bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractCorn (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

AbstractThe 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

AbstractNondestructive 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

AbstractShoot 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

AbstractNo‐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

AbstractThe 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

AbstractRapid 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

AbstractAn 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

AbstractThe 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.
Planting Patterns and Radiation Interception, Plant Nutrient Concentration, and Yield in Corn
Authors: Ottman M. J. , Welch L. F. 
Published: July 2010

AbstractThe upper leaves of corn (Zea mays L.) are radiation‐saturated while the lower leaves, the prime source of carbohydrates for nutrient uptake by roots, are radiation‐starved. This study was conducted to determine the degree to which planting patterns could influence radiation interception by layers in the canopy, plant nutrient concentration, and yield in corn. Corn was planted in the field in a high‐yielding environment on a Drummer silty clay loam (finesilty), mixed, mesic, Typic Haplaquoll) in 0.38 m single rows, 0.76 m twin rows, 0.76 m single rows, 1.14 m twin rows, and 1.52 m twin rows with 0.13 m between pairs of twin rows. Interception of solar radiation shortly after silking was generally similar for all the planting patterns except for the 1.52 m twin row spacing which intercepted 10% more incident radiation with lower rather than upper leaves compared to the other planting patterns 3 h before solar noon, but allowed 7% more incident radiation to strike the soil surface compared to the narrow row spacings (0.38 ‐ 0.76 m) at solar noon. Planting pattern had no consistent effect on nutrient concentration in the grain, stover, or cob. Grain yields averaged 9.7 Mg ha−1 for the 1.52 m twin planting pattern and 11.7 Mg ha−1 for the other planting patterns. In conclusion, wide row spacings resulted in a partial redistribution of radiation from the upper to the lower leaves but allowed more radiation to strike the soil surface, did not affect plant nutrient concentration, and decreased yield.
Genetic Contribution to Increased Wheat Yields in the USA Between 1979 and 1984
Authors: Feyerherm A. M. , Kemp K. E. , Paulsen G. M. 
Published: July 2010

AbstractGenetic yield potential of wheat (Triticum aestivum L. and T. turgidum var. durum) and its impact on production need to be documented to determine past and future gains in productivity. This study provides such documentation on growers' yields of wheat from 1979 to 1984 in states where each major class is grown. Cultivar‐specific differential yielding ability (DYA) values were calculated and weighted by sown hectarage to measure state‐wide genetically imputed increases in farmers' yields. Yield increases in spring wheat states ranged from 44 kg ha−1 in Montana to 88 kg ha−1 in South Dakota for the 5‐year period. Increases in the hard red winter region ranged from 40 kg ha−1 in South Dakota to 199 kg ha−1 in Nebraska. Soft wheat yield increases ranged from 211 to 438 kg ha−1 in Corn Belt states and was 151 kg ha−1 in Washington state. We concluded that there has been continued genetically induced improvement in farmers' wheat grain yields during the first half of the 1980s, and that productivity gains should continue at approximately the same rate into the next decade.
Sweet Corn Response to Surface and Subsurface Trickle Phosphorus Fertigation
Authors: Bar‐Yosef B. , Sagiv B. , Markovitch T. 
Published: July 2010

AbstractHigh‐frequency phosphorus fertigation may increase the time‐averaged P concentration in the soil solution above that expected from P solubility considerations. Where P is a yield‐limiting factor, frequent P fertigation may increase yield by stimulating P‐uptake by the roots. A field experiment was conducted on a loessial soil (Haploxeralf) high in NaHCO3‐extractable P (0.8 mmol kg−1 soil) to test the hypothesis that subsurface placement of emitters (SSR) is more effective in stimulating P uptake than surface placement (SR). Four concentrations of P in the water (Cp), 0.04,0.16,0.64, and 1.29 mol P m−3, were applied via surface or subsurface emitters to sweet corn [Zea mays (L.) Jubilee]. Marketable ear yield increased with Cp, yielding 22.9,24.3,24.9, and 28.9 t ha−1, respectively. Yield was higher for tricklers placed 30 cm below soil surface (25.2 t ha−1) than on the surface (23.5 t ha−1). Elevated Cp increased the soil solution P concentration, thereby increasing total P uptake and total dry matter production by the plants. Deep trickler placement significantly increased the fraction of total dry matter allocated to the ears, which resulted in higher marketable yield. Subsurface irrigation also reduced weed growth due to the dry top soil during the experiment.
Operational Estimates of Reference Evapotranspiration
Authors: Allen Richard G. , Jensen Marvin E. , Wright James L. , Burman Robert D. 
Published: July 2010

AbstractMany forms of the Penman combination equation have been proffered for estimating daily evapotranspiration (ET) by the agricultural reference crops grass and alfalfa (Medicago sativa L.). This study was conducted to evaluate popular forms of the Penman equation, and to develop and evaluate general relationships for estimating daily average values of canopy and aerodynamic resistance parameters required by the Penman‐Monteith equation. For simplicity and ease of use, resistance relationships were expressed as linear and logarithmic functions of mean plant height. The Penman‐Monteith and other forms of the Penman equation were compared at 11 international lysimeter sites, with the Penman‐Monteith method and a Penman equation with variable wind function developed at Kimberly, ID providing the best estimates of reference ET across the sites. Ratios of computed alfalfa to grass reference ET during peak months at various locations averaged 1.32, and ranged from 1.12 to 1.43. Values of computed ratios were related to local wind and humidity conditions. The development of relationships for canopy and aerodynamic resistances as functions of reference crop height allowed use of the Penman‐Monteith equation in an operational mode, and improved transferability of this resistance form of the Penman equation to a wide variety of climates.