bluuebunny/crossref_metadata_2025 huggingface dataset:
Shade Induced Changes in Flower and Pod Number and Flower and Fruit Abscission in Soybean
Authors: Jiang Hongfei , Egli D. B.
Published: July 2010

Seed number per unit area is important in determining yield in soybean [Glycine max (L.) Merr.]. Field and greenhouse experiments were conducted to evaluate the role of flowers per plant and flower and fruit abscission in determining pod and seed numbers. Two greenhouse experiments were conducted with the McCall cultivar [Maturity Group (MG) 00] and four cultivars [McCall, Hardin (MG I), Harper (MG III), Essex (MG V)] were used in field experiments in 1989 and 1990. The field experiments used either 0.38‐m (McCall and Hardin) or 0.76‐m rows (Harper and Essex) with a constant seeding rate of 26 seeds per meter. Shade cloth (63% in the greenhouse and 30 and 63% in the field) was placed over plants from R1 to maturity. Additional treatments in the greenhouse included shade from R1 to R4, R4 to R5, R5 to R6, and R4 to R8. Plants were harvested at maturity and flower and pod abscission was determined by counting both the scars marking the point of attachment of flowers and pods, and mature pods. Shade reduced pod numbers and the reductions were due to both increased flower and pod abscission and fewer flowers per plant. Both the number of nodes on the main stem and flowers per node were affected by the shade. Shade during any part of the R1 to R6 period reduced pod numbers in the greenhouse. These data indicate that environmentally induced variation in pod numbers in soybean is a result of both changes in flower and fruit abscission and the number of flowers produced.
Parameterized Model of Gramineous Crop Growth: I. Leaf Area and Dry Mass Simulation
Authors: Maas Stephan J.
Published: July 2010

Parameterization is a technique used by modelers to approximate the response of a physical system using an empirical function. This technique has the advantages that it reduces the complexity of models and often simplifies their input requirements, making the models more easily usable for operational purposes. In this study, a relatively simple model of leaf area and dry mass growth for the gramineous crops was developed to demonstrate the use of parameterization. Results of model simulations for grain sorghum [Sorghum bicolor (L.) Moench], corn (Zea mays L.), and spring wheat (Triticum aestivum L.) were in reasonable agreement with field observations. The effects of plant population, fertilization level, and water stress on crop growth were implicitly accounted for in the simulations through the appropriate assignment of parameter values in empirical functions controlling leaf area appearance and senescence.
A Crop‐Specific Drought Index for Corn: I. Model Development and Validation
Authors: Meyer Steven J. , Hubbard Kenneth G. , Wilhite Donald A.
Published: July 2010

Most popular indices in use today that address agricultural drought [e.g., the Palmer Drought Severity Index (PDSI) and the Crop Moisture Index (CMI)] do not consider specific crop responses to the drought event. Thus, values produced by indices such as the PDSI and CMI cannot be directly linked to drought impacts on crop production and yield since each crop responds differently to moisture and heat stress. This paper presents a new drought index that, unlike other drought indices, is specific to a single crop (corn—Zea mays L.) and takes into consideration water use during specific periods of growth. The Crop‐Specific Drought Index (CSDI) model was developed with 8 yr of data from Nebraska's East Central Crop Reporting District (CRD), and validated with 10 yr of data from Nebraska's East Central CRD, 9 yr of data from Missouri's Northeast CRD, 8 yr of data from Wisconsin's South Central CRD, and 9 yr of data from Indiana's Central CRD. Plots of model predicted vs. actual CSDI values yielded coefficients of determination (r2) ranging from 0.32 (Central Indiana) to 0.76 (Northeast Missouri); D‐index of agreement values ranging from 0.72 (Central Indiana) to 0.90 (South Central Wisconsin); and root mean square errors ranging from 7.7% (South Central Wisconsin) to 13.4% (Northeast Missouri). The CSDI model may provide an effective drought monitoring and assessment tool for the Corn Belt of the United States.
Yield Responses of Alfalfa to Simulated Alfalfa Weevil Injury and Development of Economic Injury Levels
Authors: Peterson Robert K. D. , Danielson Stephen D. , Higley Leon G.
Published: July 2010

Although the alfalfa weevil Hypera postica (Gyllenhal)] is an important alfalfa (Medicago sativa L.) pest, relatively little is known about how defoliation at specific plant developmental stages affects yield. This study was conducted to characterize yield responses of alfalfa to simulated alfalfa weevil injury when injury was initiated at the early bud stage of the first growth cycle and to develop economic injury levels for the alfalfa weevil. The study was conducted on a silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in a 3.6‐ha alfalfa (cv. Haymaker) field near Walton, NE. Sixteen 1 by 1‐m plots were arranged in a randomized complete block design with four treatments in each of four replicates. Treatments consisted of three levels of simulated alfalfa weevil defoliation and an undefoliated check. Leaflets were removed over 10 d. Dry matter yield and stem density responses were measured for both the first and second growth cycles. Simulated alfalfa weevil injury did not affect stem density before the first cutting or during the entire second growth cycle. When injury occurred during the early bud stage, the most significant effect was the loss of leaf tissue. Yield differences among treatments for the first growth were highly significant, and the relationship between percentage defoliation and percentage yield reduction was linear both years. Defoliation injury imposed during the early bud stage of the first growth cycle did not affect yields or stem densities of the second growth cycle. Dry matter yield responses of the first growth cycle were used to calculate economic injury levels for third and fourth instars feeding at the early bud stage of alfalfa development.
Simultaneous Selection for Yield and Stability in Crop Performance Trials: Consequences for Growers
Authors: Kang Manjit S.
Published: July 2010

Utilization of genotype × environment (GE) interaction encountered in crop performance trials is an important issue among plant breeders and agronomists. Practical integration of yield and stability of performance has not been achieved. The purposes of this paper are (i) to examine consequences to growers when researchers commit Type I (rejecting the null hypothesis or Ho when it is true) and Type II (accepting the Ho when it is false) errors under a yield‐based, conventional selection method (CM) and a proposed method (yield‐stability statistic or YSi) that uses GE interaction, and (ii) to show why a greater emphasis on the stability component would be advantageous to growers. A corn (Zea mays L.) dataset was used to compute the YSi and to estimate Type II error rates for overall mean yield comparisons and for the stability‐variance statistic, σ2i(σ2i measures contribution of ith genotype to the total GE interaction) at different α (Type I error rate) and δ (minimal detectable difference) levels. When pairwise yield comparisons are made, a higher level of a will not be as harmful to growers as a higher level of β (Type II error rate). Since researchers would prefer to have power (1 ‐ β) of a test between 0.70 and 0.80, choosing an α(1) level (one‐tailed) between 0.10 and 0.20 should be appropriate. If an α(1) value of 0.25 is selected δ between 1.0 and 1.4, the Type II error rate would be almost zero. For stability, the Ho tested was that yield means of a genotype in different environments were equal, i.e., σ2i = 0. A consequence of committing a Type I error would be that growers could miss using a stable cultivar, but a consequence of committing a Type II error can be disastrous for growers, as they could choose an unstable genotype and suffer economically. A greater emphasis on performance stability during selection would benefit growers.
Microcomputer‐Based Software System to Facilitate Mechanical Planting for Agricultural Experiments
Authors: Srinivasan G. , Herrera R.
Published: July 2010

Mechanized planting for experimental purposes such as yield trials and breeding nurseries is plagued by time consuming and often error‐prone manual arrangement of seed packets, especially with multiple row planters. At CIMMYT, a four‐row planter is used when feasible, for machine planting maize. Careful planning for error‐free planting is necessary to fully realize the benefits of mechanized planting. The software system described in this article attempts to address this concern. The MACHPLAN program is written in the Pascal language using commercially available Turbo Pascal. MACHPLAN generates planting plans which can be used for a four‐row planter. Tables, created in an ASCII file, contain the field row number (going left to right, right to left in a serpentine fashion in the field) and the four‐digit mechanical planter number (from bottom to top and top to bottom in a serpentine fashion in the field). This plan is merged with a planting plan created by the user in a spreadsheet program (e.g., Lotus 1‐2‐3). Labels are then printed either using any commercially available package or by converting the spreadsheet file to a database file (e.g., dBASE). Using the mechanical planter number as key, seed packets can be arranged for machine planting.
Barley Performance under Heavy Applications of Cattle Feedlot Manure
Authors: Chang C. , Sommerfeldt T. G. , Entz T.
Published: July 2010

Approximately 4800 cattle feedlots currently operate in Alberta, Canada. The large amount of manure produced annually creates disposal problems for feedlot operators. The objective of the present study was to evaluate the effects of long‐term annual manure application on barley (Hordeum vulgare L.) performance grown on clay loam soil (Dark Brown Chernozemic, Typic Haploboroll) near Lethbridge, AB. Feedlot cattle manure was applied annually from 1973 to 1989 to irrigated plots at 0, 60, 120, and 180 Mg ha−1 (wet wt. basis) and to nonirrigated plots at 0, 30, 60, and 90 Mg ha−1. Manure was incorporated with a cultivator plus disk, rototiller, or plow. Method of incorporation did not affect barley yields, but timeliness and amount of precipitation in the current and previous year were important in determining barley response to manure treatments. When moisture conditions were below normal, manure at any rate of application had a negative effect on yield of nonirrigated barley. Under nonirrigated conditions, average barley yield was depressed by 10 and 16% for the 60 and 90 Mg ha−1 manure rates, respectively. Barley yield increased when manure was applied under irrigation, with the 60 Mg ha−1 rate producing a 20% higher average yield than the control. Although manure was disposed of annually on the soil at up to three times the recommended rate without reducing barley yields below those of the unmanured plots under irrigated conditions, such practice is not recommended because of potential soil and water pollution.
Comparison of Near‐Infrared Spectroscopy and Other Soil Nitrogen Availability Quick Tests for Corn
Authors: Fox Richard H. , Shenk John S. , Piekielek William P. , Westerhaus Mark O. , Toth John D. , Macneal Kirsten E.
Published: July 2010

Our ability to predict N fertilizer needs for corn (Zea mays L.) is improving, but more accurate and convenient tests are still needed. This work compared a new quick test for soil N availability using a near‐infrared spectrophotometer (NIRS) with three published quick tests for predicting soil N‐supplying capability (NSC) and relative corn grain yield. The other tests were the pre‐sidedress nitrate test (PSNT), nitrate concentration (at‐plant NO3), and absorbance at 200 nm of a 0.01 M NaHCO3 extract (UV‐200 test) of 0‐ to 20‐cm soil samples taken at planting. Soil samples taken at planting from 95 field experiments in Pennsylvania were analyzed at reflectance wavelengths from 400 nm to 2500 nm with NIRS. The coefficients of determination were the same (R2 = 0.49) for both linear and quadratic regressions of NSC and NIRS test values. The abilities of the four tests to predict NSC and relative corn grain yield were compared using data from 90 of the 95 experiments. The R2 values for linear and quadratic regressions between soil test values and NSC ranged from 0.49 to 0.58 for the NIRS, PSNT, and UV‐200 tests; for the at‐plant NO3 test, R2 was lower (=0.40). Eliminating sites where corn directly followed a legume, R2 values for quadratic regressions between test values and NSC increased to =0.60 for the NIRS, PSNT, and UV‐200 tests. The PSNT test was slightly better than the other tests in predicting a grain yield response to N fertilizer, but this advantage lessened when first‐year‐after‐legume sites were eliminated. No test could accurately predict relative grain yield or NSC in fields responding to N fertilizer (R2 = 0.08−0.36). The NIRS test offers a convenient, rapid, and inexpensive alternative to the PSNT for predicting whether humid‐region corn fields will respond to N fertilizer.
GENCALC: Software to Facilitate the Use of Crop Models for Analyzing Field Experiments
Authors: Hunt L. A. , Pararajasingham S. , Jones J. W. , Hoogenboom G. , Imamura D. T. , Ogoshi R. M.
Published: July 2010

A number of crop simulation models use as model inputs certain coefficients that account for differences among cultivars. These coefficients, often referred to as genotype coefficients, allow the models to simulate performance of diverse genotypes under different soil, weather, and management conditions. The models therefore can potentially be used to resolve the genotype × environment interaction into underlying coefficients. GENCALC (Genotype Coefficient Calculator) is a software package that facilitates the calculation of these coefficients for use in existing crop models. In GENCALC, the coefficients for a genotype are estimated iteratively by running the appropriate crop model with model input data and approximate coefficients, comparing the model output with actual data, and then altering the coefficients until the simulated and measured values match. The coefficients are determined in a specified sequence, starting with those that relate to developmental aspects. GENCALC also allows for calculation of averages (±SD) for the coefficients determined from specific experiments. This facilitates the selection of coefficients with the lowest variability, which can then be stored in crop‐specific database files. GENCALC comprises several programs and requires additional models and model input files, so a hard disk with =2 Mb free space is required. GENCALC will run on any IBM or IBM‐compatible computer with DOS version 3.0 or later.
Spring Nitrogen on Winter Wheat: I. Farmer‐Field Validation of Tissue Test—Based Rate Recommendations
Authors: Scharf Peter C. , Alley Marcus M. , Lei Yong Zhen
Published: July 2010

Correct N application rates on winter wheat (Triticum aestivum L. emend. Theil) are needed to minimize NO3 leaching to ground and surface waters and to maximize profit. A system for predicting optimum spring N fertilizer rates for winter wheat in the U.S. mid‐Atlantic was previously developed from a small set of experiments using a single wheat variety and in which all cultural operations were conducted by researchers. The objective of the research reported here was to evaluate whether this system could be successfully applied to the more varied environment of farmer fields. Thirty‐nine N response experiments were carried out in farmer fields over five growing seasons encompassing a wide and representative range of soil types and wheat varieties. The relationship between wheat tissue N content at Zadoks growth stage (GS) 30 and optimum N rate at GS 30 was weaker in farmer fields (r2 = 0.51) than in the researcher‐planted experiments (r2 = 0.59) but was still strong enough to be useful. Economic analyses indicate that tissue test‐based N rate recommendations increased profit by an average of $36 ha−1 relative to traditional N application practices. Apparent fertilizer efficiency was measured in 10 of the experiments and was significantly higher for N applications based on the tissue test system than for traditional N applications.
Crop Water Stress Index Models for Bermudagrass Turf: A Comparison
Authors: Jalali‐Farahani H. R. , Slack Donald C. , Kopec David M. , Matthias Allan D.
Published: July 2010

A field study assessed the accuracy and consistency of crop water stress index (CWSI) estimates determined by two empirical models and one theoretical model for evaluation of bermudagrass [Cynodon dactylon (L.) Pers. cv. Midiron] water status. The simplest empirical model, describing canopy temperature minus air temperature (Tc — Ta) of well‐watered turf as a linear function of air vapor pressure deficit, was inadequate for estimating CWSI, since seasonal averages of CWSI for well‐watered, moderately stressed, and stressed turf had corresponding coefficients of variation of 1170, 160, and 86, respectively. The CWSI values were also highly influenced by net radiation, as indicated by coefficients of determination for regressions of calculated CWSI on net radiation of 0.68, 0.76, and 0.33 for the three levels of irrigation treatments, respectively. The second empirical model included net radiation in the regression analysis of of Tc — Ta. The inclusion of net radiation in the equation for the unstressed baseline increased the coefficient of determination from 0.76 to 0.90 as compared with Model 1. The coefficient of determination for the upper baseline (which included net radiation) was 0.872, indicating a strong dependency of CWSI on net radiation. The theoretical CWSI model yielded the most accurate estimates of turfgrass water stress, as indicated by coefficients of variation for seasonal averages of CWSI for well‐watered, moderately stressed, and stressed turf of 76, 3, and 86, respectively. Midday estimates of CWSI were related to percent available extractable water, with coefficients of determination for a regression of midday CWSI on percent available extractable water of 0.988, 0.989, and 0.991 for the empirical, modified empirical, and theoretical models, respectively. The theoretical CWSI appears to be the most promising approach for a turfgrass crop water stress index for irrigation scheduling.
Simulation by NCSWAP of Seasonal Nitrogen Dynamics in Corn: I. Soil Nitrate
Authors: Lengnick Laura L. , Fox Richard H.
Published: July 2010

Computer simulation models of crop—soil systems offer the potential to increase understanding of soil N cycle processes, thereby improving management of N resources in agricultural systems. NCSWAP (Nitrogen, Carbon, Soil, Water, And Plant) is a comprehensive, deterministic computer model of the plant‐soil system that simulates seasonal soil C and N cycles under the control of temperature, moisture, microbial activity, and crop growth. The objective of this study was to validate NCSWAP using data collected during a 3‐yr N‐rate study in central Pennsylvania that investigated seasonal N dynamics in corn (Zea mays L.) provided with N as liquid dairy manure or as NH4NO3. Seasonal soil NO3 concentration in the upper soil layer, seasonal aboveground N accumulation by corn, and water leached past 1.2 m during the second year of the study were used to calibrate input values controlling soil water flow and NO3 production from mineralization of soil organic N sources. The validation of NCSWAP identified several limitations in the water flow and C and N cycling submodels as well as in the potential of the model to simulate seasonal N dynamics in corn. Validation simulations were about as accurate as calibration simulations, reflecting the ability of the model to simulate C and N dynamics without recalibration from year to year. Much of the simulation error was related to an overestimation of NO3 leaching caused by the inability of the model's microporous flow submodel to simulate the macropore‐influenced water flow in the well‐structured soil used in the validation.
BEANGRO: A Process‐Oriented Dry Bean Model with a Versatile User Interface
Authors: Hoogenboom Gerrit , White Jeffrey W. , Jones James W , Boote Kenneth J.
Published: July 2010

Microcomputer‐based crop simulation models are increasingly used in agricultural research. Although most models have been developed for specific applications, there is a trend toward developing more versatile models, with user interfaces that permit a wide range of applications without the user having to modify the model structure. BEANGRO is such a versatile, user‐friendly simulation model for dry bean (Phaseolus vulgaris L.). It is written in the FORTRAN computer language and operates on personal computers. The flexible user interface allows researchers to specify diverse model inputs and outputs, easily compare simulation results with observed data, and conduct simulation experiments interactively through menu‐driven options for sensitivity analysis. BEANGRO follows the standard file formats of the Decision Support System for Agrotechnology Transfer (DSSAT) software system, and may be used within DSSAT to assess effects of different agricultural management practices for runs over multiple years using either historical or generated weather data. The model responds to environmental variables (including air temperature, solar radiation, precipitation, and soil moisture retention characteristics), as well as to crop management conditions. Cultivar traits are specified through an input file, and traits may be modified interactively. BEANGRO operates at daily time steps and simulates bean growth and development from planting until harvest maturity. This traditional process‐oriented dry bean model and its user interface has created an interest among nontraditional modeler users and has been distributed to researchers for application in various projects, ranging from landuse planning to plant breeding and plant physiology.
A Compression‐Suction‐Temperature (CST) Cell for Simulating the Physical Environment of Preemergent Seedlings
Authors: Weaich K. , Bristow K. L. , Cass A.
Published: July 2010

Field investigations of the influence of soil physical conditions on seedling emergence are hampered by a lack of control and reproducibility of the physical variables. Controlled environment studies frequently fail to adequately simulate field conditions and seldom permit investigation of interactive physical conditions. In this paper, we describe a compression‐suction‐temperature (CST) cell designed to enable investigation of the response of preemergent seedlings to various strength and temperature regimes under unsaturated conditions. The cells allow independent control of soil strength, temperature, and matric potential. Suction within the CST cells is controlled by a hanging water column, soil strength by application of a uniaxial load, and soil temperature by a combination of heating and cooling of the upper and lower cell boundaries. Shoot growth in six cells was uniform, reflecting the minimal temperature discrepancies between cells. Temperature profiles typical of those experienced in the field were reproduced in the cells. Maize (Zea mays L.) shoot growth was responsive to temperature, with maximum elongation rates occurring at a constant temperature of 31.5 ¼. Application of 80 kPa of pressure (estimated shear strength of 42.0 kPa) to the seedbed stopped shoot growth, demonstrating the cell's capacity to alter the strength environment of the preemergent seedling.
Nitrogen Fertilizer Requirements in an Annual Dryland Cropping System
Authors: Halvorson Ardell D. , Reule Curtis A.
Published: July 2010

Reduced tillage systems in the Central Great Plains have improved precipitation storage efficiency and increased the potential to crop more intensively than with the traditional crop‐fallow system. More intensive cropping will require additional N input to maintain economical yields. Nitrogen fertility requirements for optimum crop yields in a dryland, annual cropping system were studied. Six N fertilizer rates (0, 22, 45, 67, 90, and 134 kg N ha−1) were applied to the same plots for 8 crops on a Weld silt loam (montmorillonitic, mesic Aridic Paleustoll). Spring barley (Hordeum vulgare L.), corn (Zea mays L.), and winter wheat (Triticum aestivum L.) were grown in rotation from 1984 through 1991. Although grain yields varied with crop and year, average annual grain production was 2108, 2683, 3162, 3459, 3382, and 3411 kg ha−1 for the above N rates, respectively. This included 1 yr of zero yield, when a corn crop was lost due to hail, and 1 yr of low barley yields due to heat and water stress at anthesis. This compares with annualized winter wheat yields of 1381 kg ha−1 yr−1 produced in an adjacent crop‐fallow system with adequate applied N. Application of 67 kg N ha−1 each crop year or, based on regression analysis, an average available N (soil plus fertilizer) supply of 170 kg N ha−1 was sufficient to optimize (95% of maximum) grain yields over the 8‐yr period. These results indicate a high potential for adopting more intensive dryland cropping systems in the Central Great Plains to increase water use efficiency and better maintain soil quality.
Yield Component Differences between Naked and Conventional Oat
Authors: Peltonen‐Sainio Pirjo
Published: July 2010

Grain yield of naked oat (Avena sativa var. nuda L.) is lower than that of conventional hulled cultivars. This field study was conducted to determine yield component differences between naked and conventional oat and to assess the potential of naked oat as a grain crop for northern environments. Studies were conducted at the Viikki Experimental Farm, University of Helsinki, Finland, in 1991 and 1992. Grain yield and 24 morphophysiological traits of 10 naked and 6 hulled lines were compared. Grain yield was 30% lower in the naked lines than in the hulled ones. Due to the high hull content ( ≈ 25%) of conventional lines, they produced only 10% higher groat yields than the naked oat lines. Naked lines had fewer panicles per square meter, due to their lower emergence, suggesting that a 10% increase in planting density of naked lines may result in equal groat yields of naked and conventional lines. Compared with hulled lines, naked lines had higher vegetative phytomass associated with lower harvest index. When grains were dehulled, the harvest index of naked lines did not differ significantly from that of conventional lines. The naked oat lines were characterized by fewer spikelets per panicle and more grains per spikelet compared with hulled lines. To achieve high grain yield and increase the competitive ability of naked oat, improvement in partitioning photosynthetic assimilates into grain is needed.
Plant Nitrogen Status and Boll Load of Cotton
Authors: Gerik T. J. , Jackson B. S. , Stockle C. O. , Rosenthal W. D.
Published: July 2010

Nitrogen management is important in determining cotton (Gossypium hirsutum L.) yield and fiber quality. Plant tissue tests are often used to estimate cotton N status and determine if further fertilization is needed during the growing season. This study was conducted to examine the relationship between plant tissue tests of petiole NO3 concentration and leaf N content and cotton performance as measured by vegetative growth (i.e., leaf area) and boll load. Nitrogen rates of 0, 18, 36, 72, and 144 mMN pot−1 were applied at 2‐wk intervals beginning 13 and 26 d after emergence in 1987 and 1988 through boll maturity to a greenhousegrown cultivar, Stoneville 213. The strong relationship between leaf N and leaf area and boll number (r2 = 0.80 and r2 = 0.89) 1 wk after first flower appearance suggests that the transition period between vegetative and boll development is a critical time to assess cotton's N status in relation to yield. Nitrogen deficits had little effect on boll weight, boll period duration, and number of main stem nodes. Although boll weight decreased with increasing N deficit, final boll weight of the high‐N plants were within 20% of the plants receiving low N supply. The relationship between leaf N and petiole NO3 content, was best described by Y = a + bXC; however, with this function only one‐half of the variation in leaf N was accounted for by variation in petiole NO3 content (r2 = 0.48). Leaf area and boll number were poorly correlated with petiole NO3 content. Leaf N content was a better predictor of cotton vegetative growth (as indicated by LAI) and boll number than petiole NO3 content, particularly when measurements are made 1 wk after first flower.
Alfalfa Yield and Quality Are Affected by Soil Hydrologic Conditions
Authors: Buscaglia H. J. , van Es H. M. , Geohring L. D. , Vermeulen H. C. A. M. , Fick G. W. , Lucey R. F.
Published: July 2010

Soil water management practices may affect crop growth by reducing periods of excess or shortage of soil water. The objective of this study was to evaluate forage yield and quality as affected by soil hydrologic conditions imposed by four water management practices. The experiment was conducted on a Muskellunge sandy clay loam soil (fine, mixed, frigid Aeric Ochraqualf) in northern New York during three growing seasons (1989–1991), each involving three cuttings of an alfalfa (Medicago sativa L.)—timothy (Phleum pratense L.) intercrop. Treatments consisted of (i) drain open at all times (OD); (ii) drain closed at all times (CD); (iii) drain open in winter, closed in summer (SC); and (iv) drain open in winter and the water table at a target 0.6‐m depth using a weir and supplemental irrigation in the summer (SW). Lack of drainage under CD resulted in longer periods of soil saturation and reduced yields by 9 and 16% compared with OD in the first and second growth cycle of 1990 and by 17% during the first growth cycle of 1991. Increased soil wetness after drain closure under SC did not result in yield increases compared with conventional drainage during dry periods and caused a small decrease during a wet growth cycle. Maintaining a water table at 0.6‐m depth resulted in 30% yield increase in the dry year 1991, but none in 1989 and 1990. Soil temperatures were not affected by water management. When yields were reduced, crude protein and elemental (P, Ca, K, Mg) concentrations were generally higher, and fiber and lignin levels were generally lower, indicating that increased forage quality partially compensates for lower yields, especially under excess water conditions.
An Extended Model of Forage Grass Response to Applied Nitrogen
Authors: Overman A. R. , Wilkinson S. R. , Wilson D. M.
Published: July 2010

A simple model is needed that relates forage grass production (yield and N removal) to management factors (applied N, harvest interval, and water availability). The objective of this analysis was to extend a previous model to include quantitative coupling between yield and N removal in response to applied N for perennial grasses. The extended model was developed from three postulates: (1) annual dry matter yield follows logistic response to applied N, (2) annual plant N removal follows logistic response to applied N, and (3) the N response coefficients are the same for both. Three additional consequences derive from these postulates: (i) plant N concentration response to applied N follows a ratio of logistic functions, (ii) annual dry matter yield and plant N removal are related by a hyperbolic equation, and (iii) plant N concentration and plant N removal follow a linear relationship. Data from a field study in Louisiana with dallisgrass [Paspalum dilatation Poir.] grown on Olivier silt loam (fine‐silty, mixed, thermic Aquic Fragiudalf) were used to demonstrate applicability of the model and to illustrate procedures. Analysis of variance supported Postulate 3 for these data, with an overall correlation coefficient of 0.9990. Plant N concentration (Nc for this study was bounded by 11.8 <Nc< 27.5 g kg−1. Maximum yield for the study reached 57% of potential yield at plant N removal of 427 kg ha−1. Potential yield of 27.5 Mg ha−1 appears to be in the range of values reported in the literature. Further use of this model should provide added insight into the coupling among various mechanisms that control forage production.
Responses of Kura Clover to Sheep Grazing and Clipping: II. Below‐Ground Morphology, Persistence, and Total Nonstructural Carbohydrates
Authors: Peterson Paul. R. , Sheaffer Craig C. , Jordan Robert M. , Christians Charles J.
Published: July 2010

Below‐ground morphology and total nonstructural carbohydrate (TNC) reserve patterns may explain the excellent persistence of kura clover (Trifolium ambiguum M. Bieb.). Our objective was to determine the effects of frequent clipping and sheep (Ovis spp.) grazing on the below‐ground morphology, TNC reserves, and persistence of kura clover. Clipping and sheep grazing experiments were initiated on a 5‐yr‐old stand of ‘Rhizo’ kura clover on a Waukegan silt loam (fine‐silty over sandy, mixed, mesic Typic Hapludoll) and conducted for 3 yr. Crowns, rhizomes, and roots comprised about 25, 45, and 30%, respectively, of the total below‐ground mass sampled to a 15‐cm depth, which averaged 6600 kg ha−1. Primary crowns decreased from 95 to 55 m−2 during 2 yr of grazing, whereas secondary crowns produced by rhizomes averaged 1340 m −2 and dominated aerial shoot production. Crown, rhizome, and root TNC concentrations ranged from 87 to 212, 85 to 248, and 114 to 239 g kg −1 DM, respectively, and followed a common pattern of TNC being lowest in June and increasing linearly to a maximum in the fall. Clipping treatments ranging from three to six cuttings per year had little impact on below‐ground morphology and TNC concentrations, probably because of residual leaf area remaining after clipping. Persistence was excellent under all defoliation treatments. We conclude that established kura clover has an extensive crown‐rhizome‐root system which confers the ability to maintain adequate TNC concentrations for persistence under a range of potential defoliation regimes.
Dinitrogen Fixation and Nitrogen Transfer in Birdsfoot Trefoil–Orchardgrass Communities
Authors: Farnham Dale E. , George J. Ronald
Published: July 2010

Birdsfoot trefoil (Lotus comiculatus L.) is an important perennial forage legume used primarily for pasture. Despite its traditional usage as a source of nitrogen for cropping systems, little information is available on the amounts of atmospheric dinitrogen (N2) that birdsfoot trefoil fixes or transfers to an associated grass during long‐term stands. Field research was undertaken to compare N2 fixation and N transfer potentials of three birdsfoot trefoil cultivars and one experimental line (hereafter referred to collectively as the birdsfoot trefoil cultivars). These were seeded in binary mixtures with orchardgrass (Dactylis glomerata L.). Dinitrogen fixation and N transfer were estimated by 15N isotope dilution, using orchardgrass pure stands as a reference. Over the 2‐yr study, percentage legume N derived from fixation ranged from 93 to 95% among the birdsfoot trefoil cultivars. Dinitrogen fixation usually did not differ among cultivars within harvests. Total‐season fixed‐N yields among cultivars for the two years ranged from 90 to 138 kg ha−1. Percentage orchardgrass N derived from N2 fixation and N transfer ranged from 8 to 46%. Nitrogen transfer did not differ among birdsfoot trefoil cultivars at any harvest. Total‐season transferred‐N yields ranged from 4 to 42 kg ha−1, with no differences among cultivars. Under the conditions of this study, the birdsfoot trefoil cultivars tested generally did not differ in their abilities to fix atmospheric N2 or to transfer fixed N to associated orchardgrass.
High Pressure Water Injection and Core Cultivation of a Compacted Putting Green
Authors: Murphy James A. , Rieke P. E.
Published: July 2010

Traditional core cultivation practices are typically performed in spring and/or fall to alleviate problems associated with soil compaction on golf course putting greens. Equipment was commercially developed that provides short‐time pulse injection of highly pressurized water that could relieve soil compaction stress while limiting playing surface disturbance. This study evaluated the response of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) growing on a modified loamy sand (originally a fineloamy, mixed, mesic, Typic Hapludalf) to hollow tine cultivation (HTC) and high pressure water injection cultivation (WIC). Cultivation treatments were applied three and two times in 1988 and 1989, respectively, on an experimental putting green receiving periodic compaction from rollers (50 kPa). Water injection was equal or superior to hollow tine cultivation in reducing soil bulk density, and increasing porosity and saturated hydraulic conductivity in the 0‐ to 76‐mm depth zone. Hollow tine cultivation reduced soil strength by 1.33 MPa at the 30‐mm depth compared with no cultivation, but only water injection cultivation provided a significant reduction in soil strength of the 70‐ to 100‐mm depth zone. Both methods increased bentgrass shoot growth rate after treatment compared with no cultivation. Hollow tine cultivation reduced surface (0 to 100 mm) root weight density by 26%, as well as root numbers observed along minirhizotrons, compared with the check and WIC plots. Root and crown damage and root removal during HTC was the likely cause for this response. Water injection cultivation offers the potential for routine cultivation during periods of high site usage and environmental stresses with either no effect or an improvement in visual quality.
Soil Sampling with a Modified Chainsaw
Authors: Ashworth John , Crépin J. M. , Repski Rip
Published: July 2010

In uncultivated fields containing residual banded fertilizer, wide variability in analytical results for individual soil samples can make it extremely time‐consuming to obtain a representative composite for analysis. This study was done to test whether individual soil samples, taken from a series of slots cut across bands of residual fertilizer, would show less analytical variability than samples taken at a series of random points. A chainsaw fitted with a catcher was used to collect soil from slots cut across stubble rows, and an auger used to take point samples, on field plots with residual N, P, K, and S fertilizer banded ≈ 6 cm deep at 18‐cm spacing. Plots at eight sites on Typic Cryoborolls, mostly clay loam in texture, were sampled after harvest. The samples were analyzed for extractable N, P, K, and S. Out of 32 comparisons, coefficients of variation (CV) in analytical results were lower in 28 instances when samples were taken by chainsaw rather than by auger. Judging from CV values, a composite sample made up of soil from ≈ 15 slots would in most cases have given an accurate estimate of residual amounts of all four crop nutrients at the eight sites. With an auger, from 40 to 50 sampling points would have been required for comparable accuracy. The results suggest that, when sampling uncultivated soil containing residual banded fertilizer, a valid composite sample could be obtained more conveniently by slot‐cutting than by sampling at points.
Rhizotrons: Their Development and Use in Agricultural Research
Authors: Klepper Betty , Kaspar Thomas C.
Published: July 2010

Rhizotrons are tools for making nondestructive, repeated observations and measurements of root systems. Primary objectives of this review are to report features of several rhizotrons and to describe the types of research that have been and will be performed in them. Rhizotrons are permanent installations, generally with transparent viewing surfaces for measurement of plant roots. Typically, these facilities have control of drainage and are well instrumented for macroscopic and microscopic observations of roots. They are excellent for getting descriptive and semiquantitative data on simultaneous changes in root and shoot systems of different cultivars or species over seasons or in response to treatments. Rhizotrons can also be designed to allow measurement of mass balances of water and nutrients within the rooting volume of a crop. Future uses of rhizotrons will include research on the root‐zone behavior of soil nutrients such as NO3, detailed measurement of processes such as diffusion and mass flow of liquids and gases in soils, and development of better information on the role of soil biota in nutrient cycling and uptake. This new information will permit better definition of the role of root systems in plant growth and development.
Integration of Weed Management and Tillage Practices in Spring Dry Pea Production
Authors: Young F. L. , Ogg A. G. , Boerboom C. M. , Alldredge J. R. , Papendick R. I.
Published: July 2010

Information about long‐term efficient production systems is needed to assist growers in adopting conservation cropping practices for spring dry pea (Pisum sativum L.), a biologically important pulse crop grown in the Pacific Northwest and Canada. From 1985 to 1991, an integrated pest management field study examined the influence of three weed management levels and two tillage regimes on the productivity of spring pea grown in a winter wheat (Triticum aestivum L.)‐spring barley (Hordeum vulgare L.)‐spring pea rotation. When averaged over 6 yr, spring pea yielded the least with the minimum weed management level in either the conservation (chisel plow) or conventional (moldboard plow) tillage system. In conservation tillage, yields were similar at the moderate and maximum weed management levels and up to 335 kg ha−1 more than pea with the minimum weed management level. In contrast, in conventional tillage, yields were increased only at the maximum level of control compared with the minimum level. Yields of pea grown under conservation tillage were equal to or greater than yields in conventional tillage when averaged over weed management levels. The reduced tillage system on the integrated pest management project met conservation compliance for both planting pea into spring barley residue and planting winter wheat into pea residue. In addition to reducing erosion, the conservation pea production system did not increase substantially herbicide use and cost, thus maintaining environmental quality.
Nitrogen Use Efficiency of Split Nitrogen Applications in Soft White Winter Wheat
Authors: Sowers Karen E. , Pan William L. , Miller Baird C. , Smith Jeffrey L.
Published: July 2010

Nitrogen use efficiency (grain weight per unit of N supplied from soil or fertilizer) can be reduced by overfertilization, suboptimal yields, and N losses. Nitrogen is typically fall‐applied in eastern Washington for soft white winter wheat (Triticum aestivum L.) production, and is therefore subject to overwinter losses or accumulation in deep soil layers. Increasing grain protein levels of soft white winter wheat have been attributed in part to excessive N application rates and high residual N levels. Spring N applications were evaluated over four site‐years as an option to all‐fall applied N for reducing N inputs and improving N use efficiency, thereby allowing producers to maintain productivity while controlling grain protein. Five to six N rates ranging from 0 to 140 kg ha−1 for the all‐fall N applications were compared with fall‐spring split applications of 84 to 140 kg total N ha−1. Nitrogen was applied in the spring by topdressing (TD) or with a spoke‐wheel point‐injection (PI) system. A 15N experiment was conducted at two locations during the second year to quantify N uptake from fertilizer and soil N. High preplant residual N conditions resulted in limited responses to added N. Nitrogen use efficiency was 26 to 44% lower in the 140 kg ha−1 fall‐applied N treatments than in the zero‐N control. Reduced N use was related to N losses from the system and to decreased N utilization efficiency (grain weight produced per unit plant N). Spring‐applied N, with point injection or topdressing, maintained or increased N use efficiency compared with equivalent all‐fall N rates of 84 and 112 kg N ha−1. More 15N‐labeled fertilizer (7–16% more) was recovered with a split N application than with fall‐applied N at the same total rate of 112 kg N ha−1. At maturity, 68% of plant N was from soil sources with a split application, compared with 80% with an all‐fall application. These results suggest spring‐N applications with point injection or topdressing can improve fertilizer N recovery and N use efficiency over preplant applications in dryland winter wheat.
Growth of Soybean Stressed by Nematodes, Herbicides, and Simulated Insect Defoliation
Authors: Browde Joseph A. , Pedigo Larry P. , Owen Michael D. K. , Tylka Gregory L. , Levene Brian C.
Published: July 2010

Soybean [Glycine max (L.) Merr.] responses to combinations of stress factors generally are unknown. Research was conducted in 1989, 1990, and 1991 to quantify growth responses to stresses from soybean cyst nematode (SCN; Heterodera glycines Ichinohe), acifluorfen {5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐2‐nitrobenzoic acid} plus bentazon [3‐(1‐methylethyl)‐(1H)‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide] herbicides, and simulated green cloverworm [GCW; Plathypena scabra (F.)] defoliation. Treatments were combinations of at‐planting SCN soil density, acifluorfen plus bentazon rate, and simulated GCW defoliation level. Herbicides were applied at V6 soybean development, and GCW feeding was simulated from R2 to R4 soybean development. Plant growth was quantified at V4, R2, and R4 developmental stages. Herbicide stress was assessed by leaf stomatal conductance and visible foliar injury. Herbicides reduced conductance and caused visible injury each year, and limited growth (plant height, leaf area, pod number, and dry weight of leaf, pod, and stem plus petiole) in 1990 and 1991. Likewise, defoliation reduced leaf area each year, but reduced growth (plant height and leaf dry weight) in 1990 and 1991 only. Uncontrolled environmental factors probably confounded growth responses in 1989. Although no herbicide × defoliation effects on growth were found, defoliation caused greater reductions in canopy quantity and quality for herbicide‐injured plants in 1990 and 1991. Targeted stress from SCN was achieved in 1990, and interaction with herbicides decreased conductance, increased visible herbicide injury, and reduced leaf area, plant height, pod number, and pod dry weight. These data support the potential for stresses from SCN and acifluorfen plus bentazon to cause more‐than‐additive reductions in soybean growth.