bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Cropping 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

Previous 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

Temporary 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

Multiuse 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

Tall 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

Comparisons 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

Nitrogen 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

Monoculture 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

Before 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.
Evaluation of the Root Zone Water Quality Model for Conditions in Central Nebraska
Authors: Martin Derrel L. , Watts Darrell G.
Published: July 2010

The Root Zone Water Quality Model (RZWQM) was evaluated for a region that has a long history of irrigated corn (Zea mays L.). Imprecise irrigation and plentiful fertilizer applications have contributed to the buildup of NO3‐N in ground water, where concentrations often exceed 30 mg L−1. Experiments were conducted to evaluate the effects of management practices on corn yield, N uptake, plant biomass, leaf area development, soil water content, and soil N. Field‐measured results from 1992 were used to calibrate RZWQM. The model was evaluated by simulating three irrigation levels and five fertilizer rates for 1993 and 1994. The model simulated the soil water pattern satisfactorily during most of the growing season; however, the simulated soil profile water content was lower than field conditions in the spring and fall. Transpiration appears to be excessive when the leaf area index (LAI) is small. Simulated yields exceeded measured values, with the largest errors for small fertilizer applications in 1993 and for large fertilizer applications in 1994. The mean error between measured and modeled yields was 2.9 Mg ha−1, with a root mean square error (RMSE) equal to 46% of the mean yield for all treatments over the 3 years. Estimates of LAI and aboveground biomass were closer to measured values, with mean errors of 5% for leaf area and 1% for biomass. The relative RMSE for LAI and biomass was 26 and 17%, respectively. The model underestimated aboveground N uptake, with a mean error of 25 kg N ha−1 and a relative RMSE of 41%. While development of the comprehensive RZWQM has been constructive, improvements are still needed. Excessive depletions in the spring and fall overstate storage of off‐season precipitation, and this leads to underestimating annual leaching losses. Combining excessive yield predictions with low N uptake estimates exaggerates the N use efficiency. These discrepancies will have a profound effect on the simulated impact of management practices. Leaching losses and yield effects will be understated, which may lead to development of policies that affect producers more severely than the model implies.
Analysis of Cotton Yield Stability Across Population Densities
Authors: Bednarz Craig W. , Bridges David C. , Brown Steve M.
Published: July 2010

Final lint yield in cotton (Gossypium hirsutum L.) is relatively stable across a wide range of population densities. This study was conducted to determine (i) which components of final lint yield impart this yield stability across plant populations and (ii) how yield distribution is influenced by population density. Studies were conducted in 1997 and 1998 on a Tifton loamy sand (Fine‐loamy, kaolinitic, thermic Plinthic Kandiudults). Cotton was planted in each study on 91‐cm row widths at seeding rates ranging from 3.5 to 25.1 seeds m−2. At harvest, each plot was hand picked and boll numbers and weights were recorded at each monopodial branch and sympodial branch fruiting position. Lower population densities led to plants with more mainstem nodes and monopodial branches with increased fruit retention, resulting in greater fruit production per plant. Boll size was inversely related to population density. Mean net assimilation rate from first flower to peak bloom also was related inversely to population density. The mainstem node of peak boll set increased with population density. Fruit production on a ground area basis was greater in the first sympodial position as population density increased, while fruit production on a ground area basis in third positions and monopodial branches was greater as population density decreased. Accumulative seedcotton from sympodial branches also increased with population density. Total fruit number and seedcotton yield per area were not influenced by population density in these studies. Yield stability across population densities was achieved through manipulation of boll occurrence and weight.
Seedling Establishment and Grain Yield of Tropical Rice Sown in Puddled Soil
Authors: Yamauchi Minoru , Aragones Darryl V. , Casayuran Pablo R. , Cruz Pompe C.Sta. , Asis Constancio A. , Cruz Rolando T.
Published: July 2010

Inconsistent seedling establishment constrains wider adoption of direct sowing of rice (Oryza sativa L.) in the tropics. Farmers broadcast pregerminated seeds onto the puddled soil surface. We hypothesize that if seeds were sown into the puddled soil rather than on the soil surface, then the establishment could be more consistent. For such below‐surface sowing to be successful, however, the seedling must be able to withstand anoxic conditions. This study was conducted to clarify whether seedlings can be established by sowing below the surface in puddled soil and to analyze the difference in establishment among cultivars. Anoxia‐tolerant cultivars, which had been selected from screening trials, were evaluated in flooded soil in a container in a temperature‐controlled (29/21°C day/night) glass room under natural light and in the fields during the dry season at Los Baños and Muñoz, Philippines. In the container, pregerminated seeds of 12 cultivars were sown at the 25‐mm depth in the soil with a water level of 30 mm. In the field, pregerminated seeds of 10 cultivars and calcium peroxide–coated seeds of two cultivars were drill‐sown at Los Baños; pregerminated seeds of 12 cultivars were drill‐sown and broadcast at Muñoz. Drill sowing was conducted 1 d after puddling, while broadcast sowing was done on the same day. The anoxia‐tolerant cultivar outperformed the check cultivar in plant stand and seedling height and weight, hence producing more biomass. Plant stands at Los Baños were 80.5% for tolerant and 64.0% for check cultivars; those at Muñoz were 57.5 and 24.6% for drill sowing and 59.1 and 26.7% for broadcast sowing, respectively. Mean grain yield of short anoxia‐tolerant cultivars was 6.9 t ha−1, which was the same as that of check cultivars. It is concluded that the use of anoxia‐tolerant cultivar can stabilize seedling establishment of rice plants sown in the puddled soil.
Estimation of Leaf Area in Tropical Maize
Authors: Elings Anne
Published: July 2010

Leaf area development at regular time intervals during the growing season is estimated by many crop growth models and is needed for competition studies. In plant breeding programs, observation is generally restricted to a single leaf area estimate or assessment of the plant type. Two procedures that build on earlier studies are presented to estimate total plant leaf area of maize (Zea mays L.). Leaf area development of six tropical maize cultivars grown in 1995 and 1996 in several tropical environments in Mexico (both favorable and moisture‐ and N‐limited) was observed and analyzed. First, the validity of a bell‐shaped curve describing the area of individual leaves as a function of leaf number was investigated. When individual cultivar–environment combinations were normalized for area of the largest leaf and for total leaf number, one parameter set described all combinations. It remained difficult, however, to estimate these parameters in advance, which limits predictive applications in crop growth models. Analytical application after flowering, when parameter values can be determined, is possible. Second, a method was developed to directly estimate total leaf area when total leaf number and area of the largest leaf are known. The method makes use of the facts that the area of the largest leaf relative to total plant leaf area is constant and that this constant is linearly related to total leaf number. This study has shown that approaches previously presented by others are applicable in modified form over a wide range of environmental conditions.
Establishment of Big Bluestem and Illinois Bundleflower Mixtures with Imazapic and Imazethapyr
Authors: Beran Daniel D. , Masters Robert A. , Gaussoin Roch E. , Rivas‐Pantoja Fernando
Published: July 2010

Weeds interfere with establishment of native grasses and legumes. A study was conducted to determine the influence of imazapic1 [(±)‐2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐methyl‐3‐pyridinecarboxylic acid] and imazethapyr [2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]5‐ethyl‐3‐pyridinecarboxylic acid] on weed control and establishment of ‘Pawnee’ big bluestem (Andropogon gerardii Vitman var. gerardii Vitman) and Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill.] planted in three binary mixtures of 220:110, 165:165, and 110:220 pure live seed (PLS) m−2. Mixtures were seeded at cropland sites near Clay Center, Mead, and Lincoln, NE. Imazapic and imazethapyr were applied at 70 g a.i. ha−1 before planted species emerged. Imazapic or imazethapyr did not reduce dry matter yields of annual grass weeds, where herbicides were applied in April 1996 at Mead and Clay Center. Both grass and broadleaf weeds were controlled at Lincoln, where herbicides were applied in early June 1996. The herbicides usually improved big bluestem yields and total forage yields in 1996 and 1997 at all sites. Illinois bundleflower yields at Lincoln, where imazapic and imazethapyr were applied, were greater than 3.0 Mg ha−1 in 1996 and 1997. In 1997, Illinois bundleflower did not survive at Mead and yielded less than 0.5 Mg ha−1 at Clay Center, regardless of weed control treatment or seed mixture. Imazapic and imazethapyr can improve the establishment of big bluestem and Illinois bundleflower mixtures.
Persistence of Perennial Cool‐Season Grass and Legume Cultivars under Continuous Grazing by Beef Cattle
Authors: Brummer E. Charles , Moore Kenneth J.
Published: July 2010

Persistence of highly productive forage species in pastures is essential to maximize economic returns from grazing livestock. However, most forage cultivars are neither developed nor evaluated under grazing. The objective of this study was to evaluate several cool‐season forage species and cultivars to determine their tolerance to continuous grazing. Three grazing experiments were established in 1996 in central Iowa: (i) 20 cultivars and populations of alfalfa (Medicago sativa L.), (ii) 15 cultivars representing five cool‐season legume species, and (iii) 25 cultivars and germplasms of six cool‐season grass species. Beef cattle (Bos taurus) continuously grazed the experiments for about four months in 1997 and 1998. Alfalfa yield was measured in adjacent plots. Stand survival ratings were taken each year. Among the alfalfa entries, grazing‐tolerant ‘Alfagraze’ showed high persistence but moderate yield. Several new alfalfa populations combined excellent grazing tolerance with yield equal to the best hay‐type cultivar. Kura clover (Trifolium ambiguum Bieb.) and white clover (T. repens L.) persisted better than alfalfa, birdsfoot trefoil (Lotus corniculatus L.), and red clover (T. pratense L.), with no loss of stand after two grazing years. Orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.) persisted well, though considerable variation was present among orchardgrass cultivars after the second grazing year. Reed canarygrass (Phalaris arundinacea L.) and smooth bromegrass (Bromus inermis Leyss.) stands were reduced to <10% after one grazing year. Although the severe, continuous grazing used in these experiments is not recommended, it clearly and quickly differentiates among species and cultivars for grazing tolerance.
Simulating Inbred‐Maize Yields with CERES‐IM
Authors: Rasse Daniel P. , Ritchie Joe T. , Wilhelm Wallace W. , Wei Jun , Martin Edward C.
Published: July 2010

CERES‐Maize, which was designed for simulation of hybrid maize (Zea mays L.), cannot be applied directly to seed‐producing inbred maize because of specific field operations and physiological traits of inbred maize plants. We developed CERES‐IM, a modified version of CERES‐Maize 3.0 that accommodates these inbred‐specific operations and traits, using a set of phenological measurements conducted in Nebraska (NE), and further tested this model with a set of field data from Michigan (MI). Detasseling (i.e., removal of the tassels from the female plants) was conducted prior to silking. Male rows were removed approximately 10 d following 75% silking. The thermal time from emergence to the end of the juvenile phase (P1) and the potential number of kernels per plant (G2) were assessed from field data, and were the only two coefficients allowed to vary according to the inbred line. Rate of leaf appearance of the inbreds was accurately simulated using a measured phyllochron interval of 54 degree‐days (°Cd). Simulation of detasseling and male‐row removal improved grain yield simulation for inbreds. For a set of 35 inbred‐site‐year simulations, the model simulated grain yield with satisfactory accuracy Average grain yields were 4556 and 4721 kg ha−1 for the measured and simulated values, respectively. CERES‐IM simulations suggest that the effect of male‐row removal on grain yield is extremely sensitive to the precise date at which this operation is conducted. This would explain the inconsistent effect of male‐row removal on female grain yields reported in the literature.
Supercow
Authors: Bary Andy I. , Sullivan Dan M. , Fransen Steven C. , Cogger Craig G.
Published: July 2010

Small‐plot research in manure nutrient management requires accurate manure applicators that are easy to operate and maneuver. Our objective was to design a small‐plot liquid manure applicator that could apply variable rates of dairy manure containing up to 60 g kg−1 solids to perennial grass plots while avoiding traffic and compaction on the plots. The applicator consists of a 1000‐L fiberglass agitation tank mounted on four load cells, a delivery pump and motor, and a side‐mounted boom with four nozzles for manure application, all built onto a wagon and towed by a tractor. The side‐mounted boom allows manure application without traffic on the plots. Manure application typically was within 7% of the target rate and had a coefficient of variation ranging from 2 to 17%, measured over a series of rates from 53 to 211 Mg ha−1 (wet weight). The precision, accuracy, and ease of operation of the applicator met our research requirements. Efficiency of operation could be improved using a larger agitation tank.
Assessing Simple Wheat and Pea Models Using Data from a Long‐Term Tillage Experiment
Authors: Payne William A. , Rasmussen Paul E. , Chen Chengci , Ramig Robert E.
Published: July 2010

Fresh green pea (Pisum sativum L.) and winter wheat (Triticum aestivum L.) are grown in rotation with intensive tillage in northeast Oregon. We evaluated simple yield models for both crops using data from a long‐term experiment that included four tillage treatments and soil water content measurements. Yields were affected by tillage for some of the 21 yr of study, but there was no consistent ranking among tillage treatments from year to year and no effect when data were pooled. Standardizing pea yields to a tenderometer reading of 100 failed to improve detection of treatment effect. Tillage affected wheat water use (ET) for three of the study years and water use efficiency (WUEET) for one. Conservation tillage reduced pea ET for seven of the study years. For combined years, however, there was no tillage effect on yield, ET, or WUEET of either crop. Wheat yield was better predicted from ET (R2 = 0.41) than by the Leggett model, which uses March soil water storage and spring rain (R2 = 0.12) Yield prediction was improved when ET was divided by seasonal mean daily water vapor pressure deficit (VPD) (R2 = 0.53) Multiple‐regression equations using monthly rain predicted wheat yield well (R2 = 0.62) but coefficients differed among data sets. A model using monthly rain and heat degree day sum (HDDS) predicted pea yield much better (R2 = 0.65) than ET‐based equations (R2 = 0.30)suggesting that pea yield is limited by factors other than water. For wheat, ET/VPD‐based models should replace the Leggett model. However, for pea, multiple regression models predict yield better than ET‐based models.
Production Functions for Chickpea, Field Pea, and Lentil in the Central Great Plains
Authors: Nielsen David C.
Published: July 2010

A short‐season legume grown in rotation with winter wheat (Triticum aestivum L.) is needed to diversify and enhance dryland crop rotations in the central Great Plains. This study was conducted to determine the potential of chickpea (Cicer arietinum L.), field pea (Pisum sativum L.), and lentil (Lens culinaris Medik.) as such rotational legumes based on yield responses to water and soil water extraction patterns. The legumes were planted under a line‐source gradient irrigation system to provide a range of available water conditions. Soil water content, crop water use, and seed yield were measured to determine relationships between water use and yield. Distributions of estimated yields were produced using these relationships and the local historical rainfall record. Chickpea exhibited the greatest rate of increase in yield with increases in water use (10.6 kg ha−1 mm−1), followed by field pea (8.0 kg ha−1 mm−1) and lentil (3.3 kg ha−1 mm−1). Yields estimated from the historical rainfall record ranged from 951 to 3782 kg ha−1 (mean of 2092 kg ha−1) for chickpea, 523 to 2718 kg ha−1 (mean of 1406 kg ha−1) for field pea, and 286 to 1247 kg ha−1 (mean of 654 kg ha−1) for lentil. All three legumes have agronomic potential to be used as dryland crops ahead of winter wheat in the central Great Plains.
Residual Effects of Potassium Placement and Tillage Systems for Corn on Subsequent No‐Till Soybean
Authors: Yin Xinhua , Vyn Tony J.
Published: July 2010

Little is known about K fertility management for no‐till (NT) soybean [Glycine max (L.) Merr.]. This study was conducted to evaluate the residual effects of K application rate, timing, and placement for corn (Zea mays L.) in various tillage systems on subsequent NT soybean. Field experiments involving a corn–soybean rotation were conducted from 1998 to 2000 on long‐term NT fields with medium or high exchangeable soil K levels near Kirkton and Belmont, ON, Canada. In the corn year, treatments included the combinations of three fall K rates (0, 42, and 84 kg ha−1), spring K rates (two rates differing by 42 kg ha−1), and three tillage systems [NT, zone till (ZT), and moldboard plow (CT)]. Both CT and ZT (also known as intermittent tillage systems) reduced soil K stratification relative to continuous NT. Trifoliate leaf K concentrations increased with residual fall and spring K applications in most site‐years. Average soybean yield significantly increased by 8.3% with the application of 84 kg K ha−1 in fall plus 42 to 50 kg K ha−1 in spring to previous corn only on medium‐testing (K < 100 mg L−1) soils. Residual tillage had no effects on leaf K or yield of NT soybean. Application of fall and spring K fertilizers to corn was equally beneficial for subsequent soybean in either continuous or intermittent NT systems. Furthermore, soil K stratification and the residual effects of tillage and K placement method were not major production issues for narrow‐row NT soybean in these growing seasons.
Modeling Net Herbage Accumulation of an Orchardgrass Sward
Authors: Duru M. , Ducrocq H. , Fabre C. , Feuillerac E.
Published: July 2010

In order to simulate the effect of a wide range of defoliation regimes and levels of N supply on the net herbage accumulation of an orchardgrass (Dactylis glomerata L.) sward, we developed a model based on growth and senescence submodels. Four experiments (spring and summer regrowths), each comprising four treatments (two N rates × two amounts of residual biomass), were carried out to assess the effect of management on leaf growth, senescence, and radiation use efficiency (RUE). The growth submodel, based on RUE, depended on herbage N status and the development stage during stem elongation in spring. Increases in RUE during stem elongation depended on the percentage of reproductive tillers in the swards, which was a function of the N fertilizer rate. Leaf elongation and senescence rates at the tiller level and the mass per unit leaf area of green and senescent leaves were used to parameterize the senescence submodel. The amount of dead material depended mainly on the residual biomass at the beginning of regrowth. Complete calibration of the model was done using experiments and data from the literature. Other sets of experiments (one on orchardgrass and two others on permanent grasslands) were used for its validation. Root mean square errors for herbage yield were comprised between 11 and 55 g m−2. The chosen model structure allows the growth of other grass species to be easily simulated, knowing their leaf life spans. However, this is a sink‐driven model that is unable to assess tiller mortality and its effect on herbage accumulation rate.
Soybean Development and Yield as Affected by Three Postemergence Herbicides
Authors: Young Bryan G. , Young Julie M. , Matthews Joseph L. , Owen Micheal D. K. , Zelaya Ian A. , Hartzler Robert G. , Wax Loyd M. , Rorem Kent W. , Bollero Germán A.
Published: July 2010

Field experiments were conducted during 3 yr at four locations in Illinois and three locations in Iowa to evaluate the influence of soybean [Glycine max (L.) Merr.] planting date and postemergence herbicide application timing on soybean injury and grain yield. Glyphosate [N‐(phosphonomethyl)glycine] at 1120 g a.e. ha−1 did not cause visual soybean injury or reduce yield. Acifluorfen [5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐2‐nitrobenzoic acid] at 420 g a.i. ha−1, and imazethapyr [2‐[4,5‐hydro‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐ethyl‐3‐pyridinecarboxylic acid] at 70 g a.i. ha−1 caused visual soybean injury at 5 to 7 and 21 to 24 d after herbicide application (DAA). Overall soybean injury was greater with the late planting date compared with the early planting date. Chlorosis and stunting at 5 to 7 DAA was greater from acifluorfen and imazethapyr at the early (V2–V3 soybean stage) compared with the late (V5–V6 soybean stage) application timing. Imazethapyr and acifluorfen reduced soybean leaf area index by 5.7 to 14.3% and soybean height by 4.1 to 8.3% at 21 to 24 DAA. Soybean yield was reduced 1.5 and 2.1% by acifluorfen and imazethapyr, respectively, compared with the no‐herbicide/weed‐free plots. Soybean yield averaged across herbicide treatment and application timing was reduced 11% with the late planting date compared with the early planting date.
Productivity of Chicory and Plantain Cultivars under Grazing
Authors: Labreveux María , Hall Marvin H. , Sanderson Matt A.
Published: July 2010

The bimodal distribution of growth of cool‐season grass species generates an imbalance in the amount of forage available during the summer, which could be improved by using alternative forage species. Several chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.) cultivars were evaluated for such purpose and contrasted against ‘Pennlate’ orchardgrass (Dactylis glomerata L.) under different grazing strategies in two experiments during 3 yr. In Exp. 1, ‘Grasslands Puna’ chicory and Pennlate orchardgrass achieved similar dry matter (DM) yields during spring (6500 vs. 7250 kg DM ha−1, respectively) and summer (3350 vs. 3900 kg DM ha−1, respectively). Between plantain cultivars, yields similar to Pennlate orchardgrass were achieved by ‘Grasslands Lancelot’ (7350 kg DM ha−1) in spring and by ‘Ceres Tonic’ (3150 kg DM ha−1) in summer. Grazing every 3 wk vs. 5 wk reduced DM yield in summer (1650 vs. 4450 kg DM ha−1, P < 0.001). In Exp. 2, spring DM yields of Puna chicory were greater than those of Pennlate orchardgrass (5750 vs. 3600 kg DM ha−1, average yield over years; P < 0.05). In summer, DM yield of Puna chicory relative to that of Pennlate orchardgrass varied between years. Yield of Lancelot plantain decreased during 2000 and 2001 following decreases in plant density. Our results suggest that most cultivars tested may not increase forage availability during the summer, which may be related to plant density losses. Of all cultivars, Puna chicory appeared as the most promising. Due to very low plant survival, the plantain cultivars tested may not be appropriate for perennial pastures in northeastern USA.
Soybean Foliage Residues of Dicamba and 2,4‐D and Correlation to Application Rates and Yield
Authors: Andersen Shane M. , Clay S. A. , Wrage L. J. , Matthees D.
Published: July 2010

Plant growth regulator (PGR) herbicides dicamba (3,6‐dichloro‐2‐methyloxybenzoic acid) and 2,4‐D [(2,4‐dichlorophenoxy)acetic acid] can severely injure soybean [Glycine max (L.) Merr.] by drift or tank contamination and reduce yield. Often in regulatory disputes, tissue is analyzed for PGR residue. However, relationships between grain yield reduction and foliar residue concentrations at various times after exposure are not well documented. This 2‐yr study quantified the amount of dicamba and 2,4‐D in soybean foliage 0, 6, 12, 24, and 48 d after treatment (DAT) when treated with 1 to 20% of 0.56 kg a.e. ha−1 [labeled rate for corn (Zea mays L.)] at the three‐leaf (V3) stage of growth and determined if these concentrations were correlated to initial application rate or grain yield. Herbicide concentrations were determined using gas chromatography/mass spectrometry techniques with selective ion monitoring. Visual symptoms were slight (<10%) to severe (90%) and included leaf cupping, epinasty and, in some cases, death of the apical bud. Grain yields from dicamba‐treated plants were reduced from 14 to 93% compared with untreated plant yield, whereas only 2,4‐D at the highest rate reduced yield. In both years, foliar residue concentrations were correlated with initial application rates and yield reduction up to 24 DAT for dicamba and 12 DAT for 2,4‐D, with all treatments having residue amounts similar to untreated plants after these intervals. The data suggest that plant samples should be collected as soon as possible after suspected PGR exposure for accurate detection and quantification of PGR residue.
Nutritive Quality of Cool‐Season Grass Monocultures and Binary Grass–Alfalfa Mixtures at Late Harvest
Authors: Berdahl John D. , Karn James F. , Hendrickson John R.
Published: July 2010

Nutritive quality of hay is compromised when harvest is delayed, but reproduction of upland nesting birds in the northern Great Plains would be improved if haying operations could be deferred until mid‐July or later to allow completion of nesting. This study was conducted to determine nutritive quality of hay at a single mid‐July cutting from three cool‐season grass species that were grown in monoculture and in binary mixtures with alfalfa [Medicago sativa subsp. × varia (Martyn) Arcang.] near Mandan, ND. Grasses were intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & Dewey], smooth bromegrass (Bromus inermis Leyss.), and crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.]. Annual applications of 0 and 50 kg N ha−1 had no effect on in vitro dry matter digestibility (IVDMD) or neutral detergent fiber (NDF) levels of grass or alfalfa. Grass monocultures and alfalfa averaged 612 and 624 g kg−1, respectively, for IVDMD and 651 and 567 g kg−1, respectively, for NDF. At 0 kg N ha−1, crude protein (CP) ranged from 71 to 78 g kg−1 in grass monocultures and from 92 to 131 g kg−1 in grass–alfalfa mixtures. At 50 kg N ha−1, CP ranged from 83 to 97 g kg−1 in grass monocultures and from 99 to 133 g kg−1 in mixtures. Feasibility of deferring hay harvest to allow reproduction of upland nesting birds in the northern Great Plains depends on maintaining alfalfa or other legumes with high nutritive quality in grass mixtures to reduce NDF and increase CP levels.
Forage Soybean Yield and Quality Responses to Plant Density and Row Distance
Authors: Seiter Stefan , Altemose Craig E. , Davis Michael H.
Published: July 2010

We conducted a study to determine the effect of row distance and plant density on yield and quality components of ‘Donegal’, a soybean [Glycine max (L.) Merr.] cultivar specifically developed for forage production in the northeastern United States. Dry matter yield ranged from 4.5 to 6.3 Mg ha−1 and 8.7 to 13.9 Mg ha−1 in 2000 and 2001, respectively. Yield in rows spaced 18 cm apart was significantly higher than in rows spaced 76 cm apart. Soybean plants started to lodge between 56 and 84 d after planting. At most sampling dates, the canopy was lower, and individual plants were shorter in 18‐ compared with 76‐cm rows. Soybean attained the beginning seed (R5.5) stage before a killing frost in both years. At that stage, soybean averaged 155 g kg−1 crude protein (CP), 362 g kg−1 acid detergent fiber (ADF), and 469 g kg−1 neutral detergent fiber (NDF). Acid detergent fiber, NDF, and CP increased between beginning pod (R3) and R5.5 growth stages in 2000 and 2001. Forage quality in 2001 was lower at 76‐ compared with 18‐cm rows. Plant densities between 234650 and 555750 plants ha−1 had no consistent effect on forage yield or quality. Donegal showed good potential as a forage crop in the northeastern United States.