bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Three Methods for Estimating Defoliation in Soybean Breeding Programs
Authors: Bowers Glenn R. , Kenty Michael M. , Way Michael O. , Funderburk Joseph E. , Strayer John R.
Published: July 2010

The proper assessment of defoliation by phytophagous insects in soybean [Glycine max (L.) Merr.] is required when screening germplasm for insect resistance. The objective of this study was to evaluate the effectiveness and relative efficiency of the widely used visual or relative assessment of insect defoliation compared with a more quantitative assessment for use in soybean breeding programs. In 1985 and 1991, visual assessments (whole plot, 1985; whole plant and average of partitioned plant, 1991) were compared with an established quantitative assessment. Twenty leaflets were randomly removed from each of the upper, middle, and lower thirds of the canopy of each plot. These leaflets were compared with a template of known defoliation in 1985. In 1991, a leaf area meter was used to determine the actual amount of defoliation of each plant. In 1990 and 1991, two types of visual estimates (whole plant and average of partitioned plant) were also compared with each other. Sampling time was estimated for each method. Estimates between visual and quantitative assessments were highly correlated each year. Precision was similar for each method. Sampling time for the visual assessment was at least 30 times faster than the quantitative assessment. The results of these studies show that relative estimates can be used to assess insect defoliation accurately and quickly.
Crop Sequence and Surface Residue Effects on the Performance of No‐Till Corn Grown on a Poorly Drained Soil
Authors: Wolfe Alice M. , Eckert Donald J.
Published: July 2010

On noncrusting, poorly drained soils, yield differences between corn (Zea mays L.) grown following corn and following soybean [Glycine max (L.) Merr.] can be much greater when no‐till rather than moldboard plowing practices are used. We conducted this experiment to determine whether differences in previous crop, surface residue cover, or a combination of both contribute to yield differences when no‐till corn follows corn or soybean. Corn was grown without tillage in 1991 and 1992 on a tile‐drained Kokomo silty clay loam (fine, mixed, mesic Typic Argiaquolls), following either corn or soybean. On half of the plots, residues were switched, so that the previous crop was corn but surface residue was soybean, and vice versa. On other plots, residue was left undisturbed. Plots with corn residue cover showed slightly lower spring soil temperatures in both years, and in 1992 showed slower early development of corn plants, than did plots covered with soybean residue. In both years, however, final plant height, grain yield, and stalk mass were greater where corn followed soybean, regardless of residue cover (P < 0.05). These differences appeared greater in 1991, a dry year, than in 1992, a more favorable year for corn production. Corn following corn showed more barren stalks and fewer kernels per ear than corn following soybean in the dry year, 1991 (P < 0.05). Nutrient concentrations in ear leaves of corn plants were all above sufficiency levels, were unaffected by surface residue, and were inconsistently affected by previous crop. Results indicate that lower yields of no‐till corn following corn rather than soybean are due more to previous crop than surface residue influences.
Improved Pasture Establishment and Production on Water‐Repellent Soils
Authors: Crabtree William L. , Gilkes Robert J.
Published: July 2010

Pasture establishment and production is reduced by water‐repellent soils. Ameliorative techniques are explored with this study. Two field experiments were conducted on water‐repellent soils to investigate (i) the improvement in emergence of pasture species with furrow sowing and the use of a press wheel and banded wetting agent and (ii) the residual effectiveness (applied 2 years previously) of a wetting agent on pasture growth and composition. In the first experiment, conventional level sowing (flat planting) was compared with furrow sowing using press wheels. Five pasture species were included, and the furrow‐sown treatments involved a banded wetting agent applied at four rates. Furrow sowing with a planter having press wheels increased the average emergence at 14 days after sowing by 133% relative to the conventional treatment and emergence was further increased 44% by banding 4 L ha−1 of wetting agent in the furrows. There was a large (up to sixfold) increase in early pasture production (330 to 2010 kg ha−1) and a large effect on pasture composition due to the residual effect of a wetting agent applied 2 years previously. The proportion of subterranean clover (Trifolium subterraneum L.) in the pasture increased from 6 to 33% due to the use of a wetting agent. This study shows that the effect of water repellency on pasture emergence and productivity is severe and that these ameliorative techniques are useful tools for improving pasture emergence.
Laparascopic Sampling of Roots of Known Age from an Expandable‐Wall Minirhizotron System
Authors: Kosola Kevin R.
Published: July 2010

Root system changes in response to experimental treatments may be due to a number of factors, which can be separated only by sampling roots of known age. Minirhizotrons allow for video recording of the growth of individual roots; subsequent removal of the minirhizotron would allow sampling of the roots under observation. A design for a removable minirhizotron with mechanically expandable walls is described in this paper, along with the use of laparascopic tools for sampling roots from removable minirhizotron systems. Laparascopic tools used in conjunction with removable minirhizotrons may be useful in field studies of the effects of root age and experimental treatments on root composition, physiology, and pathology; rhizosphere microbial ecology; rhizosphere mineralogy; and the dynamics of mycorrhizal colonization.
Multifractal Analysis of Soil Spatial Variability
Authors: Kravchenko Alexandra N. , Boast Charles W. , Bullock Donald G.
Published: July 2010

Multifractal formalism was utilized to study variability of different soil properties, including soil‐test P and K, organic matter content, pH, Ca and Mg contents, and cation exchange capacity. Data from 1752 samples collected from a 259‐ha agricultural field in central Illinois were used in the study. Based on the theory of multifractals a set of generalized fractal dimensions, D(q), and an f(α) spectrum were computed for each of the studied soil properties. The D(q) curves were fitted with a three‐parameter mathematical function, which produced excellent fitting results with the coefficient of determination between measured and fitted values higher than 0.98 for all the studied data sets. We analyzed precision produced by the inverse distance interpolation procedure with different power to distance values and found the optimal power value to be related to one of the studied multifractal parameters. For the studied data, the multifractal parameter was the only data property that could be used as an a priori indicator of an optimal power value. The research demonstrated, first, that multifractal parameters reflected many of the major aspects of soil data variability and provided a unique quantitative characterization of the data spatial distributions and, second, that multifractal parameters might be useful for choosing an appropriate interpolation procedure for mapping soil data.
Development and Evaluation of Software for Spatial Record‐Keeping of Golf Course Turf
Authors: Golombek Claudio H. , Fermanian Thomas W. , Braga Paula P.
Published: July 2010

Most current golf course management record‐keeping software systems have been adapted for golf course use from accounting or inventory control systems. These are based on table or card‐filling systems that have a nonintuitive connection to the geographic features of the golf course and are not spatially referenced. A geographic information system (GIS) based management tool, Golf Course Management System (GCMS), was developed as a new approach for human–machine interaction in golf course management. GIS provides a framework within which management decisions can be related to operating equipment on the field. The interface of GCMS allows a user to view the physical areas on a map where maintenance operations were directed, determine distance and area affected, and input usage history related to record keeping and decision support. This historical database could potentially be used to measure environmental impacts, assist in budgetary estimates, or monitor equipment and/or application needs. The system was designed to provide direct interaction with a course map in a way that is more user‐friendly and intuitive. Multiple evaluations of the system were developed. Superintendents at golf courses across Illinois were the final end‐user evaluators. Users found this map‐based approach to organizing records easy for golf course superintendents to use the information contained inside the database. GCMS runs on Unix, Windows, MacOS, or any platform that supports the software ArcView.
Water Budget and Yield of Dryland Cotton Intercropped with Terminated Winter Wheat
Authors: Baumhardt R. Louis , Lascano Robert J.
Published: July 2010

A Texas South Plains production system for reducing wind erosion in irrigated cotton (Gossypium hirsutum L.), a low‐residue crop, is to plant winter wheat (Triticum aestivum L.) after cotton harvest, chemically terminate the wheat in the spring, and plant cotton using conservation tillage. The terminated wheat–cotton system (TWC) utilizes fall rain to grow wheat residue. This system has increased irrigated cotton lint yields compared with continuous clean‐tillage cotton (CCC), but there is limited information on the annual water budget and adaptability of TWC under dryland conditions. This study compares CCC and TWC effects on (i) runoff and infiltration of rain, (ii) the annual water balance, and (iii) cotton lint yield under dryland conditions. The water budget of TWC and CCC was measured in 3‐ by 30–m subplot watersheds from May 1992 to December 1995 on an Amarillo sandy loam (fine‐loamy, mixed, thermic Aridic Paleustalf) at Wellman, TX. Compared with CCC plots, the TWC residue reduced average annual runoff by 43 mm, but increased average fallow water use by 28 mm (for growing wheat). The use of TWC did not significantly increase either water conservation or cotton lint yields compared with CCC. Cotton establishment was problematic, due to limited soil water at planting in 1993 for TWC and CCC. This prevented 1994 TWC cotton establishment, thus offsetting improved establishment in 1992, when residue protected cotton seedlings during above‐average rain. In semiarid regions, inadequate soil water for crop establishment is an uncontrolled risk with dryland TWC production. Because no significant gains in water storage or cotton lint yield were observed under dryland conditions with TWC compared with CCC, undertaking the greater crop establishment risk with TWC cotton production is not recommended in the Texas South Plains.
A General Thermal Index for Maize
Authors: Dwyer Lianne M. , Stewart Douglas W. , Carrigan L. , Ma B. L. , Neave P. , Balchin D.
Published: July 2010

Thermal indices predict and describe development rate more accurately than time in days and are commonly used to rate maize (Zea mays L.) for maturity. Separate temperature response functions for the vegetative and grain‐filling periods predict more accurately time to maturity than a single function for the two periods combined. However, use of two functions requires a priori knowledge of the silking date, which becomes the transition date from the vegetative function to the grain‐filling function. The objective of this study was to evaluate the sensitivity of estimates of silking and maturity dates to the transition date between vegetative and grain‐filling functions and to develop a protocol to combine the two temperature response functions in a general thermal index (GTI) for maize. Frequency distributions of mean daily air temperatures for five 20‐d periods spanning mid‐June to late September at 19 locations in the northern USA and southern Ontario from 1992 to 1995 indicated few days (≤12%) with mean daily air temperatures less than 15°C before late August. This was significant, as the two response functions diverged significantly at temperatures below 15°C. Standard errors in estimating maturity date using different transition dates remained small (<7.5 d) unless the transition date was delayed beyond the first week of September. Based on this analysis, a standard transition date of 1 August was proposed for the GTI. Testing on an independent data set indicated that the GTI and a transition date of 1 August provided more accurate estimates of the planting to maturity period than growing degree days (GDD) or crop heat units (CHU), with a standard error of 8.2 d (compared with 14.5 d using GDD and 12.5 d using CHU).
Yield and Botanical Composition of Rhizoma Peanut‐Grass Swards Treated with Herbicides
Authors: Valencia E. , Williams M.J. , Sollenberger L.E.
Published: July 2010

Weeds are an increasing problem in rhizoma peanut (RP) (Arachis glabrata Benth.), a warm‐season perennial forage legume. The objective of this field study was to measure the effect of glyphosate [N‐(phosphonomethyl)glycine] at 1.12, 2.24, or 3.36 kg a.i. ha−1 and triclopyr {[(3,5,6‐trichloro‐2‐pyridinyl)oxy]acetic acid} at 0.56, 1.12, or 1.68 kg a.i. ha−1 applied in the summer on dry matter (DM) yield and botanical composition of weed‐infested RP–grass swards at 2 and 4 mo after application. Mexican‐tea (Chenopodium ambrosioides L.) and cogongrass [Imperata cylindrica (L.) P. Beauv.] were the most common weeds. Glyphosate, at all rates, reduced Mexican‐tea DM 2 mo after application in both years. However, substantial recovery of existing MT plants was observed 4 mo after application at all but the high rate. Glyphosate had no effect on cogongrass or other grasses in 1995 or 1996. In both years, rhizoma peanut DM declined as the rate of glyphosate increased. Some recovery of RP was noted at the low (1.12 kg ha−1) rate of glyphosate by 4 mo after application. Edible DM (RP + other grasses) was reduced due to glyphosate treatment only at the high glyphosate rate. In both years, triclopyr was effective in reducing Mexican‐tea DM 2 mo after application with limited recovery of treated plants 4 mo after application. Cogongrass and other grasses increased in the triclopyr treatments in both years, possibly due to reduced competition from Mexican‐tea. Rhizoma peanut DM decreased as the rate of triclopyr increased in 1995 at 2 and 4 mo after application, but this effect was observed only at 2 mo after application in 1996. Triclopyr application had little effect on edible DM, but this was a consequence of the substitution effect of other grasses for RP. Both triclopyr and glyphosate can be useful in weed‐infested RP stands, but glyphosate at the rates tested was not as effective as triclopyr in controlling Mexican‐tea.
Fire Effects on Weeping Lovegrass Tiller Density and Demographics
Authors: McFarland J.Brent , Mitchell Rob
Published: July 2010

Prescribed burning is a common management practice applied to weeping lovegrass [Eragrostis curvula (Schrad.) Nees], but little is known about tiller density and demographic response to burning. Our objectives were to determine fire effects on weeping lovegrass tiller density and demographics on a site, seeded in 1989, in western Texas. Tillers were sampled at 14‐d intervals in 1996 and 1997 to determine tiller density and demographics. Tiller density response to burning differed between years. Burning increased tiller density 61% compared with no burning in 1996, but did not affect tiller density in 1997. In 1996, tiller density ranged from 1068 to 2052 and 1623 to 2617 tillers m−2 in nonburned and burned areas, respectively. In 1997, tiller density ranged from 1337 to 2398 and 1313 to 2027 tillers m−2 in nonburned and burned areas, respectively. Tillers in nonburned and burned areas remained primarily vegetative throughout each growing season with few tillers advancing to reproductive and seed‐ripening stages, likely a response to poor fertility on the site. Burning increased reproductive tiller numbers by 238% compared with no burning in 1996, but few advanced to the seed‐ripening stage. In 1997, most reproductive tillers advanced to the seed‐ripening stage, likely responding to precipitation. Burning apparently altered the light environment and increased nutrient availability to weeping lovegrass. Yearly variation in the response to burning of weeping lovegrass tiller density and tiller demographics demonstrates that management must be based on current tiller populations.
Relay‐Intercropping of Sunnhemp and Cowpea into a Smallholder Maize System in Zimbabwe
Authors: Jeranyama Peter , Hesterman Oran B. , Waddington Stephen R. , Harwood Richard R.
Published: July 2010

The rising real prices of purchased inputs is driving smallholder maize (Zea mays L.) production towards lower levels of inorganic fertilizer. Legume intercrops are a source of plant N that can be produced locally and offer a practical complement to inorganic fertilizers. Field experiments conducted on a loamy sand (Typic Kandiustalf) soil evaluated the impact of relay‐intercropping two legume crops, cowpea (Vigna unguiculata L.) and sunnhemp (Crotolaria juncea L.) into smallholder maize in Zimbabwe. The objectives were to quantify: (i) biomass and N yield of intercropped legumes, (ii) the impact of the legumes on companion maize yield and N uptake, and (iii) the response of a subsequent maize crop to legumes. Dry matter yield ranged from 0.6 to 4.6 Mg ha−1 for cowpea and 0.9 to 2.9 Mg ha−1 for sunnhemp, over two years. At the most, cowpea and sunnhemp produced 154 and 82 kg N ha−1, respectively. Companion maize grain yields were not reduced when the legumes were relay‐intercropped into maize fertilized at 0 to 60 kg N ha−1. However, maize yields were reduced 18 to 31% when maize + legume intercrops were fertilized at 120 kg N ha−1. In the subsequent year, maize grain yields were increased by 8 to 27% following maize + legume when no fertilizer N was applied, compared with maize following maize. Legumes reduced fertilizer needs of a subsequent maize crop by 36 kg N ha−1. Intercropped annual legumes and small amounts of inorganic fertilizer offers a strategy to meet the N needs on smallholder farms.
Optimal Spacing of Soil Conservation Barriers
Authors: Zougmore´ Robert , Kabore´ Daniel , Lowenberg–DeBoer J.
Published: July 2010

Though construction methods vary widely, use of physical or biological barriers to conserve soil and water is common throughout the world. Rock or earthen bunds are common physical barriers. Strips of perennial grass, shrubs or trees serve as biological barriers. Often these barriers are arranged on a slope in roughly parallel contour bands. The spacing between barriers has important economic consequences, because distance from the barrier may create patterns of soil fertility and water availability that influence crop yields and because the spacing determines land available for cropping. The objective of this study was to develop a method for determining the optimal economic spacing of conservation barriers and apply that method to spacing of rock bunds in Burkina Faso. The steps in the optimization method include estimating a continuous yield response to distance between barriers, developing a mathematical expression to describe how costs change as spacing is altered, and optimizing using calculus. The method is general and can be applied to determining spacing of any conservation technique that is applied in bands. For example, this method could be adapted to spacing of grass strips, hedges, windbreaks, or terraces. This analysis suggests that the economically optimal spacing of rock bunds on the Central Plateau of Burkina Faso depends on the type of construction, materials transport cost, and how labor is organized.
Decomposition and Nitrogen Release of Prunings from Hedgerow Species Assessed for Alley Cropping in Haiti
Authors: Isaac Lionel , Wood C. Wesley , Shannon Dennis A.
Published: July 2010

Decomposition and N release patterns from prunings of eight tree species were studied under field conditions. Leaves and stems (<1 cm diam) from 4‐yr‐old hedgerows were sealed in separate litter bags and placed on soil surface at low and high elevation (1150 m) sites in Haiti. Leaves decomposed faster than stems and leaf decomposition was described by a two‐pool exponential model. At the low elevation, leaf C loss was highest (82%) in gliricidia [Gliricidia sepium (Jacq.) Kunth ex Walp.] and lowest (42%) in flamboyant [Delonix regia (Bojer ex Hook) Raf.] after 48 wk. At the high elevation, leaf C loss after 48 wk was 48% in leucaena [Leucaena leucocephala (Lam.) De Wit] and 29% in Acacia angustissima (Mill.) Kuntze. Initial N concentrations correlated with leaf C loss (Phase I) at low elevation while C:N and lignin:N correlated with leaf C loss (Phase II) at low and high elevations, respectively. Nitrogen release resembled carbon loss. At the low elevation, gliricidia, Leucaena shannonii Donn. Sm., and leucaena released >50 kg N ha−1 during the first 4 to 6 wk, whereas at high elevation A. angustissima contributed <40 kg N ha−1 during the period. Leaf N release correlated negatively with (lignin + polyphenol):N at low elevation. At the low elevation, gliricidia, L. shannonii, and leucaena provided adequate N for maize production in alley cropping. At the high elevation, A. angustissima contained adequate N, but N release rate may not meet peak N demands of an associated crop.
A Sampling Method for Measurement of Large Root Systems with Scanner‐Based Image Analysis
Authors: Costa Carlos , Dwyer Lianne M. , Hamilton Robert I. , Hamel Chantal , Nantais Line , Smith Donald L.
Published: July 2010

Measurement of relatively small (<100 m total length, <6 g fresh wt.) root systems has been simplified by image analysis, but measuring larger root systems remains time‐consuming and inaccurate. Reliability of root estimation can be improved through identification of effective sampling methods. We devised a system for the collection of homogeneous root subsamples by air‐stirring in water. We optimized the subsampling technique and used a scanner‐based image analysis system to measure total root length, mean root diameter, and root surface area of three maize (Zea mays L.) genotypes with contrasting root morphologies: leafy reduced stature (LRS), leafy normal stature (LNS), and Pioneer 3905 (P3905), a commercial hybrid. Root length was determined for 957 subsamples. Confidence intervals were generated by software using the bootstrap resampling approach for optimizing sample size. Confidence intervals for mean estimates of each sample size were defined by ordering the evaluation function values from the smallest to the largest in a set of 5000 iterations. The lower and upper bounds of confidence intervals were also calculated using the standard procedure. This system allowed collection of homogeneous subsamples. Calculations showed that ∼10% of total root volume should be analyzed for estimation of the entire root system to be accurate within 10%. Although unreplicated, these data suggest that maize genotypes with the leafy trait have greater root lengths (1.75 km for LRS, 2.37 km for LNS, and 0.49 km for conventional commercial hybrid P3905) and a greater proportion of fine roots than the nonleafy type.
Symptoms and Growth of Potato Leafhopper‐Tolerant Alfalfa in Response to Potato Leafhopper Feeding
Authors: Lefko Stephen A. , Pedigo Larry P. , Rice Marlin E.
Published: July 2010

Alfalfa (Medicago sativa L.) cultivars marketed as resistant, or tolerant, of the potato leafhopper (Empoasca fabae [Harris]) are increasingly available, yet their mechanism of resistance is poorly understood. Our objective was to determine if growth characteristics differ between potato leafhopper–tolerant and susceptible alfalfa cultivars under different pest pressures, and how differences may contribute to a greater yield potential in tolerant cultivars. Two field experiments, one near Ames, IA, and one near Chariton, IA, were planted with four potato leafhopper–tolerant alfalfa cultivars and one susceptible cultivar during the spring of 1996. Estimates of alfalfa dry matter, stem length, number of nodes, and hopperburn were taken on each harvest date, and adult potato leafhopper density in each cultivar was determined regularly over the 3‐yr study. Potato leafhopper density was significantly greater in the susceptible cultivar compared with one or more tolerant cultivars in only two of the 15 growth intervals sampled. Although there was only one harvest when dry matter differed significantly between alfalfa types, there was a trend for tolerant alfalfa to produce more dry matter than the susceptible alfalfa when the leafhopper pressure was high. Tolerant cultivars had more nodes, longer internodes, longer stems, and less hopperburn than the susceptible cultivar when the leafhopper number was high. Alfalfa cultivars tolerant of potato leafhopper feeding were not immune to this pest; however, they had favorable growth characteristics that could translate to greater yields when the leafhopper density is high.
Agronomic and Economic Analyses of Cotton Starter Fertilizers
Authors: Bednarz Craig W. , Harris Glen H. , Shurley W.Don
Published: July 2010

None of the published literature has focused on the response of cotton (Gossypium hirsutum L.) to various starter fertilizer sources. This study was conducted to determine (1) if cotton grown on Coastal Plain soils in South Georgia would respond to different starter fertilizer sources and (2) if use of starter fertilizers would result in an economic gain. Experiments were conducted in 1997 and 1998 at the Coastal Plain Experiment Station in Tifton on a Tifton loamy sand (fine‐loamy, kaolinitic, thermic Plinthic Kandiudults), the Southeast Georgia Branch Station in Midville on a Dothan loamy sand (fine‐loamy, kaolinitic, thermic Plinthic Kandiudults), and the Southwest Branch Experiment Station in Plains on a Greenville sandy clay loam (fine, kaolinitic, thermic Rhodic Kandiudults). Five starter fertilizer sources were applied 5 cm to the side of and 5 cm below the seed drill at planting in each study. Total shoot N and Ca were increased in two of the six studies with starter fertilizers. Likewise, plant height, leaf area index, and shoot dry weight was increased with starter fertilizers in two of the six studies. With the exception of micronaire, starter fertilizers did not significantly influence the fiber properties investigated. Differences in fiber properties did result in small differences in cotton price premiums or discounts. Lint yields were significantly increased with starter fertilizers at Midville and Plains in 1997, when the crop was exposed to an extended period of cool weather immediately after planting. The most appropriate cotton starter fertilizer appeared to depend on soil type.
Bt and Non‐Bt Maize Growth and Development as Affected by Temperature and Drought Stress
Authors: Traore Seydou B. , Carlson Richard E. , Pilcher Clinton D. , Rice Marlin E.
Published: July 2010

Seed companies have commercialized new transgenic maize (Zea mays L.) hybrids that are resistant to European corn borer [Ostrinia nubilalis (Hübner)]. Drought stress may affect the expression of Bt proteins in maize tissues, and its resistance to European corn borer (ECB). This study was conducted at the Iowa State University Hinds Irrigation Farm, Ames, IA, to characterize the effect of drought stress on Bt maize. Growth and development measurements were taken in 1997 and 1998 from Bt and non‐Bt maize plants subjected to various soil water deficit treatments during peak ECB egg laying periods (late June, first generation; late July, second generation) on maize plants grown in buried, 1 m deep, 123‐L containers filled with Nicollet loam soil (fine‐loamy, mixed, superactive, mesic Aquic Hapludolls). Water deficit delayed leaf appearance up to 6 d, depending on leaf number and tasseling up to 3 d. It also reduced leaf area as much as 33% and plant height by 15%, depending on leaf number and timing of water deficit. For these characteristics, there was no significant difference between Bt and non‐Bt maize plants. There were significant differences among Bt and non‐Bt plants for second generation corn borer damage with Bt plants affected the least. This resulted in significant yield differences between Bt and non‐Bt plants. Compared with non‐Bt plants, Bt plants exhibited significantly greater total plant weight in 1997 (9.7%) and grain yield in 1998 (9.4%). These differences depended on variety and seemed related to 100‐seed weights.
Allelopathy of Sorghum on Wheat under Several Tillage Systems
Authors: Roth Chad M. , Shroyer James P. , Paulsen Gary M.
Published: July 2010

Allelopathy by grain sorghum [Sorghum bicolor (L.) Moench] frequently harms wheat (Triticum aestivum L.) when the crops are grown in rotation. Responses of seven wheat cultivars to different methods of tilling sorghum stover were investigated to determine if the problem might be remedied by genetic resistance or improved management of the stover. Field trials on Kahola silt loam soil (fine‐silty, mixed mesic Cumulic Hapludolls) compared effects of fallow, tilled sorghum stover, and no‐till sorghum stover during the first season and the same treatments plus no‐till millet [Pennisetum glaucum (L.) R. Br.] stover the second season. The seven wheat cultivars were planted after the sorghum and millet were harvested and tilled, and their emergence, stand density, and yield components were measured. Tilled sorghum residue often delayed development of the following wheat crop but did not affect grain yields, probably because allelopathic compounds degraded in the soil. No‐till sorghum stover had little effect on stand establishment but frequently reduced grain yields of wheat, possibly because allelopathic compounds leached slowly. Wheat grain yields (means of all seven cultivars) were 3.3, 2.8, and 2.3 Mg/ha in fallow, tilled sorghum residue, and no‐till sorghum residue, respectively, during 2 yr and 3.1 Mg/ha in no‐till millet residue in the second year. Selection of resistant wheat cultivars is probably impractical, because differences were small and inconsistent. However, if erosion of soil is not a concern, allelopathy might be reduced by prompt tillage and other practices that promote rapid decomposition of sorghum stover.
Growth and Potential Conductivity of White Clover Roots in Dry Soil with Increasing Phosphorus Supply and Defoliation Frequency
Authors: Singh Dhananjay K. , Sale Peter W.G.
Published: July 2010

Shallow‐rooted white clover can be exposed to severe water stress during dry periods, leading to poor growth and persistence in pastures. Root growth is a primary determinant of drought tolerance and water uptake in dry soils, which may interact with P supply and defoliation frequency for grazed white clover in legume‐based pastures. Effects of four levels of P supply (0, 17, 50, and 150 mg P kg−1 soil), two defoliation frequencies (frequent and infrequent), and two soil water regimes (wet and dry) were determined on various parameters associated with root growth and plant water uptake. A microscopy study was also undertaken to measure the relative size and abundance of xylem vessels in the primary roots of frequently defoliated low (P0) and high P (P150) plants. Increased P supply increased the rate of water loss per pot, which was better related to the coarse root length density compared with the fine root length density in dry soil. Coarse root length density, leaf area, mean number and diameter of xylem vessels, and potential root hydraulic conductance increased 6.2‐, 12.4‐, 2.4‐, 1.5‐, and 12.7‐fold, respectively, for the frequently defoliated plants in dry soil between P0 and P150 treatments. It also appeared that leaf area and rate of water loss were dependent on the mean xylem diameter and associated hydraulic conductance. Increased P supply improved the ability of frequently defoliated white clover plants to tolerate dry soil conditions by lowering the resistance to water flow in roots and increasing the water uptake.
Post‐Contract Grassland Management and Winter Wheat Production on Former CRP Fields in the Southern Great Plains
Authors: Dao Thanh H. , Stiegler James H. , Banks J. C. , Bogle‐Boerngen Laurie , Adams Bud
Published: July 2010

Integrated management guidelines for postcontract land use Conservation Reserve Program lands in semiarid regions are generally lacking. We determined the relative efficacy of four systems of transitional conservation practices for producing ‘Old World' bluestem (OWB) (Bothriochlora ischaemum L.) and dryland wheat (Triticum aestivum L.) and cotton (Gossypium hirsutum L.) on former CRP fields. The sites were located on Dalhart fine sandy loam (Aridic Paleustalf) and La Casa–Aspermont clay loam (Typic Paleustoll) near Forgan and Duke, OK, respectively. Removing old growth increased cumulative OWB yields between 1994 and 1997. Applications of 67 kg N and 16.5 kg P ha−1 increased yields by 0, 70, and 180% at Forgan and 290, 70, and 280% at Duke in 1995 to 1997, respectively. Removing the old dry matter and regrowth vigor also enhanced chemical suppression and killing of the grass, the performance of conservation tillage, and achieving a uniform crop stand. Early OWB suppression conserved stored water that was vital to cool‐season crop production in the year the contract expired. First‐year wheat yields averaged 970, 490, and 1002 kg ha−1 at Forgan and 1590, 600, and 830 kg ha−1 at Duke under unfavorable weather conditions (i.e., drought, late freeze) of 1995 through 1997, respectively. No‐till generally produced higher yields, averaging 10 and 35% greater than conservation systems at Forgan and Duke, respectively. In variable semiarid environment, the chance of success for agronomic production decreased in the order of grass production, NT wheat, tilled wheat, and dryland cotton on former CRP lands.
Seeding Rate, Phosphorus Fertilization, and Location Effects on ‘Armadillo’ Burr Medic
Authors: Muir James P. , Pitman William D. , Coombs Danny F.
Published: July 2010

Availability of the recently developed cultivar Armadillo provides opportunity for use of burr medic (Medicago polymorpha L.) in the south‐central USA where the species has become extensively naturalized. Area of adaptation and effects of seeding rate and P fertilization were identified as insufficiently understood aspects of this cultivar that could potentially determine success of Armadillo burr medic plantings within the region. Thus, objectives were to assess adaptation of this cultivar to both cooler and more humid locations than the south Texas origin of the cultivar and to evaluate effects of initial seeding rate and P fertilization. Neither seeding at 11 or 22 kg ha−1 nor fertilization with 0 or 25 kg P ha−1 affected forage accumulation, which was greater (P < 0.05) in the initial year at Alexandria, LA (3330 kg ha−1) than at Rosepine, LA or Stephenville, TX. Seed production, critical for reseeding, was greatest (P < 0.05) at Stephenville, with 344 kg ha−1, and increased with P at the high seeding rate only. Soil seed reserves 11 mo after seed set was 44% of the initial seed crop at Stephenville and <20% at the two, more‐humid Louisiana sites. On the sites represented, yield potential may limit Armadillo primarily to extensively managed systems. Such systems include livestock production and wildlife in the drier western extent of the region, but they primarily involve plantings for wildlife in the eastern portion of the region. High seeding rates with P fertilization can contribute to seed production and enhanced opportunity for stand regeneration.
System Analysis of Plant Traits to Increase Grain Yield on Limited Water Supplies
Authors: Sinclair Thomas R. , Muchow Russell C.
Published: July 2010

Crop growth in commercial situations usually requires maximizing grain yield on limited available water resources, which results in maximizing the ratio of yield to evapotranspiration. A system analysis was undertaken to identify those plant traits that might be altered to improve crop yield in a water‐limited environment. A mechanistic crop model was used to simulate maize (Zea mays L.) yield over 20 yr at Columbia, MO, which had high interannual variability in precipitation. Because sorghum [Sorghum bicolor (L.) Moench] is known to be better adapted to drier environments, a number of individual plant traits were adjusted in the maize model to represent a sorghum crop. For the tested environments, it was found that decreasing leaf size and increasing seed growth rate both resulted in decreased yield and a decreased ratio of grain yield to evapotranspiration. On the other hand, increasing the depth of water extraction resulted in increased yields and an increased ratio of grain yield to evapotranspiration. Combining sorghum‐like traits in the maize model also increased yield and the ratio of grain yield to evapotranspiration when averaged for all years. For all seasons where simulated yield was less than approximately 550 g m−2, grain yields were greater for a crop with sorghum‐like traits than for a crop with maize traits.
Managing Soils to Achieve Greater Water Use Efficiency
Authors: Hatfield Jerry L. , Sauer Thomas J. , Prueger John H.
Published: July 2010

Water use efficiency (WUE) represents a given level of biomass or grain yield per unit of water used by the crop. With increasing concern about the availability of water resources in both irrigated and rainfed agriculture, there is renewed interest in trying to develop an understanding of how WUE can be improved and how farming systems can be modified to be more efficient in water use. This review and synthesis of the literature is directed toward understanding the role of soil management practices for WUE. Soil management practices affect the processes of evapotranspiration by modifying the available energy, the available water in the soil profile, or the exchange rate between the soil and the atmosphere. Plant management practices, e.g., the addition of N and P, have an indirect effect on water use through the physiological efficiency of the plant. A survey of the literature reveals a large variation in measured WUE across a range of climates, crops, and soil management practices. It is possible to increase WUE by 25 to 40% through soil management practices that involve tillage. Overall, precipitation use efficiency can be enhanced through adoption of more intensive cropping systems in semiarid environments and increased plant populations in more temperate and humid environments. Modifying nutrient management practices can increase WUE by 15 to 25%. Water use efficiency can be increased through proper management, and field‐scale experiences show that these changes positively affect crop yield.
Paper Pellets as a Mulch for Dryland Grain Sorghum Production
Authors: Unger Paul W.
Published: July 2010

Some landfills no longer accept waste paper for disposal; thus, alternative means are needed. One would be to apply pelleted paper to cropland as a mulch. This field study was conducted to determine effects of a paper pellet mulch on soil water storage and grain sorghum [Sorghum bicolor (L.) Moench] yield. Mulch rates were 0 (check), 5, 10, and 15 Mg ha−1. Wheat (Triticum aestivum L.) residue condition (retained or removed) and tillage (sweep or no‐tillage) treatments were included. Pellet applications did not affect water storage or sorghum yields, apparently because pellets absorbed precipitation, which resulted in similar evaporation from bare and mulched soils. Residue and tillage treatments had little effect on water storage and sorghum yield. Soil C concentrations were greater in mulched than bare soil in one case, but some pellet material remained, suggesting further decomposition could increase soil C. Pellet applications resulted in greater aggregate mean weight diameters and lower percentages of small aggregates. These improved conditions could improve the soil's long‐term productivity. Because crop productivity was not harmed, waste paper (e.g., pellets as used in this study) can be disposed of on cropland. However, shallow paper incorporation may be a better practice than surface applications because it should hasten its decomposition and, thereby, more rapidly improve soil conditions.
Dry Matter Yields of Cool‐Season Grass Monocultures and Grass–Alfalfa Binary Mixtures
Authors: Berdahl John D. , Karn James F. , Hendrickson John R.
Published: July 2010

Cultivars used in grass–alfalfa (Medicago sativa L.) mixtures for hay production in the semiarid Northern Great Plains have often lacked long‐term productivity. This study was conducted to compare dry matter (DM) yields of grass monocultures and grass–alfalfa binary mixtures receiving annual applications of 0 and 50 kg N ha−1 over a 5‐yr period. ‘Reliant’ and ‘Manska’ intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. and Dewey], ‘Lincoln’ smooth bromegrass (Bromus inermis Leyss.), ‘Nordan’ crested wheatgrass [Agropyron desertorum (Fisch.) Schult.], ‘Lodorm’ green needlegrass (Stipa viridula Trin.), and ‘Dacotah’ switchgrass (Panicum virgatum L.) were seeded in monoculture and in binary mixtures with ‘Rangelander’ alfalfa [Medicago sativa subsp. × varia (Martyn) Arcang.] on a Parshall fine sandy loam (coarse‐loamy, mixed, superactive, frigid, Pachic Haplustolls) near Mandan, ND. Plant stands of green needlegrass and switchgrass were inadequate, and yields were not measured. Total seasonal DM yields from two cuttings averaged 8.74 and 2.71 Mg ha−1, respectively, for grass–alfalfa mixtures and grass monocultures at 0 kg N ha−1. At 50 kg N ha−1, grass–alfalfa mixtures and grass monocultures averaged 8.72 and 5.04 Mg ha−1 DM yield, respectively. Yields of the grass component of first cut grass–alfalfa mixtures averaged 35% of total yield for intermediate wheatgrass, 33% of total yield for smooth bromegrass, and 30% of total yield for crested wheatgrass in the fifth production year. Cultivars included in this study, except those of green needlegrass and switchgrass, would be suited for use in binary grass–alfalfa mixtures for dryland hay production in the Northern Great Plains.
Development of the Crop Simulation System DIASPORA
Authors: Denisov Vitalij V.
Published: July 2010

Crop growth models are usually split into two opposite groups: complex comprehensive and simplified applied. The objective of this paper is to show how the different models can be used together to form an integrated crop modeling system. The software engineering methods that are employed include the needs of potential users in the system requirements. As a specific example, the process of development and implementation of an integrated crop simulation system, DIASPORA (DIAlog Simulator and PredictOr for Research in Agriculture), is described. The DIASPORA system is primarily designed to make more effective use of the field treatment data collected at the Lithuanian Institute of Agriculture (LIA) and to allow a multitasking application of crop growth and development models. To achieve these tasks, a simulation environment has been developed that includes the complex simulation model, model database, multilingual user interface, and the set of simplified models for particular applications. Three local research stations of the LIA—Traku Voke (south‐eastern Lithuania), Dotnuva (central Lithuania), and Vezhaichai (western Lithuania)—serve as sources of experimental information, and therefore, as sites for further implementation of the system. The models of cereal crops implemented within the system have also been verified using experimental data sets from several regions in Russia; Gornyj Lozen in Bulgaria; and Morris, MN, USA.
Integration of a Crop Growth Model with a Model of Soil Dynamics
Authors: Franko Uwe , Mirschel Wilfried
Published: July 2010

Farming systems have to be well adapted to site specific climatic conditions and soil properties to reach a high productivity level and ensure a low risk of N exports into the environment at the same time. In the past, main efforts were made to find solutions that would increase the productivity of agroecosystems, primarily based on field experiments. Now it is necessary to find an optimal relation between biomass production and nutrient release into the environment. Simulation models of C–N dynamics seem to be able to provide useful information to reach this objective. To do this, the model has to describe turnover and transport processes in a soil as well as the development of the crop. This study reports about the integration of the crop growth model AGROSIM‐ZR [AGROecosystem SIMulation—sugarbeet (ZR)] for sugarbeet (Beta vulgaris L.) with the CANDY (CArbon and Nitrogen DYnamics) model for soil‐based processes in agriculturally used landscapes.
Influence of Brown Midrib, Leafy, and Transgenic Hybrids on Corn Forage Production
Authors: Cox William J. , Cherney Debbie J.R.
Published: July 2010

Hybrid selection strongly influences corn (Zea mays L.) forage production. Limited forage production and quality information exists for leafy and transgenic hybrids [Bacillus thuringiensis (Bt) and herbicide resistant]. We compared dry matter (DM) yield, forage quality, and estimated milk yields of these and brown midrib hybrids with dual‐purpose hybrids for 3 yr at harvest densities of 66000 and 84000 plants ha−1. Transgenic hybrids had no effect on DM and milk yields, so we do not recommend Bt hybrids under conditions of low infestation of European corn borer (Ostrinia nubilalis Hubner). Leafy hybrids had similar DM and milk yields as hybrids of similar maturity. Brown midrib hybrids, which had DM yields that were about 20% less than those of hybrids of similar maturity, had 40 to 80 g kg−1 greater in vitro true digestibility (IVTD) and 70 to 200 g kg−1 greater neutral detergent fiber (NDF) digestibility. Brown midrib hybrids had the greatest or least milk yields among hybrids, depending on hybrid and year. Leafy and brown midrib hybrids mostly had low harvest index (HI) values, which had strong negative correlations with NDF in all years (−0.71, −0.44, and −0.90). Brown midrib hybrids had high NDF digestibility, which had strong positive correlations with IVTD (0.80, 0.88, and 0.86). Currently, we do not recommend brown midrib hybrids because of inconsistent milk yields and high seed costs. Development of brown midrib and leafy hybrids with greater HI values should result in excellent forage hybrids.