bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Method to Monitor Root Decomposition Demonstrates that Salt Stress Can Enhance the Rate of Tomato Root Decomposition
Authors: Snapp Sieglinde S.
Published: July 2010

This study quantified the effects of an abiotic stress, salinity, and a biotic stress, phytophthora root rot, on root mortality and decomposition in tomato (Lycopersicon esculentum Mill.). Rhizotron windows were used to measure root mortality rates in mature, container‐grown plants. A novel assay was developed to monitor root decomposition by quantifying root‐length disappearance over time using petri dishes in incubation chambers. Phytophthora root rot infection was induced by salt stress in the presence of Phytophthora parasitica Dastur inoculum; however, the moderate levels of disease induced had no effect on rates of root mortality or on root decomposition. Genotypic differences in root decomposition under salt stress were shown by the decomposition assay, the first report of intraspecific variation in root decomposition rates. High‐salt UC82B had 50% higher root mortality and a threefold higher initial root decomposition rate than low‐salt UC82B. In contrast, salinity did not enhance root mortality or decomposition in cv. CX8303. UC82B grown under salt stress had thin roots of high N concentration, whereas salt stress did not alter N concentration in CX8303 roots. On a plant by plant basis, root N concentration was correlated with initial rootlength loss in the degradation assay, whereas root diameter was not. The results indicate that an indirect consequence of salt stress could include rapid root decomposition.
Performance Comparisons of Conventional and Laboratory‐Scale Alfalfa Hay Bales in Isolated Environments
Authors: Coblentz Wayne K. , Fritz John O. , Bolsen Keith K.
Published: July 2010

Negative quality changes, including Maillard reaction damage, in alfalfa (Medicago sativa L.) hay frequently are associated with spontaneous heating resulting from packaging and storing forage at moisture levels in excess of 200 g kg−1. Forage at three moisture levels (268, 229, and 185 g kg−1) was packaged in laboratory‐scale bales at 1.0, 1.3, 1.7, and 2.0 times the density of parent, conventional bales and subsequently incubated in two different isolated environments such that all measured heat accumulation was the result of self‐generated heat. Laboratory scale hay packages generated measurable heat and exhibited quality changes when incubated (i) between straw bales stacked in an open‐air pole shed and (ii) in insulated incubator boxes in a storeroom where the minimum ambient storage temperature was set at at 25°C. Heat development and negative quality changes were greater in the box‐incubation system, indicating a need to control ambient storage temperature. At the high and medium moisture levels, acid‐detergent insoluble N (ADIN) fractions for high‐density, box‐incubated laboratory bales were at least similar (P = 0.05) to those of parent, conventional bales, despite large disadvantages in measures of accumulated heat. These responses in laboratory bales were consistent with those reported in previous haystack‐incubated studies and suggest that the environmental heat component created by adjacent conventional bales in those studies may have had a limited direct effect on ADIN content. Increasing density of laboratory bales probably rendered alfalfa proteins more susceptible to Maillard reaction damage and/or allowed the reaction to proceed more efficiently with respect to self‐generated heat than it did in conventional bales.
Winter Wheat Yield and Grain Protein across Varied Landscape Positions
Authors: Fiez Timothy E. , Miller Baird C. , Pan William L.
Published: July 2010

Winter wheat (Triticum aestivum L.) yield varies greatly among landscape positions in the Palouse region of eastern Washington, yet N fertilizer is typically applied uniformly. Varying N fertilizer rates within fields to match site‐specific N requirements can increase fertilizer use efficiency; however, spatially variable N management programs are limited by their ability to predict site‐specific yield potentials and the resultant N requirements. The objective of this study was to ascertain the role of yield components and soil properties in determining soft white winter wheat grain yield and protein when N application rates are varied among landscape positions. Nitrogen fertilizer (0 to 140 kg N ha−1) was fall‐applied on footslope, south‐backslope, shoulder, and north‐backslope landscape positions at each of two farms in 1989 and in 1990. Grain yield among landscapes varied by up to 55% in 1990 and by up to 33% in 1991. Landscape position grain yields increased by 199 kg ha−1/(cm precipitation + soil water reduction) (r2 = 0.51) and by 706 kg ha−1 per 100 spikes m‐2 (r2 = 0.76). Grain protein concentration among landscapes increased by 2.7 g kg−1 per each increase of 10 kg residual soil NO3−N ha−1 (r2 = 0.82). The large differences in grain yield among landscape positions may justify spatially variable N application. Improved N management should favorably reduce soft white winter wheat protein concentrations by minimizing high residual N levels as well as improve net returns and reduce environmental degradation. The basis for this improved N management may be site‐specific yield estimates calculated from soil water availability and spike density.
Yielding Ability and Yield Stability of Linseed in Central Europe
Authors: Diepenbrock Wulf A. , Léon Jens , Clasen Knut
Published: July 2010

Successful linseed (Linum usitatissimum L.) cropping in Central Europe depends on yielding ability and yield stability of cultivars, as well as on reliability of production systems. During 1991 and 1992, two experiments spread over 14 representative locations in Germany and one location in Switzerland were conducted to analyze the effects of cultivar, N fertilization, and seeding rate on yield and, especially, on yield stability. Experiment 1 tested the effects of seeding rate (200, 400, 600, and 800 seeds m−2) and N fertilization rate (60 and 100 kg N ha−1) at nine locations. Experiment 2 investigated yield performance and yield stability of 16 cultivars and lines at nine locations. At 60 kg N ha−1, 200 and 800 seeds m−2 resulted in the lowest yields. Additionally, 200 seeds m−2 was associated with significant yield instability. At 100 kg N ha−1, seed yields reached a plateau at seeding rates of 400 and 600 seeds m−2. At 800 seeds m−2, yield decreased significantly. Only the 400 seeds m−2 rate resulted in significant yield stability. Two cultivars (Atalante, McGregor) and two lines (DSV‐5, DSV‐6) were superior in yield to other genotypes, but only Atalante and DSV‐6 were both high yielding and stable in yield. Adjusting seeding rate in relation to soil‐available N is a useful tool to optimize linseed production in a given location. It is concluded that high‐yielding cultivars are available that respond adequately to production potential at each of the selected locations.
A Computer Program Relating Solute Potential to Solution Composition for Five Solutes
Authors: Michel Burlyn E. , Radcliffe David
Published: July 2010

Data required to prepare solutions with desired solute potentials at any temperature from 0 to 40°C are scattered, often have inappropriate units, and usually require involved calculation or are not available. We wished to prepare a program so that anyone could obtain pertinent information simply. Adequate published data could be found only for mannitol, PEG 8000, NaCl, KCl, and sucrose, with water displacement by mannitol and PEG 8000 having to be measured. The program sends tabular output to the screen and it may be written in a disk file, making observation of relationships and preparation of graphical representation simple. A sequence of data may be generated over temperature, concentration, or potential ranges by specifying an initial value, interval size, and number of intervals. Values are given for temperature, water density, molal and molar concentrations, g solute g−1 water, osmotic coefficient, g and mL water displaced g−1 solute, solute potential (MPa), and g solute and g water needed for a requested volume of solution.
Seedbed Residue and Seed Size Relationships in Winter Barley
Authors: Chastain Thomas G. , Ward Kathy J. , Wysocki Donald J.
Published: July 2010

Understanding how winter barley (Hordeum vulgare L.) seeds and seedling plants interact with crop residue in the seedbed is essential for development of planting recommendations for dryland conservation tillage systems. Field trials were conducted in 1990–1991 (Trial 1) and 1991–1992 (Trial 2) near Pendleton, OR, to determine the effects of seedbed crop residue, seed size, and cultivar on emergence, growth, and yield of winter barley. Seedbed residue cover (32–45%) did not affect seedling emergence rate in Trial 1. Seed‐soil contact was apparently reduced in high‐residue seedbeds, but emergence was reduced only when seed‐zone water content was <120 g kg−1 in Trial 2. More water was present in the seedbed at the time of seeding in Trial 1 than in Trial 2. Low‐residue seedbeds were drier than moderate‐ or high‐residue seedbeds at the time of seeding in both trials. Final stand density and subsequent plant growth were not influenced by seedbed residue (up to 49% residue) in either trial. Spike production was reduced by high residue and test weight was reduced by moderate and high residue in Trial 1. Grain yield and plumpness were lowest when barley was sown in low residue in Trial 2. Seedlings produced from large seeds emerged more rapidly and produced higher density stands than small seeds in Trial 1 but not Trial 2. Plants grown from large seed were somewhat larger in spring, but seed size had no other effect on growth or yield. Grain plumpness was greater in plants grown from large seed in Trial 1 but not Trial 2. No differences in stand establishment were detected among the cultivars tested. Higher seedbed residues should not be viewed as detrimental to achieving good winter barley performance in conservation tillage systems.
Water and Nitrogen Effects on Winter Wheat in the Southeastern Coastal Plain: II. Physiological Responses
Authors: Frederick James R. , Camberato James J.
Published: July 2010

The application of N to winter wheat (Triticum aestivum L. emend. Theil.) generally increases leaf reduced N concentration (LRN), thereby potentially increasing the rate and duration of leaf photosynthesis during grain fill. For nonirrigated winter wheat grown on the southeastern Coastal Plain of the USA, however, increasing the rate of spring‐applied N has been found to result in greater plant water deficits and lower leaf CO2 exchange rates (CER) during the grain‐filling period. This 2‐yr study was conducted to determine the effects of spring N rate on the rate and duration of leaf photosynthesis in winter wheat grown with irrigation and to examine the relationship between leaf CER and LRN as affected by spring N rate, soil water treatment, and wheat growth stage. Wheat was grown with different rates of spring‐applied N (0, 45, 90, and 135 kg N ha−1) under irrigated and nonirrigated conditions. Leaf CER generally increased with increased spring N under irrigated conditions but decreased under nonirrigated conditions. Higher leaf CER with irrigation, as opposed to without irrigation, resulted in greater vegetative dry weights during the early stages of grain fill. Leaf CER was closely associated with LRN during grain fill under irrigated conditions, but greater stomatal closure with increased spring N resulted in deviations from this relationship under nonirrigated conditions. The dates of initial decline in LRN of the flag leaf and leaf area index (LAI) were similar for all treatments and in both years. Only under irrigated conditions did increases in spring N rate delay the complete loss of leaf area and photosynthetic activity during grain fill. Compared with 1992, the rate of decline in LAI, LRN, and CER during grain fill was more rapid in 1993, when air temperatures were warmer. Results indicate that supplemental water is needed on the southeastern Coastal Plain for high rates of spring‐applied N to increase the rate and duration of leaf photosynthesis in winter wheat during the grain‐filling period.
Developing and Validating a Model for a Plant Growth Regulator
Authors: Reddy K. Raja , Boone Mariquita L. , Reddy A. R. , Hodges Harry F. , Turner Sammy B. , McKinion James M.
Published: July 2010

Mepiquat chloride (MC), 1,1‐dimethylpiperidinium chloride, is a systemic plant growth regulator used extensively to regulate vegetative growth in cotton (Gossypium hirsutum L. and G. barbadense L.). Yield responses to MC have been erratic, probably due to the difficulty in choosing the proper rate and timing of application. We developed a model based on data collected by spraying various amounts of MC on 25‐d‐old plants. The effect of MC on various physiological parameters was measured. Stem elongation rate was reduced 38% due to 30 µg g−1 of MC, while leaf area expansion rate and photosynthesis was reduced 30%. The model adjusts the projected leaf expansion, stem elongation, and photosynthetic rates based on the crop growth status and concentrations of MC in the tissues. The MC subroutine was incorporated into GOSSYM‐COMAX, a combined simulation model for plant growth and decision aid for cotton crop management. We tested the model against data for plant heights, mainstem nodes, and yields from several cropping systems across the U.S. Cotton Belt. The simulation results agreed closely with the observed field data. The new model reduced the overall variability 32% for predicting plant heights, 4% for predicting number of mainstem nodes, and 17% for predicting lint yields over the previously published MC model. When used in association with GOSSYM‐COMAX, the MC model may provide an effective tool for selecting precise timing and amounts of mepiquat chloride needed to optimize the proper use of the chemical.
Cropping Systems for Perennial Ryegrass Seed Production: II. Minimum Tillage Systems for Changing Cultivars in Certified Seed Production
Authors: Young William C. , Youngberg Harold W.
Published: July 2010

Few studies have been conducted to evaluate certified grass seed crop establishment under no‐till systems. Four field studies were conducted near Corvallis, OR, between 1985 and 1989, to evaluate the acceptability of 1‐ and 2‐yr no‐till crop rotation systems between two perennial ryegrass (Lolium perenne L.) cultivars grown for certified seed production under the genetic purity requirements of Association of Official Seed Certifying Agencies (AOSCA). Four rotation systems were used: 1‐ and 2‐yr red clover (Trifolium pratense L.), 1‐yr meadowfoam (Limnanthes alba L.), and 2‐yr meadowfoam‐spring pea (Pisum sativum L.). Afterharvest residue from a diploid perennial ryegrass was either burned or flail‐chopped (nonburned) before drill‐seeding the rotation crops. A tetraploid perennial ryegrass followed after rotation crops to assess contamination from seedlings of the first perennial ryegrass (diploid) seed crop. For all rotation sequences, the number of ryegrass plants growing between planted rows and the percentage of diploid seed in the harvested tetraploid seed crop exceeded AOSCA seed certification standards. Burning the stubble did not reduce the number of volunteer seedlings to the level acceptable for seed certification. We concluded that 1‐ or 2‐yr rotation sequences out of perennial ryegrass seed production using minimum tillage systems were not sufficient to meet the cultivar purity standards for production of certified seed, even when burning preceded establishment of the rotation crops. Also, burning ryegrass stubble prior to establishment of the rotation species had little effect on seed yield of the following ryegrass crop. Burning the stubble of the first‐year ryegrass crop established after rotation species, however, improved the seed yield of the second‐year crop.
Renovation Effects on Bahiagrass Productivity
Authors: Williams M. J. , Kalmbacher R. S.
Published: July 2010

Production declines in perennial grass swards have been attributed to soil compaction and a phenomenon referred to as root‐bound sod. The effect of renovation equipment on the productivity of bahiagrass (Paspalum notatum Flügge) was evaluated for 2 yr (1991–1993) at the USDA‐ARS Subtropical Agricultural Research Station (STARS) and the University of Florida Agricultural Research and Education Center at Ona. Water infiltration and penetrometer resistance were determined in mid‐April, immediately pre and post treatment, with either of two styles of bladed (chopper or bladed) or a spiked piece of equipment and at 12, 26, and 52 wk post treatment. Forage dry matter (DM) production and tiller density were determined every 4 wk. Penetrometer resistance was reduced in the upper 15 to 20 cm of the soil immediately post treatment (average of 3.2 and 8.0 kg cm2 at the 10‐cm depth at Ona and STARS, respectively, in 1991), but remained detectable at subsequent post‐treatment times only at STARS. Water infiltration was enhanced only once during the 2 yr (approximately 60 mm h−1 increase). Tiller density was not affected by renovation at Ona (750 tillers m−2 average), but at STARS it declined an average of 20% for bladed or chopper‐treated plots in 1991–1992, due to death of uprooted tillers (1320 tillers m−2 untreated vs. 1065 tillers m−2 average bladed‐type equipment). Forage DM production of renovated plots was less than or equal to that of the untreated plot at each sample date at both sites both years. Based on this study, use of these types of renovation equipment in April on bahiagrass swards in Florida cannot he recommended.
Use of Near Infrared Reflectance Spectroscopy to Screen Ethiopian Mustard for Seed Weight
Authors: Velasco Leonardo , FernÁndez‐MartÍnez JosÉ , De Haro Antonio
Published: July 2010

Near infrared reflectance spectroscopy (NIRS) provides a method for the simultaneous measurement of multiple quality traits in oilseed Brassica species, such as oil, protein, glucosinolate, and chlorophyll content. The incorporation of new traits into NIRS analysis should increase the information obtained from analyzed samples with little additional effort. The objective of this study was to determine the potential use of NIRS to screen intact‐seed samples of Ethiopian mustard (Brassica carinata Braun) for 1000‐seed weight. A calibration equation for this trait developed in 1992 using modified partial squares (MPLS) regression was successively expanded with new samples from the 1993 and 1994 crops. The 3‐yr calibration showed an r2 of 0.86 in external validation, indicating the reliability of NIRS for screening Ethiopian mustard samples for seed weight. This method could be particularly useful in large breeding programs, as it is less time consuming and more cost effective than conventional methods.
Yield, Psyllid Resistance, and Phenolic Concentration of Leucaena in Two Environments in Hawaii
Authors: Austin Michael T. , Early Richard J. , Brewbaker James L. , Sun Weiguo
Published: July 2010

Interspecific hybridization in the genus Leucaena produces hybrid vigor, resulting in highly adaptable varieties that expand the growth range of the genus. This study was conducted to test the total biomass (combined stem and forage fraction), total forage dry matter (DM) yield, psyllid (Heteropsylla cubana Crawford) damage, and phenolic concentration of Leucaena F1 hybrids in comparison with species‐level selections in two distinctly different environments. A total of 19 Leucaena spp. and hybrid selections were tested for 2 yr at the Waimanalo and Mealani Research Stations in Hawaii. Thirteen species and hybrid selections were replicated three times and included species selections from L. pallida Britton & Rose; L. leucocephala (Lam.) de Wit; L. diversifolia (Schlechtend.) Benth. (2n = 4x); and L. trichandra (Zucc.) Urban [syn. L. diversifolia (Schlechtend.) Benth. subsp. trichandra (Urban) F.J. Pan] (2n = 2x). Additionally, five selections were interspecific F1 hybrids and two were advanced‐generation interspecific hybrids. Six other selections were augmented in the trials. Over 2 yr, L. pallida ✕ L. leucocephala F1 hybrids (K748 ✕ K636 and K748 ✕ K584) had the highest DM yield at both locations. At Waimanalo, K748 ✕ K636 produced 53.4 Mg ha−1 total DM biomass of which 24.6 Mg ha−1 was forage, while at Mealani, K748 ✕ K636 produced 29.4 Mg ha−1 total DM biomass and 9.6 Mg ha−1 forage. These yields were twice those of L. leucocephala at Waimanalo and eight times greater at Mealani. Leucaena leucocephala was the most susceptible to psyllid damage (P < 0.001), while the most resistant was L. trichandra (2n = 2x). Leucaena pallida hybrids had intermediate levels of psyllid resistance. Psyllid damage was negatively correlated with forage DM once at Waimanalo (r = −0.37, P < 0.05, n = 42). Forage phenolic concentration averaged 110 mg g−1 for all treatments at both locations and was correlated once to psyllid damage (r = 0.32, P < 0.05, n = 42) at Waimanalo. Superior yield, psyllid resistance and cold tolerance of L. pallida ✕ L. leucocephala hybrids was observed at low and high elevation sites.
Path Analysis and Ideotypes for Plantain Breeding
Authors: Ortiz Rodomiro , Langie Hilde
Published: July 2010

Plantains (Musa spp., AAB group) are an important food crop in the humid lowlands of sub‐Saharan Africa. Understanding the relationships between growth characteristics and yield potential (t ha−1 yr−1) would be useful in developing an ideotype to guide breeding efforts for this crop. We investigated cause‐effect relationships, through path analysis, in yield potential of six plantain landraces (one giant and two medium French; one medium and one giant False Horn; one True Horn) under two production systems (perennial ratooning and replanting after harvest). Each landrace was selected as a random member of a particular type from the plantain gene bank, for a representative sample of the phenotypic diversity of the crop. The plantain landraces were grown for 6 yr in a split‐plot randomized complete block design, with four replications of 30 competing plants per subplot. Landrace was the main plot and production system was the subplot. There were few common pathways determining yield potential among the plantain landraces, so we could not define a common ideotype for plantain breeding. This suggests that plantains may possess different genes controlling similar pathways, or different traits contributing to yield potential. Also, the defined ideotypes differed for each landrace, according to the production system. Plantain breeders should consider those relationships that are affected by both genotype and production system when selecting for improved hybrid germplasm.
Using Early‐Season Leaf Traits to Predict Nitrogen Sufficiency of Burley Tobacco
Authors: MacKown Charles T. , Sutton Tommy G.
Published: July 2010

Burley tobacco (Nicotiana tabacum L.) requires large amounts of fertilizer N to produce high yields of good‐quality air‐cured leaf. On well‐drained soils, fertilizer N typically is applied as much as 4 wk before transplanting. This results in a delay of up to 9 wk before the onset of rapid growth and N accumulation at about 5 wk after transplanting. Abundant rainfall often occurs during this period and creates the potential for losses of soil and fertilizer N. An early‐season N‐sufficiency tissue test could guide the tobacco grower in adjusting fertilizer needs of the crop before the last cultivation, which normally occurs about 5 wk after transplanting. The objective of this study was to determine relationships among selected N‐nutrition‐related leaf traits of tobacco measured 3, 4, and 5 wk after transplanting and to determine if these traits are related to yields of air‐cured leaf. Burley tobacco was grown in 1993 at two locations, with 0 to 336 kg N ha−1 applied before transplanting. One site had a well‐drained soil; the other site, moderately well‐drained. Total N, extracted chlorophyll, and chlorophyll meter readings were measured on leaf lamina disks taken from lower leaves. Leaf yields at both sites were equivalent at 336 kg N ha−1, with increases in yield due to added N being less for the well‐drained soil. The response patterns of the leaf traits to fertilizer N were different for the two soil types and corresponded to the respective yield response patterns for each site. Neither extracted chlorophyll (335–760 mg m−2) nor chlorophyll meter readings (23.0–42.6 SPAD units) plateaued with increasing total N of leaf disks (3.50–6.26 g m−1, 41.2‐66.6 mg g−1 dry wt.). Models for linear relationships among leaf traits were significant (R2 = 0.60–0.66; P < 0.001). A 20% increase in relative yield corresponded to about a 25% increase in concentrations of total N and extracted chlorophyll, but only a 5% increase in chlorophyll meter readings. After more testing and calibration with comparisons to a high‐N‐fertility reference strip, these early‐season leaf tissue traits may prove useful in predicting sidedress fertilizer N requirements.
Cultivar, Nitrogen, and Moisture Effects on a Rice‐Wheat Sequence: Experimentation and Simulation
Authors: Timsina Jagadish , Singh Upendra , Badaruddin Mohammed , Meisner Craig
Published: July 2010

Rice (Oryza sativa L.) followed by wheat (Triticum aestivum L.) is a dominant cropping sequence under a range of management regimes in South Asia, with variable productivity. Simulation models can be used to extrapolate experimental results to other sites of interest in variable environments. Experiments were conducted to quantify the responses of two rice cultivars to three N regimes and two soil moisture regimes, followed by the responses of the succeeding two wheat cultivars to three N regimes, two soil moisture regimes, and two dates of planting, on a Haplaquept noncalcareous brown floodplain soil at the Wheat Research Center, Nashipur, Bangladesh. CERES‐Rice and CERES‐Wheat models were validated using the experimental data set, and then were used to estimate the grain yields at two other sites in Bangladesh. In rainfed plots, grain yields of ‘BR14’ rice were reduced by 48.8, 43.4, and 39.3% relative to irrigated plots, and those of ‘BR11’ were reduced by 49.1, 43.8, and 42.2% (P < 0.05), for 0, 90, and 135 kg N ha−1, respectively. The optimum N rate was between 90 and 135 kg ha−1. In the succeeding wheat crop, at 0 N, there were no significant differences between the two moisture regimes but, at high N (180 kg ha−1), irrigation promoted greater yield. Relative to the high‐N treatment, grain yields of irrigated ‘Kanchan’ wheat at 0 N were reduced by 73.0 and 71.6%, and of ‘Sowgat’ by 75.2 and 73.5%, for early and late plantings, respectively. Simulation investigated year‐to‐year variation in grain yields of both crops under their several N regimes. Rice yields tended to increase over years, but wheat yields had no definite trend. The simulation results indicated that, without N fertilizer application, N will be limiting across sites and long‐term weather conditions for both rainfed and irrigated crops. Field experimentation quantified actual crop responses to a range of management practices and allowed validating the models for the rice‐wheat sequence. The models were then used to extrapolate and generalize the results for two other sites in Bangladesh.
Confined Microplot Size for Nitrogen‐15 Uptake by Corn Plants in a Corn Intercrop System
Authors: Zhou Xiaomin , Leibovitch Stewart , MacKenzie Angus F. , Madramootoo Chandra A. , Dutilleul Pierre , Smith Donald L.
Published: July 2010

The high cost of labeled N fertilizer places practical limitations on measuring the fate of applied N. Applying of the labeled 15N to a microplot within a larger plot can reduce the cost. The objective of this study was to assess microplot dimensions required to produce reliable 15N data and cropping system effects on corn 15N uptake under a regime of monocropped corn (Zea mays L.) and corn intercropped with annual Italian ryegrass (Lolium multiflorum Lam.). Nitrogen was applied to large plots (15 by 75 m) at 270 kg N ha−1 on a fine, silty, mixed, nonacid, frigid Typic Humaquept soil during the 1993 and 1994 growing seasons. Enriched N fertilizer was applied to 1.15 by 1‐m2 confined microplots located in opposite halves of the large plot in each year of the study. Corn plants inside the confined microplots were sampled at 0.1, 0.3, and 0.5 m from the end borders of each microplot. In 1993, monocropping resulted in increases in leaf, stalk, and total dry matter production of 22, 41, and 30%, respectively, within microplots and relative to intercropped corn. There were no cropping system effects for these parameters in 1994. Monocropping increased atom % 15N enrichment in corn grain and stalks and increased fertilizer N recovery in all plant tissue compared with intercropping in both years. There were no differences in atom % 15N enrichment and fertilizer N recovery for plants harvested at the three sampling positions. These results suggest that a confined microplot with an area as small as 0.4 by 1.15 m can provide a reliable measure of fertilizer N recovery for corn plants in monocrop or intercrop systems. Any or all of the five plants within the microplot could be used to supply a reliable estimation of 15N recovery by corn plants.
Soybean Cultivars and Insect Defoliation: Yield Loss and Economic Injury Levels
Authors: Haile Fikru J. , Higley Leon G. , Specht James E.
Published: July 2010

Understanding the response of soybean [Glycine max (L.) Merr.] cultivars to insect defoliation is important for identifying differences in insect tolerance and compensation among soybean genotypes, for assessing yield loss differences among cultivars, and for determining if a single economic injury level (EIL) can be used for all cultivars. Therefore, this study was conducted to evaluate the relative tolerance of selected soybean cultivars to insect defoliation. Field experiments were conducted in 1994 and 1995 on three indeterminate soybean cultivars: Dunbar, Corsica, and Clark. Sequential defoliation (46‐66%) was imposed manually at the R2 stage (reproductive development of soybean at full flowering), guided by an insect consumption model. Leaf area index, percent light interception, growth, and yield data were determined. Because of ample rainfall during the soybean growing period in 1994, defoliation did not affect soybean yield; all cultivars compensated for all levels of defoliation via delayed leaf senescence and compensatory regrowth, which enhanced the light interception capacity of defoliated soybean canopies. In 1995, however, defoliation caused a significant yield reduction (15‐70%) in all cultivars; this yield reduction was greater for Dunbar than the other two cultivars. In both years, yields were directly related to the light interception capacity of soybean canopies after defoliation. There were significant EIL differences among soybean cultivars. Large differences in EILs among cultivars suggest a need to revise existing EILs for defoliating pest species.
Fertilizer and Soil Nitrogen Use by Corn and Border Crops in a Strip Intercropping System
Authors: Ghaffarzadeh Mohammadreza , Préchac Fernando García , Cruse Richard M. , Harbur Matthew M.
Published: July 2010

Corn (Zea mays L.) has greater yield potential when strip‐intercropped than when monocropped, but this potential may be compromised by a failure to understand how N requirements change with row position and the possible N competition of adjacent crops. A four block, completely randomized, split‐plot experiment was conducted on a Haig loam soil (fine, smectitic, mesic Vertic Argiaquolls) in southern Iowa, to determine crop utilization of N fertilizer pointinjected into corn rows. Nitrogen fertilizer uptake was evaluated in (i) corn rows injected with labeled N fertilizer; (ii) corn rows adjacent to the injected rows; and (iii) plants at the edge of the adjacent soybean [Glycine max (L.) Merr.] and oat (Avena sativa L.)‐alfalfa (Medicago saliva L.) strips. Main treatments consisted of three tillage systems: conventional tillage (CT), reduced tillage (RT), and no‐till (NT). Subplot treatments consisted of point injection of l5N‐enriched NH4NO3 (67 kg N ha−1) in‐row at three row positions within the corn strips. Grain and stover yield, Kjeldahl N, and isotope composition of plant materials were determined. Corn yield and labeled‐N recovery differed with tillage to the extent that tillage affected early and total season moisture availability. Labeled‐N recovery in labeled rows did not differ with row position. Labeled‐N recovery in unlabeled rows or crop borders was typically less than 5% of that recovered by labeled rows. Nitrogen is primarily recovered by the row to which it is applied; therefore, row‐by‐row precision applications seem to be an appropriate management tool.
Agricultural Advisory Committees: How They Rate Their Effectiveness in Guiding Research
Authors: Sweeney Daniel W. , Pontius Jeffrey S.
Published: July 2010

University faculty located and conducting research at off‐campus agricultural research centers often are advised by committees representing agribusiness, producers, and extension personnel. A two‐page questionnaire was sent in 1996 to the directors, faculty, and members of the advisory committees of three research centers each in Arkansas, Florida, Minnesota, Nebraska, and Texas and two research centers in Kansas to assess opinions about the composition, structure, goals, and effectiveness of agricultural advisory committees. All occupational groups surveyed felt that advisory committees can provide valuable input for agricultural research, but were less convinced that they accomplish their goals. In general, research center directors, extension personnel, and research faculty tended to be more reserved than agribusiness and producer respondents in their opinions on the performance of advisory committees. Respondents believed that agricultural research advisory committees should comprise representatives of agribusiness, area producers, extension personnel, and research faculty who are chosen by those groups, although research center directors did not support extension personnel or research faculty having a voice in the selection process. Committee members should serve a term of 3 to 4 years. Goals should be more defined and should help to identify needs and guide research by providing direction and focus, being an advocate for the research center, and providing input on fund raising and management. Improved communication, more meetings with definite agendas, and better attendance were identified to help improve the success of advisory committees. Overall, the potential for benefit is high, but agricultural advisory committees often are perceived as needing to improve their effectiveness.
Sugarbeet Nitrogen Uptake and Performance Following Heavily Fertilized Onion
Authors: Shock Clinton C. , Seddigh Majid , Saunders Lamont D. , Stieber Timothy D. , Miller John G.
Published: July 2010

Crop over‐fertilization has economic and environmental consequences. Sugarbeet (Beta vulgaris L.) N fertilizer requirements could be lower than expected when planted after shallow rooted onion (Allium cepa L.). Sugarbeet was planted on an Owyhee silt loam (coarse‐silty, mixed, mesic Xerollic Durorthid) for 2 yr, where the previous onion crop had received 0, 60, 120, 240, and 480 kg N ha−1. Soil nitrate and ammonium were measured in 0.3‐m increments to 1.8 m deep after harvesting onion, and before and after growing sugarbeet. Nitrogen uptake by plant parts, and beet and sucrose yields, were measured. Averaged across years, sugarbeet recovered 336, 316, 338, 400, and 505 kg N ha−1 when N fertilizer of the previous onion crop was 0, 60, 120, 240, and 480 kg ha−1, respectively. The corresponding reduction in available inorganic N from the top 1.8 m of the soil during sugarbeet growth was 27, 82, 62, 120, and 152 kg ha−1. Nitrogen recovered by sugarbeet was largely supplied by sources other than preplant available N. Recovered sucrose yield was near maximum when the N rate on the previous onion crop was 240 kg ha−1, which resulted in preplant NO3–N levels of about 70 kg ha−1 in the top 0.6 m of the soil. Sucrose yield did not improve when petiole NO3–N in late June exceeded 6 g kg−1. In conclusion, sugarbeet may not require fertilizer N when grown after onion fertilized with about 240 kg N ha−1
Potential of Early‐Maturing Soybean Cultivars in Late Plantings
Authors: Egli Dennis B. , Bruening William P.
Published: July 2010

Late planting reduces soybean [Glycine max (L.) Merr.] yields in soybean–winter wheat (Triticum aestivum L.) double‐cropping systems. We evaluated the hypothesis that the use of early‐maturing soybean cultivars to shift reproductive growth into a more favorable environment would avoid some or all of this yield penalty. Soybean cultivars Hardin and Kasota [maturity group (MG) I], Burlison and Elgin 87 (MG II), Pioneer 9392 and Probst (MG III), and Stressland and Pennyrile (MG IV) planted in 38‐cm rows were used in a 3‐yr irrigated experiment with two planting dates (early, mid‐May; late, late June) at Lexington, KY (38° N lat). Delayed planting reduced yield (7–36%) of all cultivars as a result of fewer seeds m−2. Cultivars from MG I and II did not produce higher yields in the late plantings. A combination of narrow rows (19 cm) and high seeding rates (105 seeds m−2) had no effect on yield of cultivars from MGs I and II in either planting date. However, early maturity did provide an earlier harvest date without significant yield loss. Seed number was significantly related to crop growth rate (CGR) during flowering and pod set (r2 = 0.36) and to length of flowering and pod set (r2 = 0.56). Radiation use efficiency (g dry matter MJ−1 intercepted photosynthetically active radiation) was generally reduced in the late plantings for MG III and IV cultivars but not for MG I and II. Early‐maturing cultivars in an irrigated environment did not reduce the yield penalty associated with late plantings.
Row Width and Weed Management Systems for Conventional Soybean Plantings in the Midsouthern USA
Authors: Heatherly Larry G. , Elmore C. Dennis , Spurlock Stan R.
Published: July 2010

Field studies were conducted from 1994 through 1996 on Sharkey clay (very fine, smectitic, thermic chromic Epiaquert) at Stoneville, MS (33°26′N lat) to determine effect of weed management treatment (WTRT) on yield and net return from Maturity Group V soybean [Glycine max (L.) Merr.] cultivars differing in height and grown in narrow rows (NRs; 50‐cm width) and wide rows (WRs; 100‐cm width) without and with irrigation. The WTRTs were (i) pre‐emergence (PRE) and postemergence (POST) broadleaf weed management; (ii) PRE broadleaf, PRE grass, and POST broadleaf weed management; (iii) POST broadleaf weed management; and (iv) POST broadleaf and POST grass weed management. Herbicides were broadcast‐applied in NRs and band‐applied (0.5‐m‐wide band centered over each row) in WRs. Postemergent cultivation was conducted in WRs. Weed management expense for NRs was greater than that for WRs in most cases. Use of NRs vs. WRs resulted in less weed cover at the end of the growing season, regardless of cultivar or WTRT. Three‐year average seed yield and net return from NRs were greater than those from WRs. Regardless of row width, cultivar, or irrigation environment, highest net returns were obtained from managing only broadleaf weeds either PRE or POST under the conditions at this site.
The Relationship between Leaf Water Potential and Stem Diameter in Sorghum
Authors: Yatapanage Kamal G. , So Hwat Bing
Published: July 2010

Leaf water potential (ψl) represents a good indicator of the water status of plants, and continuous monitoring of it can be useful in research and field applications such as scheduling irrigation. Changes in stem diameter (Sd) were used for monitoring ψl of pot‐grown sorghum [Sorghum bicolor (L.) Moench] plants in a glasshouse. This method requires occasional calibration of Sd values against ψl. Predicted values of ψl based on a single calibration show a good correlation with measured ψl values over a period of 13 d before and after the calibration. The correlation can further be improved with shorter time intervals.
A New Method to Assess Competition in Coffee Clonal Trials with Single‐Tree Plots in Côte d'Ivoire
Authors: Montagnon C. , Flori A. , Cilas C.
Published: July 2010

A new method is proposed for the assessment of competition in clonal trials with completely randomized single‐tree plots, without needing to choose a covariable a priori linked to competition. This method is applied to a coffee clonal trial planted in a completely randomized single‐tree plot design located in Côte d'Ivoire. Microenvironmental effects were first taken into account using the conventional Papadakis method. The competition effect (Ck) of each clone (k) was then estimated as the influence of its presence on the residual value, after removal of the clonal effect, of its neighbors. Residuals were thus modeled as a linear regression of the neighboring clones’ C value. Competition effects were shown this way to explain 4% of the residual yield in young trees and 10% in adult trees. Several clones had C values significantly different from 0. Some were identified as aggressive for their neighbors (C < 0), others as stimulating (i.e., promoting yield, C > 0). Architecture and vigor variables that were likely to be related to the C value of clones were then sought. For young trees, vigor, estimated by stem diameter, was best correlated to competition effects: vigorous clones were more aggressive than others. When trees became adult, the length of the orthotropic internodes (Lort) was the trait that most effectively explained (42%) the competition effect of clones: the shorter the internodes, the less aggressive was the clone. In the future, Lort may thus be used in a selection index to prevent from selecting aggressive coffee clones that would undergo their own aggressiveness when grown alone in plantations.
Carbohydrate and Protein Fractions of Fresh and Dried Common Vetch at Three Maturity Stages
Authors: Caballero Rafael , Alzueta Carmen , Ortiz Luis T. , Rodríguez Maria Luisa , Barro Carmen , Rebolé Almudena
Published: July 2010

Mixed cereal and sheep (Ovis aries) production systems in the Mediterranean area and the Middle East region rely on annual forage legumes as a source of complementary forage. Fractionation of carbohydrates (CHO) and crude protein (CP) into chemical entities of refined biological significance may improve the forage utilization of these feed resources. Fresh and dried (field‐cured) common vetch (Vicia sativa L.) samples were collected during two growing seasons (1996–1997 and 1997–1998) at La Poveda Field Station in central Spain with the objective of determining chemical CHO and CP fractions required for application of new feed models (Cornell System). Fresh and dried samples were harvested at three maturity stages—flowering (>50% of plants with flowers), seed filling phase 1 (280 g DM kg−1 seed), and seed filling phase 2 (380 g DM kg−1 seed)—and the treatments were arranged in a completely randomized design. Nonfiber carbohydrates (NFC) and neutral‐detergent fiber (NDF), corrected for neutral‐detergent insoluble protein (NDIP), were evenly distributed in fresh and dried samples, and were not affected by maturity. The B1 and B2 CHO fractions were the most abundant with mean values of 342 and 303 g kg−1 of total carbohydrates (TC), respectively, across maturities, harvest forms, and years. Fraction CP B2 was the most abundant CP fraction with mean value of 408 g kg−1 of total CP. Fraction CP B3 was <100 g kg−1 of total CP and increased with maturity. Harvesting common vetch within the seed filling phase would increase ruminal escape protein in vetch.
Economics of Lime and Phosphorus Application for Dual‐Purpose Winter Wheat Production in Low‐pH Soils
Authors: Kaitibie Simeon , Epplin Francis M. , Krenzer Eugene G. , Zhang Hailin
Published: July 2010

After decades of continuous cropping, the pH of many soils used to produce continuous winter wheat (Triticum aestivum L.) in the southern plains of Oklahoma has declined to levels that limit wheat grain and forage yield. Data from a 3‐yr study were used to determine the effect of lime and diammonium phosphate (DAP) application on fall–winter forage yield and grain yield of winter wheat grown in extremely acid soil and to determine the economically optimal strategy for dual‐purpose (forage plus grain) wheat production. A split‐split plot with sub‐subplot treatments arranged in a randomized complete block design was used, with lime in the main plots, variety in the subplots, and DAP in the sub‐subplots. Grain yield significantly increased (α = 0.05) with lime at 2800 kg ha−1 effective calcium carbonate equivalent (ECCE), DAP at 73 kg ha−1 applied in seed furrows, or DAP at 146 kg ha−1 broadcast. Forage yields were greatest when DAP was applied at 146 kg ha−1 in seed furrows (α = 0.05). When lime costs were fully assessed in the year of application, the strategy of applying 73 kg ha−1 DAP in seed furrows and zero lime generated the greatest expected returns across all forage value estimates and grain prices. With lime costs amortized over a 5‐yr period, the optimal strategy included both the application of lime before the initial season and 73 kg ha−1 DAP in seed furrows in each season.
Using the Presidedress Soil Nitrate Test and Organic Nitrogen Crediting to Improve Corn Nitrogen Recommendations
Authors: Andraski Todd W. , Bundy Larry G.
Published: July 2010

The PSNT and N crediting for organic N inputs can improve the accuracy of corn (Zea mays L.) N recommendations, but are often not used due to producer concerns about their reliability. This study compared the use of these techniques for identifying optimum N rates and quantifying economic returns in 101 N response field experiments with corn conducted during 1989–1999. The accuracy of PSNT recommendations was highest for sites with average or above average May–June air temperatures and high soil yield potential. The frequency of excess N recommendations from the PSNT increased from 16 to 59% when May–June temperatures were >0.56°C below average likely due to slower organic N mineralization. Use of N recommendations based on the PSNT or book value N credits (BVNC) lowered N rates by 90 to 102 kg ha−1 in systems with recent manure or legume N inputs and increased average economic returns for all cropping systems by $19 ha−1 compared with unadjusted N recommendations (i.e., economic gain). Economic gains using PSNT‐ or BVNC‐based recommendations were generally highest in the first year following organic N inputs with an average gain of $34 ha−1 for both methods. Conversely, economic gains were higher using the PSNT ($40 ha−1) than the BVNC ($2 ha−1) 1 to 3 yr after the organic N additions on high yield potential soils where May–June air temperatures were average or above. Results from this work confirm that adjusting N application rates for corn using the PSNT or BVNC is more profitable than not making these adjustments.