bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Rothamsted Long‐Term Experiments: Are They Still of Use?
Authors: Jenkinson D. S. 
Published: July 2010

AbstractThe Rothamsted long‐term experiments—the Classicals—were started almost 150 yr ago. These experiments were originally designed to study the N, P, K, Na, Mg, and Si needs of the field crops then grown in England. This was done by comparing these inorganic nutrients, in various combinations, with farmyard manure, the traditional source of fertility at that time. Although the questions the experiments were originally designed to answer have long been re‐solved, the experiments continue to give results of interest to agronomists, ecologists, soil scientists, plant pathologists, and others. The experiments show that grain yields can be sustained (and even increased) for almost 150 years in monocultures of wheat and barley given organic or inorganic fertilizer annually. They provide data on the long‐term effects of inorganic fertilizers and organic manures on soil organic matter levels. These data have been used to test computer‐based models for the turnover of organic matter in soil. Again, long‐term N balances show that there are considerable inputs of N to the soil/plant system, amounting to some 30 kg N ha−1 yr−1 in unfertilized wheat and up to 65 kg ha−1 yr−1 in an arable soil reverting to woodland. These and other results are used to consider the advantages and disadvantages of long‐term experiments. Wisely used, long‐term experimental sites provide information on the long‐term sustainability of agricultural systems that can be obtained in no other way.
Lysimetric Evaluation of Daily Potential Evapotranspiration Models for Grain Sorghum
Authors: Steiner J. L. , Howell T. A. , Schneider A. D. 
Published: July 2010

AbstractEvapotranspiration (Et) information is needed for many applications in agricultural and natural resource management, but commonly used prediction equations have not been adequately tested far the dry, high radiation, windy conditions of the Southern Great Plains. In order to test such equations, two precise weighing lysimeters at Bushland, TX, were used to measure daily Et from wellwatered, irrigated grain sorghum [Sorghum bicolor L.) Moench] in 1987 and 1988. Forms of the Penman, Penman‐Monteith, Jensen‐Haise, and Priestley‐Taylor models were evaluated for prediction of potential evapotranspiration (Etp). The Penman‐Monteith model provided the best predictions of Etp and predicted well across the entire range of measured Et. Forms of the Penman model with empirically fit wind functions overpredicted Etp by 20 to 409/0, and aftempts to fit a linear wind function to our data were not satisfactory The Jensen‐Hake model, requiring only daily mean temperature and solar radiation data, overpredicted by 30%, but performed consistently across the range of Et measured. Modification of the Priestley‐Taylor model with vapor pressure deficit or temperature advection terms is recommended. Without such modification, the model overpredicts at low Et rates and underpredicts at high Et rates.
Plant Population Effects on Growth and Yield in Water‐Seeded Rice
Authors: Miller Baird C. , Hill James E. , Roberts Stacey R. 
Published: July 2010

AbstractInitial management strategies, such as established plant stand, significantly affect rice (Oryza sativa L.) crop development, grain yield, and final profits. Critical rice plant population for optimum yield differs greatly among various cultural systems. The objectives of this study were to: (i) characterize effects of increasing plant population on tillering, yield components, yield, and phytomass development in continuously flooded, direct water‐seeded rice culture; and (ii) identify which crop development parameters are associated with optimum grain yield in this cultural system. Two cultivars, S‐201 and M‐201, were seeded at rates ranging from 120 to 840 seeds m−2 on Stockton clays (fine, montmorillonite, thermic, Typic Pelloxererts) in Butte and Colusa counties, California, in 1984 and 1985. Plant populations ranged from 122 to 458 plants m−2. Initial rapid tillering resulted in a maximum tiller density within 37 to 63 d after seeding (DAS). Total above‐ground phytomass (TAGPM) was not significantly different among the plant populations, either during or at the end of the growing season. Although final vegetative above‐ground phytomass (VAGPM) increased as a function of tiller density, VAGPM above 850 g m2 did not result in further yield increases. Grain yields were dependent on final tiller density (FTD) rather than plant population, with yields increasing as FTD increased to 700 tillers m−2, Panicles m−2, a direct result of FTD, was the most important component of yield accounting for 89% of the variation in yield. Final tiller density or the tillering capacity of the rice crop is determined by the environmental limitations and favorability of the growing conditions. Under continuously flooded, direct water‐seeded culture, the rice crop functioned more as a population of tillers than a population of plants.
Inhibition of Weed Seed Germination by Microwaves
Authors: Barker Allen V. , Craker Lyle E. 
Published: July 2010

AbstractIrradiation with radiofrequency energy (RF), which includes microwaves, brings about dielectric heating of moist materials. Some agricultural applications of dielectric heating by RF have included insects control in stored grains and improved germination of seed stocks. The objective of the present research was to evaluate microwave heating of soils as a technique for weed control. Approximately 800‐g masses of soil of variable wetness (10‐280 g H2O/kg soil) containing seeds of oat (Arena sativa L.) and indigenous weeds were heated in a microwave (2.45 GHz) oven for 15 to 240 s. Soil masses were 5 cm deep in flats. Oat seeds were placed 2 cm deep into the soil. Hearing of soils to 80 °C or higher inhibited emergence of oats and weed species. About 120 s of heating were needed to reach 80 °C. Maintaining this temperature for 30 s was needed for strong inhibition. Moisture content in this experiment had little effect on dielectric heating. Time required to heat soil to killing temperatures appears to be a factor limiting application of this technique. The procedure may be applicable to soil sterilization in cases in which other physical processes or chemical means are inconvenient or undesirable.
Model for Steady State Coupled Transport in Xylem and Phloem
Authors: Boersma L. , Lindstrom F. T. , Childs S. W. 
Published: July 2010

AbstractKnowledge of water potentials throughout the xylem and phloem elements is required for understanding effects of water stress on transport of water, solutes, and carbohydrates in plants. The interaction between water potentials in xylem and phloem is of particular concern. This knowledge is difficult to obtain through experimentation but insights can be gained by means of computer programs based on mathematical statements of the processes involved. A steady state transport model was developed to gain better understanding of this interaction. The model consists of a set of equations developed from compartmental analysis of coupled xylem and phloem transport in plant roots, stems, and leaves. The set of equations is solved using a Newton‐Raphson iterative procedure. Simulations with user specified air temperature, relative humidity, water potential at the root surface, and carbohydrate concentrations in leaf and root as input variables show the effect of water stress on rate of xylem and phloem transport at six points in time during a 1 d cycle of changing air temperature and relative humidity. Maintenance of phloem pressure gradients is shown to be very sensitive to changing environmental conditions. Using user specified input, xylem and phloem transport rates were highest at midday. At 1800 h the xylem and phloem transport rates were 83 and 30% of maximum rates that occurred for both rates at 1200 h. The model provides a basis for conceptual analysis of effects of water stress on the food distribution in plants. Further development requires a systematic sensitivity analysis and comparison with experimental results.
Yield, Digestibility, and Chemical Composition of Endophyte Free and Infected Tall Fescue
Authors: Fritz J. O. , Collins M. 
Published: July 2010

AbstractUtilization of low‐endophyte (Acremonium coenophialum Morgan‐Jones and Gams) cultivars of tall fescue (Festuca arundinacea Schreb.) has been shown to improve animal performance; however, insufficient information is available on the direct effects of endophyte infection on the productivity and composition of tall fescue herbage. A 2‐yr field study was conducted to assess the effects of A. coenophialum infection on the yield, digestibility, and chemical composition of tall fescue. Endophyte‐free (EF) and endophyte‐infected (EI) plots for each of two tall fescue cultivars (Kenhy and Kentucky 31) were established in August 1985 on a Maury silt loam (fine, mixed, mesic Typic Paleudalt) soil. Dry matter yields were determined for three harvests made in 1986 and 1987. Total N, fiber composition, and in vitro rate and extent of neutral detergent fiber (NDF) digestion were determined on samples of first and second harvest forage. Dry matter yields were not affected by infection status and averaged 0.80 and 0.83 Mg ha−1 in 1986 and 1.69 and 1.79 Mg ha−1 in 1987 for EF and EI tall fescue, respectively. Endophyte infection status had no effect on the rate or extent of NDF digestion. Rate of NDF digestion averaged 0.056 and 0.055 h−1 for EF and El tall fescue, respectively. Endophytic infection also had no influence on the N concentration or fiber composition of tall fescue. The results of this study suggests that A. coenophialum does not have a significant effect on the digestibility or chemical composition of tall fescue.
Nitrogen Effects on Yield and Forage Quality of Perennial Ryegrass and Tall Fescue
Authors: Collins Michael 
Published: July 2010

AbstractNegative animal effects of tall fescue (Festuca arundinacea Schreb.) infected (EI) with the endophytic fungus Acremonium coenophialum Morgan‐Jones and Gams are reduced by substituting endophyte‐ free (EF) tall fescue or other forage species. A field experiment was conducted on Maury silt loam (fine, mixed, mesic, Typic Paleudults) soil from 1986 to 1988 to compare forage yields and quality of ‘Kenhy’‐EF, Kenhy‐EI, and ‘Johnstone’ tall fescue with ‘Ensilo’ (diploid) and ‘Reveille’ (tetraploid) perennial ryegrass (Lolium perenne L.) and ‘Bison’ ryegrass (Lolium intermediate). Each cultivar received 0, 75, or 150 kg ha−1 of N annually. At 150 kg ha−1 of N, Johnstone produced the highest 1987 to 1988 average dry matter (DM) yields of 6.7 Mg ha−1 compared with 5.7 Mg ha−1 for Kenhy‐EI. Tall fescue generally produced higher yields than ryegrass. Ground cover after 3 yr for Reveille of 72% did not differ from Kenhy‐EI (79%), but Ensilo (61%) and Bison (31%) were lower. Endophyte effects on yield and quality of Kenhy were seldom significant. Two‐year weighted average in vitro dry matter disappearance (IVDMD) values were 685, 663, 626, 628, and 641 g kg−1 for Reveille, Ensilo, Kenhy‐EF, Kenhy‐EI, and Johnstone, respectively. Increasing N levels increased N concentration of tall fescue but did not consistently affect that of ryegrass. These results indicate that some cultivars of ryegrass can persist at this location, but that summer productivity is well below that of tall fescue. However, some potential may exist for germplasm improvement of perennial ryegrass based on existing cultivars. Endophyte effects on yield and quality of Kenhy tall fescue under the conditions of this study were small.
Aflatoxin in Corn Hybrids Field Inoculated with Aspergillus flavus
Authors: Scott G. E. , Zummo N. , Lillehoj E. B. , Widstrom N. W. , Kang M. S. , West D. R. , Payne G. A. , Cleveland T. E. , Calvert O. H. , Fortnum B. A. 
Published: July 2010

AbstractCorn (Zea mays L.) genotypes with resistance to Aspergillus flavus Link ex Fr. are needed to reduce aflatoxin contamination of grain. The primary objective of this study was to determine if the pinbar inoculation technique was effective in separating hybrids for resistance and susceptibility to kernel infection by A. flavus and aflatoxin contamination of the grain at a number of locations, but other inoculation techniques were evaluated at individual locations. Two single crosses, Mo18W × Mp313E and SC54 × Tx601, previously classified as resistant to kernel infection by A. flavus and two susceptible crosses, Mp68:616 × SC212M and GT106 × T202, were used. We found that hybrids previously classified as resistant to kernel infection by A. flavus had fewer kernels infected and lower aflatoxin concentration in the corn grain at harvest. However, these differences were not significant at all locations. Over six locations, resistant hybrids contained 58% less aflatoxin in the grain and 41% fewer infected kernels than susceptible hybrids. In addition to the pinbar, the side‐needle, and to a lesser extent the knife inoculation technique, differentiated hybrid response to ear inoculation with A. flavus.
Sorghum Harvest Index in Relation to Plant Size, Environment, and Cultivar
Authors: Prihar S. S. , Stewart B. A. 
Published: July 2010

AbstractThere are reports in the literature showing that harvest index (HI) does and does not increase with increase in plant size. The slope of the upper‐bound line passing through the origin in the grain yield vs. dry matter yield plots has been proposed to approximate the “genetic” HI for a given environment and inter‐cultivar comparison. The objectives of this study were to determine what changes occur in HI of sorghum [Sorghum bicolor (L.) Moench] as plant size, environment, and cultivar vary. Several environments were established in two replicated field experiments on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll), one with eight cultivars, and the other with two cultivars, three seeding dates, and three irrigation regimes. Cultivar DK‐41Y were common to both experiments. Variation in plant size was created by thinning the original stands to varying degrees. Harvest index was determined for different plant densities based on individual plant data. Lack of non‐zero intercepts of grain‐yield vs. dry‐matter‐per‐plant regressions and constancy of HI with change in plant mass, under a given environmental condition, showed that HI was independent of plant size. Harvest index values, based both on average grain and dry matter yield, and slope of the upper‐bound line, were sensitive to environments. Upperbound HI values of cultivars DK‐42, DK‐41Y, and Sprint (0.50–0.52) were significantly higher than those of Funks 499, Richardson 9112, and DK‐46 (0.46–0.48).
Single Leaf and Canopy Photosynthesis Response to Plant Age in Cotton
Authors: Peng Shaobing , Krieg Daniel R. 
Published: July 2010

AbstractThis study was conducted to determine the single leaf and canopy photosynthesis response to plant age in cotton (Gossypium hirsutum L.). Field experiments were conducted with different row spacings and leaf types to provide a range of plant and leaf distribution patterns. Single leaf gas exchange measurements were made on uppermost, fully expanded, main stem leaves throughout the growing season when air temperature was about 27 °C and photosynthetically active radiation exceeded 1800 μmol m−2 s−1. Canopy photosynthetic rate per unit ground area was measured concurrently with the single leaf gas exchange rate. Leaf water potential and light interception were determined when the gas exchange measurements were made. Leaf area was measured to calculate canopy photosynthetic rate per unit leaf area. Single leaf photosynthetic rates declined 27 to 38% as plant age increased from 70 to 115 d after planting, the period of maximum dry matter accumulation. The canopy photosynthetic rate per unit ground area reached a maximum between 80 and 90 days after planting, as leaf area increased, but then declined rapidly. The decline in canopy photosynthetic rate per unit ground area was mainly due to the decline in single leaf photosynthesis rather than loss of existing leaf area as plant age increased, as indicated by a corresponding decline in canopy photosynthetic rate per unit leaf area. The decline in photosynthesis as plants aged was not caused by environmental limitations or carbon evolution from the soil. The rapidly developing fruit load and associated C evolution accounted for only 20% of the decline in canopy photosynthetic rate per unit ground area.
Reflectances from Four Wheat Residue Cover Densities as Influenced by Three Soil Backgrounds
Authors: Aase J. K. , Tanaka D. L. 
Published: July 2010

AbstractIt is important to know quantity of crop residue on the soil surface to maintain or to improve soil physical and chemical properties and to assess the soil's susceptibility to erosion. Our objective was to use remote sensing techniques to examine the potential for remotely differentiating among wheat residue quantities and bare soils. We used three soils of the northern Great Plains (Williams loam [fineloamy, mixed Typic Argiboroll], Vanda Clay [fine‐silty, mixed calcareous, frigid Ustic Torriorthents], and Lambert silt loam [finesilty, mixed calcareous, frigid Typic Ustorthents]) that had either dry or wet surfaces and 0, 33, 66, and 100% wheat residue covering the soil surfaces. A portable spectroradiometer, and a hand‐held four‐band radiometer were used to measure spectral response and an infrared thermometer to measure surface temperatures. The infrared thermometer results allowed for differentiation among wet and dry surfaces and among residue quantities when the soil background was wet. Temperature differences between wet and dry surfaces became smaller as residue quantities increased and were near the same at 100% cover. Data obtained from the two radiometers were similar. Based on the type of measurements made in our study and indices calculated, the conclusions are that remotely sensed temperatures may be useful to assess surface soil residue covers when all soil backgrounds are wet. Linear combinations of n spectral bands in n‐dimensional space were calculated to form spectral indices, referred to as n‐space indices. The first n‐space index probably holds the best promise for developing any type of relationship to determine amount of residue cover on an otherwise bare soil surface, albeit, it appears from the data that the usefulness of such a relationship would be limited to soils that are naturally dark colored or that are darkened by the effect of water.
Instrument for Indirect Measurement of Canopy Architecture
Authors: Welles J. M. , Norman J. M. 
Published: July 2010

AbstractLeaf area index (LAI) and leaf angle distribution are widely used indices of vegetative canopy structure that are difficult to measure directly. This study was conducted to test a commercially available instrument for rapidly determining LAI and foliage inclination information from “fisheye” measurements of light interception. The instrument's estimates of LAI are compared with direct measurements in soybean [Glycine max (L.) Merr.], winter wheat (Triticum aestivum L.), and prairie grass. The dominant grass species in the plots were indian grass [Sorghastrum nutans (L.) Nash], switchgrass (Panicum virgatum L.), and big bluestem (Andropogon gerardii Vitman). The instrument's LAI resolution was better than 3%, and its LAI error was generally less than 15%. Variations in sky brightness patterns caused variations in LAI estimates in winter wheat of less than 10%, and the presence of direct solar radiation increased LAI errors to more than 30% in canopies of differing species and LAI. In the presence of gaps in the canopy, the sensor's azimuthal view should be reduced. A simple test indicates if a canopy's gaps are significant.
Statistical Analysis of Yield Trials with MATMODEL
Authors: Gauch H. G. , Furnas R. E. 
Published: July 2010

AbstractYield trials guide agronomic recommendations and breeding selections, but often are limited by inaccuracy, missing data, and the difficulty of understanding complex genotype‐environment interactions. Recent studies have shown that a statistical model rather new to agriculturalists, the Additive Main Effects and Multiplicative Interaction (AMMI) model, can reduce these limitations. This paper introduces MATMODEL, a convenient program for the required calculations that runs on IBM compatible personal computers with MS‐DOS (PC‐DOS) 2.1 or higher and on the Apple Macintosh. MATMODEL enables one to (i) increase the accuracy of yield estimates, (ii) improve selections, (iii) impute missing data, (iv) model and understand the genotypes, environments, and interaction, particularly with a biplot graph, and (v) design flexible and efficient experiments. MATMODEL routinely provides yield estimates as accurate as raw treatment means based upon two to five times as many replications, so MATMODEL offers a remarkably cost‐effective option for gaining accuracy. This option is particularly valuable in light of recent trends towards testing genotypes in more environments with fewer replications.
Chlorophyll Meter to Predict Nitrogen Topdress Requirement for Semidwarf Rice
Authors: Turner Fred T. , Jund Michael F. 
Published: July 2010

AbstractSemidwarf rice (Oryza sativa L.) tolerates excessive N fertilizer without lodging. In fact, it is difficult to maximize semidwarf rice yield without applying excessive N fertilizer since most farmers have not found a quick, unbiased, reliable method for assessing the N requirement for rice plants. A portable chlorophyll meter that instantly provides a measure of leaf chlorophyll may quickly monitor the need for additional N fertilizer. The Minolta model SPAD 502 chlorophyll meter was evaluated during a 3‐yr period for its potential to determine the need for N fertilizer by semidwarf ‘Lemont’ rice grown in research plots on several soils and locations in Texas. Preplant N rates ranging from 56 to 280 kg N ha−1 were applied to paired plots to develop plots with a range in leaf chlorophyll. At one of four plant growth stages, one of the pair of plots was topdressed with 50 kg N ha−1 after measuring leaf chlorophyll. At the prepanicle initiation and panicle differentiation stages, the rice yield increase due to N topdressing dropped from about 1600 to 100 kg ha−1 as the chlorophyll meter readings of the most recently matured leaf increased from 24 to 42, respectively. As chlorophyll readings exceeded 40, N fertilizer did not increase yield. However, at the tillering and heading growth stages chlorophyll readings were not well correlated with N fertilizer needs. These data provide evidence that the chlorophyll meter can be used to determine topdress N needs of semidwarf rice at pre‐panicle initiation and panicle differentiation.