptoms of ‘fescue foot’, whereas, none of the animals on the low‐infested grass exhibited any symptoms. Forage production was low and there was a loss of stand in the pastures with low levels of the endophyte. This study supports previous research findings on the effect of the endophyte in tall fescue on animal weight gains, summer syndrome, and drought resistance. An association of this endophyte with fescue foot was observed.
Nitrogen Management and Interseeding Effects on Irrigated Corn and Sorghum and on Soil Strength1
Authors: Olson R. A. , Raun W. R. , Chun yang Shou , Skopp J.
Published: July 2010

A 15‐yr experiment on Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) investigated N management effects on corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench] grown side by side, under identical furrow‐irrigated conditions. Included were comparisons of anhydrous ammonia (AA) and N solution (UAN) as N sources, planting time (UAN‐PL) vs. summer sidedressing (UAN‐SD) application of the N, and rates of 90,180, and 270 kg N ha−1. Additionally, interseeding of rye (Secale cereale L.) into high N plots and alfalfa (Medicago sativa L.) into check plots of corn was accomplished at the time of ridging for furrow irrigation. The objectives were to evaluate the long term effects of varied management of the two N carriers and the interseedings on grain yields and N utilization, and the relative effects of these treatments on soil strength. Grain sorghum was the more productive crop under conditions of low N availability while corn responded to higher N rates, becoming the more economic crop with yields approaching 10 Mg ha−1 when N was plentiful. Yield increases averaged 5% greater for UAN‐SD over UAN‐PL, and AA was slightly more effective than UAN‐SD for both crops. Interseeded alfalfa and rye green manures provided average corn yield increases of 880 and 585 kg ha−1, respectively, explainable in part by improved N economy. No significant differences in penetrometer or vane shear tests were found between soils from AA and UAN‐SD plots, although there was a tendency toward lower soil‐strength values with both N carriers, relative to check plots.
Sealed Chamber Digestion for Plant Nutrient Analyses1
Authors: Anderson D. L. , Henderson L. J.
Published: July 2010

A sealed chamber digestion (SCD), using perchloric acid and hydrogen peroxide, was developed as an alternative to conventional procedures for plant tissue digestion. The SCD procedure was evaluated using eight plant tissue standards obtained from the National Bureau of Standards, University of Georgia, and the University of Florida. The results of the SCD did not differ greatly from reported standard values. The advantages of SCD are (i) the low volume of reagents used and the ability to utilize low volume dilutions, (ii) low temperature of digestion, (iii) use of a closed system eliminating the need for a fume hood, (iv) micro‐sample analyses capabilities, (v) minimal equipment investment, and (vi) simplicity.
Soybean Response to Tillage and Nitrogen, Phosphorus, and Potassium Fertilization1
Authors: Bharati M. P. , Whigham D. K. , Voss R. D.
Published: July 2010

Conservation tillage is being increasingly recommended as a means of reducing both cost of tillage and soil erosion. A study was conducted for two years with the objective of evaluating the performance of a determinate soybean [Glycine max (L.) Merr.) cultivar, Sprite, planted in narrow rows on a Nicollet (Aquic Hapludo1ls)‐Webster (Typic Haplaquolls) complex, with different tillage systems and different levels of N, P, K fertilization for higher yield. Variables studied included: (i) three tillage systems (disk, chisel plow, and moldboard plow tillage) and (ii) three levels of N, P, and K fertilization (P at 0,74 and 111 kg/ha; K at 0,186, and 279 kg/ha; and N at 0, 135, and 270 kg/ha). Plant population was unaffected by the treatments. Phosphorus and K applications increased soil and leaf P and K contents over time and with application levels. Tillage had no significant effect on grain yield. Lodging was significantly increased by P application. Lodging, plant height, and grain yield were significantly increased by K application. Nitrogen application increased lodging and plant height, but not yield. It was concluded that soybean can be successfully grown with reduced tillage in central Iowa without a yield reduction or change in fertility requirement. Soybean responded to K application when the soil test levels were medium to high.
Effect of Particulates (Dust) on Cotton Growth, Photosynthesis, and Respiration1
Authors: Armbrust D. V.
Published: July 2010

Wind erosion suspends large quantities of dust in the atmosphere that settle back to the earth's surface and are deposited on plant leaves when wind velocities decrease. The object of this research was to determine the effect of wind‐erodible size dust particles on upland cotton [Gossypium hirsutum (L.) ‘Dunn 120’] growth and physiology. Dust (< 0.106 mm) at concentrations of 0, 10.8, 15.2, 16.5, 22.1, 28.6, 38.5, and 51.1 µg m−2 was settled onto leaves of 22‐day‐old growth‐chamber‐grown cotton plants in a dust chamber. Net photosynthesis, dark respiration, dust concentration, leaf area, and dry weight were measured 1, 3, 7, and 14 days after dust was applied. Applied dust (> 15.2 µg m−2 ) resulted in reduced dry weight at 3, 7, and 14 days after application, but dry weight accumulation was not reduced by increasing dust concentration after day 3. The dry weight reduction was due to reduced photosynthesis, 1 and 3 days after dust application, and increased dark respiration, 1, 3, and 7 days after application when dust application rates exceeded 28.6 µg m−2. This study indicates that particulate deposits can alter cotton growth without physical damage to the plant and without toxic materials present in the dust. However, rapid removal of particulates by wind and rain and low natural deposition rates (1.5 µg m−2 day−1) indicate that dust deposits on leaves should not be a major problem in cotton production.
Harvest Methods for Estimated Ethanol Yields from Relative Fermentable Carbohydrate Accumulation in Maize Hybrids1
Authors: Widstrom N. W. , Carr M. E. , Bagby M. O. , Black L. T.
Published: July 2010

Recurring energy shortages suggest the need for evaluation of alternate fuel energy sources. Conversion of plant carbohydrate to ethanol, as a fuel source, is considered a viable option with efficient energy‐producing crops such as maize, Zea mays L. Three maize hybrids (‘Coker 77’, ‘Pioneer 3369A’, and ‘Sokota Sugar Chop’) were grown in a Norfolk loamy sand (fine‐loamy, silicious Typic Paleudult) from 1981 to 1983 to evaluate four procedures for harvesting. The objective was to identify procedure(s) that maximize carbohydrate production potential, measured as estimated fermentable carbohydrate converted to ethanol. Ethanol yield estimates, calculated from grain or stalk sugars, or both, to make possible direct comparisons of harvest treatments, were analyzed as a split‐plot design with 10 replicates. Whole plots were hybrids, and subplots were harvest treatments. The treatments consisted of (i) covered ear shoots (EC); (ii) removed ear shoots (ER); (iii) grain and stalks harvested simultaneously (P‐SimH); and (iv) stalks harvested separately, 1 to 2 weeks after grain harvest (P‐ SepH). Coker 77 produced the least grain but significantly greater estimated ethanol yields than did the other hybrids in 2 of 3 yr because of greater stalk sugar yields. The P‐SepH and P‐SimH treatments of this hybrid produced less than twice as much estimated ethanol per plant, and other hybrids produced about three times as much as the EC and ER treatments of Coker 77. Differences between the P‐SimH and P‐SepH treatments were nonsignificant, and simultaneous harvest of grain and stalk sugar at physiological maturity proved an efficient procedure to produce high estimated ethanol yields.
Measurement of Nitrogen Utilization Efficiency in Rice Genotypes1
Authors: Broadbent F. E. , De Datta S. K. , Laureles E. V.
Published: July 2010

Recent research suggests that there is considerable potential for exploiting genotypic differences in N utilization efficiency by crops. Our research attempted to identify traits associated with rice (Oryza sativa L.) genotypes that support maximum grain production with a minimum input of fertilizer. From field experiments on an Andaqueptic Haplaquoll in three consecutive seasons we identified a group of plant parameters associated with efficiency of N utilization to determine if the different genotypes exhibited consistent and significant variations in these parameters. A group of nine parameters was selected, and rankings based upon different combinations of these parameters were developed and compared. Statistically significant differences among genotypes were observed, and reasonably consistent rankings were obtained from season to season. For example, IR183429‐3‐2‐1‐2 ranked first in two seasons and third in the other. IR18349‐135‐2‐3‐2‐1 ranked second, third, and fifth in the three seasons. These are medium maturity rices. IR42, which is known to perform well on low N soils, ranked between ninth and 17th. The consistency of performance of outstanding genotypes demonstrated in these experiments suggests that the methodology is feasible and practical for use in research on genetic improvement of N utilization efficiency.
Differences in Drought Resistance between Two Corn Hybrids. I. Water Relations and Root Length Density1
Authors: Lorens G. F. , Bennett J. M. , Loggale L. B.
Published: July 2010

Corn (Zea mays L.) hybrids are often selected for near optimal conditions of water availability, yet frequently are grown under less than ideal soil moisture. Different responses among corn hybrids to drought stress have been observed, but the physiological and morphological differences that confer drought resistance or susceptibility are not well understood. The objective of this study was to identify differences in leaf water relations, stomatal activity, and root length density distribution between two corn hybrids known to differ in their response to water stress. During the 1983 and 1984 growing seasons, two corn hybrids (Pioneer Brands 3192 and 3165) were subjected to three water management treatments: irrigated, rainfed, and stress during vegetative (1983) or reproductive (1984) growth. During periods of water stress, hybrid 3192 wilted 2 to 3 days sooner and maintained leaf water potentials (ΨL) and leaf turgor potentials (Ψp) that were 0.2 to 0.5 MPa and 0.1 to 0.3 MPa lower, respectively, than those of hybrid 3165. Water stressed plants of hybrid 3192 closed their stomata earlier during periods of water stress, but the relationship between leaf diffusive resistance and Ψp was similar for both hybrids, with stomata beginning to close as Ψp decreased below 0.4 MPa. Regardless of the stage of ontogeny, hybrid 3165 always maintained a lower Ψp at a given ΨL than hybrid 3192. However, the primary difference observed between the two hybrids was the ability of hybrid 3165 to simply avoid tissue desiccation by maintaining higher ΨL and Ψp. The deeper rooting profile of hybrid 3165 may have contributed to the maintenance of higher ΨL and Ψp during water stress.
Response of Corn to Nitrogen‐15‐Labeled Anhydrous Ammonia with and without Nitrapyrin in Iowa
Authors: Blackmer A. M. , Sanchez C. A.
Published: July 2010

The response of corn (Zea mays L.) to 15N‐labeled anhydrous ammonia applied at 112 and 224 kg N ha−1 with and without nitrapyrin [2‐chloro‐6‐(trichloromethyl) pyridine] was studied at two sites in Iowa during 1982, 1983, and 1984 to obtain a better understanding of why nitrification inhibitors often do not increase grain yields in the western part of the Corn Belt. Significant increases in grain yields were observed in response to N at both sites, but the response was significant only for the first increment of N at one site. Nitrapyrin had a statistically significant effect on grain yields at only two of the 12 rate‐site years, and this effect was negative. Results showing that nitrapyrin sometimes increased the N content of tissues to above critical levels without increasing yields to plateau levels suggest that this compound sometimes had adverse effects on plant growth when yield decreases were not observed. Application of fertilizer N in excess of plant needs probably is a major reason for lack of positive yield responses to nitrapyrin in this study in which mid‐season moisture stress often limited maximum grain yield and plant need for N. The exact nature of the adverse effects could not be determined, but it seems likely that nitrapyrin may have increased the susceptibility of plants to moisture stress or induced an ammonia toxicity in the plants. Because other researchers also have observed yield depressions, it must be suspected that negative effects of nitrification inhibitors often outweigh or mask the benefits of these compounds. Learning more about the nature of these negative effects and how to avoid them should receive greater attention as a viable strategy for attaining the potential benefits of using nitrification inhibitors during crop production.
Monitoring Corn Root Development with a Mini‐Rhizotron in Confined Growth Boxes
Authors: Keng J. C. W.
Published: July 2010

Nondestructive monitoring of the dynamic growth of crop root systems is important for research and teaching procedures studying root response to soil environment. Two commonly used nondestructive methods are (i) traditional rhizotrons that use flat‐sided viewing panels for root observaton, and (ii) mini‐rhizotrons that use viewing tubes and fiber optical borescope techniques. The objective of this study was to compare these two methods in the monitoring of corn (Zea mays L.) root development under greenhouse conditions. Wooden containers, 350 by 350 mm and 1.00 m in height, were constructed with a plastic, side viewing panel and a 43‐mm inner diameter borescope tube for root observations. Root intensity (root length per unit area) at 100‐mm depth intervals was calculated using the Newman equation on the 50th, 74th, and 99th days after planting. Coefficients of variance for total root intensities ranged from 10.8 to 37.4%, with the viewing tube data being more variable than those obtained from the side viewing panels. Multivariate analyses of variance (MANOVA) suggested significant difference at the 95% level between the two methods. Further simultaneous confidence interval (SCI) calculations indicated that different root growth patterns at the 0‐ to 100‐mm depth interval contributed to the significant difference between the tested methods.
Response of Field Grown Alfalfa to Root Waterlogging and Shoot Removal. I. Plant Injury and Carbohydrate and Mineral Content of Roots
Authors: Barta A. L.
Published: July 2010

Shoot removal represents a significant stress to plants, especially forage legumes subjected to frequent harvest. Since it has been reported that alfalfa (Medicago sativa L.) injury due to flooding is increased after clipping, this study examined cultivar response and root chemical composition (minerals and carbohydrates) in response to increasing duration of flooding and shoot removal stress. The objective was to characterize physiological responses related to flooding‐induced injury. Experiments were conducted on a fine, loamy, mixed mesic Typic Fragiudalf soil that was water saturated for up to 14 d. Young plants of ‘Vernal’ and ‘Answer’ alfalfa were used at the flowering stage of growth. Responses of Vernal and Answer alfalfa were not significantly different from each other in terms of growth or root chemical composition. Shoot removal 2 and 12 d prior to initiation of soil flooding reduced regrowth dry matter accumulation 56 and 33%, respectively. Non‐clipped plants were not injured with flooding duration up to 14 d. Root K+ content was significantly reduced by flooding stress only in the clipped treatments. Significant accumulation of Mn+2 or Fe+2 in flooded roots was not observed. Waterlogging had no effect, while clipping significantly reduced root starch concentration. In contrast, concentrations of both sucrose and glucose increased significantly with increased flooding stress for all shoot treatments. However, there was no apparent relationship between availability of soluble carbohydrates, as affected by clipping treatment, and flooding injury. Supply of fermentable carbohydrates does not appear to be limiting for fermentation reactions and is thus probably not a critical factor in flooding tolerance.
Nitrogen Fertilization of No‐Till Winter Wheat and Rye. II. Influence on Grain Protein
Authors: Fowler D. B. , Brydon J. , Baker R. J.
Published: July 2010

No‐till seeding into standing stubble immediately after harvest of the previous crop (‘stubbling‐in’) has been employed to successfully produce winter wheat (Triticum aestivum L.) and rye (Secale cereale L.) on the western Canadian prairies. Soil N deficiencies, which result in low grain protein concentrations, are often associated with stubbled‐in winter cereals. In the present study, the effect of N fertilization on protein concentration and protein yield of stubbled‐in winter wheat and rye was evaluated in 40 field trials conducted over a wide range of soil types and environmental conditions in Saskatchewan, Canada. Grain protein concentrations exhibited sigmoidal responses to N fertilization with minimums of 98.8 and 93.0 and maximums that varied from 130 to 231 and 107 to 177 g protein kg−1 dry grain for wheat and rye, respectively. The Gompertz equation was employed to describe the relationship between protein concentration and total available N, providing an average reduction in sums of squares, due to the model, of 96 and 97% for wheat and rye, respectively. Grain protein yield response to N fertilizer was described by an inverse polynomial function that provided an average reduction in sums of squares, due to the model, of 99% for both wheat and rye. Although grain protein concentration was significantly higher for winter wheat in most trials, winter rye demonstrated a greater N use efficiency for grain production. Higher grain yields for rye compensated for lower protein concentrations, and at equal N rates rye produced as much or more protein per hectare than wheat in all comparable trials except two.
Effect of the Tall Fescue Endophyte on Plant Response to Environmental Stress
Authors: Arachevaleta M. , Bacon C. W. , Hoveland C. S. , Radcliffe D. E.
Published: July 2010

The adverse effect of the tall fescue (Festuca arundinacea Schreb.) fungal endophyte (Acremonium coenophialum Morgan‐Jones and Gams) on animal performance is well recognized but the mutualistic effect of this fungus‐grass association under environmental stress is not well understood. The objective of this study was to evaluate endophyte‐free (EF) and endophyte‐infected (El) tall fescue plants from one clone for morphological and physiological responses to flooding, N rates (11, 73, and 220 mg N pof−1), and −0.03, −0.05 and −0.50 MPa drought stress in the greenhouse. Plants were grown in a synthetic mixture of the following by volume: Cecil sandy clay loam (clayey, kaolinitic, thermic Typic Hapludult) (33%), sand (16%), peat moss (17%), perlite (17%), and vermiculite (17%). Leaf blades of El, as compared to EF plants were thicker and narrower regardless of flooding, N rate, or drought stress. Plant ultrastructure was not appreciably altered by the endophyte. Herbage growth was 50% greater on El than EF plants, especially at higher N levels. Tillering increased on El plants but only at the highest N rate. The El plants were more productive than EF plants at mild soil moisture stress (−0.05 MPa). At more severe stress (−0.5 MPa) 75% of EF plants died and all El plants survived. Leaf rolling under drought stress was much more common in El than EF plants. Regrowth after harvest with abundant watering of previously drought‐stressed plants was much greater on El than EF plants. There was little or no difference in digestibility of forage from El and EF plants. The results indicate that there are positive benefits derived from association of an endophyte with tall fescue resulting in growth stimulation, improved survival, and drought tolerance to the host plant that could be important in plant competition.
Leaf Water Potential, Relative Water Content, and Diffusive Resistance as Screening Techniques for Drought Resistance in Barley
Authors: Matin M. A. , Brown Jarvis H. , Ferguson Hayden
Published: July 2010

Rapid drought resistance screening techniques could accelerate selection of improved cultivars for semiarid areas. This study was conducted to determine if total leaf water potential, leaf relative water content, and leaf diffusive resistance could be used to differentiate between barley (Hordeum vulgare L.) cultivars differing in apparent drought resistance. Resistant and susceptible cultivars were selected by regressing individual cultivar yields against site mean yield for numerous yield trials. Individual plants were grown in cone‐tainers (plastic tubes 25 mm in diameter and 123 mm long). The lower 30 mm of the cone‐tainers were imbedded in sand so that roots emerging from the bottom of the cone‐tainers were in the capillary fringe above a water table in the sand. Fifty plants were grown at a time in a sand bed, five replications each of five resistant and five susceptible barley cultivars of either two‐ or six‐row head types. At the three‐leaf growth stage total leaf water potential (Ψt) was measured on the third leaf of each plant under low stress conditions (predawn). Water was then drained from the sand bed to stress the plants. Leaf diffusive resistance (LDR) was measured at 1000 and 1300 h each day as stress developed. When the PM diffusive resistance reached about 1000 s m−1, relative water content (RWC) of the second leaf was determined. All measurements were repeated in three different trials for each head type. Relative water content and Ψt differentiated between drought‐resistant and drought‐susceptible groups of two and six‐rowed barley at the 0.01 probability level in every trial. Leaf diffusive resistance differentiated between resistant and susceptible groups at the 0.01 or 0.05 level under low and high stress conditions. Neither RWC nor LDR allowed separation of cultivars within resistant or susceptible groups, but Ψ, did show differences between cultivars within groups. These techniques provide an easy method to screen for drought‐resistant barley.
Reflectance, Transmittance, and Absorptance of Light by Normal, Etiolated, and Albino Corn Leaves
Authors: Maas S. J. , Dunlap J. R.
Published: July 2010

An understanding of the optical properties of plant leaves is basic to the application of remote sensing to agriculture. This study was conducted to demonstrate the effects of pigments on light reflectance, transmittance and absorptance spectra of corn (Zea mays L.) leaves. Three treatments were used to produce corn seedlings with different pigmentations. Normal seedlings contained the natural complement of colored pigments (predominantly chlorophylls and carotenoids). Etiolated seedlings (grown in the dark) contained carotenoids but not chlorophylls. Albino seedlings, produced by treating seeds with fluridone (l‐methyl‐3‐phenyl‐5‐[3‐(trifluromethyl) phenyl]‐4(1H)‐ pyridinone) contained no colored pigments. The morphology and histology of seedlings in the three treatments were basically similar, except that the leaves of the etiolated seedlings were characteristically elongated. Pigments did not affect leaf reflectance, transmittance, and absorptance spectra at infrared (< 2500 nm) wavelengths. Over most of the visible waveband, albino leaf reflectance was the same as the maximum observed at infrared wavelengths. The leaf absorptance spectrum of the etiolated seedlings at ultraviolet (> 350 nm) and visible wavelengths resembled the in vitro absorptance spectrum of β‐carotene masked by the background absorptance of the unpigmented albino system. Because fluridone‐induced albino seedlings can be used to separate the contributions of pigments from leaf structure and water content, they represent a potentially important tool in studying leaf optical properties.
Optimizing Soil and Fertilizer Nitrogen Use by Intensively Managed Winter Wheat. II. Critical Levels and Optimum Rates of Nitrogen Fertilizer
Authors: Baethgen W. E. , Alley M. M.
Published: July 2010

The assessment of optimum N fertilizer rates for winter wheat (Triticum aestivum L.) production is a major unsolved problem, particularly in humid climates. Eight field experiments were conducted in the Coastal Plain and Ridge and Valley regions of Virginia during the 1981–1982 through 1985–1986 winter wheat growing seasons to determine critical N levels and optimum rates of N fertilization. The treatments in these experiments consisted of various N fertilizer rates applied at Zadoks growth stage (GS) 25 and GS 30. Plant N concentration (NCON30) and crop N uptake (NUP30) at GS 30 were measured immediately prior to the N fertilizer application. Nitrogen critical levels were defined as the NCON30 or NUP30 values that produced 90% of maximum grain yields in each experimental site with no further N fertilizer application. Two nonlinear models were developed to determine critical levels at GS 30 using NCON30 and NUP30 as the independent variable. The calculated critical levels for the models using NCON30 and NUP30 were 39.5 g N/kg and 95 kg N/ha, respectively, with R2 values for the models being 0.87 (NCON30) and 0.79 (NUP30). A family of response curves of grain yield to N fertilizer applied at GS 30 was fitted at each ex‐ perimental site. The amount of N fertilizer required at GS 30 to obtain maximum grain yield (NMAX30) was calculated for each response curve. Regression analysis was used to develop modells for estimating the amount of N fertilizer required at GS 30 to produce maximum grain yields for any given value of NCON30 or NUP30. Best models were selected considering fit, significance of the regression coefficients, and predictive ability. The best models in both cases were simple linear regressions. The model using NUP30 as the independent variable had a larger correlation coefficient (r = –0.87) and a better predicting ability than the model using NCON30. Regression analysis was also used to develop models to estimate the amount of N fertilizer required at GS 30 to produce economically optimum yields at three fertilizer/wheat price. ratios (2.0, 4.0, and 6.0) using NUP30 as the independent variable. The three simple linear regression models were similar and presented large correlation coefficients (–0.88, –0.89, and –0.88, respectively). The results indicate that further field experimentation using the same methodology described in this research should be conducted under varying soils and climatic conditions to develop a model for predicting economically optimum N fertilizer rates for grower fields.