bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation by NCSWAP of Seasonal Nitrogen Dynamics in Corn: II. Corn Growth and Yield
Authors: Lengnick Laura L. , Fox Richard H.
Published: July 2010

The accurate simulation of crop growth is important in the effort to apply computer simulation models to improvements in the management of N resources in agricultural systems. The objective of this study was to validate the crop growth submodel of the model NCSWAP using seasonal corn (Zea mays L.) growth and final grain yields from a 3‐yr N rate‐study conducted in central Pennsylvania. The results of the validation suggest that the model poorly simulated crop growth response under conditions of limited water or N availability. However, NCSWAP accurately simulated observed seasonal corn growth and harvested yields in treatments with no N or water limitations. The crop growth submodel has the potential to be useful in simulation of crop production, because with a minimum of inputs it can be calibrated for any crop and can incorporate variables that influence crop growth and are specific to a local environment. Improvements in the simulation of crop growth under N and water deficits would enhance the usefulness of NCSWAP to researchers exploring seasonal N cycling in soils and crops.
Estimating Leaf Mass from Light Interception Measurements on Isolated Plants of Erythroxylum Species
Authors: Acock M. C. , Daughtry C. S. T. , Beinhart G. , Hirschmann E. , Acock B.
Published: July 2010

To determine the extent of coca (Erythroxylum spp.) production in the world, some method for estimating yield (leaf mass) in a variety of habitats is required. A computer model that simulates the growth of coca plants has the versatility for making these estimates, but there must be some reliable method to validate the model. The objective of this research was to validate the use of measurements of light interception and specific leaf area (SLA, m2 kg−1) for estimating yield. Leaf area was calculated from light interception measurements made on plants grown as hedgerow or as isolated plants, then converted to leaf mass using measurements of SLA. Light interception was measured with the Decagon Sunfleck Ceptometer (SC) and the LI‐COR Plant Canopy Analyzer (PCA). Leaf disks of known area from Erythroxylum coca var. coca and Erythroxylum novogranatense var. novogranatense were cut, dried, and weighed to determine SLA values. Leaf fresh weights were measured and corrected to dry weight using the fresh to dry weight ratio obtained from a sample at harvest. Estimated leaf mass regressed on observed leaf mass demonstrated that PCA was superior to SC in estimating leaf mass on isolated plants of various sizes using the techniques described in this paper. Leaf area was consistently underestimated by the SC. The estimates of leaf mass from the PCA gave the lower mean, absolute mean, and root mean square error terms compared with SC, and the slope of the regression line of observed leaf mass vs. predicted leaf mass was closest to a value of 1.0.
A Method for Infesting Small Field Plots with Soybean Cyst Nematode
Authors: Browde J. A. , Tylka G. L. , Pedigo L. P. , Owen M. D. K.
Published: July 2010

Field experimentation with soybean cyst nematode (Heterodera glycines Ichinohe) is difficult, because of problems in obtaining plots with desired population densities. Therefore, a technique was developed for infesting small field plots with soybean cyst nematode. In 1990 and 1991, cysts, eggs, and infective juveniles were mixed with soil and applied with a commercial fertilizer spreader. Infected soybean [Glycine max (L.) Merr.] root segments were distributed by hand. Infested soil and roots were incorporated with a tractor‐drawn herbicide incorporator, and plots were planted to susceptible soybean. At‐planting egg densities in 1990 and 1991 averaged 184 and 100 eggs 100 cm−3 soil, respectively, representing 78 and 90% of expected egg densities. Resultant low densities of encysted eggs, which are highly aggregated, probably prevented detection of eggs in some plots. No soybean cyst nematode was detected in uninfested plots at planting, although some contamination was noted at harvest. This method may be appropriate for establishing soybean cyst nematode population densities for some small‐plot research.
Residual Maize Fertilizer Nitrogen Availability to Wheat on the Southeastern Coastal Plain
Authors: Camberato J. J. , Frederick J. R.
Published: July 2010

In southeastern Coastal Plain soils, little emphasis is placed on adjusting N fertilization of a crop based on the residual N left from the preceding crop because of the perception of coarse‐textured surface soils, winter rainfall in excess of evapotranspiration, and shallow‐rooted crops. However, estimates of annual water surplus do not include a winter crop, which may reduce NO3‐N leaching, nor consider current tillage practices, which enable deep rooting, and assimilation of subsoil NO3‐N. This study was conducted to determine the contribution of N applied to a maize (Zea mays L.) crop to the N supply of a subsequent winter wheat (Triticum aestivum L.) crop. Wheat was grown following maize fertilized with various rates of N and poultry litter on a Rains/Lynchburg sandy loam soil complex (fine‐loamy, siliceous, thermic Typic/Aeric Paleaquult) in 1990 and on a Noboco loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudult) in 1991. Maize fertilizer N increased soil NO3‐N at the time of wheat planting. Residual N increased wheat dry matter, N content, and grain yield. An increase in maize N rate of 134 kg N ha−1 increased N supply to the subsequent wheat crop by approximately 15 kg ha−1 and increased wheat grain yield by 0.8 Mg ha−1. Poultry litter did not differ from fertilizer N in providing residual N to the wheat. This research demonstrates that previous crop fertilization rate may impact N supply to the subsequent crop, even on coarse‐textured Coastal Plain soils.
Water‐Yield Relationships for Irrigated and Dryland Wheat in the U.S. Southern Plains
Authors: Musick Jack T. , Jones Ordie R. , Stewart Bobby A. , Dusek Donald A.
Published: July 2010

A climate with high evaporative demand and limited precipitation restrict yields of winter wheat (Triticum aestivum L.) grown in the semiarid U.S. southern High Plains. Stress effects can be avoided or minimized by management practices that increase soil water storage at planting or by application of irrigation water. We analyzed a 178 crop‐year database of irrigated and dryland wheat data from Bushland, TX, to develop relationships that define the grain yield and water‐use efficiency (WUE) response to a wide range in seasonal evapotranspiration (ET) associated with water deficits and to evaluate yield response to stored soil water at planting. The ET‐grain yield relationship was determined as linear, with a regression slope of 1.22 kg grain per m3 ET above the ET threshold of 208 mm required to initiate grain yield. Maximum yields (>7.0 Mg ha−1) required 650 to 800 mm seasonal ET. Maximum yields observed in the combined database were 2.8 and 8.2 Mg ha−1 for dryland and irrigated wheat, respectively. The linear regression response of grain yield to soil water stored at planting, 1.57 kg m−3, was significantly higher than the yield response to seasonal ET. Largely similar WUE values occurred over a wide range of seasonal ET within irrigated and dryland data sets; however, WUE values for irrigated wheat averaged about double the values for dryland wheat. A curvilinear relationship determined between WUE and yield emphasizes the importance of obtaining high yields for efficient water use.
Sulfur Fertilization of Smooth Bromegrass in Kansas
Authors: Lamond Ray E. , Whitney David A. , Marsh Brian H.
Published: July 2010

Sulfur deficiencies have been identified throughout the central USA with increasing frequency in recent years, yet little work has been reported on S needs of perennial cool‐season forage grasses. Field studies were initiated on established smooth bromegrass (Bromus inermis Leyss.) at three sites in eastern Kansas to evaluate the effects of S fertilization on forage production and quality. Sulfur rates (0, 17, 34 kg ha−1) and sources (ammonium sulfate and ammonium thiosulfate) were evaluated with a uniform N application of 134 kg ha−1. Sulfur fertilization generally increased bromegrass forage production. Averaged across site‐years, forage yields were increased 700 kg ha‐1 annually by S application. The 17 kg S ha−1 rate was sufficient to achieve forage yield increases. Sulfur fertilization had little effect on bromegrass forage protein levels at normal harvest time, but did increase forage S concentrations. Forage protein levels of early‐season forage samples were increased by S application. When N /S ratios of the no‐S check treatments were 20:1 or greater, forage yields were increased with S application. Ammonium sulfate and ammonium thiosulfate performed equally well as S sources.
A Simple Conductimetric CO2 Analyzer with Automatic Recalibration: III. Dynamic Response
Authors: Wall Gerard W. , Acock Basil
Published: July 2010

Conductimetric CO2 analyzers provide an economical means of monitoring and controlling carbon dioxide concentration ([CO2]) in plant growth cabinets. When conductimetric CO2 analyzers are being used to measure canopy CO2 uptake over a period and compare that with light received, it is essential to know the time between an air sample leaving the canopy and its [CO2] being registered by the analyzer. A four‐way analysis of variance in three replicates of a split split‐plot design was used to examine the response time of the conductimetric CO2 analyzers to successive step changes in [CO2] (∆[CO2]) from 200 to 400, 600, 800, and 1000 μL L−1, at temperatures of 10, 20, 30, and 40°C, at air flows rates of 540, 1880, and 3700 mm3 s‐1, and at water flow rates of 1.0, 0.66, and 0.33 mL s−1. Response times ranged from 30 to 542 s across all treatments. Significant differences were observed between individual conductimetric CO2 analyzers, with response time means ranging from 99 to 145 s. Each analyzer, therefore, is unique and must be recalibrated following a change in any one component. A significant water flow rate ✕ temperature interaction was observed (response time means ranged from 86 to 177 s). Comparing these response time means to the 900‐s sampling period indicates that an individual conductimetric CO2 analyzer will adjust to the new steady state following a change in control within 9.5 to 20% of the sampling period. Only 1 data record out of 96 within a diurnal cycle is lost if an alteration in the CO2 control set point for the plant growth cabinet is made. This data loss is acceptable.
Potential for Discriminating Crop Residues from Soil by Reflectance and Fluorescence
Authors: Daughtry C. S. T. , McMurtrey J. E. , Chappelle E. W. , Dulaney W. P. , Irons J. R. , Satterwhite M. B.
Published: July 2010

Crop residues left in the field after harvest can be important in controlling soil erosion. Current methods for quantifying percent crop residue cover are tedious and somewhat subjective. There is a need for new methods to quantify residue cover that are rapid, accurate, and objective. We evaluated reflectance and fluorescence techniques for discriminating crop residues from a wide range of soils. Reflectance and fluorescence spectra of 37 agricultural soils (wet and dry) and of recently harvested and weathered corn (Zea mays L.), soybean [Glycine max (L.) Merr.], sorghum [Sorghum bicolor (L.) Moench], and wheat (Triticum aestivutn L.) residues were measured in the lab. Reflectance factors in the visible or near‐infrared wavelengths did not uniquely distinguish all soils from all crop residues. Crop residues may be brighter or darker than a given soil, depending on soil moisture and residue age. When illuminated with ultraviolet radiation, however, the crop residues fluoresced more than most of the soils. Fluorescence of crop residues was a broad‐band phenomenon centered between 420 to 520 nm and induced by a relatively broad range of excitation wavelengths centered betweert 350 to 400 nm. More than 90% of the crop residues <2 yr old could be discriminated from 33 of 37 dry soils and 36 of 37 wet soils using fluorescence. The threshold for discrimination can be optimized for classification accuracy for each soil. Fluorescence techniques are less ambiguous than reflectance methods and are better suited for discriminating crop residues on soils. Furthermore, if properly implemented, fluorescence techniques can be used to quantify crop residue cover in the field.
Analysis of Deterministic Simulation Models Using Methods Applicable to Two‐Way Treatment Structures without Replication
Authors: Willers Jeffrey L. , Wagner Terrence L. , Sequeira Ronaldo A. , Theseira Gary W. , Boykin Deborah L.
Published: July 2010

Separate executions of deterministic simulation models are not independent replications in the strictest sense and, therefore, it is difficult to statistically analyze model output, since estimates of the error variance for the model are difficult to obtain. However, an analysis of simulation output is desirable. Presented here is a method that permits the statistical analysis of deterministic simulation output or its comparison to other output or experimental data. These analyses are possible when conditions imposed on the computer‐generated experiment conform to a two‐way treatment structure. The response data can be comprised of (i) model output, (ii) differences between experimental means and the model, or (iii) differences between individual output across treatment levels. The additive main effects and multiplicative interaction (AMMI) model for unreplicated data supplies several statistical tests. Foremost, the characteristic root test indicates if interaction exists between the two treatments. If interaction exists, the AMMI model can be used to determine which treatment combinations are involved. Once sources of interaction have been identified, it is then possible to obtain a good estimate of the error variance, even though these data are unreplicated. Using this estimate of the error variance, it is possible to test hypotheses of interest on model performance. An AMMI analysis comparing the output of a deterministic soil hydrology model to (replicated) experimental data is presented.
Yield and Yield Components of Spring‐Sown White Lupin in the Southeastern USA
Authors: Noffsinger Steven L. , van Santen Edzard
Published: July 2010

Management studies must be conducted to realize the full potential of white lupin (Lupinus albus L.) as a grain crop for the southeastern USA. This experiment examined planting date, row spacing, and seeding rate effects on grain and biomass yield of spring‐sown white lupin. In 1991 and 1992, field studies were conducted in northern Alabama on a Wynnville fine sandy loam (fine‐loamy, siliceous, thermic Glossic Fragiudult), in central Alabama on a Hiwassee sandy loam (clayey, kaolinitic, thermic Typic Kanhapludult), and in southern Alabama on a Lucedale fine sandy loam (fine‐loamy, siliceous, thermic Rhodic Paleudult). Treatments included three planting dates, three row spacings (17.5, 35, and 70 cm), three seeding rates (17.5, 35, and 52.5 seeds m−1), and two cultivars (Primorsky and Ultra). Prevailing weather allowed only one planting date in northern Alabama in 1991 and 1992. In the second year of the study, only one and two plantings were successful in central and southern Alabama, respectively. Grain yields averaged 551 kg ha−1 in 1991 and 604 kg ha−1 in 1992. Grain and biomass yield was always highest in northern Alabama. Planting date affected grain and biomass yield the most in central and southern Alabama in 1991. Decreased row spacing increased grain yields as much as 10 kg ha−1 per unit decrease in spacing. Grain yields increased as much as 19 kg ha−1 for every unit increase in seeding rate. Principal component analysis of yield components created factors branch, seed mass, and mainstem, which accounted for 57, 23, and 14% of the original variance, respectively. Factors branch and mainstem were highly correlated (r < 0.75) with grain and biomass yield. Seed mass and mainstem were highly correlated with harvest index (r < 0.65). For the southeastern USA, high yields in spring‐sown white lupin will require (i) early seeding, (ii) narrow row spacing, and (iii) high seeding rates.
Diagnosing Nutrient Deficiencies in Soybean, Using M‐DRIS and Critical Nutrient Level Procedures
Authors: Bell Paul F. , Hallmark William B. , Sabbe W. E. , Dombeck D. G.
Published: July 2010

Plant nutrient deficiencies may be diagnosed with DRIS (diagnosis and recommendation integrated system) or critical nutrient level (CNL) procedures. While extensive efforts have been made to improve diagnoses by DRIS and M‐DRIS, little has been done to refine CNL diagnoses for soybean [Glycine max (L.) Merr.]. In this study, we compare diagnoses made by M‐DRIS with those from CNL and modify these procedures to improve their diagnostic accuracy. Two databases of R2 (full bloom) soybean leaf nutrient concentrations from 828 field observations of known K, Mn, Zn, or P deficiencies or sufficiencies were used for comparing the procedures. We optimized critical nutrient levels (modified CNL) using the same cases from a database that was used earlier to improveM‐DRIS. Using this optimization database, the M‐DRIS and modified‐CNL procedures had ≤ 13 misdiagnoses each of K nutrient status compared to 81 by unmodified CNL. M‐DRIS was more accurate than the two CNL procedures in diagnosing P deficiencies from cases in the optimized and independent data sets. Unmodified CNL produced 18 misdiagnoses for Zn status from cases in the independent data set, versus >27 for M‐DRIS or modified CNL. Generally, M‐DRIS was the same or more accurate than CNL methods in diagnosing nutrient status. We recommend CNL concentrations for R2 stage soybean of 3.1 g P kg−1, 15.1 g K kg−1, 17 mg Mn kg−1, and 21 mg Zn kg−1. For M‐DRIS, we recommend critical index values of zero for K and Mn, 18 for P, and −19 for Zn.
Establishment, Forage Production, and Nutritive Value of Leucaena in Central Florida
Authors: Austin M. T. , Williams M. J. , Hammond A. C. , Frank J. H. , Chambliss C. G.
Published: July 2010

Tree and shrub legumes are increasingly being recommended for forage use in the tropics and subtropics. A forage production trial to evaluate members of the genus Leucaena varying in their level of resistance to the leucaena psyllid, Heteropsylla cubana Crawford, was conducted for 3 yr at the USDA‐ARS Subtropical Agricultural Research Station in central Florida. A total of eight selections (one or more of L. leucocephala, L. pallida, or L. esculenta, and hybrids L. diversifolia ✕ L. pallida, L. pallida ✕ L. leucocephala, and L. diversifolia ✕ L. leucocephala) were evaluated for establishment, winter survival, total dry matter (DM), edible DM (stems < 6 mm diam. + leaves), percentage of edible DM, and N and in vitro organic matter digestibility (IVOMD) concentration of the edible DM. Seedlings were transplanted in a double hedgerow pattern (two rows 1 m apart, with 0.25 m within‐row spacing) in Blichton loamy fine sand (Arenic Plinthic Paleaquult) in June 1989. Winter survival of the selections ranged from 48 to 62% and did not differ among selections. The three L. leucocephala selections had the highest edible DM yields averaging 14 Mg ha−1 yr−1 DM in yr 2 and 3. Nitrogen concentration ranged from 31 to 49 g kg−1 and IVOMD concentration from 350 to 560 g kg−1, with the L. leucocephala selections exhibiting the highest IVOMD. Leucaena esculenta had lower levels of both N and IVOMD concentration, averaging 37 and 380 g kg−1, respectively. Based on yield and nutritive value, L. leucocephala selections K584 and K636, although having less psyllid resistance than the hybrids or other species, appear to be better suited for central Florida.
Traffic Pattern and Tillage System Effects on Corn Root and Shoot Growth
Authors: Kaspar Thomas C. , Logsdon Sally D. , Prieksat Mark A.
Published: July 2010

Controlled wheel traffic is one way to manage compaction in no‐till and ridge‐till systems. This study was conducted from 1990 to 1992 at Kanawha, IA, on a Webster silty clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll) to examine the effect of a wheel traffic pattern on corn (Zea mays L.) root distribution, shoot growth, and yield in no‐till, ridge‐till, and chisel‐plow tillage systems. The wheel traffic pattern was configured so that some rows would have wheel tracks on both sides, on one side, or on neither side. Bulk density, hydraulic conductivity, root length density, shoot dry weight, and yield were measured at several positions across the traffic pattern. In general, the effect of tillage systems was not significant averaged across positions. Position relative to the traffic pattern had some effect, however, on all measured parameters. Bulk density was greatest in trafficked interrows (1.36 Mg m~3) and least in untrafficked interrows (1.09 Mg m−3). Hydraulic conductivity near saturation was less in trafficked (39.4 μm s−1) than in untrafficked (104.7 μm s−1) interrows. Root length density in trafficked interrows was on average one‐third of that in untrafficked interrows. Root length density in a particular interrow also was influenced by the traffic pattern in the adjacent interrows. In 2 of the 3 yr, yields of rows with a trafficked interrow on only one side were 7% less than those of rows without trafficked interrows on either side. The wheel traffic pattern, and not just the presence or absence of wheel traffic, affected corn root growth and yield.
Carrousel Sprayer: A Self‐Cleaning Plot Sprayer for Large‐Scale Field Trials
Authors: Loussaert Dale
Published: July 2010

Large‐scale chemical screening requires efficient, accurate means for treating a large number of small experimental units. A new, self‐cleaning chemical field sprayer design was developed to increase productivity, reduce costs, and improve precision. Sprayer units are arranged symmetrically on a carrousel‐like fixture, so the sprayer units can be rotated to various fixed stations around the carrousel. The different sprayer units are loaded, sprayed, and rinsed simultaneously at the different stations as the sprayer moves through a plot. The sprayer units are rotated to the next station between plots, to allow continuous loading, application, and cleaning of the sprayer units as treatments are applied. One‐meter test plots can be sprayed every 4 s with less than 0.2% contamination between samples. The sprayer provides the capability of treating 5000 to 6000 plots per day.
Seedling Vigor and Grain Yield of ‘Roblin’ Wheat Affected by Seed Size
Authors: Gan Yantai , Stobbe Elmer H.
Published: July 2010

Commercial spring wheat (Triticum aestivum L.) seedlots contain a small proportion of small‐sized seeds. Wheat producers often remove small‐sized seeds, attempting to increase seedling vigor and grain yield. A 3‐yr study was conducted from 1989 to 1991 on a Neuhorst clay loam (Aquic Haploborolls) to determine the effect of seed size and proportion of small seeds in a seedlot on emergence, dry matter (DM) production, and grain yield of ‘Roblin’ wheat. A commercial seedlot containing seeds >2.2 but <3.2 mm in width was designated as the original seedlot and was divided into 11 sublots: five with uniform seed sizes (2.2‐2.4, 2.4‐2.6, 2.6‐2.8, 2.8‐3.0, and 3.0‐3.2 mm wide), three with variable seed sizes (2.4‐3.2, 2.6‐3.2, and 2.8‐3.2 mm wide), and three more sublots from which seeds <2.2, <2.4, and <2.6 mm wide were successively removed, with the remaining seeds planted at correspondingly reduced planting density. The use of uniform large seeds increased shoot DM in 1990 and 1991, but not in 1989. Grain yield was increased with uniform large seeds only for the early planting in 1990, where soil temperature was low. A small proportion of small seeds in a seedlot decreased shoot DM in two of six cases, but in no case decreased percent emergence or grain yield. When small seeds were removed, the remaining seeds, planted at 278 and 236 seeds m−2. had grain yields equivalent to that of the original seedlot planted at 300 seeds m−2. There is thus no need to remove small seeds from a seedlot that has been commercially cleaned, and, if uniform large seeds are available for planting, seeding rate can be reduced.
Grain Yield and Water Consumption of Ethephon‐Treated Corn under Different Irrigation Regimes
Authors: d'Andria Riccardo , Chiarandà Fabrizio Quaglietta , Lavini Antonella , Mori Mauro
Published: July 2010

Ethephon (2‐chloroethyl phosphonic acid) has been widely studied under field conditions as a growth regulator to enhance yield in corn (Zea mays L.) by controlling lodging. However, few studies have examined the interaction between ethephon and soil water availability on grain yield and growth patterns of corn. The objective of this research was to study the effects of ethephon rates and timing of applications in combination with different irrigation levels on water use, yield and its attributes, total dry matter accumulation, LAI, and plant height. The 2‐yr study (1993–1994) was carried out at the CNR Irrigation Institute experimental farm in southern Italy (14°50' E, 40°07' N; sandy‐clay soil) using corn (cv. Aida, FAO class 500). Treatments consisted of four irrigation regimes and four and six ethephon treatments for 1993 and 1994, respectively, in a randomized complete block design with three replicates. Irrigation regimes were a rainfed control (T0) and three treatments replenishing the soil water profile to field capacity to a depth of 0.7 m at different frequencies: Tw, weekly irrigation; T2, irrigation at two growth stages (VT and R1); and T4, irrigation at four stages (V7, VT, R1, and R4). Ethephon was applied both years at the V5 stage at rates of 280, 560, and 840 g a.i. ha−1. In 1994, two additional treatments were included by applying, at the V9 stage, an additional 280 g ha−1 of ethephon to treatments that had previously received 280 or 560 g a.i. ha−1. Increasing ethephon rates caused a significant reduction in LAI, plant height, and dry matter accumulation, resulting in a reduction in water consumption. In the rainfed control, increasing the ethephon rate resulted in a linear increase in yield, with maximum increase of about 200% (1.6 t ha−1) and 75% (1.7 t ha−1) in 1993 and 1994, respectively. By contrast, treatments irrigated four times showed a linear decrease of about 13% in both years. Ethephon treatment had no effect on grain yield in the Tw and T2 treatments. Kernel number was the yield component with the greatest influence on grain production. Our results suggest that ethephon may increase grain yield when natural or artificial water supply is a limiting factor.
Influence of Seeding Variables on ‘Tifton 9’ Bahiagrass Establishment
Authors: Gates Roger N. , Mullahey J. Jeffrey
Published: July 2010

‘Tifton 9’ possesses attributes similar to ‘Pensacola’ bahiagrass (Paspalum notatum Flügge var. saurae Parodi) including persistence, wide adaptation, and positive rotation effects for subsequent crops. Seed dormancy has been implicated as a cause of slow establishment of bahiagrass. Our objective was to evaluate dormancy‐reducing seed treatments on multiple seed lots with a range of seeding rates during spring, summer, or fall planting. Tifton 9 seed lots with high or low dormant seed fractions were planted without treatment, after solid matrix priming (SMP), or after accelerated aging (AA) at elevated temperature and humidity. Seed was planted during 2 yr at Tifton, GA (31°26' N, 83°35' W), or Immokalee, FL (26°27' N, 81°26' W), using seeding rates of 5.6, 16.8, or 50.4 kg ha−1. Tiller counts at 1 and 2 mo following planting, stand occupation the year following planting and dry matter harvested were obtained to monitor establishment. Seed lot had no influence on any variable evaluated. Initial stands were improved by SMP, indicating enhanced early emergence; however, SMP did not increase second‐year stands and forage yield compared with other seed treatments. Accelerated aging provided no advantage. Increasing the seeding rate resulted in greater emergence and second‐year stand coverage, but yield advantages were small. Response to planting season varied with year and location. A November freeze damaged October‐planted stands at Tifton in 1993. Stand establishment was hastened with a high seeding rate, but any advantage of high seeding rates was short lived. Seed treatments examined in this research provided little benefit, and it may be possible to reduce standard seeding rate recommendations without impairing long term establishment.
Interrupting Yield Depression in Monoculture Corn: Comparative Effectiveness of Grasses and Dicots
Authors: Porter Paul M. , Crookston R. Kent , Ford J. Harlan , Huggins David R. , Lueschen William E.
Published: July 2010

It has been well documented that monoculture corn (Zea mays L.) yields less than corn grown in certain rotations. This field study conducted from 1992 through 1995 investigated several agronomic crops, rotated with corn, for their relative effectiveness in interrupting the yield depression associated with corn monoculture. The study was conducted on a Webster clay loam (fine‐loamy, mixed, mesic Typic Endoaquolls) near Lamberton, MN. Corn grain yields were increased by a single‐year interruption with either alfalfa (Medicago sativa L.) or sunflower (Helianthus annuus L.) for each of 4 yr, with the exception of sunflower in 1992. Averaged cross 4 yr, corn yields were increased from 7.81 Mg ha−4 for continuous corn by 19 and 17% following a single year of alfalfa and sunflower, respectively. A single year of sorghum [Sorghum bicolor (L.) Moench], sorghum × sudangrass (intraspecific S. bicolor hybrid), or fallow did not improve corn yields compared with corn monoculture. This was true for each year, and when averaged across 4 yr, with the exception of the corn‐fallow rotation in 1995. Averaged across 4 yr, a 2‐yr interruption with sunflower followed by alfalfa increased corn yield by 22%. A 2‐yr interruption of sorghum followed by sorghum × sudangrass increased corn yield by 6% over that of monoculture. We conclude that the closely related grasses were relatively ineffective rotation crops for corn. Leguminous alfalfa and nonleguminous sunflower were equally effective in alleviating the corn monoculture yield depression.
Effect of Clipping on Yield and Nutritive Value of ‘Suerte’ Paspalum atratum
Authors: Kalmbacher Robert S. , Mullahey J. Jeffrey , Martin Frank G. , Kretschmer Albert E.
Published: July 2010

‘Suerte’ Paspalum atratum Swallen, a recent introduction from Brazil, is a leafy, perennial bunchgrass that may provide good cattle weight gains during the summer on wet, acid soils. Yield and nutritive value of Suerte were evaluated by clipping at 10‐ and 25‐cm stubble heights every 20, 40, and 60 d over 240‐ to 248‐d growing seasons for 2 yr at Ona and Immokalee, FL. Annual dry matter (DM) yield was affected by year and location, with 14.8 and 13.9 Mg ha−1 produced at Ona in 1992 and 1993, respectively, and 8.3 and 6.0 Mg ha−1 at Immokalee in 1993 and 1994. Eighty percent of DM yield was produced during the rainy June to September period, with little growth in cool or dry months. Location and clipping intervals also interacted for annual DM yield, which was 10.6, 17.2, and 15.1 Mg ha−1 at Ona and 5.6, 8.9, and 6.8 Mg ha−1 at Immokalee for the 20‐, 40‐, and 60‐d clipping intervals, respectively. Stubble height had no effect on annual DM yield. Yield averaged 680, 2180, and 2740 kg ha−1 at each of the 12, 6, and 4 harvests for the 20‐, 40‐, and 60‐d clipping intervals. Tiller number per plant (measured at three dates during the growing season) and plant basal area at the end of the studies increased linearly as clipping interval increased. There was no loss of plants after 2 yr of clipping at Ona, but there was a 12% loss at Immokalee. Both crude protein (CP) (97, 82, and 52 g kg−1 for 20, 40, and 60 d, respectively) and in vitro organic matter digestion (IVOMD) (578, 552, and 520 g kg−1, respectively) decreased linearly over clipping intervals. These indices changed quadratically over the growing season with greatest values in April or May (91 g CP kg−1 and 600 g kg−1 IVOMD) and lowest values in August or September (72 g CP kg−1 and 510 g kg−1 IVOMD). When rotationally grazed, Suerte should have a 20‐ to 40‐d rest period between grazings to provide high DM yield and nutritive value.
Biomass Production and Nitrogen Uptake in Corn‐Ryegrass Systems
Authors: Zhou X. M. , Madramootoo C. A. , MacKenzie A. F. , Smith D. L.
Published: July 2010

Cropping systems, plant growth stages, and applied N fertilizer rates all directly affect N uptake. A 2‐yr study was conducted to evaluate the effects of cropping system [monocrop corn (Zea mays L.) and corn intercropped with annual ryegrass (Lolium multiflorum Lam.)] on dry matter (DM) production and distribution and on N uptake and allocation in the plants during the development of corn. Each of these corn systems was produced on a fine sandy loam (Typic Humaquept), using an application of 270 kg N ha−1 in each spring. Zero N (control) and conventional N rate (180 kg N ha−1) treatments were included for monocropped corn with conventional drainage. Plant tissues of all treatments were sampled at six‐leaf, tasseling, and mid‐grain filling stages, and after physiological maturity. In both years, DM production and N uptake of intercropped corn were lower than, or not different from, the monocropped corn (depending on growth stage). The total N uptake and DM production of the intercropping system (corn + ryegrass + weeds) were greater than those of the monocrop system. Application of 270 kg N ha−1 resulted in 20% less N recovery than 180 kg N ha−1 with monocropped corn production using free drainage. Both the corn‐ryegrass intercropping system and applied N rates altered the allocation of DM and N among different parts of the corn plants. The ryegrass and weeds were not able to take up enough of the extra N after the high N rate was applied for two consecutive years. The effect of precipitation on annual ryegrass growth was an important factor in N uptake by the intercropping system.
Resistance of Cotton with δ‐Endotoxin Genes from Bacillus thuringiensis var. kurstaki on Selected Lepidopteran Insects
Authors: Jenkins Johnie N. , McCarty Jack C. , Buehler Robert E. , Kiser Jack , Williams Curtis , Wofford Tom
Published: July 2010

Transgenic cotton (Gossypium hirsutum L.) plants that express truncated versions of insect control protein genes cryIA (c) and cryIIA of Bacillus thuringiensis Berliner var. kurstaki (Bt) have been developed for managing lepidopteran pests. However, agronomic traits and pest resistance can vary among transformation events. We examined selected agronomic traits and resistance, in laboratory and field, against tobacco budworm [Heliothis virescens (F.)] and bollworm [Helicoverpa zea (Boddie)] for various transformation events of the cryIA(c) and cryIIA genes. Monsanto events with cryIIA were as resistant to tobacco budworm and bollworm as the M531 Bt event of cryIA(c), but showed some yield loss. Calgene events ST 807, ST 808, and ST 317 expressing cryIA(c) were similar to the M531 Bt event of cryIA(c) in control of tobacco budworm and bollworm. Backcrossed cultivars NuCOTN 33B and NuCOTN 35B from Delta & Pine Land Co. with event M531 Bt of cryIA(c) were highly resistant to tobacco budworm, producing more than 1400 kg ha−1 (vs. 0 on nontransgenic recurrent parents) under high levels of tobacco budworm infestation. These NuCOTN cultivars also yielded 450 to 550 kg ha−1 more lint than the recurrent parents under high levels of natural infestation of tobacco budworm in the insecticide control treatment; in the absence of tobacco budworm, NuCOTN yields were equal to or greater than for recurrent parents. The Paymaster Technologies lines with event M757 Bt of cryIA(c) were not pure for the gene, but showed excellent field resistance to tobacco budworm. Lines HX2 BG and HX3 BG showed resistance equal to the donor event M757 and yields equal to H1244. Reduced performance of event M757 in HX6 BG relative to other Paymaster lines with this event indicates a significant genotype × event interaction. Laboratory survival of bollworm after 7 d on transgenic leaves and squares was greater than survival of tobacco budworm; however, weight of surviving larvae of each species was only 10 to 15% of that on nontransgenic controls. Survival of fall armyworm [Spodoptera frugiperda (J.E. Smith)] at 7 d was only slightly lower than on nontransgenics, and weights were slightly lower. Careful evaluation of transgenic events and cultivars is necessary to ensure that the final cultivar is both resistant to target pests and has acceptable yield.
Mechanical Straw Mulching of Irrigation Furrows: Soil Erosion and Nutrient Losses
Authors: Shock Clinton C. , Hobson Joe H. , Seddigh Majid , Shock Byron M. , Stieber Timothy D. , Saunders Lamont D.
Published: July 2010

There is widespread concern about loss of sediments, NO‐3, and phosphate into surface water from irrigated farmlands. We studied the effects of 900 kg ha−1 wheat (Triticum spp.) straw, mechanically applied to irrigation furrows, on sediments and on N and P losses in the runoff. The field was on a Nyssa silt loam soil (coarse‐silty, mixed, mesic Xerollic Haplodurid) with 3% slope planted to onion (Allium cepa L.), and received 0, 50, or 200 kg P ha−1 incorporated to 0.1 m deep. Furrows were side‐dressed with 200 kg ha−1 N. Averaged across 17 irrigations, straw reduced runoff volume by 43%. Cumulative sediment lost after 17 irrigations was 17 Mg ha−1 for mulched and 333 Mg ha−1 for unmulched furrows. Straw also reduced NO‐3 and NH+4 losses in runoff solution and sediments. Total N losses during the first 6 irrigations were 33 kg ha−1 from mulched and 230 kg ha−1 from unmulched furrows. Straw effect on N loss was only through changes in the runoff volume and sediment loss. In contrast, as fertilizer P increased, PO4 concentrations in runoff solution and sediments also increased. Averaged across the first 6 irrigations, straw mulch reduced PO4 losses in the runoff solution by 59, 61, and 72%, for the 0, 50, and 200 kg P ha−1 treatments, respectively. Straw reduced PO4 losses in the sediment 15‐, 11‐, and 15‐fold for the 0, 50, and 200 kg P ha−1 treatments, respectively. Averaged across P fertilizer rates, total P lost after 6 irrigations was 18 kg ha−1 from mulched and 215 kg ha−1 from unmulched furrows. Mechanically applied straw mulch in irrigation furrows can substantially reduce soil erosion and N and P losses to surface water runoff.
Interhybrid Competition Affects Sunflower Character Expression
Authors: Johnson Burton L. , Schneiter Albert A.
Published: July 2010

Field researchers are confronted with selection of the proper plot design to assure agreement of small‐scale experimental plot results with large‐scale commercial field production. The objective of this research was to investigate the effect of plot design on expression of hybrid sunflower (Helianthus annuus L.) characters. Field studies were conducted in North Dakota at three dryland sites: Carrington, Fargo, and Prosper. lnterhybrid and intrahybrid competitive situations were attained by using one‐row or two‐row hybrid arrangements with three hybrids as possible borders. Competitive effects were determined on achene yield, achene oil concentration, achene weight, test weight, days to anthesis, head diameter, plant height, and leaf number. Plot achene yield was 20% greater when the border hybrid was a semidwarf than when border hybrids were of more conventional height. Border hybrid competitive influences on achene yield were approximately twice as great for one‐row as for two‐row arrangements. Other characters influenced by interhybrid competition were test weight, head diameter, and plant height. Characters not influenced by interhybrid competition included achene weight, achene oil concentration, days to anthesis, and leaf number. Plot border rows are recommended when evaluating characters subject to interhybrid competitive influences. An alternative approach is using one‐row or two‐row arrangements and grouping hybrids similar in plant height and maturity in the same field proximity.
Efficacy of Treatments for Delaying Senescence of Wheat Leaves: II. Senescence and Grain Yield under Field Conditions
Authors: Benbella Mohamed , Paulsen Gary M.
Published: July 2010

Longevity of leaves directly influences grain yield of wheat (Triticum aestivum L.), but is greatly diminished by environmental stresses. The objective of these studies was to identify treatments that might delay senescence of wheat leaves and increase grain yield. ‘Nesma’ wheat was grown on a heavy clay soil at Meknes, Morocco, for two seasons, the first characterized by mild stress and the second by more severe stress from inadequate precipitation and high temperature. Three planting dates, two seeding rates, and foliar applications of NH4NO3, and KH2PO4 in randomized complete block designs were tested for efficacy in delaying senescence of leaves as measured by proteolytic activity, chlorophyll and protein concentrations, and grain yield. Advancing the planting date from early December, the optimum time, to November in the first year and delaying planting until January in the second year reduced grain yields in both seasons. Increasing the seeding rate from 200 to 400 kernels in m‐2 increased grain yields only in the second year, and foliar applications of 10 kg N as NH4NO3 ha−1 were ineffective in both years. Foliar applications of 5 to 10 kg ha−1 KH2PO4, in contrast, often increased grain yields by 1 Mg ha−1 or more. Senescence processes were enhanced by late planting because of high temperatures during maturation and by dense seeding because of interplant competition. Treatments that increased grain yields usually slowed senescence processes. Applying dilute solutions of KH2PO4 was most effective and, after further testing, might have merit for wheat in regions where drought and high‐temperature environmental stresses occur.
Field‐Scale Nitrogen Balances Associated with Long‐Term Continuous Corn Production
Authors: Karlen Douglas L. , Kramer Larry A. , Logsdon Sally D.
Published: July 2010

Excessive residual soil NO3‐N indicates economic inefficiency for producers and increases the potential for nonpoint leaching of N to water resources. Our objective was to construct an approximate fieldscale N budget for continuous corn (Zea mays L.) grown on deep loess soils in four 30‐ to 60‐ha field‐scale watersheds in western Iowa. Preplant and postemergence soil NO3‐N levels were determined for the 0‐ to 30‐cm, 30‐ to 60‐cm, and 60‐ to 90‐cm depths in April before N fertilizer was applied and again at the V6 growth stage. A simple root‐zone water balance and N removal by corn grain were determined. The 4‐yr average showed approximately 100 kg ha−1 of NO3‐N in the upper 90 cm of the root zone before an average of 168 kg of fertilizer N ha−1 was applied. Grain removal accounted for 30 to 70% of the fertilizer N. There were significant differences in grain yield and N removal among the four watersheds. Factors contributing to those differences included different fertilizer rates, tillage practices, and application times. During the four study years, an average of 50% of the applied N was available for leaching, denitrification, and/ or NH3 volatilization. High levels of residual soil NO3‐N following continuous corn production coupled with steady percolation of precipitation that infiltrated but was not used by the corn crop appear to be the two major factors supplying NO3‐N to groundwater baseflow that enters streams draining the watersheds. Based on the seasonal water balance, the most successful N management strategies will be those that minimize the amount of residual NO3‐N remaining in the soil profile at the end of the growing season.
Winter Wheat Yield Depression from Legume Green Fallow
Authors: Vigil Merle F. , Nielsen David C.
Published: July 2010

Increases in N fertilizer costs have caused some farmers to consider the use of a legume during the fallow phase of a wheat‐fallow system as an alternative N source for dryland wheat. Farmers need to know how this system will affect winter wheat (Triticum aestivum L.) production and economic returns. The objectives of this research were (i) to determine the effect of legume green fallow on subsequent winter wheat yields and economic returns and (ii) to determine optimal legume termination dates during the legume phase. Wheat yields following three legumes [Austrian winter pea, Pisum sativum L. subsp. sativum var. arvense (L.) Poir.; spring field pea, P. sativum L.; and black lentil, Lens culinaris Medikus] were compared with wheat yields following fertilized traditional summer fallow. Legume biomass, biomass N, and water use were measured at four termination dates during the green‐fallow phase of the rotation. Wheat yields following the annual legume were reduced, compared with traditional summer fallow, by 400 kg ha−1 at the earliest legume termination date and by at least 1050 kg ha−1 at all other dates. Economic analysis indicates that in drier than normal years, that returns are maximized when the legume is not grown during the fallow phase. In 1996, a wet year, returns were maximized when the legume was terminated at the second termination date or after 70% of the potential maximum legume water use. We found that 88% of the variability in winter wheat yield could be explained by legume water use the previous year. In general, the competitiveness of legume green fallow with winter wheat fallow is highly weather‐dependent and inconsistent. At current fertilizer costs, legume N (in this system) was too expensive to be considered a reasonable alternative to chemical fertilizer.
Patterns of Seed Softening in Subterranean Clover in a Cool, Temperate Environment
Authors: Evans Pedro M. , Smith Fiona A.
Published: July 2010

Asbtracts

Environmental conditions affect seed softening patterns of annual legumes. These patterns have not been well established for cool, temperate environments. This work examines the effect of genotype and of growing and softening environments on the short‐term loss of dormancy in subterranean clover (Trifolium subterraneum L.) during the summer and early autumn. Burrs of six cultivars and one accession of subterranean clover that varied widely in maturity and hardseed level were placed to soften on the soil surface, over the summerautumn period, under two contrasting environments in western Victoria, Australia: Hamilton and Telopea Downs. There were significant differences (P < 0.05) in the rate of hardseed breakdown both among cultivars and at the two locations. At the cooler site, Hamilton, the levels of residual hardseed after the summer averaged 75% (over all cultivars and growing sites), compared with 66% at Telopea Downs. There was no interaction between cultivar and location of softening. At the end of the period of field exposure the ranking from lowest to highest residual hardseed was ‘Enfield’ < ‘Leura’ = ‘Gosse’ < ‘Dalkeith’ < ‘York’ = SE008 = ‘Nungarin’. High levels of embryo dormancy in Leura indicate that this cultivar has the capacity for delayed germination via embryo dormancy. The results suggest that in cool temperate environments high seed banks of subterranean clover can be achieved due to a lower percentage of seed softening, which in turn means a potentially greater long‐term persistence of subterranean clover and the possibility of conducting 1:1 pasture‐crop rotations in a rainfall zone where consistently high grain yields may be expected.