bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rainfall‐Induced Leaching and Leaf Losses from Drying Alfalfa Forage
Authors: Smith D. Mark , Brown D. Murray 
Published: July 2010

AbstractEfforts to construct models of forage yield and quality loss during the field drying of hay are hindered by a lack of quantitative information concerning several modes of loss. This study attempted to quantify leaching and rainfall‐induced leaf shatter from drying alfalfa (Medicago sativa L. ‘Magnum’) forage. A rainfall simulator was used to treat samples from four forage cuttings in 1989 and 1990 at four levels of tissue moisture between 760 and 150 g kg−1 (wet basis). Rainfall amounts of 0 (control), 5, 10, 15, and 20 mm were used at intensity levels of 20 and 40 mm h−1. Leaves lost due to rainfall were collected, samples of forage tissue were analyzed for quality and yield changes and samples of leachate water were collected from beneath hay samples for analysis. Results showed that leaf shatter is not directly induced by rainfall. Analysis of forage tissue showed that leaching of soluble dry matter caused dry weight losses and increases (P ≤ 0.05) in the proportion of fiber in tissue. Leachate analysis provided a more precise measure of leaching losses. Analysis of leachates for total dissolved and suspended dry matter demonstrated that leaching increases with rainfall amount and as tissue moisture levels decline. At 700 g kg−1 (wet basis) moisture, leaching losses reached only 0.3% of initial sample dry matter, while at 170 g kg−1 moisture they were as great as 1.7%. Leaching was also greater (P ≤ 0.05) under rainfall at 20 mm h−1 than 40 mm h−1. A regression equation generated from the leachate data can be used to model leaching losses within prescribed limits.
Effect of Crop Density on Weed Interference in Maize
Authors: Tollenaar M. , Dibo A. A. , Aguilera A. , Weise S. F. , Swanton C. J. 
Published: July 2010

AbstractDevelopment of an integrated weed management system requires detailed information on crop‐weed interactions, including the impact of the relative competitive ability of the crop during various phases of development on weed growth. The objective of this study was to quantify effects of maize (Zea mays L.) plant density on weed interference in maize throughout the growing season. Experiments were carried out during 1990, 1991, and 1992 at the Elora Research Station, Elora, ON, on a London loam (Aquic Hapludalf) soil that had been tile drained. Maize was grown at three plant densities (4, 7, and 10 plants m−2) under three weed pressures. Weed pressures were established by varying the weedfree period after maize planting: all season (weed free), planting to 5‐ to 7‐leaf stage of maize (medium weed pressure), and planting to 3‐ to 4‐leaf stage of maize (high weed pressure). Maize and weed biomass and composition were evaluated at 3 wk presilking, silking, 3 wk postsilking, and at physiological maturity. Maize leaf area index, leaf chlorophyll content, and photosynthetic photon flux density transmittance with and without weeds were also measured. Increasing maize plant density from 4 to 10 plants m−2 reduced weed biomass by up to 50%. The impact of high weed‐pressure treatments on maize dry matter accumulation remained in a narrow range of 18 to 21% throughout the growing season. The grain yield reductions attributable to high weed pressure were 26, 17, and 13% for the maize plant densities of 4, 7, and 10 plants m−2, respectively. Results of this study show that the competitiveness of maize with weeds can be enhanced by increasing plant density.
Predicting Pineapple Harvest Date in Different Environments, Using a Computer Simulation Model
Authors: Malézieux Eric , Zhang Jingbo , Sinclair Eric R. , Bartholomew Duane P. 
Published: July 2010

AbstractPrediction of pineapple [Ananas comosus (L.) Merr.] fruit harvest date is essential to the scheduling of labor and fresh fruit marketing efforts. A previously developed heat‐unit model for pineapple in the Smooth Cayenne group could not satisfactorily predict fruit harvest date in the range of environments in which it is grown in Hawaii. Our objective was to develop a model based on daily maximum and minimum air temperature for the prediction of pineapple fruit harvest date in the wide range of environments where the crop is grown. For modeling, two phases of fruit development are distinguished: the time from induction of fruit development with a growth regulator (forcing, DAYFOR) to opening of the first flower (DAYFF), and from DAYFF to harvest (DAYH50, the date when 50% of the fruits are one‐third yellow). From DAYFOR to DAYFF, predictions are based on the accumulation of heatunits, based primarily on air temperature. After DAYFF, heat‐units are accumulated from estimated fruit temperature. The decrease in development rate at above‐optimum temperatures during the day is also simulated. The model was calibrated and tested using data sets from several important producing countries with different environments (southeastern Queensland, Australia, 26° S lat; Côte d'Ivoire, 5° N lat; Hawaii, 20° N lat; and Thailand, 13.5° N lat). The model predicted harvest date with a mean error of 11, 3, 12, and 5 d in Australia, Côte d'Ivoire, Hawaii, and Thailand, respectively. We believe this margin of error would be acceptable to most pineapple growers. Improvements in the model are likely to come when the relationship between fruit temperature and environmental factors is better understood.
Selection Pressures for Diclofop‐Methyl Resistance and Germination Time of Italian Ryegrass
Authors: Ghersa C. M. , Martínez‐Ghersa M. A. , Brewer T. G. , Roush M. L. 
Published: July 2010

AbstractTo formulate strategies for controlling herbicide resistance in Italian ryegrass (Lolium multiflorum Lam.), the selective pressures acting on wild Italian ryegrass populations to encourage evolution of resistance must be identified. Field and greenhouse experiments were conducted in 1990 to 1992 to compare the seedling emergence patterns of diclofopmethyl‐resistant and susceptible Italian ryegrass. Timing of seedling emergence in full sunlight differed for the two biotypes. In general, the herbicide‐susceptible biotype emerged earlier than the resistant biotype. Greatest emergence for the susceptible biotype was in August and September, the period prior to typical winter cereal crop sowing. Soil shading enhanced resistant seedling emergence during August and September, suggesting that soil temperature plays an important role in regulating seed germination of this biotype. Before current‐year seed shed, the seed bank in the experimental plots was found to contain three times as many viable resistant seeds as susceptible seeds. In a corroborating experiment, we found that Italian ryegrass seeds with a greater degree of dormancy were more likely to be herbicide resistant than those with a lesser degree of dormancy. Our results support the hypothesis that the timing of field tillages and herbicide use is a selective force for increasing seed dormancy and thus for changing seedling emergence patterns as herbicide‐resistant Italian ryegrass weed populations evolve. The linkage between changes in seed dormancy and herbicide resistance traits has ecological and agronomical implications.
Frequency of Nitrogen Fertilizer Carryover in the Humid Midwest
Authors: Vanotti Matias B. , Bundy Larry G. 
Published: July 2010

AbstractSoil tests for residual NO‐3 can improve prediction of crop N fertilizer requirements in the humid Midwest, but their adoption as a standard procedure in fertilizer N recommendation programs depends on the frequency of significant profile NO‐3‐N carryover. Data from a 25‐yr crop sequence experiment (1967 to 1991) on a Rozetta silt loam soil (finesilty, mixed, mesic Typic Hapludalf) at Lancaster, WI, were used to estimate the frequency and extent of N fertilizer carryover. Sequences studied included unfertilized oat (Avena sativa L.) grown after corn (Zea mays L.) that received a range of N rates. Oat yields were influenced by the residual effects of the previous year's N application in 21 of the 25 yr, with yield responses varying from 500 to 1500 kg ha−1. Soil profile measurements (0 to 90 cm) taken before seeding oat in spring 1987 through 1991 showed substantial NO‐3‐N carryover that was usually found below the 30‐cm depth. Significant increases in profile NO‐3‐N content occurred at low N rates (56 to 112 kg N ha−1) in years with limited rainfall during the preceding corn growing season, but only at higher N rates under optimum corn growing conditions. Total N uptake by oat was also significantly affected by corn N treatments, and it was well correlated with profile NO‐3‐N. A nutrient efficiency index that characterized the yield response of oat to profile NO‐3‐N was used to estimate carryover NO‐3‐N from 1967 to 1986 oat yield data. Expected N fertilizer carryover values (P = 80%) ranged from 32 to 106 for a 168 kg N ha−1 rate, and from 63 to 151 kg NO‐3‐N for a 224 kg N ha−1 rate. The wide variation of expected amounts of N carryover reflects typical year‐to‐year changes in conditions affecting N recovery by corn and retention by soil. Results of this study indicate that significant residual profile NO‐3‐N occurs in most years on well‐drained silt loam soils in Wisconsin, and that year‐specific tests for profile NO‐3‐N are needed to adjust N recommendations for varying amounts of NO‐3‐N carryover.
Iron and Manganese Accumulation by the brz Pea Mutant Grown in Soils
Authors: Cary Earle E. , Norvell Wendell A. , Grunes David L. , Welch Ross M. , Reid W. Shaw 
Published: July 2010

AbstractLeaf composition of the bronze (brz) mutant pea [Pisum sativum L. cv. Sparkle E107 (brz brz)] and its parent genotype (cv. Sparkle) have been compared when grown in nutrient culture, but not when grown in soil where pH has been adjusted to reduce readily available Fe and Mn. Both genotypes were grown in a growth chamber in five soils that differed in pH and DTPA‐extractable Fe and Mn. The brz genotype accumulated very high, and often toxic, concentrations of Fe and Mn when grown in acidic soils, while Sparkle did not. Liming reduced leaf‐Fe and leaf‐Mn concentrations in the brz mutant, but Fe toxicity symptoms were still evident in older leaves. In the acidic soils, leaves of the brz plants also accumulated significantly more Zn, Cu, Ca, Mg, K, Na, Al, and P than did leaves of Sparkle plants. Roots of the brz genotype depressed soil pH by several tenths of a pH unit more than did roots of Sparkle. In contrast to results obtained in the acidic and near‐neutral soils, the brz mutant and its parent grew similarly in a calcareous soil (pH 8.2), which contained low concentrations of DTPA‐extractable Fe and Mn. In conclusion, the brz mutant pea consistently accumulates high levels of Fe and Mn when these metal ions are present in readily available forms. Liming an acid soil to near‐neutral pH did not prohibit the brz mutant from accumulating potentially toxic concentrations of Fe, but growing the mutant in a calcareous soil did.
Estimation of Yield and Nitrogen Removal by Corn
Authors: Overman Allen R. , Wilson Denise M. , Kamprath Eugene J. 
Published: July 2010

AbstractA wide variety of mathematical models have been used to relate crop production to management factors such as applied N and water availability. These include power functions and exponential functions. The objective of this analysis was to use an extended logistic model to relate dry matter yields and plant N removal to applied N for corn (Zea mays L.) for three soils in North Carolina. In this model, response of both dry matter yield and plant N removal to applied N were described by logistic equations. Plant N concentration was then related to applied N by the ratio of these logistic equations. Model parameters were estimated by nonlinear regression. Analysis of variance showed that the N response coefficient c was common for dry matter yield and plant N removal for each soil. Overall correlation coefficients of yield and plant N removal with applied N were very high for all three soils (R> 0.99). It was shown that ≈50% of the total dry matter and 80% of total plant N were contained in the grain at all applied N levels. Maximum potential grain yield of 25.9 Mg ha−1 agreed closely with an estimate in the literature of 26.5 Mg ha−1 (500 bushels acre−1). Dependence of plant N concentration on plant N removal was shown to follow a linear relationship. The present model provides a rational basis for coupling of dry matter yield and plant N removal in response to applied N. It can be used in design and management decisions related to agricultural production and environmental quality.
Cover Crop Production for Several Planting and Harvest Dates in Eastern Nebraska
Authors: Power James F. , Koerner Paul T. 
Published: July 2010

AbstractSpecies used for cover crops vary greatly in their growth response to water availability, soil temperature, length of growing period, day length, and related environmental factors. Few reports compare growth of different species at different times during the growing season. This 4‐yr field experiment at Lincoln, NE, compared growth of some 20 species as affected by planting date and length of the growth period. All species were planted as early as possible each spring, with a second seeding in early summer (25 June–17 July). Additional seedings were made at other times in most years. All plots were periodically sampled for dry matter production until maturity or frost. At most samplings, growth of soybean [Glycine max L. (Merr.)] was equal to or greater than (sometimes double) that of the next species. In most situations, hairy vetch (Vicia villosa Roth) also performed well. Field pea (Pisum sativum L.) or Austrian winter pea [P. sativum L. subsp. sativum var. arvense (L.) Poir.] and fava‐bean (Vicia faba L.) grew very rapidly for the first 60 to 90 d after planting. Lespedeza [Kummerowia stipulacea (Maxim.) Makino] grew relatively well when seeded in early summer, as did tinga pea (Lathyrus tingitanus L.) and cowpea [Vigna unguiculata (L.) Walp. subsp. unguiculata]. Rye (Secale cereale L.) was usually intermediate, and small‐seeded legumes generally exhibited relatively slow growth the first 60 d. Results suggest that certain large‐seeded, cool‐season legumes would produce best for early spring seeding before row crops or summer fallow, whereas some warm‐season species would be better suited for summer seeding after small grain harvest. Soybean and hairy vetch were well suited for almost all situations in this environment.
Automating a Commercial Swather for Harvesting Forage Plots
Authors: Pearson Calvin H. , Robinson Lot 
Published: July 2010

AbstractForage plot harvesters having sicklebars are representative of technology currently used by commercial forage producers. Commercially built forage plot harvesters that are highly automated have been developed in recent years, but because of their small size they are not wellsuited for operating in fields with rough terrain, particularly fields with furrows. Furthermore, automated forage plot harvesters that use sicklebars are highly expensive, costing $30 000 and more. An automated forage plot harvester was developed at Colorado State University using a field‐scale commercial swather. A weigh bin was designed and fabricated that attaches underneath the swather directly behind the hay conditioner. This article describes, in detail, how to construct the forage plot harvester. The plot harvester can be modified quickly for use in harvesting both research plots and commercial fields. It has an electronic weighing system and a belt conveyor in the bottom of the weigh bin for discharging weighed samples. The plot harvester has performed well in furrow‐irrigated fields. Alfalfa samples weighing up to 68 kg have been harvested, and the average time required to harvest small plots was 50 s. The cost of materials for the weigh bin, including the electronic weighing system, was $2550.
Total Nonstructural Carbohydrate Accumulation in Roots of Annual Lespedeza
Authors: Davis David K. , McGraw Robert L. , Beuselinck Paul R. , Roberts Craig A. 
Published: July 2010

AbstractTotal nonstructural carbohydrates (TNC) stored in roots are thought to be an important energy source for growth following herbage removal in many forage legumes. This study was conducted to determine if root TNC levels fluctuate during harvest and regrowth cycles of annual lespedeza (Kummerowia spp.). Annual lespedeza management treatments consisted of harvesting at a 6‐ or 12‐cm stubble height at the end of July and a nonharvested control. Seeding‐year ‘Nitro’ alfalfa (Medicago sativa L.) and ‘Norcen’ birdsfoot trefoil (Lotus corniculatus L.) were included for comparison. Alfalfa was harvested four times at early bloom and birdsfoot trefoil three times at early bloom. Alfalfa exhibited a cyclic pattern of TNC utilization and storage in response to herbage removal and regrowth, respectively. Seedling alfalfa accumulated >150 g kg−1 TNC in the roots by 10 June, and >450 g kg−1 by first harvest. Seedling birdsfoot trefoil maintained <70 g kg−1 TNC in the roots through mid‐September and did not exhibit as much TNC cycling as did alfalfa. Annual lespedeza averaged ≈ 20 g kg−1 TNC in the roots prior to harvest and maintained <40 g kg−1 throughout the growing season. Harvesting annual lespedeza at 6 cm decreased root TNC levels for ≈ 5 wk compared with harvesting at 12 cm and the nonharvested controls; however, the total amount of reduction was small. Root TNC levels decreased by 6.1 g kg−1 with cutting at 6 cm. As annual lespedeza maintains relatively small amounts of root TNC, leaving residual leaf area at harvest may be important for regrowth.
A Computer Program to Analyze Multiple‐Season Crop Model Outputs
Authors: Thornton Philip K. , Hoogenboom Gerrit , Wilkens Paul W. , Bowen Walter T. 
Published: July 2010

AbstractManagement‐oriented simulation models of the growth, development, and yield of annual crops are useful tools for screening management options on the computer. Until recently, a limitation of these models has been the inability to simulate more than one cropping season at a time. The capability to simulate long‐term field experiments with such models now exists, in which the simulated soil water, N, organic C, and crop residue outputs from one model run become the input conditions for the next. Simulations of crop rotations can produce large quantities of data, especially if the simulation experiment involves replications across different years. Computer software was written to perform simple analyses of such simulation experiments. The major purpose of the software is to allow the user to investigate the stability and profitability of crop sequences. The program calculates summary statistics for model output variables; these are presented to the user in tabular and graphical forms. Net monetary returns or gross margins can also be calculated, and price and cost variability can be taken into account in the analysis. The program allows rapid, preliminary analysis of a particular crop sequence from replicated simulation experiments and can help the user to assess whether the sequence warrants further evaluation. The program can also be used to summarize the results from historical long‐term field trials. The analyses performed constitute a first step in investigating the sustainability of a particular cropping sequence for a specified length of time.
Carbon Dioxide Effects on Crop Energy Balance: Testing ecosys with a Free‐Air CO2 Enrichment (FACE) Experiment
Authors: Grant Robert F. , Kimball Bruce A. , Pinter Paul J. , Wall Gerard W. , Garcia Richard L. , La Morte Robert L. , Hunsaker Douglas J. 
Published: July 2010

AbstractElevated CO2 concentrations (Ce) have been observed to decrease short‐term plant water use under controlled conditions by increasing stomatal resistance. The extent to which this decrease occurs over a growing season in the field is uncertain, however, because stomatal resistance is only one of many mechanisms that control water use. In this study, we tested the ecosystem simulation model ecosys, which reproduces an hourly energy balance through soil‐vegetation systems under defined atmospheric boundary conditions, using energy exchange data measured as part of the Free‐Air CO2 Enrichment (FACE) experiment at Ce = 550 vs. 370 µmol mol−1. The model reproduced reductions in measured upward latent heat fluxes that varied from −10 to +40 W m−2, depending on atmospheric conditions. In the model, the primary effect of elevated Ce on latent heat fluxes was through canopy stomatal conductance. This effect was largely offset by secondary effects through canopy temperature that enabled the model to reproduce measured changes in sensible heat fluxes. The total effect simulated by ecosys of Ce = 550 vs. 370 µmol mol−1 on evapotranspiration during the entire FACE experiment was a reduction of 7%. This reduction compares with one of 11% estimated from accumulated daily measurements of latent heat flux. In the model, the different effects of Ce on plant water use depend on atmosphere and soil boundary conditions, and are highly dynamic. Consequently the simulated Ce‐water use relationship is likely to be sitespecific. The use of models such as ecosys allows site‐specific boundary conditions to be considered in the study of Ce effects on plant growth and water use.
Reduced Preplant‐Incorporated Imazaquin Rates for Broadleaf Weed Control in Soybean
Authors: Jones Darrin Scott , Lin Htain , Kane Mark V. , Grabau Larry J. 
Published: July 2010

AbstractPublic pressure and economic distress have together provided a strong incentive for reduced chemical use in U.S. agriculture. This field study was designed to determine if preplant‐incorporated imazaquin {2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐3‐quinoline‐carboxylic acid} rates could be reduced from the labeled rates when applied with alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide] without incurring yield penalties due to broadleaf weed infestations. Imazaquin was applied at 0, 47, 93, and 141 g ha−1 in earlyplanted soybean [Glycine max (L.) Merr.] studies in Fayette County in 1989, 1990, and 1991 and in Simpson County (1989), Hardin County (1990), and Hopkins County (1991), Kentucky. Preplant‐incorporated alachlor was followed by postemergence fluazifop‐P‐butyl {butyl(R)‐2‐[4[[5‐(triliuoromethyl)‐2‐pyridinyl]oxy]phenoxy]propanoate} (as needed) to minimize grass competition. Perennial broadleaf weeds were controlled with hand‐wicked glyphosate [isopropylamine salt of N‐(phosphonomethyl) glycine]. Acceptable broadleaf control was obtained at sub‐label imazaquin rates, except for Fayette 1991, where ivyleaf morning‐glory [Ipomoea hederacea (L.) Jacq.] and velvetleaf (Abutilon theophrasti Medic.) were planted. Two studies (Simpson 1989 and Hopkins 1991) showed minimal broadleaf weed pressure at any imazaquin rate; this may have been a result of the early planting dates used. The common lambsquarters (Chenopodium album L.) and Pennsylvania smartweed (Polygonum pennsylvanicum L.), which dominated in Fayette 1989 and 1990, were successfully controlled with 47 g ha−1 imazaquin. While alachlor provides some control for these two species, their competition with soybean was severe without the addition of imazaquin. Producers who can accumulate detailed knowledge of the broadleaf weed species present in their soybean fields could potentially use such information to select herbicides likely to control their broadleaves at sub‐label rates.