bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory System for Evaluation of Hay Preservatives
Authors: Baron V.S. , Dick A.C. , Young D.G.
Published: July 2010

The evaluation of additives for the preservation of moist hay through field experiments is made difficult by large and variable experimental units and environmental effects. A laboratory system was developed to rapidly screen hay preservative treatments. Ovendried hay was rehydrated with water and a preservative to the desired moisture concentration. Polyvinyl chloride (PVC) tubes provided the storage vessel. A constant initial density (200 kg m−3) was achieved using a mechanical press. Aeration was by diffusion through the open vessel top. Resistance to heat loss was provided by a fixed, polystyrene bed into which PVC tubes were inserted during a 21‐d incubation at 25 °C. Temperature data handling was facilitated through the use of a mutiplexer and datalogger. Efficacy of a propionate preservative duplicated the performance of previous laboratory systems for temperature and visible mold evaluation. Forage quality parameters followed the same general response to propionate rate within moisture levels as temperature and mold evaluation. Daily temperatures in the laboratory model were comparable to conventional small square bales, but lower than in large round bales.
Soybean Cultivar Response to Planting Rate and Tillage
Authors: Elmore Roger W.
Published: July 2010

abstract

Previous research has shown that soybean [Glycine max (L.) Merr.] cultivar yield responses to tillage systems can vary in specific environments due to drought stress, diseases, or herbicides. In one of 3 yr in a previous study ‘Mead’ yielded 15% more in no‐tillage than in tilled systems while ‘Williams 82’ yielded 8% less in notillage than in tilled systems. This was thought to be due to either a slight difference in plant populations between the two cultivars or genetic variability that could be used to develop tillage‐specific cultivars. The study reported here was conducted to determine if planting rate of these two cultivars affected their responses to tillage. A 2‐yr field study was conducted with two cultivars (Mead and Williams 82) at four planting rates (11.1, 34.6, 58.1, and 81.5 seeds m−2) and two tillage systems (no‐tillage and triple disk). In 1986, the study was conducted on a Crete silt loam soil (fine, montmorillonitic, mesic Pachic Argiustoll), which is moderately well drained with slow permeability. In 1987, the study was conducted on a Hastings silt loam soil (fine, montmorillonitic, mesic Udic Argiustoll), which is well drained with moderately slow permeability. When averaged over planting rate, the cultivars responded similarly to tillage systems. Planting rate did not affect the responses of the cultivars to tillage system. Mead and Williams 82 appear to respond similarly to tillage systems in most environments regardless of planting rate.
Limitations to Bromide Determinations in Alfalfa Using the Bromide‐Selective Electrode
Authors: Meyers L. L. , Russelle M. P.
Published: July 2010

Bromide is a potential tracer of nutrient uptake by plant roots in soil‐plant systems, yet traditional methods of Br analysis have been time consuming, expensive, or difficult to complete. The bromide‐selective electrode (BrSE) has been used with some success as a simple means to accurately determine Br in soils and plant materials. We tested 0.1 M NaNO3 and 0.025 M Al2(SO4)3 as extractants of Br in alfalfa (Medicago sativa L.) for determination with a BrSE and investigated BrSE interferences from Cl and soluble proteins. Sodium nitrate was eliminated as an extractant due to unstable potentials and gross overestimation of added Br. Extraction with Al2(SO4)3 resulted in stable potentials and accurate recovery of added Br, but x‐ray fluorescence analysis showed that the BrSE overestimated tissue Br by 1.3 to 14 times. Overestimation of Br was strongly correlated with the ratio of Cl:Br in the extracts and the BrSE was affected by relatively low [Cl] at [Br] lower than 4 mg L−1. The BrSE is neither an accurate nor a simple means of Br analysis in alfalfa.
Relationship of Diagnostic Nutrient Expressions to Soybean Phosphorus and Potassium Diagnoses
Authors: Hallmark W. B. , Beverly R. B. , deMooy C. J. , Pesek John
Published: July 2010

Research is lacking as to whether forms of nutrient expression (e.g., N/P vs. P/N, etc.) and placement of nutrient variables (N, P, K, etc.) and/or dry matter (DM) exclusively in the numerator vs. the denominator of function values affects nutrient diagnoses by the modified‐diagnosis and recommendation integrated system (M‐DRIS) using the Jones (J) and Traditional (T) methods. Consequently, a soybean [Glycine max (L.) Merr.] cultivar‐by‐P‐by‐K‐by‐limestone soil fertility field study conducted on a Cresco loam (fine loamy mixed, mesic Typic Argiudoll) was used to determine whether these variations affect P and K diagnoses. Forms of expression affected T diagnoses, and placement of DM in the numerator vs. the denominator of functions had an effect on both T and J diagnoses. Effects of nutrient expression and DM placement on T diagnoses were caused by systematic errors in the M‐DRIS norms. These biases were largely alleviated when nutrient indices were calculated so that the variable under consideration always appeared in the numerator or the denominator of the function. Diagnoses by J were more accurate, however, when variables were placed in the denominator. Our results show that the effects of nutrient expression, calculating functions by T and J, and DM placement on M‐DRIS diagnoses can be largely alleviated when index values are calculated so that the variable under consideration is always in the numerator or denominator of the function.
Temperature Effects on Cotton Fruit Retention
Authors: Reddy K. R. , Hodges H. F. , Reddy V. R.
Published: July 2010

Temperature is a major environmental factor that affects cotton (Gossypium hirsutum L.) production. Temperatures of 35 to 40°C are frequently observed in cotton‐producing areas. High‐temperature environments are sometimes associated with cotton sterility and boll retention problems; however, there is little specific information available on cotton sensitivity to temperature. We conducted a series of experiments in naturally lit growth chambers where the temperature was accurately controlled so we could measure its effects on cotton fruiting site production, abscission of flower buds (squares), flowers, and bolls. Cotton plants grown from seedlings at 40°C for 12 h d−1 shed all their squares. Plants grown from seedlings in the natural environment, then exposed to daytime temperatures of 30, 35, or 40°C during the fruiting period accumulated 47, 5.7, and <1%, respectively, of their mass as bolls. The time of day when plants were exposed to high temperature did not influence percent boll retention. Number of bolls produced, bolls retained, and percent retention were progressively reduced as time per day at 40°C was increased. Three week exposure to 40°C for 2 or 12 h d−1 resulted in 64 or 0% bolls, respectively, retained on the plants. Cultivars appeared to be similar in sensitivity to high temperature. Cultivars tolerant to short periods of high temperature would probably be more productive in today's environment and increased tolerance to high temperature will be even more essential in a warmer environment.
Theory for Leaf Segment Lengths for Plant Canopies
Authors: Walthall C.L. , Norman J.M.
Published: July 2010

Leaves are considered the most important architectural components when studying the interaction of solar radiation with vegetation canopies. Models used in the study of solar radiation interaction with canopies generally assume randomly distributed leaves, with little or no attention to the arrangement of leaves and inter‐leaf gaps. This study was conducted to develop a model to describe the distribution of lengths of overlapping or contiguous leaves along a transect. The model describes the cumulative distribution of leaf segment lengths using a modified form of an equation previously used to describe interleaf gap length distributions. The leaf segment distribution model estimates were tested by comparisons with measurements of simulated physical canopies made of paper labels on clear plexiglass sheets. A comparison of model estimates with measurements of the simulated physical canopy showed generally good agreement. This study demonstrates that the distribution of leaf segment lengths along a transect within a canopy, like that of inter‐leaf gaps, is a function of canopy density and individual leaf dimensions. This is important as the leaf segment length distribution provides a technique for indirect canopy structure determination.
Soybean Seed Quality Response to Drought Stress and Pod Position
Authors: Smiciklas K.D. , Mullen R.E. , Carlson R.E. , Knapp A.D.
Published: July 2010

The effects of drought stress on soybean [Glycine max (L.) Merr.] seed quality may be influenced by morphological plant characteristics and the timing of drought stress. Determinate soybean plants were grown near Ames, IA, to ascertain the influences of the timing and frequency of drought stress and pod position on seed quality (as measured by germination, seedling dry weight, and seed leachate current). Plants were well‐watered (high reproductive load) or drought‐stressed at flowering (R2) to decrease potential seed number (low reproductive load). Subsequent drought stresses were implemented at the full pod (R4), seed formation (R5), and full seed (R6) stages, in addition to a nonstressed treatment. The harvested pods were grouped into the top main stem, bottom main stem, and branch positions for seed quality testing. An R2 drought‐stress (low reproductive load) did not prevent reductions in seed quality from occurring when additional stress was imposed at R4, R5, or R6 plant stages. However, the R2 + R4 stress treatment increased seedling weight by 7% and weight per seed by 12% compared with the R4 drought‐stress treatment. Top main stem seeds were of better quality and greater weight than seed harvested from the bottom main stem or branch positions. Branch or bottom main stem seeds were most sensitive to quality reductions when drought occurred during the R5 or R6 stages. The results indicate that variable seed quality resulting from drought stress can be attributed to the timing of stress and pod position on the plant.
Limpograss Sod Management and Aeschynomene Seed Reserve Effects on Legume Reestablishment
Authors: Chaparro C.J. , Sollenberger L.E. , Jones C.S.
Published: July 2010

Aeschynomene (Aeschynomene americana L.) is a warm‐season, annual legume that is well adapted to wet habitats. Stands must regenerate from seed each year, so size of seed reserve and management of the associated grass in winter and spring are important. In 1988 and 1989, effects of aeschynomene soil‐seed reserve (simulated by broadcasting known quantities of seed in the pod) and winter‐spring management of a limpograss [Hemarthria altissima (Poir.) Stapf and Hubb.] sod on legume reestablishment were evaluated on Smyrna (sandy, siliceous, hyperthermic Aerie Haplaquods) and Pomona (sandy, siliceous, hyperthermic Ultic Haplaquods) sands. All combinations of three tillage procedures (no disking, disking in spring, or disking in early summer) and two grazing treatments (grass grazed to a 10‐cm stubble or not grazed) were allocated as main plots in a split‐plot arrangement. Subplots were four quantities of seed applied the previous December (20, 60, 180, and 540 kg ha−1). Dry weather in late spring and early summer 1988 reduced grass competition to legume seedlings that had established in April, and grazing had no effect on percentage legume (PCL) in harvested forage. Within each disking treatment, PCL increased linearly with size of seed reserve, but summer disking reduced legume contribution relative to spring and no disking. With near optimal rainfall in 1989, PCL for the grazed swards was three to six times greater than for ungrazed swards. For all disk treatments, PCL increased linearly with size of seed reserve, but spring disking was superior to no disking and summer disking. Results suggest that aeschynomene reestablishment in limpograss is favored by spring disking and grazing limpograss until legume seedlings are 5 to 8 cm tall. Using this management in 1988 and 1989, seed reserves of 25 to 135 kg ha−1 were needed for successful aeschynomene reestablishment.
Seed Germination Response for Eleven Forage Cultivars of Brassica to Temperature
Authors: Wilson R.E. , Jensen E.H. , Fernandez G.C.J.
Published: July 2010

Slow germination and poor seedling vigor limit stand establishment of forage Brassica spp. Soil temperature is a major factor influencing both processes. Temperature effects on germination of 11 forage brassica cultivars, comprised of three species plus one hybrid, were studied in an incubator. The species and cultivars tested were turnip (B. rapa L.): Civastro‐R, Polaris, Purple Top, Stubble, and Forage Star; rape (B. napus L.): Emerald, Fodder, and Dwarf Essex; kale (B. oleracea L.): Premier, and Marls Kestral; and the turnip × Chinese cabbage hybrid [B. rapa L. × B. pekinensis (Lovr.) Rupr.]: Tyfon. Germination studies were conducted in the dark at 10 constant temperatures (0, 2, 5, 10, 15, 20, 30, 35, 40, and 50°C). Number of seeds germinated were counted on Day 4 and 14 after planting. Cultivars differed significantly (P ≤ 0.001) for percentage germination on both day 4 and 14 at all temperature treatments except 2 and 40°C. Under the cool temperatures (5 and 10°C), Civastro‐R, Polaris, Purple Top, and Stubble were the earliest germinating cultivars. At the 40°C temperature regime, Marls Kestral initiated germination earlier than that of the other cultivars, but total germination was highest for Polaris. The cultivars Civastro‐R, Polaris, Purple Top, and Stubble could serve as potential parents of a new cultivar because of their ability to germinate rapidly over a wide range of temperatures.
Temperature Effects on Early Season Cotton Growth and Development
Authors: Reddy K.R. , Reddy V. R. , Hodges H.F.
Published: July 2010

Temperature is a primary environmental factor controlling growth and developmental rates of plants, yet little specific information is available regarding cotton (Gossypium hirsutum L.) responses to temperature. Information covering a wide range of temperatures would be useful for predicting both developmental and growth rates in cotton. Therefore, an experiment was conducted in naturally lit, temperature‐ and CO2‐controlled cabinets from soon after emergence until 56 d after emergence (DAE). The cabinets were maintained at 20/12, 25/17, 30/22, 35/27, and 40/32°C day/night cycles. Plant heights, number of nodes, and leaf areas were determined weekly throughout the experiment, and dry weight measurements were obtained at three intervals. Mainstem elongation, leaf area growth, and biomass accumulation rates were very sensitive to temperature about 3 wk after emergence. Prior to that time, they were relatively insensitive to temperature. The temperature optimum for stem elongation, leaf area expansion, and biomass accumulation was 30/22°C. Developmental rates, as depicted by number of mainstem nodes produced, number of fruiting branches, and fruiting branch nodes, were not as sensitive to temperatures above 30/22°C as were growth rates. Four times as many fruiting branches were produced at 30/22°C as at 20/12°C; whereas more vegetative branches were produced at low temperatures. All flower buds (squares) abscised from plants grown at 40/32°C. Essentially, all bolls and squares were retained at 30/22 °C while a 10% boll and square loss was observed at 35/27 °C during the early reproductive period. Less time was required for this cultivar to produce squares at any temperature, suitable for growing cotton, than was suggested by previous experiments.
Notes: Data Collection Software for the Psion Organiser II
Authors: Panter D.M. , Allen F.L.
Published: July 2010

Using notebook‐sized computers to record field and laboratory data has become commonplace among agricultural researchers. However, the physical size, mass, and limited battery life of notebook‐sized computers reduce their attractiveness for field data recording. Several manufacturers have developed small, hand‐held computers designed primarily for field data recording, but the cost of many of these systems is prohibitive. Our objective was to develop data recording software for the Psion Organiser II Model XP (Psion PLC, London)1, an inexpensive, calculator‐sized computer with long battery life and nonvolatile data storage capabilities. Our software, named NOTES, is a menu‐driven program written in Organiser Programming Language that accepts both character and numeric data, provides a simple method for recording data variables, and supplies utilities for managing data files. Data can be stored on non‐volatile EPROM modules, making them safe from loss of battery power to the computer. Uploading data files to an RS232‐equipped MS‐DOS computer is automated through a file management utility built into the program and data files are stored on the host computer in ASCII format. This hardware/software system provides an easy to use, inexpensive method to increase the efficiency of recording field and laboratory data while virtually eliminating data loss due to battery failure.
Turf Response to Triazine Carriers as Influenced by Pseudomonas Inoculant
Authors: Peacock Charles H. , DiPaola Joseph M.
Published: July 2010

Triazines have potential for use as slow‐release N fertilizers. Their degradation by microbial activity and subsequent N mineralization rate is reduced in less microbially active soils. The objective of this study was to determine the influence of Pseudomonas inoculant on the efficacy of triazine fertilizers. Turf response to ammeline (4,5‐diamino‐1,3,5‐triazin‐2(1H)‐one) and melamine (1,3,4‐triazine‐2,4,6‐triamine) inoculated with a 1, 5, or 10% Pseudomonas sp. bacterial culture was investigated on ‘Tifway’ bermudagrass (Cynodon dactylon L. Pers. ✕ C. transvaalensis Burtt‐Davy) and compared to IBDU (isobutylidenediurea) and urea N carriers. During 2 yr of study, overall turf quality was acceptable for all carriers, but was best for those plots receiving IBDU, ammeline, and melamine/urea (M/U) with quality ranging from 6.9 to 7.7. Turf growth was not influenced by N sources the first year. During the second year, weekly shoot growth was greater from plots receiving ammeline and IBDU compared to melamine and M/U (up to 30%). Addition of inoculant to the melamine lowered turf quality by almost a whole point and weekly shoot growth was as much as 40% greater where no inoculant was added. Turf quality reductions with melamine were inoculant‐rate responsive. Inoculant addition failed to provide a microbially competitive advantage over naturally occurring soil organisms to stimulate increased degradation and N release for turf performance.
Comparison of Cellulase Solutions for Use in Digesting Forage Samples
Authors: Bughrara S. S. , Sleper D. A. , Beuselinck P. R.
Published: July 2010

Prepared cellulase solutions from different origins may differ in their relative effectiveness in providing accurate estimates of in vitro dry matter digestibility (IVDMD) of forages. Our objectives were to compare prepared cellulase solutions from different commercial sources with our non‐commercial prepared cellulase solution and evaluate their effectiveness in obtaining meaningful estimates of IVDMD for three grass and three legume species. A total of 46 samples were evaluated from six different forage species including switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), tall fescue (Festuca arundinacea Schreb.), alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), and lespedeza (Kummerowia striata Thunb.). Significant differences for IVDMD were found among the prepared cellulase solution sources. Correlations between IVDMD estimates using the prepared cellulase solutions and in vitro rumen fermentation ranged from 0.57 to 0.95. The highest correlation (r = 0.95) was observed using a non‐commercial prepared cellulase solution and the next (r = 0.91) was obtained from cellulase procured from Worthington Biochemical Corp (Freehold, NJ). We concluded that the cellulase solution prepared from cellulase obtained from Worthington Biochemical Corp. was an alternative to our non‐commercial source in obtaining estimates of IVDMD.
Potassium/Magnesium Ratio Effects on Aluminum Tolerance and Mineral Composition of Wheat Forage
Authors: Huang J.W. , Grunes D.L.
Published: July 2010

Knowledge of cation amelioration of Al toxicity may improve our understanding of differential Al‐tolerance mechanisms among winter wheat (Triticum aestivum L.) forage genotypes, and the causes of tetany in grazing cattle. A solution culture experiment was conducted using two winter wheat cultivars (Atlas 66 and Scout 66), two Al levels (0 and 50 μM), and three K/Mg ratios (0.1, 0.7 and 2.3, on a mol Lc−1 basis). Root dry weights were decreased significantly by Al for Al‐sensitive Scout 66, but not for Al‐tolerant Atlas 66. Increasing the K/Mg ratio in the presence of Al significantly decreased root dry weight, root length, and the root tolerance index for Scout 66, but not for Atlas 66. Shoot and root Mg concentrations were always significantly lower for Scout 66 than for Atlas 66. Without Al, shoot K and Ca concentrations for the two cultivars were not significantly different. With Al, shoot K, Ca and Mg concentrations were depressed more for Scout 66 than for Atlas 66. The K(Ca + Mg) ratios increased significantly in Scout 66 with added Al, thereby causing an increased tetany hazard. Adding Al reduced shoot Cu and Zn concentrations in both cultivars, and Fe and Mn concentrations in Scout 66. Increasing the proportion of Mg in solution increased the Al tolerance for Scout 66, indicating that an appropriate K/Mg ratio is important in selecting for Al‐tolerant wheat cultivars.
Growth and Root Morphology of Corn as Influenced by Nitrogen Form
Authors: Teyker R. H. , Hobbs D. C.
Published: July 2010

Public concern about NO‐3 levels in potable waters, together with improving techniques for maintaining NH4+ availability in soils, has renewed research interest in the effects of N form on crop growth. The effects of NO‐3 versus NH+4 on growth and morphology of juvenile corn (Zea mays L.) were investigated in two experiments. In Exp. 1, 16‐d‐old, solution‐grown plants produced less shoot fresh weight when grown with NH+4 than with NO‐3 nutrition. Root fresh weights were similar, but elongation of the primary root axis and its longest first order lateral was less with NH+4 nutrition. Under NH+4 nutrition, apparent thickness (grams per meter) of primary roots was 54% greater, and the frequency of first order laterals with second order laterals was 65% greater, than under NO‐3 nutrition. In Exp. 2, plants were grown in the greenhouse until 40 d after emergence in a slightly alkaline 3:1 sand:soil mix. Nitrogen (75 mg N kg−1) was supplied as either Ca(NO3)2 or (NH4)2SO4 plus nitrapyrin [2‐chloro‐6‐(trichloromethyl) pyridine]. Ammonium‐grown plants produced 2.3 times the dry matter and had higher concentrations of N in both stems (18.5%) and leaves (27.5%) compared to NO‐3‐ grown plants. Tillering was increased by NH+4‐ nutrition. Apparent root thickness was again greater under NH+4 nutrition, but the difference between N regimes was only 15%. Results indicate that under conditions of course‐textured soils and slightly alkaline pH an enhanced NH+4‐ N regime may be advantageous for growth of corn. Differences in pH regimes between the hydroponic and soil‐based experiments may account for the contrasting results.
Intercropping Sorghum and Pinto Bean in a Cool Semiarid Region
Authors: Carr P.M. , Schatz B.G. , Gardner J.C. , Zwinger S.F.
Published: July 2010

Intercropping corn (Zea mays L.) with soybean [Glycine max (L.) Merr.] has been found to yield a greater harvest of total grain protein than a sole crop of corn in northern temperate regions. Similarly, it may be possible to increase the total grain protein yield in regions of lower precipitation with an intercrop of grain sorghum [Sorghum bicolor (L.) Moench] and a pulse crop. Our objective was to determine if sorghum could successfully be intercropped with dry bean (Phaseolus vulgaris L.) to produce a grain for feed. A field experiment was conducted during 1989 and 1990 near Carrington, ND (45°30'N, 99°7'W). Sorghum was established at 16 plants m−2 as a sole crop and intercropped in the same row with pinto bean at three different sorghum to bean plant ratios: 8:1, 4:1, and 2:1. Grain yield of sorghum was not reduced by intercropping at the low (8:1) and moderate (4:1) bean plant densities, but yield was reduced (P < 0.05) at a sorghum:pinto bean plant ratio of 2:1. Yield of pinto bean ranged from 0.22 to 0.70 Mg ha−1, depending on population and annual growing conditions. Grain protein yield tended to increase as bean comprised more of the total plant population, although a significant difference between treatments was not detected. While this investigation demonstrates that sorghum can successfully be intercropped with dry bean, other sorghum‐pulse intercrops might be more advantageous in increasing the total yield of grain protein.
Yield and Yield Component Response of Spring Barley to Fertilizer Nitrogen
Authors: Bulman Patrick , Smith Donald L.
Published: July 2010

Barley (Hordeum vulgare L.) is an important cereal crop in eastern Canada, where it is used mainly as a source of energy for monogastric animals. A 4‐yr field experiment was conducted to evaluate the effects of N application on the yield of spring barley. Three cultivars, Cadette, Leger (adapted feed types), and Argyle (unadapted malting type) were grown with 0, 50, 100, 150, or 200 kg N ha−1 applied as ammonium nitrate at seeding. Two other treatments consisted of 100 kg N ha−1 at seeding plus 50 kg N ha‐1 as ammonium nitrate (broadcast) or urea (foliar spray) applied at Zadoks growth stage 50 (spike emergence). Grain yield generally did not respond to N treatments. Separate determination of main stem (MS) and tiller yield components revealed that the lack of response to progressively higher rates of N was due to the stable nature of MS yield components and to the relatively small contribution of tillers to grain yield. Very high levels of N occasionally reduced the grain set and yield of MS spikes. Mean weight per MS grain showed little variation among growing seasons and N treatments. High rates and split applications of N had few significant effects on tiller yield and yield components. Tiller spike densities were consistently low (81–147 spikes per square meter). Tiller spikes produced only 7 to 15 grains, with individual grains weighing 60 to 75% of the weight of MS grains. Previous cropping practices and environmental conditions seemed to affect spike development and grain‐set more than application of fertilizer N.
Model of Integrated Effects of Boron, Inert Salt, and Water Flow on Crop Yield
Authors: Shani U. , Hanks R. J.
Published: July 2010

High boron concentration in the soil causes yield reduction. Recently, a piecewise linear response curve was applied to describe yield response to B in near steady‐state conditions. However, application of similar curves to field situations where water, B, and other ion contents are transient and nonhomogeneous is limited. The objective of this study was to develop a model for simulation of the integrated effects of B, inert salt, and water on crop yield under field conditions. The model computes water flow in response to irrigation, rain, or evapotranspiration processes and subsequently computes inert salt and B transport. Crop yield is related to soil matric and osmotic potentials and B toxicity. Effects of B toxicity are considered by adapting the steady‐state approach to the transient situation. Field experiments with barley (Hordeum vulgare L.) and corn (Zea mays L.) were conducted on the Utah Power & Light Co. research farm (Huntington, UT). Soil was Penoyer loam [coarse‐silty, mixed (calcareous), mesic Typic Torriorthent]. Line source irrigation was used to obtain different irrigation levels. The effects of B, Salt (mixture of Na, Ca, Cl, and SO4), and B+Salt on yield were studied in barley. The effect of B + Salt was studied also in corn. Measurements and simulations were in close agreement for both crops. Barley yield ranked B + Salt < B < Salt < control. Corn yield ranked B + Salt < control. The B adsorption properties result in less leaching than do those of an inert ion like Cl. The effects of initial and boundary conditions together with the B adsorption characteristics on B concentration in the soil solution and the subsequent yield reduction are presented. This model can serve for an analysis of the long‐term effects of high B and help in understanding the relative effects of available water, inert salt, and B on yields.
Modeling Pepper Seedling Growth and Nutrient Uptake as a Function of Cultural Conditions
Authors: Bar‐Tal A. , Bar‐Yosef B. , Kafkafi U.
Published: July 2010

A mechanistic model was developed to describe pepper seedling growth, and water, N, and P uptake as a function of N and P concentrations in the irrigation solution, growth medium volume per plant, planting density, and growth substrate characteristics. Such a model will help optimize irrigation and fertilization of transplants and elucidate some of the mechanisms involved in seedling production. The main assumptions in the model were that (i) the potential shoot and root growth rates depend on the N and P concentration in each organ; (ii) the actual growth rate of each organ is determined by the dry matter production rate, which is a function of plant leaf area, N and P concentration in the leaves, and assimilate partitioning between shoot and root, which itself depends on the ratio between potential growth rates of shoot and root; and (iii) the rates of N and P uptake per unit root weight are described by the Michaelis‐Menten equation. Model parameters and functions were fitted from data on pepper seedlings grown in a solution culture. The model predicted satisfactorily the effects of steady and transient N and P supply, and growth substrate characteristics and volume per plant on dry matter production, and N and P uptake as a function of time. The parameters of major importance are those that relate the plant dry matter production rate and the nutrient uptake rate per root unit to the nutrient content in the shoot and root. Of secondary importance are the root radius, the growth medium water content, and the impedance factor to ion diffusion.
Nutrient and Structural Carbohydrate Partitioning in Pearl Millet
Authors: Powell J. M. , Fussell L. K.
Published: July 2010

Cereal stovers and other crop residues are vital feeds for ruminants during the 6‐ to 8‐mo dry season in mixed farming systems of semiarid West Africa. Reducing the competition between livestock and soil fertility is crucial to the sustained productivity of these farming systems. A 2‐yr field study was conducted in Niger on a sandy siliceous isohyperthermic Psammentic Paleustalf to determine the effects of fertilizer N (15 and 45 kg ha−1) and P (4.4 and 17.4 kg ha−1) on dry matter (DM), N, P, and structural carbohydrate distribution in plant parts of pearl millet [Pennisetum glaucum (L.) R. Br.]. Fertilizer N increased total millet DM by 13%, N uptake by 63%, and P uptake by 29%. Fertilizer P increased total millet DM by 100%, N uptake by 80%, and P uptake by 140%. Fertilizer N increased millet grain yield only during the year of adequate rainfall, whereas fertilizer P increased yields during both years. Fertilizer N increased and fertilizer P decreased the N concentrations in millet stover. Fertilizer P increased the P concentrations in all upper plant parts. The average total millet DM of 2.75 Mg ha−1 was partitioned into grain (18%); animal feed consisting of chaff, immature panicles, upper stover and tillers (41%); and middle and lower stover components for soil conservation (41%). Partitioning was not affected by fertilizer addition. Of the total N (33.4 kg ha−1) and P (5.2 kg ha−1) uptake, 32 and 40% were contained in grain, 41 and 40% in animal feed, and 27 and 20% in components for soil conservation. Results of our study show the importance of N and especially P in increasing grain and forage yield and quality, and that stover can be managed more effectively to raise both crops and livestock in a more sustainable manner.
Wheat Planting Date Effects on Soil Water Extraction and Grain Yield
Authors: Winter S. R. , Musick J. T.
Published: July 2010

Due to a wide range of irrigated and dryland production systems and highly variable weather, planting date of winter wheat (Triticum aestivum L.) grown in the Southern High Plains varies from August to November. A 2‐yr field study was conducted at Bushland, TX, to evaluate planting date effects on soil water extraction and grain yield. ‘TAM 107’ wheat was planted in late August to simulate a grazed production system, early October to represent an optimum date for grain production, and early November on preirrigated Pullman clay loam soil (fine mixed thermic Torrertic Paleustoll) and grown to maturity without further irrigation. Gravimetric soil water content to 3.6 m depth was determined at the beginning and end of winter dormancy and at anthesis. Water extraction prior to winter dormancy occurred to a depth of 1.8, 0.9, and 0.15 m for the early, normal, and late planting dates, respectively. Depth of water extraction at anthesis was 2.4, 2.4, and 1.2 m for the three dates. The fraction of total preanthesis soil water extraction that occurred during a critical 60‐d period immediately prior to anthesis was 0.22, 0.59, and 0.91 for the early to late planting dates, respectively. Planting in August greatly increased depth and amount of soil water extraction prior to winter dormancy; however, water deficits in the spring contributed to low head density and grain yield. Wheat planted in early October extracted as much soil water as the August planting by anthesis and produced high grain yield. Wheat planted in early November rooted only one‐half as deep, extracted two‐thirds as much water, and yielded two‐thirds as much grain as the October planting date. In conclusion, planting in August as compared with October did not increase soil water extraction at anthesis and grain yield was reduced because the period of major soil water extraction was shifted from spring to fall. Planting in November reduced grain yield because of insufficient rooting to fully extract soil water from below 1.2 m.
Nematode Population Changes under Crop Rotation Sequences: Consequences for Potato Production
Authors: Ferris Howard , Westerdahl Becky B. , Carlson Harry L.
Published: July 2010

Soils of the Klamath basin of northeast California and southeast Oregon that are used for a potato (Solanum tuberosum L.) cropping system are frequently infested with Meloidogyne chitwoodi (Golden, O'Bannon, Santo & Finley) and Pratylenchus neglectus (Filipjev & Schuurmans‐Stekhoven). These studies were conducted over a 7‐yr period to determine nematode population changes under crop rotation sequences, and the impact of those changes on potato crop yield and quality. The surface blemish rating of a summer‐grown potato crop has a log‐linear relationship with the population level of M. chitwoodi measured either the previous fall, or with lower reliability, in the spring before potato planting. Yield of Grade no. 1 potato was negatively related to population levels of M. chitwoodi measured the previous fall, although total yields were not affected. On crops that are hosts to M. chitwoodi or P. neglectus, seasonal multiplication rates of the nematodes were log‐linearly related to populations measured the previous fall. The relationship between crop yields, or nematode multiplication rates, and spring nematode population levels were weaker due to the imprecision of spring population assessments. Overwinter survival rates of both nematode species were log‐linearly related to population levels measured in the fall. Preliminary analysis of the impact of seasonal climatic variation suggests that the models may underpredict potato tuber blemish and nematode population increase one year in five, when higher soil temperatures prevail. The predictions of crop damage and nematode population change allow crop and nematode management decisions based on population assessment.
Soybean Yield and Pest Management as Influenced by Nematodes, Herbicides, and Defoliating Insects
Authors: Browde J. A. , Pedigo L. P. , Owen M. D. K. , Tylka G. L.
Published: July 2010

Pest management strategies based on crop losses from single stress factors may be inadequate where multiple stresses occur. Consequently, experiments were conducted in 1989, 1990, and 1991 to quantify interactive effects of stresses from soybean cyst nematode (Heterodera glycines Ichinohe), acifluorfen (5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐2‐nitrobenzoic acid) plus bentazon [3‐(1‐methylethyl)‐(1H)‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide] herbicides, and green cloverworm [Plathypena scabra (F.)] on seed yield of soybean [Glycine max (L.) Merr.]. Treatments were combinations of at‐planting soybean cyst nematode soil density, acifluorfen plus bentazon rate, and green cloverworm defoliation level. Herbicides were applied at V6 soybean development, while green cloverworm feeding was simulated during R2 to R4 soybean development. Plot yield and yield components (pods per plant, seeds per pod, and weight per seed) were determined. Herbicide injury and defoliation independently reduced yield in 1990 and 1991. Yield reductions from defoliation were attributed to fewer pods per plant, while herbicide injury decreased pods per plant (1990) and weight per seed (1990 and 1991). Moreover, herbicide injury and defoliation interacted over 1990 and 1991 to decrease yield. Although stress from soybean cyst nematode alone never affected yield, interactions with herbicides and with defoliation reduced yield in 1990. No treatment effects on yield were found in 1989, probably due to uncontrolled environmental factors. Because of the 2‐yr herbicides × defoliation effect, lower economic injury levels for green cloverworm were developed for soybean treated with acifluorfen plus bentazon. To account for potential interactions involving soybean cyst nematode, growers will be advised to consider adjusting weed and insect management strategies for soybean fields infested with soybean cyst nematode.
Effectiveness and Economics of Dryland Conservation Tillage Systems in the Southern Great Plains
Authors: Wiese A. F. , Harman W. L. , Bean B. W. , Salisbury C. D.
Published: July 2010

Precipitation is limited in the Southern Great Plains, and farmers must minimize production costs and control erosion. The purpose of this research was to determine economic feasibility of dryland no‐ and reduced‐tillage systems compared with sweep plowing on Pullman clay loam soil (fine, mixed, mesic Torrertic Paleustoll) in continuous winter wheat (Triticum aestivum L. emend. Thell) and in a winter wheat‐sorghum [Sorghum bicolor (L.) Moench]‐fallow rotation with two crops produced in 3 yr. Economic analyses considered 4‐yr averages of income and treatment costs. In continuous winter wheat, sweep plowing yielded significantly less (425 kg ha−1) than the best no‐tillage treatment in 2 of 4 yr. Because of low variable costs, sweeping was most profitable in the short‐term, and when machinery depreciation was considered for the long‐term, sweep tillage followed by glyphosate lost the least money. In the fallow period between sorghum and wheat, sweep plowing yielded significantly less than the best no‐tillage 2 of 4 yr or an average of 275 kg ha−1. However, because of low variable costs, sweep plowing was the most profitable in the short run, $84 ha−1, but $3 ha−1 less profitable in the long run than sweep plowing followed by glyphosate. In the wheat‐sorghum part of the rotation, using paraquat or glyphosate alone resulted in lowest yields because of poor weed control. Sweep plowing yielded less than the best no‐tillage 1 of 4 yr, but lower costs made it the most profitable, both short and long term.
Boron Deficiency in Two Wheat Genotypes in a Warm, Subtropical Region
Authors: Rerkasem Benjavan , Loneragan Jack F.
Published: July 2010

Yield losses due to boron deficiency are becoming common in the warmer subtropical regions into which wheat has been expanding. This study evaluated the B response of two wheat (Triticum aestivum L.) genotypes (SW41 and Sonora 64) in Chiang Mai, Thailand. A sand culture experiment imposed six B levels in nutrient solution (0, 0.1, 0.2, 0.5, 1, and 10 µM B). A series of field experiments in a sandy loam (Typic Tropaqualf) under rainfed conditions imposed four levels of borax application (0, 0.5, 1, and 2 kg B ha−1) over three successive years. In sand culture, B deficiency depressed the number of grains per spikelet in both genotypes (more strongly in SW41 than in Sonora 64). At 0 µM B, SW41 had no grain in any spikelet. In the field, B deficiency depressed grain number and grain yield of SW41 but not Sonora 64. Flag leaf B at boot stage of both genotypes grown in sand culture was closely related to the number of grains per spikelet at maturity; the critical level was determined to be 3 mg B kg−1. For field‐grown plants, the data suggest that, at the boot stage, flag leaf B concentrations of <5 mg kg−1 are deficient, and >7 are sufficient. Boron deficiency can depress wheat yield through grain set failure, but susceptibility to B deficiency varies with genotype. Sensitivity to B deficiency should be included as a criterion for breeding programs for low‐B soils.
From Cell Growth to Leaf Growth: II. Simulation of a File of Cells
Authors: Arkebauer Timothy J. , Norman John M.
Published: July 2010

Certain plant parts have cells arranged end to end in more or less distinct files (e.g., monocot leaves, roots, filamentous algae). Modeling the growth and development of such files of cells can give us insights into processes governing cell division and cell expansion. The objectives of this research were to construct a cell‐based model of a growing file of cells and to examine the effects of the daughter ratio vs. time function on the growth of the file. The file is considered to be a group of cells along the length of a monocot leaf. Cell expansion is described by water flux equations. Cell division is determined by a daughter ratio vs. time function. The daughter ratio is defined as the proportion of cells that remain proliferative (capable of further division) after each cell division event. Outputs from the model include the elongation rate of the entire file, the growth rate distribution along the file, and the proliferative fractions for groups of cells along the file. Outputs are compared with field measurements of leaf elongation in sorghum [Sorghum bicolor (L.) Moench] plants. The model overestimates the length of the expanding zone compared with the field measurements. There is close agreement between model outputs and field measurements of relative growth rates along expanding portions of leaves and estimated proliferative fractions of expanding leaves. The effects of using different daughter ratio vs. time functions on model outputs are also examined.
Device for Precision Peanut Seed Placement
Authors: Wright F Scott , Mozingo R. Walton
Published: July 2010

An important agronomic factor affecting peanut (Arachis hypogaea L.) plant growth, pod yield, and seed grade is seed placement. A tractormounted device was designed and constructed to aid in performing field experiments to accurately evaluate seed placement on plant growth and yield. Peanut seed were spaced in three alternative diamond‐shaped configurations. Although some hand labor was required, seed placement was precise because the human element of spacing seed in the soil was eliminated. The amount of labor required for precise seed placement was less tedious and labor productivity was doubled.
Modeling Flowering Time of Rice Plants under Natural Photoperiod and Constant Air Temperature
Authors: Kawakata Toshikazu , Yajima Masaharu
Published: July 2010

Rice (Oryza sativa L.) plants respond to variations in photoperiod. The prediction of flowering time of photoperiod‐sensitive rice plants is important for crop management. The objective of this study was to analyze the photoperiod sensitivity of rice plants under natural photoperiod and constant air temperature, and to derive a simple model to predict flowering time under these conditions. Rice cultivars were sown at 2‐wk intervals during 1 yr in a greenhouse maintained at a constant air temperature. The number of days required from emergence to flowering was constant for rice plants sown between August and February, while those sown between March and July required more time. On the basis of these results, the authors derived an equation describing the cumulative water temperature over the time required for flowering as a function of photoperiod [f(P)] and sowing date. The form of f(P) was calculated using nonparametric methods. The value of f(P) was almost zero when the photoperiod was shorter than the critical photoperiod (Po); when the photoperiod was longer, however, the value of f(P) increased proportionally. The function was simplified to represent the effective photoperiod. The equations of this model were able to analyze quantitatively the photoperiod sensitivity of rice plants, and the observed flowering time was accurately estimated.
Why Scientists Should Talk to Economists
Authors: Antle John M. , Wagenet Robert J.
Published: July 2010

This essay explains how economics plays a key role in enhancing the value of publicly funded agricultural research. Economics provides research institutions with the tools they need to be accountable to society and better able to set research priorities and design research programs that are consistent with public policy objectives while meeting the standards of good science. We first describe a multidisciplinary approach to setting research priorities and assessing research impacts. A systematic framework is required, so that economic data and data from other scientific disciplines can be collected and integrated using common units of measurement. Second, we address research designs needed to meet the standards of good science while also satisfying the standards of accountability and policy relevance. As scientists become involved in the priority setting process, they become aware of the ways that their research can contribute to the mission of publicly funded research. Finally, we address the problems that arise in valuing the economic, environmental, and human health impacts of agricultural production systems for priority setting and impact assessment. As with the priority setting and design stages of research, multidisciplinary collaboration is also a critical element of the valuation stage of impact assessment.