bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of a Heat Balance Stem Flow Gauge during High Flow
Authors: Ham J. M. , Heilman J. l. 
Published: July 2010

AbstractThe heat balance technique shows promise as a method for determining mass flow of sap in stems of intact plants. Previous work has been limited to plants with stems diameters near 10 mm transpiring at low rates. We evaluated the performance of several heat balance stem flow gauges during periods of high transpiration in sunflower (Helianthus annuus L.) with stems approximately 16 mm in diameter. Measurements in a controlled environment were used to compare gauge measurements to gravimetric estimates of transpiration. Gauges having heater widths of 10 mm severely overestimated flow as transpiration approached 200 g/h. Dynamics of the heat balance and temperature profiles suggested that failure of the gauge was due to a lack of thermal equilibrium between the xylem fluid and sensors on the stem surface. Increasing the heat applied to the stem did not improve gauge performance. A gauge with a heater width of 20 mm was constructed and evaluated under similar conditions. Increasing the heater width greatly improved gauge performance and the sensitivity of the measurement during high flow. Additionally, the gauge had the ability to react to large changes in flow over short time intervals. The gauge with the wide heater measured cumulative water loss over a 15‐h period to within 5% of that determined gravimetrically. The study indicates that the relationship between stem diameter and heater width is a crucial component of gauge design, and should be rigorously evaluated when applying the technique to stems with previously untested characteristics. Results suggest that heater width should be enlarged as stem diameter increases.
Herbage Production and Nitrogen Accumulation by Alfalfa and Cicer Milkvetch in the Southern Plains
Authors: Berg William A. 
Published: July 2010

AbstractSixty to 100 yr of farming upland soils in the Southern Plains has depleted much of the N available to plants. This field study valuated alfalfa (Medicago sativa L.) and cicer milkvetch (Astragalus cicer L.) for persistence, herbage production, and N accumulation on two N‐deficient soils (Woodward fine sandy loam, coarsesilty, mixed, thermic Typic Ustocrept; Pratt loamy sand, sandy, mixed, thermic Psammentic Haplustalf). A grass (Bothriochloa ischaemum L.) was grown as a control against which to measure N accumulation. After establishment in 1981 with sprinkle irrigation, the study was conducted under dryland conditions the following 5 yr when precipitation was near the long‐term mean of 596 mm yr−1, Herbage was not harvested the year of establishment. On the Woodward sandy loam, average herbage yields were: alfalfa 4.5, cicer milkvetch 3.1, and grass 1.0 ha−1 yr−1; herbage N yields were 171, 124, and 9 kg N ha−1 yr−1, respectively. Residual N in stubble, crowns, litter, roots, and surface 10 cm of soil after six growing seasons was 1670, 1364, and 996 kg N ha−1 for alfalfa, cicer milkvetch, and grass, respectively. Cicer milkvetch on the Pratt loamy sand died during the dry summer of the second harvest season. Thus, cicer milkvetch appears marginally adapted to loamy upland soils and not adapted to deep sandy soils in the Southern Plains. Alfalfa persisted on the Pratt loamy sand with herbage yields about 87% of yields on the Woodward sandy loam. The performance of alfalfa, including apparent N2 fixation averaging 219 kg N ha−1 yr−1, is encouraging for use on marginal farmlands in the region.
Compatibility of Cicer Milkvetch in Mixtures with Cool‐Season Grasses
Authors: Townsend C. E. , Kenno H. , Brick M. A. 
Published: July 2010

AbstractCicer milkvetch (Astragalus cicer L.) is a promising forage legume, but little information is available on its forage production potential, particularly in mixtures with grasses. The objectives of these studies were to: (i) determine the compatibility of irrigated cicer milkvetch (CMV) with seven cool‐season grasses each planted in alternate rows, and (ii) compare the influence of three planting patterns on the compatibility of irrigated CMV with each of four cool‐season grasses. The seven grass species used in the first study were: smooth bromegrass (Bromus inermis Leyss.), meadow bromegrass (B. biebersteinii Roem. and Schult.), crested wheatgrass [Agropyron cristatum (L.) Beauv. ssp. pectinatum (Bieb.) Tzvel.], intermediate wheatgrass [Thinopyrum intermedium (Host.) Barkworth & Dewey], pubescent wheatgrass [T. intermedium ssp. barbulatum (Schur.)], tall wheatgrass [T. elongatum (Host.) Dewey], and creeping foxtail (Alopecurus arundinaceus Poir.). The grasses used in the second study were smooth bromegrass, meadow bromegrass, intermediate wheatgrass, and orchardgrass (Dactylis glomerata L.). The soil was a Nunn clay loam (mesic Aridic Agriustoll). Tall wheatgrass did not persist beyond the second harvest year. There was little, if any, difference among the other six grasses for compatibility with CMV because by the sixth harvest year the amount of CMV in the mixtures ranged from 76 to 83%. By the third harvest year, the legume content of the forage for the three planting patterns was similar and ranged from about 80 to 90%. Once established, CMV was very competitive with all cool‐season grasses and its forage yields alone and in grass mixtures were very similar to those of alfalfa.
Critical Phosphorus Levels for Corn and Cowpea in a Brazilian Amazon Oxisol
Authors: Smyth T. J. , Cravo M. S. 
Published: July 2010

AbstractPhosphorus soil test interpretations in the Brazilian Amazon currently do not account for differences in P requirements among crops and lack information on the changes in available soil P per unit of applied fertilizer P. A long‐term P experiment in a Xanthic Hapludox near Manaus, Brazil was used to determine soil and leaf P critical levels for corn (Zea mays L.) and cowpea (Vigna unguiculata L.). A total of six corn crops were planted in annual rotation with five crops of cowpea during five consecutive years. Critical levels were established by a segmented linear regression, a linear plateau, of relative crop yields on soil test or leaf P concentrations for each crop species. Mehlich 1 (1:10) critical P levels were 6 and 8 mg kg−1 for corn and cowpea, respectively. Relationships between soil test P and crop yields were similar for fertilizer P placement as either broadcast and/or frequent bands. Fertilizer P required to raise the initial Mehlich 1 soil P to the critical levels were 41 and 60 kg P ha−1 for corn and cowpea, respectively. Higher amounts of P were extracted by Bray 1 than by Mehlich 1, but both extractants were effective in relating available soil P to yield and applied fertilizer P. Critical foliar P concentrations for corn and cowpea were 1.6 and 1.8 g kg−1, respectively. Higher soil and leaf P critical levels for cowpea relative to corn were attributed to greater P requirements for plants depending on symbiotic N2 fixation for their N supply.
Chemical Regulation of Tall Fescue Reproductive Development and Quality with Amidochlor
Authors: Roberts C. A. , Moore K. J. 
Published: July 2010

AbstractMany studies have shown that the quality of tall fescue (Festuca arundinacea Schreb.) forage can be improved by chemically regulating reproductive development. This study was conducted in order to determine whether tall fescue reproductive development and quality could be regulated by amidochlor {N‐[(acetylamino)methyl]2‐chloro‐N‐(2,6‐diethylphenyl)acetamide}, a growth regulating chemical currently used for industrial turf management. In 1985 and 1986, unimproved tall fescue pastures which were located on an Alford silt loam (fine‐silty, mixed, mesic Typic Hapludalf) soil at the Dixon Springs Agricultural Research Center, near Simpson, IL, received amidochlor at 0,0.56, and 1.12 kg a.i. ha−1, Initial growth was harvested at 0, 14, 28, and 42 d after boot stage and regrowth harvested at 6 wk after initial cutting. Each year, treatments were replicated four times and plots were randomized in a split‐plot design. Because of unusual seedhead production during 1986, data were different between years and were not combined for statistical analysis. In 1985, seedhead formation decreased as amidochlor rate increased. For both initial growth and regrowth, crude protein and in vitro dry matter digestibility increased and cell wall concentration decreased as amidochlor increased. In 1986, however, untreated plots contained only 45 seedheads m−2 and amidochlor did not regulate flowering. The higher quality of forage in 1986 resulted from prevalent vegetative tissue. We concluded that amidochlor can improve forage quality of tall fescue if tillering has not been limited the previous fall.
Salinity Effects on Emergence, Vegetative Growth, and Seed Yield of Guar
Authors: Francois L. E. , Donovan T. J. , Maas E. V. 
Published: July 2010

AbstractGuar [Cyamopsis tetragonoloba (L.) Taub] seed is an important source of galactomannan gum used in food and industrial products. Increased demand and an insufficient domestic supply has led to an increased interest in this crop in the semi‐arid western USA where many soils are, or have the potential to become, highly saline. This study was conducted to determine the effect of soil salinity on vegetative growth and seed yield of two cultivars, 'Kinman' and 'Esser,' grown under field conditions. Six salinity treatments were imposed on a Holtville silty clay [clayey over loamy, montmorillonitic (calcareous), hyperthermic Typic Torrifluvent] by irrigating with waters salinized with NaCl and CaCl2 (1:1 by weight). Electrical conductivities of the irrigation waters were 1.3, 2.5, 5.0, 7.4,10.0, and 12.4 dS/m during the 1st yr, and 1.2, 2.5, 4.5, 5.5, 6.5, and 7.5 dS/m during the 2nd yr. Seed yield of both cultivars was unaffected by soil salinity up to 8.8 dS/m (mean electrical conductivity of the saturated‐soil extracts in the rootzone). Each unit increase in salinity above 8.8 dS/m reduced seed yield by 17%, which places guar in the moderately tolerant category for seed production. Reduction in the number of pods per plant and weight per seed were the primary factors contributing to reduced yields. Vegetative growth was decreased 9.6% for each unit increase in salinity above 4.9 dS/m. Plant emergence was determined in greenhouse sand cultures with irrigation waters of 0.8, 4.4, 8.5,11.3,15.7, and 18.8 dS/m. Emergence was unaffected by salt levels up to 8.5 dS/m; greater levels delayed but did not significantly reduce the percent emerged.
Norm Range Size Effects in Calculating Diagnosis and Recommendation Integrated System Indices
Authors: Savoy H. J. , Robinson D. L. 
Published: July 2010

AbstractCalculation of Diagnosis and Recommendation Integrated System (DRIS) indices using a norm range may minimize incorrectly diagnosed deficiencies and maximize correct diagnoses of nutrient balance. This study evaluated the effects of size of the norm range on DRIS P and K overall‐diagnostic and response‐prediction accuracies in order to identify an optimum norm range for practical application. Field data were obtained from P and K rate experiments with Louisiana S‐1 white clover (Trifolium repens) on Dexter loam (fine‐silty, mixed, thermic Ultic Hapludalf) and Providence silt loam (fine‐silty, mixed, thermic Typic Fragiudalf) soils of adequate and relatively low, respectively, P and K levels. The DRIS indices were calculated at norm ranges of 0/3 (the norm value ±0), 4/3, 8/3,12/3, and 16/3 σ and verified for correctness. The use of a norm range in the calculation of DRIS indices increased P and K overall‐diagnostic accuracies as much as 23 and 27%, respectively, on the Dexter soil. for the Providence soil these values were 5 and 21%, respectively. Widest norm ranges resulted in a decrease in P and K responseprediction accuracies of 10 and 23%, respectively, on the responsive Providence soil. The importance of using a norm range for the calculation of DRIS indices was demonstrated by these results. It appears that the greatest benefit may be realized in nonresponsive to moderately responsive systems. The norm range of 8/3 σ appears to be an acceptable compromise for calculation of DRIS indices at sites where the nutrients of interest are in relatively low supply. A wider norm range of 12/3 or 16/3 σ was indicated at sites with adequate nutrient supplies.
Relationships between Grain Nitrogen Concentrations and the Nitrogen Status of Corn
Authors: Cerrato M. E. , Blackmer A. M. 
Published: July 2010

AbstractGrain analysis is frequently used to determine the N status of corn (Zea mays L.). The objective of this study was to assess the reliability of N concentration in grain as an indicator of the N status of corn. The study involved 12 site‐years of data, each having 10 rates of N applied preplanting. Nitrogen concentrations in grain tended to increase with increases in rates of N application. Nitrogen concentrations also tended to increase with increases in relative yields, but the relationships often were C‐shaped, and there was no basis for establishing critical N concentrations. The relationships between N concentrations in grain and adjusted rates of N fertilization (i.e., rates of fertilization expressed relative to economic optimum) were statistically significant, but they had low predictability. For example, only 19% of the variability in N concentrations could be explained by a model that considered only data between ± 100 kg N ha−1 from economic optimum rates of fertilization. Only 1% of the variability could be explained by a model that considered only data between ±50 kg N ha−1 from economic optimum. These observations indicate that, especially where the availability of N is near or above optimal, N concentration in grain does not provide a reliable indicator of the N status of corn.
Line‐Source vs. Irrigated/Nonirrigated Treatments for Evaluation of Genotype Drought Response
Authors: Mahalakshmi V. , Bidinger F. R. , Rao G. D. P. 
Published: July 2010

AbstractThe need for efficient and effective screening for drought response of crops is well recognized. The line‐source sprinkler technique used in many crop breeding programs to evaluate genotype response to drought stress has the advantage over the traditional irrigated/nonirrigated or uniform plot technique in that it creates a continuous range of moisture deficits which permit the estimation of genotype response. In situations where the response is linear, however, the line source may not provide additional information compared to that available from the uniform plot, if both techniques sample the same range of moisture deficits. Field experiments were conducted over 2 yr to compare both screening techniques for evaluating genotype response of pearl millet [Pennisetum glaucum (L.) R. Br.] to water deficit at grain filling. The soil was an Alfisol (Udic Rhodustalf) with approximately 60 mm of plant‐available moisture. Mean grain yields for individual positions along the moisture gradient in the line source, and means over genotypes for each replicate in the uniform plot were used as independent variables (environment means) to estimate individual genotype stress response by regression. Predicted genotype grain yield at 250 g m−2 mean yield and genotype regression coefficients were compared. There were no differences in the estimated genotype grain yields at 250 g m−2 mean grain yield from the two techniques in either year. Slopes differed in only four of the 32 genotypes in 1982 and two of the eight genotypes in 1984. When genotype response to the stress gradient is linear, the simpler uniform plot technique can be used for preliminary genotype evaluation with little loss of information.
Plant Height, Disk, and Capacitance Meters Used to Estimate Bermudagrass Herbage Mass
Authors: Gonzalez M. A. , Hussey M. A. , Conrad B. E. 
Published: July 2010

AbstractRapid and reliable techniques for estimating herbage mass (HM) are essential for germplasm evaluation and proper grazing management. Since hand‐clipping small quadrats is time consuming, mathematical relationships between easy to use, nondestructive techniques and hand‐clipped estimates of HM (double sampling) have been utilized. This study was conducted to quantify relationships between HM and three commonly utilized nondestructive sward measurement techniques [plant height (HT), settled disk meter height (DISK), and capacitance (CAP)] in field plantings of ‘Brazos’ bermudagrass [Cynodon dactylon (L.) Pers.]. Estimates of HM, HT, DISK, and CAP were obtained from the same location in irrigated plots and nonirrigated, grazed pastures. Linear equations were observed to describe the relationship between HM and HT [ Y = 414 + 12.9X (r2 = 0.86), Y = 37 + 21.7X (r2 = 0.86)] and CAP [ Y = ‐1276 + 2.4X(r2 = 0.77), Y = 1289 + 2.8X (r2 = 0.89)] for plots and pastures, respectively. The relationship between HM and DISK was linear [ Y = 282 + 29.3X (r2 = 0.91)] and quadratic [ Y = 421 + 44.9X ‐ 0.7X2 (r2 = 0.80)] for the pasture and plot studies, respectively. For all HM relationships, the ability to predict HM was generally better in pastures than in small plots. Problems associated with lodged herbage in plots greatly influenced the HM predictive relationships of all techniques presumably by increasing the variability at high HM levels. Due to the large differences in the range of HM, in tiller height and tiller density, separate equations were required to predict HM in pastures and plots, regardless of the technique utilized. No single technique was observed to best predict HM. In the pastures, CAP and DISK were more efficient at estimating HM, while in the plots HT was the most efficient estimator of HM. This study suggests, while double‐sampling may allow for the estimation of HM in bermudagrass, factors such as tiller height and tiller density will influence the predictive relationships of all techniques requiring separate prediction equations to be developed where differences in sward composition are expected.
Seedling Kentucky Bluegrass Growth Responses to Chelated Iron and Biostimulator Materials
Authors: Goatley J. M. , Schmidt R. E. 
Published: July 2010

AbstractEnhanced growth of seedling turfgrasses with biostimulator materials or chelated Fe could accelerate the rate of establishment. Field experiments in the spring and fall of 1987 and in the greenhouse in the winter of 1988 were designed to measure seedling Kentucky bluegrass (Poa pratensis L.) growth responses to foliar applications of benzyladenine (BA, 6‐benzylaminopurine), propiconazole [1‐{[2‐(2,4‐dichlorophenyl)‐4‐propyl‐1,3‐dioxolan‐2‐yl]methyl}‐l‐(1H‐1,2,4‐triazole], triadimefon [l‐(4‐chlorophenoxy)‐3,3‐dimethyl‐l‐(1H‐1,2,4‐triazol‐1‐yl)‐2‐butanone], or a fortified seaweed extract (SWE, containing 500 µg L−1 of glycol kinetin and 500 µg L−1 gibberellins) applied alone or in combination with chelated Fe (8% Fephosphate citrate). The seaweed extract (0.03 mL product m−2) significantly increased root and shoot growth 6 wk after treatment (WAT) in the spring experiment, and 4 and 6 WAT in the winter greenhouse experiment. The SWE also increased the gross CO2 exchange rate (CER) on a land area basis 4 and 6 WAT in the winter experiment. Propiconazole (42 mg m−2) significantly increased seedling leaf number 6 WAT in the fall experiment. Triadimefon (150 mg m−2)or BA (6 mg m−2)applications generally were not as effective in increasing seedling growth as were the SWE or propiconazole. Foliar Fe applications (112 mg m−2), either alone or in combination with biostimulators, significantly increased root and shoot growth and gross CER on a land area basis 4 and 6 WAT in the winter greenhouse experiment. Applications of Fe increased root dry weight 6 WAT in the spring field experiment. Growth responses to individual biostimulator and Fe combinations were highly variable among experiments, suggesting possible interactions between the growth response mechanisms of the treatments.
Irrigation of Turfgrass with Secondary Sewage Effluent: I. Soil and Leachate Water Quality
Authors: Hayes A. R. , Mancino C. F. , Pepper I. L. 
Published: July 2010

AbstractIn arid climates water is a limited resource, and turfgrass is often irrigated with municipal effluent. However, the effects of continuous turfgrass irrigation with sewage effluent on soil and leachate water quality needs to be evaluated. The objective of this field experiment was to evaluate the effect of secondary treated municipal effluent irrigation on soil and leachate properties under a turf groundcover during the first 16 mo of irrigation. Research plots were irrigated identically with either effluent or potable water using a leaching fraction of approximately 20%. Effluent irrigation resulted in significant changes in soil properties after a relatively short period of time. After 16 mo of use, when compared with potable irrigation, effluent was found to increase electrical conductivity (EC) by 0.5 dS m−1, NO3–N by 7.8 mg kg−1, P by 31.7 mg kg−1, K by 134 mg kg−, Na by 6.0 mmol L−1 and the exchangeable sodium percentage (ESP) by 6.8. Soil Ca + Mg concentrations were greater under effluent irrigation by 0.5 mmol L−1 but decreased during the study period. Soil pH was not significantly different from potable irrigation. Leachates collected at 0.61‐m depth indicated that effluent soil leachates were higher than potable leachates primarily in EC by 0.2 dS m−1 and Na content by 0.8 mmol L−1. The increase did not exceed current recommended limits for drinking water quality.
A Concise Table for Path Analysis Statistics
Authors: Williams W. A. , Demment M. W. , Jones M. B. 
Published: July 2010

AbstractA concise format for presenting path analysis statistics is demonstrated in which the path coefficients are placed in the main diagonal of a matrix, and the indirect effects are placed as off‐diagonal elements. This arrangement makes it easier to compare within and among path analyses than with the currently used format, thus facilitating interpretation.
Rainfall Distribution under a Corn Canopy: Implications for Managing Agrochemicals
Authors: Parkin T. B. , Codling E. E. 
Published: July 2010

AbstractA greater understanding of the spatial patterns of water inputs to soil will aid the development of agricultural practices to reduce leaching and runoff of agrochemicals. This study was initiated to investigate the process of stemflow, and to provide quantitative data on the distribution of rainfall under a corn (Zea mays L.) canopy. Rainfall distribution under the canopies of replicate conventional till corn plots was investigated by placing rainfall collectors at discrete locations within small 1.6‐m by 0.76‐m areas of the plots. Collection cups were also fixed around the stalks of individual corn plants to quantify stemflow. Results obtained from eight storm events in 1987 revealed that corn plants channel 19 to 49% of the total rain inputs down the stem to the base of the stalk. This stemflow plus the rainfall impinging directly in the planting furrow, accounted for approximately 42% of the total water inputs from a given storm event. These increased water inputs to the planting furrow may have implications in modeling solute leaching and runoff as well as to modifying current fertilizer and pesticide application methods.
Rapid Measurement of Crop Canopy Cover
Authors: Armbrust D. V. 
Published: July 2010

AbstractStudies of photosynthesis, transpiration, water erosion, and wind erosion can require measurement of crop canopy cover, the percent of the soil surface covered by plant foliage. This study was conducted to evaluate the meter‐stick method and an electronic method of measuring canopy cover for accuracy, speed, and ease of use. Canopy cover of winter wheat [Triticum aestivum L.], corn [Zea mays L.], and soybean [Glycine max (L.) Merr] was measured weekly in 1988, using a meter stick and a DECAGON Ceptometer. Canopy cover ranged from 74 to 97% for wheat, 2 to 95% for corn, and 2 to 65% for soybean. There were no significant differences in canopy cover determinations by the two methods. The Ceptometer was faster, simpler, and as accurate as the meter stick.