bluuebunny/crossref_metadata_2025_split huggingface dataset:
Root Distribution and Soil Moisture Depletion Pattern of a Drought‐Resistant Soybean Plant Introduction
Authors: Hudak Colleen M. , Patterson Robert P. 
Published: July 2010

AbstractIn the southeastern USA, soybean [Glycine max (L.) Merr.] yield is often limited by water availability. Breeders have explored the use of exotic germplasm as a means of developing a root system capable of exploiting soil water reserves more fully. In this study, the drought‐resistant PI 416937 was compared with ‘Forrest’ for soil moisture utilization and root distribution on a Dothan loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudults). Water treatments (well‐watered and water‐deficient) were established during R4 to late R6 with rain exclusion shelters and differential irrigation. Soil moisture utilization in row and interrow areas was monitored via neutron attenuation and tensiometry. A direct measurement of root distribution was obtained on a second site by a trench profile technique. Results suggest that PI 416937's advantage may reside in its ability to exploit upper soil horizons (above 68 cm) with a network of fibrous roots. Localized measurements of soil moisture tension indicated that PI 416937's rate of soil desiccation was slower than Forrest's, but it appeared to exploit a larger total soil volume. Trench profile results indicated that the lateral spread of PI 416937's root system was greater than that of Forrest. The usefulness of PI 416937 may lie in the opportunity it provides soybean breeders for adding diversity to the root morphology of present soybean cultivars.
Maize Nodal Root Response to Time of Soil Ridging
Authors: Thomas Andrew L. , Kaspar Thomas C. 
Published: July 2010

AbstractAn improved understanding of maize (Zea mays L.) nodal root response to soil ridging is needed to allow farmers to maximize the benefits of ridge‐till tillage systems. Greenhouse (three trials, 1992 to 1994) and field (two sites in Iowa, 1992 and 1993) experiments were conducted with one maize hybrid to examine the effect of time of soil ridging on nodal root development, internode elongation, shoot dry matter, and grain yield. Maize root clumps were evaluated from unridged plants and from plants ridged either at early V4 to V6) or late (V7) growth stages. Total numbers of nodal roots, numbers of roots per node, numbers of nodes developing functional roots, internode lengths, shoot dry matter, and grain yields (field study) were determined. Time of ridging significantly affected nodal root numbers and internode lengths. In two of the field trials, unridged maize plants produced 42.7 and 48.3 functional nodal roots, whereas plants ridged at growth stage V7 developed significantly more, 47.0 and 56.0 roots, respectively. Internodes 6 and 7, covered with soil during ridging, increased in length by as much as 124% in the field and 175% in the greenhouse when plants were ridged early rather than late. In one field trial, Internode 6 elongated to 44.1 mm with early ridging, but to less than 17.0 mm with either late or no ridging. Shoot dry matter and grain yields generally were not affected by ridging treatments in either field or greenhouse experiments. Later ridging tends to result in shorter internodes and more functional nodal roots which may be important to maize plants in terms of lodging resistance and recovery from corn rootworm (Diabrotica spp.) damage.
Cropping System Effects on Nitrogen Removal, Soil Nitrogen, Aggregate Stability, and Subsequent Corn Grain Yield
Authors: Anderson Irvin C. , Buxton Dwayne R. , Karlen Douglas L. , Cambardella Cynthia 
Published: July 2010

AbstractCropping systems can affect soil quality and productivity of subsequent crops. We conducted this study to evaluate effects of several annual and perennial crop species on N removal, residual soil N, aggregate stability, and subsequent corn (Zea mays L.) production. Thirteen cropping systems were grown with various rates of N fertilizer for 6 yr on a Typic Calciaquoll soil in central Iowa. Perennial plant species were then killed, corn was planted, and half of each plot was fertilized with 224 kg N ha−1 and half was left unfertilized. Plant analyses showed that the perennial C4 species, switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman var. gerardii), consistently removed the least N. There was little difference for soil total N, NH4‐N, or NO3‐N concentrations to a depth of 1 m among reed canarygrass (Phalaris arundinacea L.), switchgrass, sweet sorghum [Sorghum bicolor (L.) Moench], and alfalfa (Medicago sativa L.). Residual NO3‐N concentrations were higher to a depth of 1 m for subplots fertilized with 280 kg N ha−1 for 6 yr than for plots fertilized with less N. Aggregate stability did not differ following reed canarygrass, switchgrass, sweet sorghum, or alfalfa. Without N during the 7th yr, corn following sweet sorghum produced the lowest yield (7.5 t ha−1), whereas the highest yield following a nonlegume crop was for corn after big bluestem (11.8 t ha−1). Corn without N following soybean [Glycine max (L.) Merr.] yielded 11.1 t ha−1, while that following alfalfa yielded 13.6 t ha−1. Fertilizer N reduced the rotation effect, but increased profile N with both perennial and annual crops. Corn following reed canarygrass, big bluestem, alfalfa, soybean, and sorghum intercropped into alfalfa had significantly higher yields (14.1, 14.2, 15.7, 14.2, and 15.3 t ha−1, respectively) than corn following corn (13.0 t ha−1). Non‐N rotation effects (those remaining despite applied N) could not be explained by residual soil N or aggregate stability measurements.
Sulfur Source and Placement Effects on Forage Yield and Quality of Established Tall Fescue
Authors: Sweeney Daniel W. , Moyer Joseph L. 
Published: July 2010

AbstractPrevious research indicates that tall fescue (Festuca arundinacea Schreb.) may respond to S fertilization. However, data are limited concerning S management options to improve yield and quality of tall fescue. Thus, a field study was conducted from 1988 to 1990 to determine the effects of S source (ammonium thiosulfate [ATS] and ammonium sulfate [AS]), rate (17 and 34 kg S ha−1), and placement (broadcast, dribble [surface band], and knife [subsurface band]) on yield and quality of established, endophyte‐infected tall fescue. Compared with a no‐fertilizer control, adding N alone more than doubled hay production, to 7.15 Mg ha−1, but the addition of fertilizer S had little effect on early‐season production or later hay yields. Sulfur fertilization, especially in the ATS form, increased tissue S concentration, lowered N/S ratios, and, to a lesser extent, increased tissue N concentration in the hay harvest. Few differences in measured parameters were related to S rate. Correlation analyses suggested that lowering N/S ratios may reduce neutral‐detergent fiber content and improve in vitro dry matter digestibility. Fescue sampled to simulate grazing in early spring was lower in yield and tissue S concentrations, but higher in N/S ratios, when S was knifed rather than surface applied. At hay harvest, knifing fertilizers increased yield approximately 20% and increased N concentration by 10% compared with surface application methods, but produced lower in vitro dry matter digestibility.
Influence of Seedling Growth Stage on Flooding Injury in Alfalfa
Authors: Teutsch Christopher D. , Sulc R. Mark 
Published: July 2010

AbstractTemporary flooding of alfalfa (Medicago sativa L.) seedings frequently occurs in the midwestern USA, often resulting in total or partial stand establishment failures. This study evaluated the effect of seedling growth stage on the severity of flooding injury in alfalfa grown in the greenhouse. Alfalfa seedlings of ‘WL 323’, rated as highly resistant to root rot caused by Phytophthora medicaginis E.M. Hans. & Maxwell and resistant to root rot caused by Aphanomyces euteiches Drechs., were flooded for 14 d at three vegetative growth stages: (i) early seedling development (1–2 trifoliolates), (ii) eaely vegetative (3–6 trifoliolates), and (iii) mid to late vegetative (5–11 branches on the main stem). Root and shoot dry weights (DW) were recorded at the initiation of flooding, 0 days after flooding (DAF), 18 DAF (shoots only), and 36 DAF (18 d of regrowth from the 18 DAF harvest). The experiment was conducted twice. Flooding significantly (P < 0.01) reduced root and shoot DW, regardless of growth stage, and adversely impacted regrowth potential of alfalfa. There was a growth stage × flooding treatment interaction (P < 0.01) for root DW at 0 and 36 DAF in Trial 1, and at 0 DAF in Trial 2. Generally, flooding reduced root DW the least when seedlings were in the mid to late vegetative growth stage. Averaged over experimental trials, flooding reduced root DW at 36 DAF by 78% for early seedling, 73% for early vegetative, and 64% for mid to late vegetative growth stages, compared with unflooded controls. There was a growth stage × flooding treatment interaction (P < 0.01) for shoot DW at 0, 18, and 36 DAF in Trial 1, and at 36 DAF in Trial 2. Averaged over trials, flooding reduced alfalfa shoot DW measured at 36 DAF by 57% for early seedling, 40% for early vegetative, and 19% for mid to late vegetative growth stages, compared with unflooded controls. We conclude that older and more vegetatively advanced alfalfa seedlings recover shoot regrowth potential after temporary flooding better than do seedlings in the early trifoliolate stages.
Residue Height Influences Stand Dynamics of Alfalfa Grown on a Shallow Soil
Authors: Belesky David P. , Fedders James M. 
Published: July 2010

AbstractMultiuse alfalfa (Medicago sativa L.) cultivars have been developed to meet the need for high‐quality and productive forages. A continuum of residual tissue quantities can occur in a stand because of management factors or livestock selectivity, depending on the production system. We conducted a field study to determine the influence of residual herbage height on the productivity and persistence of alfalfa under natural rainfall on a shallow, acidic soil (Lily series; fine‐loamy, siliceous, mesic Typic Hapludults) typical of those found throughout the Appalachian Plateau. Three replicates of ‘Alfagraze’, ‘Apollo’, and ‘Cimarron’ alfalfa in each block of a randomized complete block design were clipped to residue heights of <2, 5, or 10 cm. Averaged over the experiment, Apollo yield was greatest, at 8.7 Mg ha−1; Alfagraze (8.0) and Cimarron (7.9) yields were about 10% less than Apollo. Clipping to 10 cm produced yields that were as much as 38% less than with shorter heights. Crown density decreased from about 400 to about 80 crowns m−2 during the experiment. Clipping to <2 cm caused the greatest variation in crown density among cultivars, with Alfagraze having the most and Cimarron the fewest crowns. With a 10‐cm residue, weed competition increased and plant size and shoot number were depressed, especially in Alfagraze. Plants with large crowns produced more stems, which compensated for the gradual decline in plant population. The loss of larger‐crowned plants during 1994 to 1995 was reflected in fewer shoots and reduced yield, and created a situation where increased productivity per plant could no longer compensate for plant losses. Reestablishment recommendations based on shoot numbers should be determined after the first clip in the growing season, and not in spring (when shoot numbers are changing rapidly). Our findings suggest that acceptable alfalfa yields can be obtained on a shallow acidic soil with surface liming, fertilizer input, and close clipping. The range of residue heights likely to occur in a stand of alfalfa influence productivity and persistence. Allowing a 10‐cm residue to remain would probably accelerate plant loss and yield reduction from the stand.
Management Studies on Seed Production of Turf‐Type Tall Fescue: I. Seed Yield
Authors: Young William C. , Youngberg Harold W. , Silberstein Thomas B. 
Published: July 2010

AbstractTall fescue (Festuca arundinacea Schreber) is rapidly gaining popularity as a turfgrass. Limited information is available on seed yield response of turf‐type cultivars to seed production management practices. We tested effects of four management variables on seed yield of Bonanza (late‐maturing turf type), Rebel (mid‐maturing turf type), Falcon (early‐maturing turf type), and Fawn (forage type) tall fescue cultivars. Variables were spring‐applied N rates (100, 145, and 190 kg ha−1), N application timing (double‐ridge stage, spikelet initiation, and equally split between the two), row spacing (0.3 and 0.6 m), and post‐harvest residue managements after removing the straw (flailchopping or burning the stubble). Seed yields of the second through fifth crops were measured. Nitrogen application timing did not affect seed yield of any cultivar. Effects of the other three variables on seed yield interacted with each other. For both Fawn and Rebel, high seed yields were achieved when 100 kg N ha−1 was applied and residue was burned, irrespective of row spacing. Bonanza produced high seed yields with 145 kg N ha−1, 0.6‐m row spacing, and flail‐chopping. In contrast, 0.3‐m row spacing and residue burning was required for maximum seed yield in Falcon, whereas N rates did not have an effect. We conclude that seed yield responses of Fawn and Rebel to management practices are similar. Results further suggest that, compared with Fawn, the optimum spring N rate was higher for Bonanza seed production, and the optimum row spacing was narrower for Falcon seed production. Also, residue burning was needed for maintaining high seed yield in Fawn, Rebel, and Falcon, whereas, at optimum row spacing and N rate, mechanical removal of post‐harvest residue was as effective as burning for Bonanza seed production.
Irrigated Corn Yield and Nitrogen Accumulation Response in a Comparison of No‐till and Conventional Till: Tillage and Surface‐Residue Variables
Authors: Sims Albert L. , Schepers James S. , Olson Robert A. , Power James F. 
Published: July 2010

AbstractComparisons between no‐till and conventional‐till management are often confounded by variation in both tillage and residue placement. The objective of this research was to separate the tillage variable from the surface‐residue variable associated with no‐till and conventional‐till management comparisons in irrigated continuous corn (Zea mays L.) production. Two Nebraska locations (Mead and Clay Center) with differences in soil types and climate were selected. Four tillage‐residue treatments [NT‐NR (no‐till, residue removed), NT‐R (no‐till, surface residue), T‐NR (till, residue removed), T‐R (conventional till, surface residue)] were fertilized by either broadcasting at planting or sidedressing at the 6‐leaf stage with rates of 0, 56, 112, and 168 kg N ha−1. At Clay Center, grain yields and total N accumulation were similar for all tillage‐residue treatment combinations in all years when the highest fertilizer N rate was used. In 2 of 3 yr at Mead, grain yields and total N accumulation were less for no‐till than conventionaltill treatments, but in 1 yr the yields and total N accumulations were greater in no‐till than conventional‐till treatments. At Mead, surface residue resulted in lower grain yields and total N accumulation compared with bare soil at lower N rates, but not at greater N rates, in 2 of 3 yr. Sidedressing fertilizer N was generally a more efficient N placement than broadcasting. Differences between tillage and residue effects at Clay Center and residue effects at Mead were overcome with higher rates of fertilizer N. Tillage effects at Mead did not appear to be N‐related. The data suggest that tillage may be necessary to maintain optimum production levels on finer‐textured soils when spring soil temperatures are cool and slow to warm. When spring soil temperatures are warm, no‐till strategies can be used for optimum production levels on these soils.
Localized Soil Management in Fertilizer Injection Zone to Reduce Nitrate Leaching
Authors: Ressler Daniel E. , Horton Robert , Kaspar Thomas C. , Baker James L. 
Published: July 2010

AbstractNitrogen fertilization of row crops in humid regions can result in leaching of NO3, which represents an inefficient use of resources and may result in environmental degradation. A localized compaction and doming (LCD) fertilizer injector was developed to alter the physical properties of soil surrounding knife‐injected N. Injection by LCD includes smearing macropores below the injection slot, formation of a localized compacted soil layer over the injected N, and formation of a surface dome to cover the compacted soil layer and the fertilizer band. The LCD injector was tested, along with a conventional knife injector (without a covering disk), to evaluate its effect on leaching by determining NO3 and Br tracer redistribution after NO3 fertilizer injection. Chemical distributions were determined by intensive soil sampling to 0.8 m below the soil surface. In a second experiment, corn (Zea mays L.) yield response to both N injectors was evaluated. Four fertilization rates (67, 112, 157, and 202 kg N ha−1 of UAN [urea‐ammonium nitrate]) were used to define yield response. During seasons when rainfall was below average, neither NO3 redistribution nor crop yield showed a response to fertilizer injection technique. During a growing season with above‐average rainfall, 26 kg ha−1 more NO3 and 25 kg ha−1 more Br remained in the top 0.8 m of soil when LCD‐injected. LCD injection increased crop yield approximately 0.48 Mg ha−1 over injection by the conventional knife method during an above‐average rainfall season, indicating that one‐fifth of the conventional knife‐applied N was lost prior to crop uptake during the wet year. These findings suggest that the LCD injector may be effective at reducing leaching losses during growing seasons when rainfall is abundant.
Predicting Rice Yield Losses Caused by Multispecies Weed Competition
Authors: Florez Jaime A. , Fischer Albert J. , Ramirez Hector , Duque Miryam C. 
Published: July 2010

AbstractMonoculture of irrigated rice (Oryza sativa L.) in Latin America has led to serious weed problems and intensive herbicide use. Yield loss prediction enables the economic analysis of weed control, providing a basis for strategic use of herbicides and diversified weed management, but site differences restrict predictions to the environments for which the models are calibrated. We developed an algorithm for predicting rice yield losses based on early assessments of multispecies weed infestations emerging in successive flushes within variable crop stands. Rice was drill‐seeded near Palmira, Colombia, at 75, 150, 200, 250, and 300 kg ha−1, and grown under nonflood intermittent irrigation for two growing seasons. Five common weeds were allowed to emerge at 15, 24, and 30 days after rice emergence (DAE), when farmers usually decide about early, intermediate, and late herbicide applications. Yield losses were predicted using hyperbolic models with independent variables describing the mixed‐weed infestations in terms of density (no. of plants m−2), leaf area index, dry matter m−2, relative density [weed/(weed + rice)], relative leaf area (RLA), and a visual estimate of relative ground cover (RCv). With early weed emergence (15 DAE), weed density accounted poorly (r2 = 0.77) for yield loss. Regression fits improved when RLA (r2 = 0.86) and RCv (r2 = 0.90) were used as independent variables to describe weed infestations in terms of the light apportionment between rice and weed canopies. Measured in terms of RCv, late‐emerging (24 and 30 DAE) weeds had lower effects on yield loss variability (r2 = 0.69 and 0.59, respectively). Although subjective, RCv is easier to estimate than RLA, and was the best single variable to describe the competitiveness of a mixedweed infestation. An additional variable was needed only when yield losses were predicted from weed density. Predictions based on RLA were further improved (by 36%) when each species' RLA was measured separately and the model was extended for additive effects of all species. Yield loss predictions using empirical equations cannot be extrapolated widely across different locations; however, these data suggest that meaningful independent variables can strengthen the usefulness of hyperbolic equations for predicting rice yield losses over a range of situations, such as mixtures of weed species at various densities and times of emergence, and different rice seeding rates.
Evaluation of the Root Zone Water Quality Model Using Data from the Iowa MSEA
Authors: Jaynes Dan B. , Miller John G. 
Published: July 2010

AbstractBefore simulation models can be used to evaluate the benefits of alternative management systems, their accuracy needs to be examined. This study evaluated the performance of the Root Zone Water Quality Model (RZWQM Version 3.2) against crop yield and water, nitrate, and herbicide fate and transport during four years of a corn‐soybean [Zea mays L.‐Glycine max (L.) Merr.] rotation. The model was calibrated and initialized using default values supplied with the model and adjusting model parameters to obtain stable organic matter and microorganism pools. The model was further calibrated to match crop yields for the first two years of measurements. For the second two years, predicted soybean yield was within 60 kg ha−1 (3%) of measured yield but predicted corn yield was underpredicted by 790 kg ha−1 (10%). Disagreements between modeled and measured yields may be due to factors not included in the model such as disease and insect damage. The model estimated total soil nitrate content well, although nitrification rates during winter were overestimated. Predicted nitrate leaching out of the root zone agreed well with measured losses to tile drainage. Predictions of herbicide residues with the one‐parameter lumped dissipation model option were best after reducing the expected half‐lives of metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4H)‐one], or atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], by a factor of four. The two‐parameter lumped half‐life model option improved the prediction for atrazine but not for metribuzin. Predictions of herbicide losses in drainage water were overestimated in the second year following herbicide application. Neither nitrate nor herbicide concentrations in the soil profile were modeled satisfactorily. Invoking the macropore option of the model did not consistently improve model prediction of herbicide leaching. Overall, the model shows promise in predicting the interplay of climate, soil, and management on crop yield and nitrate fate, but evaluation over a wider range of conditions is needed.