bluuebunny/crossref_metadata_2025 huggingface dataset:
Populations of Foliage‐Inhabiting Arthropods on Soybean with Reduced Tillage and Herbicide Use
Authors: Buntin G. David , Hargrove William L. , McCracken Daniel V.
Published: July 2010

Modification of tillage and herbicide use patterns to reduce adverse environmental effects on soybean [Glycine max (L.) Merr.] production may impact arthropod populations and damage in soybean. The objectives of this field study were to examine the effect of reduced tillage and herbicide use on populations of foliage‐inhabiting phytophagous and beneficial arthropods and their damage in soybean. Tillage treatments of no‐tillage, chisel‐plow with disking, and moldboard plow with disking and herbicide regimes of high (preplant and postemergence control), reduced (postemergence control), and no herbicide use were established in a 2‐yr rotation of corn (Zea mays L.), winter wheat (Triticum aestivum L.), and soybean. Phytophagous and predatory arthropods were sampled from soybean foliage with the shake‐cloth technique throughout the season in 1988, 1990, and 1992. Tillage treatments did not consistently affect any arthropod groups except stink bugs (Pentatomidae), which were more abundant in no‐tillage than plow‐tillage treatments, and bigeyed bugs (Geocoris spp.), which were more abundant in both plow‐tillage treatments than in no‐tillage. Herbicide regime also had no consistent effect on abundance of any taxa. Additionally, tillage and herbicide regimes had little consistent effect on soybean lepidopteran defoliation and pod damage caused by the bean leaf beetle [Cerotoma trifurcata (Forster)] over the 3 yr. There were extensive stand losses due to rodent damage (cotton rat; Sigmodon hispidis Say & Ord) in the no‐tillage, no‐herbicide system in 1992, where crabgrass [Digitaria sanguinalis (L.) Scop.] was prevalent. These results suggest that tillage and herbicide use practices can be modified without greatly affecting arthropod populations and their damage in soybean. However, these results imply that the potential for managing arthropod populations by modified tillage and herbicide use is limited in soybean.
Maize Silage Utilization of Fertilizer and Soil Nitrogen on a Hill‐land Ultisol Relative to Tillage Method
Authors: Staley Thomas E. , Perry H. Douglas
Published: July 2010

Few studies have compared N utilization by maize (Zea mays L.) under conventional tillage (CT) and no‐tillage (NT) in the Appalachian region. Silage production (TDM) and fertilizer N and soil N uptake, were investigated in a 3‐yr study on a Gilpin silt loam (fine‐loamy, mixed, mesic Typic Hapludult) in West Virginia previously cropped to pasture. 15N‐depleted N fertilizer was band‐applied, within‐row, at 0, 56, 112, and 224 kg N ha−1, 4 wk after planting. Tillage method did not affect silage production, N concentration or total N uptake at any N rate. Maximal silage production under NT (13.2 Mg ha−1) was calculated to require just 24 kg ha−1 more fertilizer N than under CT (12.6 Mg ha−1). Fertilizer N uptake (kg ha−1) was similarly unaffected by tillage method, with annual fertilizer N use efficiencies (% recovery) of 55, 54, and 49% under NT, and 57, 57, and 48% under CT, at application rates of 56, 112, and 224 kg ha−1, respectively. Similar percentages for cumulative fertilizer N use efficiencies, which account for any labeled N carried over from year to year, suggest that there was little residuum available to the crop, particularly at near‐optimal N rates. Soil N uptake decreased by 17% with N additions below (56 kg ha−1) or above (224 kg ha−1) the optimum, but was generally unaffected by tillage method. These similarities between NT and CT for maize silage production and N use, despite using a management system contrived to show differences, emphasize the importance of edaphic and climatological factors in predicting N responses under various tillage methods. Nonetheless, these results show that reasonably high levels of silage can be produced without excessive fertilizer N requirements ( ≈ 170 kg N ha−1) or losses (< 50%) when pastures are converted to NT maize.
Root Growth and Distribution are Affected by Corn‐Soybean Cropping Sequence
Authors: Nickel S. E. , Crookston R. Kent , Russelle Michael P.
Published: July 2010

Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yield better when grown in rotation than when grown in monoculture, even under high inputs. The explanation for this yield increase due to rotation is not yet known. The objective of this study was to evaluate the effect of cropping sequence on seasonal root development of corn and soybean. We hypothesized that there would be more roots on rotated crops than on crops held in a continuous monoculture. The research was conducted in 1991 and 1992 at the Univ. of Minnesota Southwest Experiment Station on a Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll). Destructive root sampling via soil cores was performed at the seedling and flowering stages of both crops. Nondestructive root monitoring was performed weekly and recorded on video cassette tapes via an agricultural research video camera inserted into minirhizotron tubes that had been placed into the soil beneath crop rows. Our hypothesis that there would be more roots on first‐year corn than continuous corn was generally supported. Minirhizotron monitoring suggested that corn grown in rotation had greater root length density than continuous corn, with the exception of the top 12.5 cm, where continuous corn had greater root length density early in the season. Soil cores confirmed 22% more seedling roots in the top 12.5 cm on continuous corn. Our hypothesis that there would be more roots on first‐year soybean than continuous soybean was generally not supported. Minirhizotron monitoring indicated that when there were differences, continuous soybean had more roots than rotated soybean, with the single exception of depths of 37.5 to 50 cm, where rotated soybean had more than twice as many roots at flowering in 1992. Root length density data obtained from soil cores also indicated that rotated soybean had approximately twice as many roots at depths of 36 and 48 cm at flowering. Growth and distribution of both corn and soybean roots were thus affected by cropping sequence. Fewer roots in continuous corn may have been the result of autotoxins from decomposing roots of the previous corn crop. We do not have an explanation for increased soybean roots under monoculture.
Establishment and Persistence of Legumes Interseeded into Switchgrass
Authors: Blanchet Kevin M. , George J. Ronald , Gettle Randall M. , Buxton Dwayne R. , Moore Kenneth J.
Published: July 2010

Little information is available for renovation of established switch‐grass (Panicum virgatum L.) with cool‐season forage legumes. Field experiments were conducted to determine seeding success, persistence, and impact on grass when 10 forage legumes and a legume mixture were no‐till interseeded into established ‘Cave‐in‐Rock’ switchgrass near Ames, IA. Legumes interseeded in early April 1991 and 1992 were biennial ‘Polara’ white‐flowered sweetclover (Melilotus alba Medik.) and ‘Madrid’ yellow‐flowered sweetclover (‘Melilotus officinalis’ Lam.), ‘Norcen’ and ‘Fergus’ birdsfoot trefoil (Lotus corniculatus L.), ‘Apollo Supreme’ and ‘Alfagraze’ alfalfa (‘Medicago saliva’ L.), Mammoth and ‘Redland II’ red clover (Trifolium pratense L.), ‘Emerald’ crownvetch (Coronilla varia L.), common hairy vetch (Vicia villosa Roth.), and a 50:50 mixture of Norcen trefoil and medium red clover. Legume renovation was compared with grass fertilized with N at 0, 60, 120, and 240 kg ha−1. Excellent legume establishment was observed in June, about 2.5 mo after interseedings, with mean legume plant density of 195 and 163 plants m−2 for 1991 and 1992 seedings, respectively. Both alfalfa cultivars and hairy vetch had highest percentage establishment. Average legume persistence to June of the second year was nearly 50% for 1991 and 30% for 1992 seedings (less in 1992 because of greater winter losses). Grass stem density during the establishment year was not affected by legume renovation. Decline in grass stems during the second year was greatest for trefoil and the trefoil‐red clover mixture, and intermediate for alfalfa and red clover, with minimal to no effect for the sweetclovers, crownvetch, and hairy vetch. Hence, legumes can be successfully established into switchgrass and can be maintained into the second year
Ratoon Cropping Forage Sorghum for Silage: Yield, Fermentation, and Nutrition
Authors: McCormick M. E. , Morris D. R. , Ackerson B. A. , Blouin D. C.
Published: July 2010

Two field experiments were conducted on Lexington silt loam soil (fine‐silty, mixed, thermic Typic Paleudalf) to identify a harvest regime that would improve the nutritive value of ensiled whole‐plant sorghum [Sorghum bicolor (L.) Moench] while maintaining silage yield. In a 1‐yr preliminary study, first‐cut sorghum was harvested at mid‐vegetative, late‐vegetative, boot, bloom, and hard‐dough stages of maturity. Regrowth was harvested in late August. In a 2‐yr experiment, yield, ensiling losses, intake, and in vivo apparent digestibility of vegetative sorghum (initial and ratoon cute wilted 24 h) were compared with direct cut hard‐dough‐stage sorghum. Forages were stored in 1.8‐Mg‐capacity (fresh wt.) experimental silos and, upon opening, were fed to lambs (Ovis aries}. Results from the preliminary experiment indicated that dry matter (DM) yield of first‐cut sorghum was greatest at the hard‐dough stage; however, nutritional value was greatest for the mid‐vegetative stage. Maximum yield for the combined harvests was obtained when first harvest was made at boot stage. The 2‐yr experiment average DM yields were 7.3 Mg ha−1 for combined initial (mid‐vegetative stage) and ratoon crops, compared with 6.7 Mg ha−1 for the single hard‐dough‐stage harvest. Ensiling fosses did not differ with harvest regime. Vegetative sorghum was more digestible than sorghum harvested at the hard‐dough stage (670 vs. 570 g kg−1). These studies suggest that sorghum harvested twice per season (with wilting) will produce a higher quality silage than a single hard‐dough stage cutting, without yield reduction
Dry Matter and Seed Yield of Mediterranean Annual Legume Species
Authors: Martiniello Pasquale , Ciola Antonio
Published: July 2010

Knowledge of the effects of seeding rate, irrigation, and forage harvest management on annual legume crops is essential for their proper agronomical exploitation. Cultivars and ecotypes of berseem clover (Trifolium alexandrinum L.), common vetch (Vicia sativa L.), and fieldbean (Vicia faba L.) were compared at two seeding rates, with and without irrigation, and under two harvest managements. These experiments were conducted in Foggia (southern Italy) during 1990 and 1991. Irrigation increased and stabilized forage and seed production reducing the consequences of erratic rainfall. Mean dry matter and seed yield increases due to irrigation were, respectively: 26 and 14% in common vetch, 25 and 9% in field‐bean, and 24 and 28% in berseem clover. Berseem clover showed an increase of 48% in seed yield with forage harvest management under irrigation. Seeding rate interacted mainly with irrigation treatment and length of vegetative period. The high seeding rate under irrigation in common vetch and field‐bean increased forage production more than seed yield. The herbage and seed yield components that responded to the high seeding rate under irrigation were plant height, stems per square meter for all legumes, pods per stem, and seeds per pod for field‐bean and common vetch, and heads per stem and seeds per head for berseem. Adapted varieties and ecotypes identified within each species represent genotypes with superior genetic potential for dry matter production and seed yield under a Mediterranean environment.
Calcium‐Ammonium Effects on Growth and Yield of Small Grains
Authors: Fenn L. B. , Hasanein B. , Burks C. M.
Published: July 2010

Calcium (Ca++) is known to stimulate potassium (K+) and ammonium (NH+4) absorption rates by plants. Increased NH+4 absorption stimulates plant growth and development. However, little is known about the effect of Ca++ with NH+4 on small‐grain crops. The objective of this research was to examine the effect of Ca++/NH+4 on growth and development of wheat (Triticum aestivum L.), oat (Avena sativa L.), and barley (Hordeum vulgare L.). Treatments consisted of growing small grains using complete nutrient solutions with a molar ratio of 0, 0.30, 0.60, 1.20, and 1.80 Ca++/NH+4, and a check with NO‐3‐N. Plants were grown in the greenhouse to seedling (30 d), intermediate (elongating, 60 d), and mature (booting, 90 d) growth stages on a NO‐3 nutrient solution and then treated for 7 d with the Ca++/NH+4 fertilizer solutions. One set of plants was fertilized solely with the Ca++/NH+4 solution and another with a NO‐3 fertilizer solution. The addition of Ca++ with NH+4 to small grains resulted in increased N absorption, grain yield, tiller formation, dry matter, and grain weight per unit of plant dry matter, but the extent varied with the crop. Calcium apparently caused a redirection of foliar metabolites to grains. Short‐term treatments with Ca++/NH+4 at different growth stages showed the least results at the seedling stage, whereas maximum results were obtained at the intermediate growth stage (initiation of jointing) and good stimulation of plant growth and tillering at the mature (booting) stage. Calcium increased NH+4 absorption, leading to increased tillering, increased weight per head of grain produced, and consequently higher grain yields. Calcium added with NH+4‐N increases plant N use efficiency by more rapid absorption, greater rates of tillering, greater metabolite deposition in seeds, and possibly increases in photosynthesis.
Synchrony between Legume Nitrogen Release and Corn Demand in the Upper Midwest
Authors: Stute James K. , Posner Joshua L.
Published: July 2010

If legume cover crops are to be an effective, environmentally sound N source for corn (Zea mays L.), there must be a synchrony between legume N release and corn demand. A field study was conducted in Wisconsin during 1991 and 1992 that measured the release of legume N throughout the growing season using mesh bags, and compared resultant levels of soil mineral N following legume incorporation to those following fertilizer N applied at the recommended rate (179 kg N ha−1) and a control (no cover crop, no fertilizer) in a conventional tillage (CT) system. Corn N uptake during the growing season was also measured to determine if legume N could meet uptake demands. Hairy vetch (Vicia villosa Roth) and red clover (Trifolium pratense L.) residues decomposed rapidly, releasing half of their N within 4 wk after burial, while very little N was released after 10 wk (corresponding to corn silking). Soil tests indicated an increase in mineral N levels corresponding to legume N release, similar to those following an application of 179 kg ha−1 fertilizer N, occurring before the period of rapid N uptake by corn. Mean corn grain yields of 11.25 Mg ha−1 in 1991 and 10.89 Mg ha−1 in 1992 following the legumes were similar to those produced with 179 kg ha−1 fertilizer N, indicating that, in addition to releasing N in synchrony with the uptake pattern of corn, legumes released N in adequate amounts for corn production. Finally, postharvest levels of potentially leachable soil NO3‐N following the legumes were similar to or less than when following fertilizer. Therefore, legume cover crops can be an effective N source for corn in the Upper Midwest.
Observed and Calculated Potassium Uptake by Maize as Affected by Soil Water Content and Bulk Density
Authors: Seiffert Stefan , Kaselowsky Joachim , Jungk Albrecht , Claassen Norbert
Published: July 2010

Potassium uptake of field crops may be restricted when the upper soil layer, which is usually high in available K, dries out or is compacted. To evaluate the factors involved, the effect of soil water content and bulk density on maize (Zea mays L.) root growth, soil solution K concentration, and K mobility in soil was studied. Plants were grown in soil‐filled pots where roots could penetrate the bottom into a K‐free nutrient solution underneath. The soil was adjusted to bulk densities of 1.2, 1.4, and 1.6 g cm‐3 and gravimetric water contents (ω) of 10.7 to 19.0% w/w (corresponding to pF of 4.2 to 3.0), with a low (0.2 mol m−3) and a high (1.5 mol m−3) soil solution K concentration (CLi). Plants were harvested 11 and 19 d after sowing and root length, shoot dry weight, and K content were determined. High bulk density reduced root growth up to the first harvest. Thereafter, relative root growth rate varied from 1.0 × 10−6 s−1 at low to 2.3 × 10−6 s−1 at high water content independent of soil strength. Potassium uptake decreased with decreasing soil water content, because both root length and K influx were reduced at low water content by about 50%. Increasing soil bulk density tended to increase K influx because the volumetric water content (θ) increased when the gravimetric water content (ω) was kept constant. Drying the soil increased CLi, but its influence on K uptake was counteracted by the decrease of both θ and the impedance factor for diffusion (f). Model calculations simulating K transport in soil and K uptake by roots agreed fairly well with observed data, except at high soil water content, low K application, and high bulk density. Under these conditions, measured influx was lower than the calculated influx. It is concluded that this was due to uneven root distribution in compacted soil, which led to interroot competition. At high CLi, K influx was almost unimpaired by low water content because, as model calculations showed, the reduced K mobility was compensated by an increase of the K concentration gradient towards the root.
Nitrogen Cycling in an Alfalfa and Bromegrass Sward via Litterfall and Harvest Losses
Authors: Tomm Gilberto O. , Walley Frances L. , van Kessel Chris , Slinkard Alfred E.
Published: July 2010

Belowground transfer of N from legumes to associated grasses has been extensively documented; however, transfer of N via decomposition of plant material and reabsorption of released N remains poorly understood. This study was conducted to (i) assess the intensity of litterfall and harvest losses of alfalfa (Medicago sativa L.) and meadow bromegrass (Bromus riparius Rhem.) under field conditions and (ii) determine the quantity of N transferred from aboveground plant components. Litterfall and harvest losses were quantified over 3 yr. Nitrogen transfer was estimated using the 15N isotope dilution technique. The return of N to the soil via litterfall losses of alfalfa and bromegrass was 13 and 4 kg N ha−1 yr−1, respectively. Alfalfa returned an additional 15 kg N ha−1 yr−1 to the soil via harvest losses; bromegrass contributed an additional 7 kg N ha−1 yr−1. Bromegrass remained a source of N to the N2‐fixing alfalfa, even though it was N‐limited, and alfalfa successfully competed with the N‐stressed bromegrass for available N derived from litterfall and harvest losses. Alfalfa accumulated twice the amount of N from litterfall and harvest losses compared with bromegrass (2 vs. 1 kg N ha−1 yr−1). Clearly, alfalfa was a strong competitor for available N and acted as both a source and a strong sink for recycled N. The total amount of N transferred from alfalfa to bromegrass and vice versa via decomposition of aboveground plant components was found to be remarkably similar (≈ 1 kg N ha−1 yr−1). Therefore, the net flow of N between alfalfa and bromegrass was negligible, and no net N contribution of alfalfa to associated bromegrass from the decomposition of litterfall and harvest losses was detected. We concluded that, although alfalfa released more N through the decomposition of litterfall and harvest losses than bromegrass, alfalfa also reabsorbed more recycled N. Published estimates of net N transfer between alfalfa and bromegrass, therefore, could not be explained by the input of N from litterfall and harvest losses.
A Peanut Simulation Model: I. Model Development and Testing
Authors: Hammer Graeme L. , Sinclair Thomas R. , Boote Kenneth J. , Wright Graeme C. , Meinke Holger , Bell Mike J.
Published: July 2010

A biophysically robust crop simulation model can assist industry planning and farmer decision‐making via simulation analyses to quantify production potential and production risks. Accordingly, we developed a simple, yet mechanistic peanut simulation model for use in assessing climatic risks to production potential for both irrigated and dryland conditions. The model simulates pod yield, biomass accumulation, crop leaf area, phenology, and soil water balance and is suitable for application over a diverse range of production environments. The model uses a daily time step, utilizes readily available weather and soil information, and assumes no nutrient limitations. The model was tested on numerous data from experiments spanning a broad range of environments in the tropics and subtropics. The model performed satisfactorily, accounting for 89% of the variation in pod yield on data sets derived from independent experiments, which included crops yielding from 1 to 71 t ha−1. Limitations of the model and aspects requiring better understanding to improve quantification are discussed. Despite some limitations, the model attains a useful degree of predictive skill for a broad range of situations and environments. This outcome is testimony to the utility of the simple, generic framework used as the basis for this model. The model is suitable for simulation studies aimed at assisting industry planning and farmer decision‐making.
Fine Root Dynamics of Alfalfa after Multiple Cuttings and During a Late Invasion by Weeds
Authors: Pietola Liisa M. , Smucker Alvin J. M.
Published: July 2010

The dynamics of fine root systems for alfalfa (Medicago sativa L.) during seasonal harvests are important for plant regrowth, yet they are not well understood. The primary objective of this study was to determine fine root responses to multiple cuttings of an alfalfa crop for a 5‐yr period and during an invasion of companion weed plants during the last 2 yr of the study. Root development, distribution, and turnover rates were evaluated by minirhizotron (MR) and microvideo camera methods on a Kalamazoo loam (fine‐loamy, mixed, mesic Typic Hapludalfs). The development and distribution of alfalfa fine roots were modified more by season and age of the plants than by defoliation. New root development occurred primarily in the spring and immediately following rainfall interruptions of extended dry periods. Spatial accumulations of roots were observed at the interface of the Bt and 2Bt soil horizons, which also accumulated water and nutrients. More roots died with the progression of each season, especially when plants were 3 to 5 yr of age. New root growth decreased and root death rates increased at soil depths from 0 to 1.1 m, during the period between cuttings from July and August 1993 in the aging alfalfa stand, whose active region of root growth exceeded the depths of the MR observation tubes. New alfalfa root growth appeared at progressively greater depths, especially after 3 yr of cropping. Therefore, mature alfalfa root systems should be sampled to soil depths greater than 1 m. Root systems of encroaching weeds appeared to accumulate in the 0‐ to 0.6‐m region of the soil profile.
Interactions Involving Allelopathy in Cropping Systems
Authors: Einhellig Frank A.
Published: July 2010

Allelopathic inhibition typically results from the combined action of a group of allelochemicals which, collectively, interfere with several physiological processes. The objectives of this paper are to summarize research that illustrates the joint action of allelochemicals, and to provide evidence that both the amount and detrimental action of these compounds depends on the extent of associated abiotic and biotic stresses. Allelopathy is strongly coupled with other stresses of the crop environment, including insects and disease, temperature extremes, nutrient and moisture variables, radiation, and herbicides. These stress conditions often enhance allelochemical production, thus increasing the potential for allelopathic interference. In the paradigm of interactions, the data indicate that crops are more sensitive to allelopathy when moisture, temperature, or nutrient conditions are less than optimal. For example, the inhibition threshold concentration for ferulic acid to affect seedling growth was reduced with even minor moisture stress (Ψ = − 0.15 MPa) or a growth temperature at the higher end of the normal range for a species. Under greenhouse conditions, additive inhibition resulted from the joint action of ferulic acid with low levels of alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide], atrazine [6‐chloro‐N‐ethyl‐N’‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], or trifluralin [2,6‐dinitro‐N,N‐dipropyl‐4‐(trifluoromethyl)benzenamine]. Interactions of multiple stresses in crop environments will determine the relative impact of allelopathy. Allelopathystress interactions also have implications for herbicide and residue management strategies, crop rotations, biological control measures, and tillage practices that can contribute to a more sustainable agriculture.
Restoration of Productivity to a Desurfaced Soil with Livestock Manure, Crop Residue, and Fertilizer Amendments
Authors: Larney Francis J. , Janzen H. Henry
Published: July 2010

Many agricultural fields on the semiarid Canadian prairies have areas of inherently low productivity associated with loss of soil quality due to erosion. This study compared the efficacy of various amendments in restoring productivity to a desurfaced fine‐loamy, mixed Typic Haploboroll (Lethbridge series) in southern Alberta. In spring 1992, 14 amendment treatments (including livestock manures, crop residues, combinations of straw and chemical fertilizer, and fertilizer alone) were applied to a site where the Ap horizon (≈ 15‐cm depth) had been mechanically removed to simulate erosion. The manures and crop materials were incorporated into the degraded surface on an equivalent dry‐weight basis at 20 Mg ha−1. The plots were seeded to spring wheat (Triticum aestivum L.) in 1992, 1993, and 1994. The overall best amendments were hog manure, poultry manure, and alfalfa hay. In all years, yields from desurfaced plots amended with hog or poultry manure were not significantly different from plots with no topsoil removal. Nitrate‐N concentration in the 0‐ to 60‐cm soil depth explained 71% of the variation in restorative ability of the amendments, while extractable P concentrations in the 0‐ to 15‐cm depth explained 16% of this variation. Results demonstrate that livestock manures and crop residues can restore productivity to eroded soils by substituting for lost topsoil. Application of high rates of manure to severely eroded soils offers a means of utilizing the large amounts of manure generated by southern Alberta feedlot operations.
Double‐Emitter Source (DES) for Irrigation Experiments in Salinity and Fertilization
Authors: De Malach Y. , Ben‐Asher Jiftah , Sagih M. , Alert A.
Published: July 2010

A double‐emitter source (DES) irrigation system was designed, using trickle instead of sprinkler irrigation. Two trickle laterals and their emitters connected to two tanks of stock solutions are coupled together to form a double‐joint lateral. The emitters of the two lines have different and varying discharges to obtain various mixings between the two stock solutions while maintaining constant application rates. The layout produces a sequence of intermediates between maximal and minimal concentrations. The method was tested for a salinity experiment on globe artichoke (Cynara scolymus L.) and a fertilization experiment for amaryllis (Hippeastrum hybrid). Average electrical conductivity (EC) of the fresh and saline laterals was 1.5 and 6.2 dS m−1, respectively. The N and K concentrations in the stock solution were 13.12 g L−1 and 9.38 g L−1, respectively, for a mixed and diluted maximum of 777 and 556 mg L−1 N and K at the irrigation solution. Artichoke yield declined by 60% due to salinity when EC increased from 1.5 to 6.2 dS m−1. Hippeastrum bulb diameter and weight increased 35% with high N and low K application. We condude that the double‐emitter source can be used for precise application of varying salts or nutrients in multivariable experiments. Advantages include prevention of canopy wetting by saline water, precise distribution of the factor to be evaluated, and small experimental plots (reducing time, area, and labor requirements).
Leaf Azimuth in Strip‐Intercropped Corn
Authors: Fortin M.‐C. , Pierce F. J.
Published: July 2010

In strip‐intercropping conditions where rows of corn (Zea mays L.) are subjected to widely different levels of radiation interception and of water and nutrient competition, leaf azimuthal direction may be an important determinant of yield. Observations of ear leaf direction were made on two outside rows and one middle row of a corn strip grown with small‐grain cereal and soybean [Glycine max (L.) Merr.] stripintercrops in four trials with north‐south rows in Ontario and Michigan. The objectives were to assess if row position within the strip and seed orientation at planting affect leaf azimuth and to find out if ear leaf azimuth and yield are related. In only one of the four trials was there a correlation between yield and the frequency of ears from ear leaves pointing in a specific direction (west). In both locations, row position affected the proportion of ear leaves in a direction perpendicular to the row and toward the inside of the strip rather than toward the outside in the case of border rows. When seed orientation at planting was controlled, 60 to 74% of ear leaves (leaves 11 or 12) developed in the same direction as the embryo orientation or opposite this orientation. Random orientation of the seed resulted in random ear leaf azimuths, except in a very dry growing season, when leaf azimuthal directions were mostly parallel to row direction, minimizing interception of radiation. This suggests that leaf azimuth could be an indicator of water deficit.
Packing Summer Fallow in the Pacific Northwest: Agronomic Benefits and Environmental Concerns
Authors: Schillinger William F.
Published: July 2010

Winter wheat (Triticum aestivum L.) is sown as deep as 20 cm below the summer fallow soil surface in dry years in the semiarid Pacific Northwest (PNW). Many growers pack the summer fallow mulch in late August before seeding winter wheat to improve stand establishment. But packing may increase blowing dust, which is a major soil loss and air quality concern. A 2‐yr study was conducted on two silt loam soil types in 280 mm and 230 mm average annual precipitation zones in eastern Washington to determine the agronomic benefits and potential wind erosion hazards associated with packing. Packing a loose, thick surface mulch increased soil bulk density (BD) between the 5‐ to 12‐cm depth. This significantly benefited wheat seedling emergence and stand establishment, which subsequently increased grain yield 9% over nonpacked plots. But packing a soil with a thin mulch layer overlying a high BD tillage pan had no effect on soil BD, wheat seedling emergence, or grain yield. Packing rendered the soil more vulnerable to wind erosion at both locations by reducing soil clod mass 55% and surface residue 38% compared with not packing. There are agronomic benefits from packing summer fallow mulch before seeding, but packing should be practiced judiciously, and not considered when surface residue or soil clods are lacking. This is especially true for poorly aggregated coarse‐textured soils where soil structure is difficult to maintain.
Shoot‐to‐Root Relations in Field‐Grown Maize Seedlings
Authors: Richner W. , Soldati A. , Stamp P.
Published: July 2010

In northern latitudes, maize (Zea mays L.) seedling growth is generally limited by low temperatures. A better knowledge of mechanisms limiting maize seedling growth at suboptimal temperatures is needed for improving growth models and, ultimately, for breeding of genotypes with improved vegetative growth at low temperatures. Shoot‐to‐root ratios are known to be sensitive to suboptimal temperatures, but information for field conditions is scarce. In three environments with mean soil temperatures of 14.6, 16.9, and 18.0°C at the 5‐cm depth, we investigated shoot‐to‐root relations at the 2−, 3−, and 4‐leaf stages in two maize inbred lines differing in chilling tolerance. Environment characteristically influenced temporal patterns of the shoot‐to‐root dry matter ratio (SDM/RDM), leaf area to root length ratio (LA/RL), and leaf area to root surface area ratio (LA/RSA). The chilling‐sensitive Penjalinan showed close LA/RL and LA/RSA ratios only in the warmest environment, whereas the same traits in chilling‐tolerant Z 7 were almost unaffected by environment, mainly due to Z 7’s temperature‐stable root development. Since root dry matter of Penjalinan was not affected by environments, the inefficient conversion of dry matter into root length and root surface area was responsible for the unbalanced relationship between shoot and root of this genotype at suboptimal temperatures. Our results indicate that already relatively small reductions of 2 to 3°C in soil temperatures near 15°C may distinctly reduce root development in chillingsensitive maize seedlings under field conditions.
Frost‐Seeding Legumesin to Established Switchgrass: Establishment, Density, Persistence, and Sward Composition
Authors: Gettle Randall M. , George J. Ronald , Blanchet Kevin M. , Moore Kenneth J. , Buxton Dwayne R.
Published: July 2010

Legumes incorporated into established switchgrass (Panicum virgatum L.) could provide symbiotic N, improve herbage quality, and extend the grazing season. Almost no information exists for legume renovation of switchgrass by frost‐seeding. The objective of this study was to identify cool‐season legumes that can be established into switchgrass by frostseeding, yet not provide excessive competition to the associated grass. Six legumes [biennial ‘Polara’ white‐flowered sweetclover (Melilotus alba Medik.), biennial ‘Madrid’ yellow‐flowered sweetclover (Melilotus officinalis Lam.), ‘Norcen’ birdsfoot trefoil (Lotus corniculatus L.), ‘Redland II’ medium red clover (Trifolium pratense L.), ‘Apollo Supreme’ alfalfa (Medicago sativa L.), and a 50:50 mixture of Redland II red clover and Norcen birdsfoot trefoil] were inoculated with rhizobia and frost‐seeded into established ‘Cave‐in‐Rock’ switchgrass in mid‐March of 1991 and 1992. These mixtures were compared with switchgrass fertilized at four N levels (0, 60, 120, and 240 kg ha−1). Successful legume establishment was observed, with an average of 24 and 25% of viable seed producing seedlings by June for 1991 and 1992 seedings, respectively. Mean legume density was 160 and 170 plants m−2 by June of the seeding year (YR 1) and 95 and 55 plants m−2 by June of the second year (YR 2) for 1991 and 1992 seedings, respectively. Legume renovation of switchgrass stands did not affect grass stem density by July YR 1. Mean forage stand composition (based on stem counts) was 87, 67, and 45% legume in June, July, and August YR 2, respectively, for 1991 seedings, and 54, 29, and 23% legume during the same time periods for 1992 seedings. Legumes did not seriously reduce switchgrass stem density, although red clover, birdsfoot trefoil, and their mixture were more competitive than others. Legumes can be successfully introduced into established Cave‐in‐Rock switchgrass by frost‐seeding and they will persist for at least 2 yr with favorable weather.
Performance of ‘Grasslands Puna’ Chicory at Different Management Levels
Authors: Jung Gerald A. , Shaffer John A. , Everhart John R. , Varga Gabriella A.
Published: July 2010

‘Grasslands Puna’ chicory (Cichorium intybus L.) is a perennial taprooted herb that shows potential to produce high yields of palatable forage for ruminants. Our objective was to determine management effects on herbage production and quality, and stand persistence. Chicory and ‘Pennlate’ orchardgrass (Dactylis glomerata L.) were established on Hagerstown silt loam (fine, mixed, mesic Typic Hapludalf) soil at Rock Springs, PA. Treatments were intensive, moderate, and lenient management, corresponding to 25‐, 37‐, and 50‐cm chicory canopy height at harvest, with N fertilizer applied after each harvest except the last. The experimental design was a 2 × 3 (species × managements) factorial with five replications. Total yields of forage averaged 9A Mg ha−1 for chicory and 7.9 Mg ha−1 for orchardgrass in 1992 and 1993. Management did not affect total yield of chicory the first harvest year, nor that of orchardgrass in either year. Chicory yield was greatest from plants under lenient management the second year. Mean crude protein concentration in chicory and orchardgrass was 200 g kg−1 and 185 g kg −1 respectively, but both species showed a potential to accumulate concentrations greater than 250 g kg−1. Low concentrations (110 g kg−1) were associated with floral stem production. Chicory herbage had higher concentrations of Ca, Mg, Na, Fe, Cu, and Zn, than did orchardgrass. Our results show that Grasslands Puna can withstand a range of defoliation intensities while maintaining excellent productivity.
Assessing Ecological Sustainability of Slash‐and‐Burn Agriculture through Soil Fertility Indicators
Authors: Kleinman Peter J. A. , Bryant Ray B. , Pimentel David
Published: July 2010

The objective of this study was to assess the near‐ and long‐term impact of traditional slash‐and‐burn agriculture on soil fertility in the village of Kembera, West Kalimantan, Indonesia. Soil fertility is widely viewed as one of the key limits to sustainable production in slash‐and‐burn agroecosystems. A chronosequence of sites ranging from currently cultivated swiddens to a 28‐yr fallow was surveyed. Organic C, cation exchange capacity (CEC), pH, nitrate, extractable basic cations, available and total P, and extractable Al were measured as indicators of soil fertility. Inferred short‐term trends point to significantly improved soil fertility conditions after burning in currently cropped swiddens relative to fallows. During the fallow, soil organic C, CEC, nitrate, total P, and extractable basic cations all manifest positive associations with fallow length after 3 to 11 yr of fallow. No declines in soil parameters were detected between plots based on the frequency of past slash‐and‐burn activity. Therefore, there is no evidence that slash‐and‐burn agriculture in Kembera has degraded these soil resources. While the results of this study suggest that slash‐and‐burn agriculture in Kembera has been ecologically sustainable, recent changes in socioeconomic factors influencing farmer's land‐use decisions cast doubt upon the future sustainability of this agroecosystem.
Evaluating Cotton Nitrogen Dynamics in the GOSSYM Simulation Model
Authors: Stevens William E. , Varco Jac J. , Johnson Joseph R.
Published: July 2010

Prediction of cotton (Gossypium hirsutum L.) N requirements would be useful in preventing excessive vegetative growth and negative environmental effects from overapplication of fertilizer N. Field research studies were conducted at Holly Springs, MS, to evaluate early‐maturing and full‐season cultivar effects on N nutrition and yield. Cotton was grown across a range of N application rates and results were compared with simulations of the cotton model GOSSYM. Cotton cultivars Stoneville 825 and DES 119 were grown on a Grenada silt loam soil (fine‐silty, mixed, thermic Glossic Fragiudalfs) in 1989 and 1990, and Deltapine 20 on a Loring silt loam soil (fine‐silty, mixed, thermic Typic Fragiudalfs) in 1990, all with N rates of 0, 45, 90, 135, and 180 kg ha−1. Rainfall in May through September 1990 was only 52% of the rainfall during the same period in 1989. Cultivar effects on yield and cotton N nutrition were minimal. Averaged across cultivars and N rates, 24% of total plant N on the Grenada soil and 20% on the Loring soil in 1990 was in ground litter at first open boll, compared with 13% in 1989 on the Grenada soil. GOSSYM accurately predicted litter N for the Grenada site in 1990, but overpredicted N in litter in 1989 at this site and in 1990 for the Loring site. On the Grenada soil in 1989, an average of 61% of the total plant N at first open boll was in seed and burrs, while in 1990 it was 41%, due to a lower boll load. For both soils, N availability without fertilizer ranged from 68 to 77 kg N ha−1. GOSSYM overestimated soil N availability by 10 to 30 kg N ha−1. Averaged across cultivars on the Grenada soil in 1989, GOSSYM underpredicted yield on cotton with no fertilizer N by 463 kg lint ha−1. Fertilizer N recovery was overpredicted by the model. These results point to the need for more accurate prediction of N dynamics if the model is to be used for N management on fragipan soils.
Fusarium Head Blight in Hard Red Spring Wheat: Cultivar Responses to Natural Epidemics
Authors: Wiersma John V. , Peters Eugene L. , Hanson Mark A. , Bouvette Robert J. , Busch Robert H.
Published: July 2010

Fusarium head blight (FHB), caused primarily by Fusarium graminearum Schwabe, is an important but sporadic disease throughout major spring wheat (Triticum aestivum L.) production areas in Canada and the USA. Our objectives were to (i) examine the effects of years, planting dates, cultivars, and their interactions on FHB measures and agronomic traits and (ii) characterize cultivar responses across a range of environments. Eight planting dates and 16 hard red spring wheat cultivars were studied in field trials during 1993 and 1994 at Crookston, MN. Normal and above‐normal rain during June and July provided moist conditions during anthesis of most cultivars across several planting dates each year. Incidence and severity of FHB varied markedly with planting date, anthesis date, year, and cultivar. Cultivars that achieved higher than average grain yield and test weight over all environments did so because they performed well in environments that favored FHB. Cultivar mean grain yield (r = −0.75, P = 0.01) and test weight (r = −0.93, P = 0.01) were inversely correlated with cultivar mean FHB incidence. ‘Butte‐86’, ‘Grandin’, ‘Marshall’, and ‘Nordic’ generally had lower mean FHB incidence and severity and were less responsive to environments favorable for disease than other cultivars. These cultivars also had higher grain yield and test weight than most other cultivars. ‘Norm’, ‘Minnpro’, ‘Sonja’, and ‘Bergen’ were representative of more susceptible cultivars. They had higher levels of disease, were more responsive to environments favorable for disease, and had lower grain yield and test weight. Attempts to avoid FHB by varying planting date were not successful. Careful cultivar selection for tolerance to FHB should provide moderate increases in grain yield (10−20%) and test weight (5−10%) for spring wheat producers in northwest Minnesota.
Evaluation of Optimum and Above‐Optimum Phosphorus Supplies for Corn by Analysis of Plant Parts
Authors: Mallarino Antonio P.
Published: July 2010

The concentration of nutrients in the ear leaves of corn (Zea mays L.) often is used to evaluate the nutrient status of this crop. A recent report showed, however, that the P concentration of ear leaves does not evaluate excess P supplies appropriately. This study evaluated the capacity of tests based on the P concentrations of four plant parts to evaluate the P status of corn in soils testing in the optimum to above‐optimum availability range. The plant parts tested were young plants (at V5 to V6 growth stages), ear‐leaf blades at silking, lower stalk sections after physiological maturity, and harvested grain. Grain yields and tissue samples were collected from plots of 25 field trials in Iowa. Treatments were 0, 25, 50, and 75 kg P ha−1. There was a significant yield response to P at 6 sites. The P treatments increased the P concentrations of young plants at 5 sites, of leaves at 13 sites, of stalks at 3 sites, and of grain at 11 sites. Differences in tissue P concentrations among sites often were greater than differences among treatments. Relationships between grain yield response and P concentrations of the tissues showed that P deficiency usually was correctly identified by tests of young plants and leaves. Determined critical concentrations were 3.4 g P kg−1 for plants and 2.4 g P kg−1 for leaves. The P concentrations of plants and leaves increased with soil‐test P until a plateau was reached, which suggests that these tissues have upper limits for luxury accumulation of P. The limits for young plants and for leaves occurred at soil‐test P values only slightly higher than values needed to obtain maximum economic yields of corn. The P concentrations of stalks were not related to yield responses or soil‐test P. Luxury accumulation of P in grain had no clear upper limit but P concentrations were very poorly related with yield responses or soil‐test P. The results showed that tests based on the P concentrations of young plants and ear leaves have similar capacities for identifying severe P deficiencies. None of the four tests evaluated would be a reliable diagnostic tool to evaluate P supplies for corn in the optimum to above optimum availability range.
Potential Carbon Sequestration by Afforestation of Pasture in the South‐Central United States
Authors: Lee Jeffrey J. , Dodson Rusty
Published: July 2010

Climate models indicate that increasing atmospheric concentrations of CO2 and other greenhouse gases could alter climate globally. The Climate Change Action Plan commits the USA to reducing net greenhouse gas emissions by 106 ✕ 106 Mg C yr−1 by the year 2000. One suggestion for reducing net emissions is to convert marginal grass pastures to pine (Pinus spp.) plantations in the South‐Central USA. We used the Erosion/Productivity Impact Calculator (EPIC) model to estimate the amount of atmospheric C that could be sequestered by this suggested change in land use. Carbon flow dynamics at each of 100 randomly selected sites were simulated for 50 yr under two assumptions: (i) continuous pasture for 50 yr or (ii) pine plantations harvested every 25 yr. Carbon sequestered by conversion to pine plantations was calculated as the net change in off‐site storage (i.e., in long‐lived products and landfills), plus the change in soil organic C, plus (for the first harvest period) stand establishment. Average C‐sequestration (±SE) was 40 ± 2 and 18 ± 2 Mg C ha−1 for the first and second 25‐yr harvest periods, respectively. In contrast, sequestration would have been 8.3 ± 0.6 Mg C ha−1 as soil organic C if the sites had been left in continuous pasture for 50 yr, or 3 Mg C ha−1 after correcting for release of C during manufacture of N‐fertilizer. Extrapolated to the region, conversion of 3.6 × 106 ha of marginal grass pasture to pine plantations could sequester 5.6 × 106 C yr−1 for the first 25 yr and 1.1 × 106 Mg for the second 25 yr. If all types of marginal agricultural land in the region (4.6 × 106 ha) were converted to forestry, the corresponding sequestration rates would be 7.4 × 10,6 and 1.4 × 106 Mg C yr−1 . In contrast, maintaining the land in continuous pasture would sequester 0.3 × 106 Mg C yr−1.
Model of Leaf Area Expansion in Field Pea Subjected to Soil Water Deficits
Authors: Lecoeur Jérémie , Wery Jacques , Sinclair Thomas R.
Published: July 2010

Yield of field pea (Pisum sativum) is sensitive to soil water deficits. An important component of this sensitivity is the response of leaf area to drought. A simple, mechanistic model was developed to allow predictions of leaf area development in response to soil water deficits. The model calculates leaf areas of individual drought‐stressed leaves relative to leaves on well‐watered plants as the product of the number of cells and the size of the cells. Therefore, distinct phases of cell division and cell expansion were identified and temporally distinguished in the model. Cell division and cell expansion in the model were both sensitive to the fraction of transpirable soil water. The model proved capable of predicting the temporal development and the final area (r2 = 0.91) of individual leaves on pea plants in response to soil water deficits.