bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractCereal 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

AbstractDue 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

AbstractSoils 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

AbstractPest 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

AbstractPrecipitation 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

AbstractYield 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

AbstractCertain 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

AbstractAn 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

AbstractRice (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

AbstractThis 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.
Influence of Autumn Management on Orchardgrass–White Clover Swards
Authors: Belesky David P. , Fedders James M. 
Published: July 2010

AbstractThe influence of autumn management on the productivity, morphology, and botanical composition of an orchardgrass (Dactylis glomerata L.) and white clover (Trifolium repens L.) sward was investigated over 3 yr. Stockpiled (nongrazed) canopies were clipped at fixed intervals throughout autumn from exclosures established in each of nine paddocks to determine growth rates and productivity of standing herbage. Pastures were grazed by weaned lambs (Ovis aries) beginning in August in each of 3 yr. Grazing animals were removed from three replicate paddocks after 30 (early closed), 60, or 90 d (late closed). Paddocks were sampled at 2‐wk intervals to determine herbage mass, botanical composition, and total nonstructural carbohydrate concentrations of grasses and legumes. Early‐closed paddocks continued to accumulate herbage during autumn, resulting in greater senescence over winter than in lateclosed paddocks. Herbage mass in spring was not affected by autumn management. Late‐closed paddocks had significantly more clover than did early‐closed paddocks in spring. Early‐closed paddocks were comprised of grass plants that had relatively few and large tillers and by white clover plants that had fewer growing points than those in lateclosed paddocks. In comparison, late‐closed paddocks had grass plants comprised of many small tillers and white clover plants with about twice as many growing points. Stolon mass was greater, but total nonstructural carbohydrate concentrations were less during autumn in late‐ than in early‐closed paddocks. The decrease in clover mass over the course of the experiment coincided with a decrease in total herbage mass. A delicate balance between growing points and carbohydrates may be involved in clover presence in mixed swards.
Spring Nitrogen Rate and Timing Influence on Seed Yield Components of Perennial Ryegrass
Authors: Young William C. , Youngberg Harold W. , Chilcote David O. 
Published: July 2010

AbstractSpring application of N generally increases seed yield of perennial ryegrass (Lolium perenne L.). Understanding the influence of N rates and timings on seed yield components can be used to improve N use efficiencies and seed yield. Field experiments during 1982 and 1983 at Oregon State University studied the effects of 60, 90, and 120 kg N ha−1, applied either at double‐ridge stage (DR) or at spikelet initiation stage (SI), on seed yield and yield components of the cultivar Pennfine. Control plots with no spring‐applied N were also included. Little lodging was observed in 1982, but all plots severely lodged by maturity in 1983. Timing of N application did not affect seed yield in either year. Compared with the control, spring N increased seed yield 43% in 1982 and 39% in 1983 when averaged across rates. In 1982, seed yield did not vary with N rates applied at DR, but 120 kg N ha−1 produced greater seed yield than 60 kg N ha−1 when applied at SI. In 1983, seed yield was maximized by 90 kg N ha−1 applied at DR, and by 120 kg N ha−1 applied at SI. Nitrogen application did not affect the number of spikes per unit area, but increased seed number per spike in 1982 and weight per seed in 1983. Averaged across rates and timings, N increased total number of seeds produced per unit area 43% in 1982 and 30% in 1983. Seed yield was correlated with the number of seeds per spike in both 1982 (r2 = 0.68) and 1983 (r2 = 0.72). In 1983, seed yield was also correlated with weight per seed (r2 = 0.55). We concluded that in the absence of severe lodging, 60 kg N ha−1 applied at DR is adequate for achieving maximum seed yield. If fertilization is postponed until SI, however, higher rates of N may be required. Results also suggest that modifications in N fertilization should focus on improving seed set per spike and seed growth rather than increasing the number of spikes per unit area or floret sites per spike.
Tall Fescue Growth after Paraquat Application to Elongating or Mature Leaves
Authors: Skinner R. Howard , Nelson Curtis J. , Coutts John H. 
Published: July 2010

AbstractParaquat (1,1'‐dimethyl‐4,4'‐bipyridinium dichloride) is commonly used to kill endophyte‐infected stands of tall fescue (Festuca arundinacea Schreb.) prior to reseeding with endophyte‐free cultivars. Regrowth of infected plants, however, is often a problem, even when control initially appears to be adequate. Our objective was to evaluate the effect of leaf developmental stage on sensitivity to paraquat applications. Ten 0.5‐μL drops of paraquat at 0‐ to 60‐mM concentrations were applied to either fully elongated blades, or to emerged portions of elongating leaves of 3‐ and 6‐wk‐old seedlings growing in a growth chamber, and to endophyte‐infected plants in the field. Leaf elongation rate in the growth chamber decreased 4 h after paraquat application to elongating leaves of 6‐wk‐old plants. Paraquat did not affect leaf elongation in the field until considerable damage to the elongating leaf had occurred. Visible damage to the treated leaf also occurred faster in the growth chamber than in the field. In both environments, injury was greater when elongating compared with fully elongated leaves were treated. When fully elongated leaves were treated, damage was often limited to the treated leaf, while the shoot apex remained alive and capable of initiating new leaves and tillers. Treatment of elongating leaves, however, increased the probability that the entire plant would be killed. To increase effectiveness, paraquat should be applied to young, elongating leaves. However, these leaf blades are vertically oriented, slightly rolled, lower in leaf area, and narrower than fully elongated leaves, making their treatment more difficult.