bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant Nutrient Flow in the Managed Pathways of an Intensive Dairy Farm
Authors: Bacon S. C. , Lanyon L. E. , Schlauder R. M.
Published: July 2010

The magnitude, and spatial and temporal patterns of nutrient flow in the managed pathways of a farm are related to farm management decisions and interact with the biological processes of the farm. These descriptions of nutrient flow can be part of a nutrient management process that is consistent with the specifics of individual farm operations and particular farm performance goals. Nutrient flow in the managed pathways of a Pennsylvania dairy farm was measured at farm, field, and livestock unit boundaries using on‐farm equipment scales, farm records, and material sampling and analysis. Farm nutrient inputs of N, P, and K were twofold or more greater than outputs of these nutrients in the managed pathways. The temporal distribution of flows was closely related to the livestock activities on the farm. Manure storage capacity and crop developmental stage were significant factors influencing the timing of nutrient flows to and from the fields. Nutrient inputs and outputs in the managed flows at the boundary for the set of all fields were approximately equal except for the negative calculated crop available N balance. However, the range in balances for individual fields was large. Manure N and potential biological N fixation were not used efficiently on this farm due primarily to the volatilization of N from manure and the application of manure to alfalfa. Additions of nutrients to the farm in the managed flows decreased by 26, 60, and 43% for N, P, and K, respectively, in the 2nd yr of the study due primarily to less purchased animal feeds.
Pepper Transplant Response to Root Volume and Nutrition in the Nursery
Authors: Bar‐Tal A. , Bar‐Yosef B. , Kafkafi U.
Published: July 2010

The use of pepper (Capsicum annuum L.) seedlings for transplanting in the field is common. However, very little is known about the effects of root volume and nutrition in the nursery on transplant performance in the field. The objective of this work was to study the effects of N and P supply to various root volumes on pepper seedling development and growth in the nursery, and fruit yield and harvest earliness in the field. Seedlings were grown in trays packed with a peat/vermiculite mixture, 1:1 (v/v). The plants were irrigated by soaking the trays in the studied nutrient solutions. Phosphorus and N concentrations in the test solutions were 0.1, 0.5 and 1.0 mM P and 1, 5, 10 and 15 mM N (NH4/NO3 = 1:1). Root volumes (V) were 5, 15, 35, 65 and 700 cm3 plant−1. Following transplanting, all plants in the field received identical, optimal irrigation and fertilization. Seedling weight increased with increasing root volume and nutrient concentrations in the irrigation water. The optimal solution for pepper seedlings in the studied growth medium was 5 mM N and 0.5 mM P. Nitrogen, P and K contents in tops of optimal seedlings (V = 700 cm3) were 39, 5.5 and 67 g kg−1 dry matter, respectively. Seedling development was retarded when top's content was <25 mg N kg−1 and <3.1 mg P kg−1. Four weeks after transplanting plant weight in the field increased and fruit ripening was hastened when the top's dry weight at planting time increased from 63 to 285 mg plant−1. Plant relative growth rate and total fruit yield were unaffected by nursery treatments.
Root Quantification by Edge Discrimination Using a Desktop Scanner
Authors: Pan W. L. , Bolton R. P.
Published: July 2010

Root characterization methods are constrained by one or more of the following factors: cost, limited resolution, or time of analysis. Most length‐determination methods are based on the line‐intersect principle. An alternate method using a flatbed scanner and a microcomputer was developed. Algorithms were developed to estimate root area, length, and diameter (mean root width). Two‐dimensional area is estimated by summing the number of pixels representing a single or group of gray scales. Length and width are calculated as a function of the area, the number of edge pixels, and the number of pixels on diagonal edges. Human hair, plastic line, and root samples, with widths from 0.13 to 1.65 mm and lengths near 100 cm, were measured manually and with image analysis. Mean lengths of four repeated scans after reorientation were within 0.4 to 1.2% of manually determined lengths. Four repeated scans (118 pixels cm−1) of reoriented roots yielded length estimates with C.V.'s from 0.31 to 2.18% on low density samples (<500 cm). At higher densities, increased frequency of adjoining edges resulted in underestimated lengths and overestimated widths. A correction for these inaccuracies, based on the determination of mean width on a low density subsample, provided accurate root length estimates up to 10 m. Overall, this method overcomes limitations of other procedures such as (i) the requirement for random orientation of the sample necessary with the line‐intersect method, (ii) reliance on a comparison to a standard curve from non‐root objects, and (iii) inadequate imaging resolution.
Ear Position and Vertical Distribution of Leaf Area in Corn
Authors: Dwyer L.M. , Stewart D.W. , Hamilton R.I. , Houwing L.
Published: July 2010

Leaf area distribution determines the interception of radiation for photosynthesis. A method of analysis was developed to quantifiy differences in vertical leaf area distribution in a corn (Zea mays L.) canopy. A third‐order polynomial accurately described the relationship between leaf area index (LAI) and plant height (both normalized with respect to their maxima) for a range of normal and “leafy” licensed and experimental plant lines during the late vegetative and early grainfilling stages (r2≥0.85). The shape of the polynomial reflected the bell shape of individual leaf area versus leaf number curves, with the densest leaf area in the mid‐portion of the canopy. When ear position was marked on the polynomial plot, the proportion of leaf area above the ear was easily compared among lines. The proportion of total LAI above the ear varied from 0.52 to 0.83 in 1986 and from 0.63 to 0.86 in 1987. The actual LAI above the ear was in a relatively narrow range of 2.0 to 3.2 for all tested licensed lines. The analysis described will facilitate comparison of ear position and vertical distribution of leaf area among different plant lines and crop management practices.
Soybean Planting Patterns in Relation to Yield and Yield Components
Authors: Ikeda T.
Published: July 2010

Research on the effect of soybean [Glycine max (L.) Merr.] planting patterns on yield have produced variable conclusions; some indicated that high yield was produced by equidistant patterns, but others indicated that clear differences in yield were not found. Therefore, the objective of this study was to determine whether different planting patterns effect soybean yield, and to determine which planting patterns produce the highest yield. These experiments were conducted in the field at Niigata University, Niigata, Japan for 3 yr on a loamy sand soil at a plant population of 25 plants/m2, using the cultivar Enrei (Group VII). Planting patterns varied across years and included wide rows (70 or 80 cm), square and rectangular patterns, and twin row arrangements with two narrow rows 10 or 20 cm apart with 50 or 60 cm between the twin rows. The results indicated that (i) yield tended to decrease with wider row widths and narrower within row spacings. Thus, it should be possible to increase yield with square patterns, (ii) A constant 70‐cm width with the twin‐zigzag patterns (plants in the twin rows offset from each other) yielded higher than twin‐rectangular ones (plants in the twin rows across from each other). In all cases, the increased yields came from an increase in seeds per plant; weight per seed was not affected.
Integrated Weed Management Techniques to Reduce Herbicide Inputs in Soybean
Authors: Buhler Douglas D. , Gunsolus Jeffrey L. , Ralston Donald F.
Published: July 2010

Information on integrated weed management systems is needed so that producers can develop systems that minimize the environmental impacts of weed control without sacrificing profitability of crop production. Reduced rates of broadcast‐ or band‐applied alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide] plus metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4H)‐one] and rotary hoeing, each in combination with between‐row cultivation, were evaluated for weed control in soybean [Glycine max (L.) Merr.]. One or two between‐row cultivations allowed for a 50 to 75% reduction in the amount of herbicide used without reducing weed control or soybean yield. Reducing herbicide rates also decreased soybean injury. Two passes of a rotary hoe reduced weed densities up to 75% and increased the effectiveness of subsequent cultivations. However, two passes of the rotary hoe reduced soybean density as compared to other treatments. In 1989, under low weed densities, several mechanical weed control systems resulted in soybean yields similar to the weed‐free control. In 1990, under greater weed densities, mechanical weed control systems resulted in reduced soybean yields compared to weed control systems that included herbicides. Based on the results of this research, switching from chemical‐intensive systems to mechanical weed management systems under high weed pressure is not advisable. Under high weed pressure, reduced rates of herbicide, broadcasted or banded over the soybean row, in combination with cultivation provided excellent weed control. Mechanical weed control as a part of an integrated weed management system should maximize weed control while minimizing herbicide use.
Animal Preference of Tall Fescue during Reproductive Growth in the Spring
Authors: van Santen Edzard
Published: July 2010

Animal preference may create problems when diverse tall fescue (Festuca arundinacea Schreb.) germplasm is evaluated under grazing. The objective of this experiment was to relate differences in animal preference of tall fescue populations to maturity and genetic background. In 1988, 25 entries were established in small plots at the Black Belt Substation, Marion Junction, AL on a Eutaw clay (very‐fine, montmorillonitic, thermic, Entic Peluderts) within each of four 0.8‐ha pastures. Pastures were grazed during the spring 1990 and 1991 seasons at stocking rates of 2.5, 3.75, 5.0, and 6.25 crossbred yearling Angus steers ha±1 (Bos spp.). Animal preference was measured by visually rating the amount of forage removed at 3, 6, and 13 d after grazing was begun in 1990, and after 3 and 6 d in 1991. Population‐by‐stocking‐rate interaction was significant for all preference ratings, but accounted for only 2 to 5% of the total variation. Changes in magnitude were not important. Based on bivariate plots of preference during spring reproductive growth vs. maturity, three groups were distinguishable: (i) two very early maturing populations with a low preference score, (ii) a group of 17 medium‐maturing populations with a medium to low preference score, and (iii) six late maturing populations with a high preference score. Low preference during grazing of tall fescue during spring reproductive growth was an attribute of mediterranean germplasm and of populations selected in the southern USA. A comparison of ‘Georgia 5’ EI vs. EF tall fescue revealed that cattle preferred the endophyte free material at all rating times during reproductive growth in the spring in both years. This preference can be uniquely attributed to the absence of the endophytic fungus Acremonium coenophialum Morgan‐Jones and Gams.
Contribution of Bean Morphological Characteristics to Weed Suppression
Authors: Wortmann Charles S.
Published: July 2010

Weed control has a high labor requirement in small‐scale bean (Phaseolus vulgaris L.) production systems in eastern Africa, and productivity of these systems often is constrained by labor availability at weeding times. This study was conducted to determine which morphological characteristics of bean contribute to weed suppression and to assess the feasibility of breeding genotypes for improved ability to suppress weeds. Morphological characteristics and grain yield of 16 to 20 bean genotypes, and weed biomass weight at harvest, were measured over three seasons. Mean weed biomass at time of bean harvest ranged from 55 to 120 g m−2 for the 15 genotypes evaluated for three seasons. The ability to suppress weeds was found to be independent of bean growth habit, but was related to leaf size, leaf area index, and plant growth rate. Leaf size and leaf area index accounted for 73% of the variation among genotypes for weed biomass at the time of bean harvest. These traits were related positively to bean seed yield. Inclusion of large leaf size and high leaf area index as criteria for selecting high‐yielding genotypes with improved ability to suppress weeds should be feasible.
Nitrogen Fertilization of Cotton Cultivars of Differing Maturity
Authors: McConnell J. Scott , Baker William H. , Miller David M. , Frizzell B. Stephen , Varvil J. Joseph
Published: July 2010

Management of N nutrition of cotton (Gossypium hirsutum L.) is one of the most critical aspects of successful cotton production, but growth and yield responses of individual cotton cultivars to N fertilization is relatively unknown. The objective of this research was to evaluate the responses of three cotton cultivars (Arkot 518, Stoneville 453, and Deltapine 90) to soil‐applied N fertilization rates. The study was conducted for 3 yr on a Hebert silt loam soil (fine‐silty, mixed, thermic Aeric Ochraqualf). Few significant (ɑ = 0.05) cultivar × N rate interaction differences were found, although main effects of the N treatments and the cultivars were evident. The most pronounced responses of the cotton were found as an effect of the N‐fertilization treatments. Nitrogen rates in excess of 112 kg N ha−1 did not significantly increase seed cotton yields in any year of the study. The mean yield of the cultivars among N rates was significantly different in only one year of the study. Earliness of the cotton was reduced by increasing N rate, as indicated by significant differences in nodes above white flower (NAWF) measurements. Significant differences were also found in the NAWF measurements for the cultivars, thereby inferring maturity differences among the cultivars tested. Of the cultivars evaluated, Arkot 518 was earliest, followed by Stoneville 453, and then Deltapine 90. Significant interactions of cultivar and N rate were found only in three dates of NAWF (1991), and one date of petiole NO‐3‐N content (1990). Soil samples taken after 3 yr of continuous fertilization treatments showed a significant NO‐3‐N accumulation at the 15‐ to 45‐cm depth only in plots treated with 224 kg N ha−1.
Modeling the Influence of Postdirected Sethoxydim on Corn Yields
Authors: Smart James R. , Weiss Albert , Mortensen David A.
Published: July 2010

Postdirected sethoxydim 2‐[1‐(ethoxyimino)butyl]‐5‐[2‐(ethylthio) propyl]‐3‐hydroxy‐2‐cyclohexen‐1‐one, used to control monocot weeds, is known to reduce corn (Zea mays L.) yields. The objective was to develop an integrative model combining a growing plant with the effect of sethoxydim. CERES‐Maize (version 1.0) was modified to respond to herbicide‐induced grain yield reductions by incorporating a herbicide stress factor and the stress duration into calculation of the daily biomass production. Herbicide stress was defined as the difference in net photosynthesis between treated and nontreated plants. A seasonal herbicide stress factor (0–1) was determined from field measurements of treated and nontreated corn yields as a function of sethoxydim concentration (110 and 220 g a.i. ha−1) for all application dates. This factor was modified to reflect the period of the herbicide stress duration by scaling it to the fraction of time the sethoxydim was active. Field experiments were conducted using four corn hybrids (Pioneer 3475, 3379, 3377, and 3183). Data from 1988 field experiments were used to calibrate the genetic inputs for each hybrid and develop a herbicide stress relationship. The data collected in 1989 were used to validate the modifications made to CERES‐Maize. Overall, the model predicted that sethoxydim use would reduce corn yields, and this trend was consistent with independently measured field data. Based on the ratio of treated to nontreated yields for simulations and measurements, the model predictions underestimated the sethoxydim effect for the hybrids 3475, 3379, and 3183.
Time of Salt Stress Affects Growth and Yield Components of Irrigated Wheat
Authors: Francois Leland E. , Grieve Catherine M. , Maas Eugene V. , Lesch Scott M.
Published: July 2010

Salt tolerance of wheat (Triticum aestivum L.) is known to change during different stages of growth. The effects of salinity on growth and yield components of wheat at different stages of growth were determined in a 2‐yr field plot study at Brawley, CA. Four salinity levels were imposed on a Holtville silty clay [clayey over loamy, montmorillonitic (calcareous), hyperthermic Typic Torrifluvent] by irrigating with waters salinized with NaCl and CaCl2(1:1 w/w). Electrical conductivities of the irrigation waters were 1.4, 10.0, 20.0, and 30.0 dS m−1 in 1989, and 1.4, 8.0, 16.0, and 24.0 dS m−1 in 1990. The three irrigation treatments were (i) salinity imposed throughout the growing season, (ii) saline irrigation initiated after terminal spikelet differentiation (TSD), and (iii) saline irrigation discontinued at TSD. Growth and yield components measured were straw yield, total above ground biomass, number of spikelets per spike, number of kernels per spike, individual kernel weight, number of tillers per plant, and number of tiller spikes. Continuous salinity throughout the growing season significantly reduced all growth and yield components. Salinity imposed prior to TSD reduced the number of spikelets per spike and the number of tillers per plant, whereas salinity imposed after TSD significantly reduced only kernel number and weight. In general, the effect of salinity appears to be most pronounced on the yield components that are growing or developing at the time the salt stress is imposed. Total grain yields were maintained when moderately saline irrigation waters were substituted for good quality water during part of the growing season.
Rye Residue Geometry for Faster Corn Development
Authors: Fortin M.‐C. , Hamill A. S.
Published: July 2010

Winter cereals used as cover crops in corn (Zea mays L.) production physically modify the soil‐plant environment. Springtime killing of the cover crops with herbicides leaves surface residues either standing, flat, or a combination of the two at corn planting. This study was conducted to verify how standing rye (Secale cereale L.) residue affected soil temperature, soil water, and corn development compared with flat rye residue in a sandy loam in Harrow, ON, in 1990, 1991, and 1992. In the 3 yr, volumetric soil water content was similar in both treatments, but seed zone daily maximum temperatures were higher under standing than under flat residue. Corn development in standing residue was faster (2 to 3 d) compared with flat residue, except if seed zone maximum temperatures were regularly in the 28 to 32° range for both treatments, such as in 1991. During vegetative stages in 1990 and 1992, plants in the standing residue were taller than plants in the flat residue. Most of these height differences were related to differences in development that were related to soil temperature. In 1991, however, which was a hot and dry year, phyllochron values indicate that developmental rates under both treatments were affected by a factor other than temperature, most likely by a lack of soil water. In 2 of 3 yr, when seed zone temperatures were often below the optimal range for corn development, standing rye residue resulted in faster plant development than flat rye residue due to a warmer seed zone. Residue treatments did not affect yield.
Grain Yield, Kernel Weight, and Disease Responses of Winter Wheat Cultivars to Chloride Fertilization
Authors: Engel Richard E. , Eckhoff Joyce , Berg Robert K.
Published: July 2010

Wheat yields in the Great Plains are frequently improved by potash (0‐0‐60 N‐P‐K) application on soils with seemingly abundant supplies of available K. The CI component in this fertilizer may cause many of the observed yield responses. Field research was undertaken to determine the effects of CI on grain yield, plant CI, kernel weight and growth rate, and foliar disease and/or disease‐like symptoms of winter wheat cultivars. Two sites with five CI levels (0, 22, 45, 90, and 135 kg ha−1) and two cultivars (Redwin, Cree) were used in 1988. Seven sites with two CI levels (0 and 45 kg ha−1) and six cultivars (Redwin, Cree, Weston, Manning, QT542, Neeley) were used from 1991 to 1992. Chloride increased yield by an average of 267 kg ha−1 (7%) at seven responsive sites. Size of yield response to CI was generally not affected by cultivar selection, but differed greatly with location. Whole‐plant CI analyses were useful in discriminating between yield responsive (≤ 3.0 g kg−1) and nonresponsive (>3.0 g kg−1) sites to CI fertilization. Improved CI nutrition enhanced plant development, increase immature kernel weights, and accelerated kernel growth during the grain‐fill period. Fertilizer CI increased mature kernel weights, up to 17%, at eight sites. Kernel weight was the most important yield component affected by CI. Physiological leaf spot in Redwin and Manning, flag leaf senescence in Weston and QT542, powdery mildew (Erysiphe graminis DC. f. sp. tritici Em. Marchal), and leaf rust (Puccinia recondita Roberge ex Desmaz. f. sp. tritici) were suppressed by fertilizer CI. These phenomena may explain in part the yield responses to CI; however, yield response to CI occurred even without foliar disease and disease‐like suppression.
Seeding Rate and Kill Date Effects on Hairy Vetch‐Cereal Rye Cover Crop Mixtures for Corn Production
Authors: Clark Andrew J. , Decker A. Morris , Meisinger John J.
Published: July 2010

Hairy vetch (Vicia villosa Roth) fixes N for corn (Zea mays L.) production, and cereal rye (Secale cereale L.) accumulates soil N to reduce potential N losses. The objective of this research was to identify optimum seeding rates of vetch‐rye cover crop mixtures at Coastal Plain and Piedmont locations in Maryland. Mixtures evaluated were 14, 21, and 28 kg vetch ha−1, and 47 or 94 kg rye ha−1 in complete factorial combination. Pure vetch, rye, and no cover crop were used as controls. Cover crops were killed in early April (early kill) and early May (late kill), followed by no‐till corn without fertilizer N. Corn grain yields were significantly higher following late‐killed covers. Coastal Plain grain yields ranged from 3.1 to 7.0 Mg ha−1 and Piedmont yields ranged from 5.2 to 10.7 Mg ha−1. Within each kill date, corn yield was highest following vetch, lowest following rye, and intermediate following all six mixtures. Cover crop yield increased by 160% in the Piedmont and 83% at the Coastal Plain location when kill was delayed. Except for pure rye, N content was 1.6 to 2 times greater by the late kill date. Total N content was equal for all vetch‐rye mixtures at each date and within location, ranging from 74 to 109 kg ha−1 for early kill, and from 136 to 219 kg ha−1 for late kill. Carbon‐to‐nitrogen ratios (C/N) were 25:1 for all mixture combinations at the Piedmont location and for mixtures with low rye component at the Coastal Plain location. The best seeding rate mixture for corn production was 21 kg vetch ha−1 and 47 kg rye ha−1. The vetch‐rye mixture can scavenge potentially leachable N, while maintaining corn yields by adding fixed N to the cropping system.
Sorghum Grain Yield Reductions Caused by Duration and Timing of Freezing Temperatures
Authors: Staggenborg Scott A. , Vanderlip Richard L.
Published: July 2010

Management practices, as well as below‐normal temperatures that occur late in the growing‐season, can delay grain sorghum [Sorghum bicolor (L.) Moench] maturity in the northern Great Plains. Delaying maturity increases the probability of a freeze occurring before the crop reaches physiological maturity. Studies were conducted during 1988 and 1989 using greenhouse‐ and field‐grown plants in Kansas to determine caryopsis weight and test weight reductions from exposure to subfreezing air temperatures. Treatments of 0, −2, and −4°C air temperatures for 2, 4, and 8 h were conducted in a growth chamber when developing grain had attained approximately one‐half of its maximum weight. A second experiment studied the effects of exposure to −2°C for 4 h at different stages of grainfill. Caryopsis weights were progressively reduced as air temperature was reduced from 0 to −4°C. Effects of exposure time to subfreezing air temperatures on caryopsis weight were not consistent from year to year. Air temperatures of −2°C or lower reduced test weight of grain from field‐grown plants, whereas only exposure to −4°C reduced test weight of grain from greenhouse‐grown plants. Exposure to −2°C for 4 h reduced caryopsis weights 81% at 200, 57% at 300, 25% at 450, and 3% at 600 growing degree days (GDD, base temperature 5.7°C) after anthesis (maturity = 850 GDD). Test weight response was similar to caryopsis weight response with test weights from plants exposed to freezing temperatures at 200 and 300 GDD after anthesis lower than at other treatment times or the control. These results indicate that minimum air temperature is the primary factor in determining caryopsis weight and test weight when grain sorghum is exposed to subfreezing air temperatures.
Conductimetric Measurement of CO2 Concentration: Theoretical Basis and Its Verification
Authors: Baker John M. , Spaans Egbert J. A. , Reece Clive F.
Published: July 2010

Atmospheric CO2 is important to plant growth and also plays a key role in the global energy balance. Thus, there are needs for reliable methods for measuring CO2 concentrations, [CO2]. One approach has been the conductimetric method, where sampled gas is bubbled through deionized water. Some of the CO2 in the air dissolves and ionizes, causing an increase in solution electrical conductivity. The method is inexpensive relative to other techniques, but usage has been limited, possibly due to its apparently empirical basis and suggestions that it must be frequently checked to correct for shifts due to temperature and other effects. We have derived the fundamental basis for the method and equations that allow [CO2] to be directly determined from measurements of solution electrical conductivity and temperature, with no empirical calibration. The equilibrium constants and ionic conductivities that are used are temperature dependent, but those dependences are well known and easily computed. The approach was tested with a system in which the conductivity was measured with time‐domain reflectometry (TDR), using a coaxial cell through which the aerated water was circulated. To maximize sensitivity, a long cell (1 m) of low impedance (19.3 Ω) was used. The system was compared against an infrared gas analyzer (IRGA) over a range of [CO2] from 0 to 1000 μmol mol−1, at three different temperatures (5, 19, and 34°C). Regression of [CO2] calculated directly from the conductivity measurements against the IRGA measurements produced a slope of 1.00, r2 of 0.997 and a standard error of estimate of 16.1 μmol mol−1. Resolution was approximately 1 to 2 μmol mol−1, too large for micrometeorological flux measurements but sufficient for many monitoring applications. The approach should work with any accurate device for measuring solution conductivity.
Winter Rye as a Cover Crop Following Soybean under Conservation Tillage
Authors: Kessavalou Anabayan , Walters Daniel T.
Published: July 2010

Rotation of corn (Zea mays L.) with soybean [Glycine max (L.) Merr.] provides certain economic and environmental advantages over monoculture corn. Low soybean residue production and persistence, however, promote potentially excessive soil erosion following soybean harvest. An irrigated field experiment was conducted in eastern Nebraska for 4 yr (1990–1993) under various tillage treatments and N rates to evaluate the effects of a winter rye (Secale cereale L.) cover crop following soybean on (i) rye dry matter yield, (ii) surface residue cover for erosion protection, and (iii) corn establishment and production. The soil was a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls). Treatments were (i) no‐tillage and disk tillage; (ii) corn following soybean with a winter rye cover crop (CBR), corn following soybean without rye (CB) and corn following corn (CC); and (iii) 0, 50, 100, 150, and 300 kg N ha−1 (applied to corn). Rye aboveground dry matter yield, surface residue cover, and corn yield parameters were estimated. Rye dry matter yield ranged from 0.25 to 2.9 Mg ha−1 and was influenced by tillage, N rate, and weather conditions in different years. During the years of high rye dry matter yield, presence of rye in the corn‐soybean system gave approximately 16% additional surface residue cover prior to planting through cultivation, compared with soybean residue alone. Surface cover by rye and soybean residues in CBR was equivalent to corn residue in CC under both disk and no‐till management. In 1 of the 3 yr, corn plant population and grain yield were reduced following rye (CBR) compared with the no rye system (CB), possibly due to apparent allelopathic effects related to the age of rye. No significant difference in N response was observed between CBR and CB corn yields. In general, rotation of corn with soybean (with and without rye) resulted in an increase of approximately 27% in corn grain yield and N uptake over continuous corn. During the years of high rye dry matter production, rye accumulated approximately 45 kg N ha−1 through aboveground dry matter. Overall, including a winter rye cover crop in the corn‐soybean rotation system was beneficial.
Banded Phosphorus Effects on Alfalfa Seedling Growth and Productivity After Temporary Waterlogging
Authors: Teutsch Christopher D. , Sulc R. Mark , Barta Allan L.
Published: July 2010

Phosphorus applied in a band below alfalfa (Medicago sativa L.) seed can increase seedling growth. A field study was conducted to evaluate the effect of banded‐P and temporary flooding stress on alfalfa seedling growth in the autumn and subsequent productivity. Experiments were seeded in late August 1994 and 1995 at two locations in Ohio on soils having P levels typical for the region. Fertilizer treatments included no fertilizer P and 27 kg P ha−1 (62 kg P2O5 ha−1) banded under the seed. Flooded and unflooded treatments were imposed 21 to 26 d after seeding. Flooding was maintained for 11 to 18 d, then plots were allowed to drain naturally. Before flooding was imposed, banded‐P increased seedling dry weight by an average of 60%. Flooding reduced seedling dry weight regardless of P treatment. At end of the flooding period, seedlings with banded‐P were larger than the flooded, no‐P controls at three of the four locations. In November, flooded seedlings with banded‐P had greater root dry weight at two locations and greater shoot dry weight at one location compared with the flooded, no‐P controls. Flooding in the autumn reduced dry matter yield the next year at two locations. In 1995, banded‐P increased yield the year after seeding ∼15% in the unflooded treatment at one location and ∼15% in the flooded treatment at the other location. Although banded‐P increased seedling growth in the autumn regardless of flooding treatment, its effect on stand density and yield the year after establishment was minimal.
Sulfur Nutrition of Maize in Four Regions of Malawi
Authors: Weil Ray R. , Mughogho Spider K.
Published: July 2010

Sulfur, though widely deficient in Africa, has received little attention by soil fertility researchers. Shifts to low‐S, high‐analysis fertilizers, continuous cropping, and higher‐yielding varieties may have increased S limitations in maize (Zea mays L.) production. We aimed to characterize maize S nutritional status in farmers’ fields in four regions of Malawi and determine maize response to S. Four 42 to 68 km2 study areas were delineated, two with low‐elevation lacustrine soils, and two with highly weathered residual upland soils. Maize plants in 238 farmer fields were sampled for nutrient analysis at 8‐ to 12‐leaf vegetative and tasseling growth stages. Replicated experiments were conducted in two years on a total of 20 farms to determine maize yield responses to S with and without N and/or P. Sampling areas differed significantly in maize S concentrations, S Diagnosis and Recommendation Integrated System (DRIS) indices, and N:S ratios. For earleaves, means were 1.46 g/kg S; S DRIS index, 12.2; and N:S ratio, 11.5. The ratio of N:S in the earleaf was the best predictor of maize yield response to Maize yields showed a N × S interaction such that there were no responses to S unless N was also supplied. With 80 kg/ha N, a significant response to S was shown by maize in all but one of 20 experiments. A response curve for S showed that 5 to 10 kg/ha of S was optimal, with mean yield responses ranging from 90 to 142 kg grain/kg S.
Crop Rotation and Nitrogen Effects on Normalized Grain Yields in a Long‐Term Study
Authors: Varvel Gary E.
Published: July 2010

Effects of year‐to‐year variability in agricultural production systems have always been a concern, but few studies are conducted for a long enough period of time where management system evaluations and assessments can be made. Given this limitation, questions about whether management systems are effective at reducing temporal variability remain in production agriculture. These questions prompted investigation of a long‐term crop rotation study to determine effects of crop rotation and N fertilization practices in a rainfed environment on normalized grain yields. Sixteen years of grain yield data from an experiment with seven cropping systems (three monoculture, two 2‐yr rotations, and two 4‐yr rotations) and three N fertilizer rates are included in the study. Grain yields from 1983 through 1998 for each crop and N fertilizer treatment were normalized and then relative grain yield within a cropping system and N fertilizer treatment were combined, which resulted in relative yields for each cropping system and N fertilizer treatment combination in each year. Using the normalized yields, overall analyses of the 16 yr of data were conducted to assess what effects cropping systems and N fertilizer have on yield variability. These analyses demonstrated that crop rotation systems are more effective at reducing long‐term yield variability than monoculture systems, even with N fertilizer. As expected, N fertility, obtained from either fertilizer or legumes in monoculture or rotation systems, is probably one of the most, if not the most important aspect in reducing yield variability. Analyses of normalized yields also demonstrated that reductions in yield variability could be obtained in many of our cropping systems with proper management.
Forecasting Spring Wheat Yield Using Time Series Analysis
Authors: Boken Vijendra Kumar
Published: July 2010

Techniques commonly used for wheat (Triticum aestivum L.) yield estimation employ weather data over the growing season. However, yield estimates are also required before wheat is sown—particularly by the grain‐exporting agencies to help them determine, in advance, wheat‐export targets. In that case, time series techniques relying on past yield data can be used for yield forecasting. In this paper, a procedure for applying time series analysis to forecast yield is described. A few techniques (linear trend, quadratic trend, simple exponential smoothing, double exponential smoothing, simple moving averaging, and double moving averaging) were tested to model the average spring wheat yield series for Saskatchewan, Canada. Using 1975–1993, 1975–1994, and 1975–1995 spring wheat yield data, yields were forecasted for 1994, 1995, and 1996, respectively. Based on a deterministic measure (i.e., mean squared error, MSE), it was found that the quadratic model produced the most accurate forecast during the model development periods (1975–1993, 1975–1994, and 1975–1995) and model testing periods (1994, 1995, and 1996). Further, a discussion is provided on improving the forecast by forecasting the yield for the homogeneous subareas (within Saskatchewan) instead for the entire Saskatchewan as a unit. The subareas could be constructed on the basis of soil‐climatic conditions or yield fluctuation, using a geographic information system.
Tillage Intensity, Mycorrhizal and Nonmycorrhizal Fungi, and Nutrient Concentrations in Maize, Wheat, and Canola
Authors: Mozafar Ahmad , Anken Thomas , Ruh Richard , Frossard Emmanuel
Published: July 2010

Reduced tillage can change numerous physico‐chemical properties of soil and the activity of various microorganisms including mycorrhizal and pathogenic soil fungi, and thus influence nutrient uptake by plant roots. We studied the colonization of roots by mycorrhizal and nonmycorrhizal fungi and nutrient concentrations in plant tops grown during a 3‐yr rotation of maize (Zea mays L.), winter wheat (Triticum aestivum L.), and canola (Brassica napus L.) in two sites in Switzerland where fields have been under three tillage treatments (conventional, CT; chisel plow, CP; and no‐tillage, NT) since 1987. Maize roots were colonized to a greater extent by mycorrhizal fungi with NT than with CP or CT treatments. Wheat roots were equally and weakly colonized by mycorrhizal fungi in all treatments but were relatively heavily (up to 35% of the root length) colonized by several nonmycorrhizal fungi such as Olpidium, Polymyxa, and Gaeumannomyces–Phialophora complex. Canola roots, as expected, were not colonized by any mycorrhizal fungi but were colonized by O. brassicae Reduced tillage intensity altered the concentration of some nutrients in the leaves of mycorrhizal host plants (maize and wheat) but did not change those in nonhost canola. Changes in nutrient concentrations in maize and wheat leaves were likely due to the combined effects of colonization of their roots by various mycorrhizal and nonmycorrhizal fungi and not to some changes in the physical or chemical properties of soils. Cluster analysis showed that Mn concentration in wheat leaves was closely related to the Gaeumannomyces–Phialophora complex and concentrations of Ca, K, and Zn were related to tillage intensity and to the Polymyxa colonization of roots. We conclude that the colonization of roots by nonmycorrhizal root parasites, and especially by nonfilamentous obligate fungi, need to be taken into account in mycorrhizal studies conducted under field conditions.
Statistical Methods for Predicting Responses to Applied Nitrogen and Calculating Optimal Nitrogen Rates
Authors: Makowski David , Wallach Daniel , Meynard Jean‐Marc
Published: July 2010

Models of response to applied N can be useful for deriving improved N dose recommendations. Here we show how response model parameters can be estimated and how model predictions and model N dose recommendations can be evaluated. For parameter estimation, we use a statistical approach based on random parameter models. Two methods for evaluating models are applied. The first method is to calculate mean squared error of prediction (MSEP) by cross validation, and the second is to perform nonparametric regressions to evaluate the profitability of calculated optimal N rates. The proposed methods are used with a data set consisting of 37 winter wheat (Triticum aestivum L.) experiments. Different functions taking into account end‐of‐winter mineral soil N are evaluated. The results show that the different functions all have similar MSEP values for predictions of yield and grain protein content and lead to N recommendations of similar profitability. However, there are substantial differences in MSEP for residual mineral N at harvest. One of these models is then compared with a model that does not include any site‐year characteristic and with a model that does not have random parameters. We find that using the model without a site‐year characteristic leads to predictions that are less accurate and optimal N rates that are less profitable by F 17 to F 105 ha−1. Another result is that the gross margin obtained with the optimal N rates calculated using the model without random parameters is lower by F 438 to F 550 ha−1.
Weed Management Systems for Conventional and Glyphosate‐Resistant Soybean with and without Irrigation
Authors: Heatherly Larry G. , Elmore C. Dennis , Spurlock Stan R.
Published: July 2010

Management inputs that maximize economic return from the early soybean [Glycine max (L.) Merr.] production system have not been evaluated fully. The objective was to determine the effect of weed management on yield and net return from early planted maturity group (MG) IV and MG V glyphosate [N‐(phosphonomethyl)‐glycine]‐resistant (GR) and conventional (CONV) soybean cultivars grown in the early soybean production system with (IRR) and without (NI) irrigation. Field studies were conducted from 1996 through 1999 on Sharkey clay (very‐fine, smectitic, thermic Chromic Epiaquert) at Stoneville, MS (33°26′ N lat). Weed management systems were (i) pre‐emergent (PRE) broadleaf followed by postemergent (POST) broadleaf and grass weed management (PRE + POST) and (ii) POST broadleaf and grass weed management (POST). Use of POST‐only weed management was cheaper, yielded more, and resulted in greater net returns than did use of PRE + POST weed management with both CONV and GR cultivars. Under the conditions of this study, use of GR vs. CONV cultivars in an NI or low‐yield environment resulted in greater profit ($52 vs. −$17 ha−1 3‐yr average, respectively). Use of CONV vs. GR cultivars resulted in greater profit in an IRR or high yield environment ($382 vs. $266 ha−1 3‐yr average, respectively). These results indicate that use of GR cultivars with POST‐only weed management will result in greater profit in an NI environment while use of CONV cultivars with POST‐only weed management will result in greater profit in an IRR environment.
Osmotic and Autotoxic Effects of Leaf Extracts on Germination and Seedling Growth of Alfalfa
Authors: Chon Sang‐Uk , Nelson C. J. , Coutts J. H.
Published: July 2010

Alfalfa (Medicago sativa L.) is autotoxic to seed germination and root growth of alfalfa seedlings. The objective was to determine if effects of leaf extracts were due to toxic factors, osmotic factors, or both. Rates of imbibition were slowed slightly by the leaf extract, mainly by osmotic factors. Germination at 22°C occurred in 20 h when imbibed with distilled water but was progressively delayed at higher extract concentrations. Initiation of germination events occurred in less than 10 h, and seed had completed germination when water content was 65% of total weight. An exudate with toxic activity to root growth was released during imbibition. Seed imbibed in extract solution for 10 h and then transferred to water‐agar medium had a slight delay in germination but no effect on root elongation rate (RER). Conversely, seed imbibed in water for 10 h before transfer to the extract showed a delay in germination and strong inhibition of RER as extract concentrations increased. Transfer to polyethylene glycol (PEG 8000) at 10 h showed some of the germination delay was due to osmotic properties. Root elongation rate was increased slightly by PEG solutions greater than −0.20 MPa, which was lower than those of the strongest extracts, −0.10 MPa in agar and −0.05 MPa on filter paper. These extracts reduced RER by up to 90% due to the toxicity factors. Inhibition was slowed mainly by osmotic factors whereas delayed seed germination and, especially, reduced root elongation were due mainly to toxic factors of the leaf extract.
Fractionation and Characterization of a Soil Polysaccharide Extract
Authors: Thomas R. L. , Mortenson J. L. , Himes F. L.
Published: July 2010

Soil polysaccharides from the Brookston soil were extracted with hot water and purified by precipitation, dialysis, and de‐ proteinization with chloroform. The purified polysaccharides were fractionated on a column of diethyaminoethyl‐cellulose by elution with phosphate buffers and an increasing gradient of NaOH concentration. The five fractions obtained could not be distinguished on the basis of their monosaccharide composition. Differences could be detected in the nitrogen and uronic acid contents and the electrophoretic mobility of the five fractions. The electrophoretic mobility as determined by free‐boundary electrophoresis could be related to the uronic acid content of each fraction. The electrophoretic patterns indicated that all five fractions were still not homogeneous preparations.
Estimating Losses of Efficacy Due to Pesticide Biodegradation in Soil: Model Simulations
Authors: Shelton Daniel R. , Doherty Michael A.
Published: July 2010

A model was developed for describing rates of pesticide‐substrate biodegradation, accounting for bioavailability and microbial growth. The model was used to simulate losses of efficacy for soil‐applied pesticides. The model requires rate constants for rapid sorption‐desorption to and from soil surfaces (k1/k‐1 = Kd1); diffusion into and out of soil aggregates‐organic matter particles (k2/k‐2 = Kd2); microbial growth [yield (Y), maximum growth rate (µmax), half‐saturation growth constant (Ks), and initial biomass concentration (X0)]; initial mass of substrate (s0); and gravimetric water content (θg). Simulations of microbial growth and substrate depletion were conducted assuming no sorption (aqueous solution), sorption to soil surfaces only, and sorption in conjunction with diffusion. The time required to achieve a soil solution concentration of 1 µg mL−1 was defined as a hypothetical loss of efficacy (LE1). Certain relationships were consistently observed, regardless of sorption or diffusion: LE1 was found to be related to Ks linearly, to X0 logarithmically, to µmax geometrically, and to initial pesticide‐substrate concentration (S0) nonlinearly. Sorption to soil surfaces resulted in decreased equilibrium soil solution concentration (Se), depending on the magnitude of θg and Kd1. Rates of biodegradation‐growth were a function of Se, as opposed to total (soluble + sorbed) concentration. Sorption coupled with diffusion decreased both Se and time‐dependent availability, resulting in slower rates of biodegradation. In general, larger values of S0 resulted in faster rates of biodegradation, i.e., decreased the time required for a loss of efficacy.
John White's Journal of a voyage to new South Wales (London 1790): bibliographic notes
Authors: NELSON E. CHARLES
Published: July 2010

Two issues of this handsome, illustrated, First Fleet book are described in detail. John White's Journal of a voyage to new South Wales has literal amendments in “A list of plates” and on p 215, and substantial textual alterations on pp 240, 255 and 256. Copies with new leaves tipped-in and with an entire gathering reprinted and replaced are reported. A simple classification of copies is not possible because of anomalies in the make-up of several copies. A copy with the title-page printed on watermarked paper dated 1798, 8 years after initial publication, is also reported. All the copies surveyed are listed and their states annotated, and a list of plates with the corresponding names of the artists who prepared the original templates is also appended.
Archibald Menzies (1754–1842), an early botanist on the northwestern seaboard of North America, 1792–1794, with further notes on his life and work
Authors: GROVES ERIC W.
Published: July 2010

ABSTRACT:

This paper includes a short biography of Menzies and an outline of the historical events on the northwest Pacific coast leading up to Vancouver's voyage. A table listing the botanical visitors to that area prior to 1792 is given followed by a résumé of the evolution of Menzies's journal. Sources used in compiling the chronology of his movements during Vancouver's voyage are then set down, ending the section with an account of Menzies's own visit, 1792–1794. His method of plant collecting is discussed along with an account of his collections and their subsequent disposal. The paper concludes with details of Menzies's later life, his connection with other botanists of the day, and an assessment of his achievements.