bluuebunny/crossref_metadata_2025 huggingface dataset:
Early Planted, Early Maturing Soybean Cropping System: Growth, Development, and Yield
Authors: Kane M. V. , Grabau L. J.
Published: July 2010

An early planted, early maturing soybean [Glycine mar (L.) Merr.] cropping system could stagger harvest maturity and increase the number of options available for subsequent crops. However, premature flowering of early maturing cultivars could reduce canopy closure at flowering (CCR1) or at beginning seed fill (CCR5) as well as vegetative mass at R5 (VMR5). This study was conducted to determine the Maturity Group (MG) best suited for this early planted cropping system, and to relate growth, development, and environmental parameters to yield. Two cultivars each from MG 00,0,I,II,III, and IV were planted in six Kentucky field environments ranging from 36°40' to 38°7'N lat from 1986 to 1989. Vegetative, pod‐set, and seed‐fill durations were generally shorter in early‐maturing cultivars, but also interacted with environment. Maturity groups 00 and 0 had inadequate canopy closure at R1 and R5, inadequate vegetative mass at R5, and produced lowest overall yields. While MG I and II appeared to be most sensitive to vegetative and pod‐set rainfall and seed‐fill temperatures, MG II produced the best mean yield. Seed‐fill duration and rainfall were apparently more important for MG III and IV than for earlier MGs. Maturity Group II appears to be more adaptable than other MGs in these early planted, early maturing soybean cropping systems in Kentucky.
Rhizome Characteristics and Canopy Light Interception of Grazed Rhizoma Peanut Pastures
Authors: Ortega‐S. J. A. , Sollenberger L.E. , Bennett J.M. , Cornell J.A.
Published: July 2010

‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.) is a promising pasture legume for warm climates. In 1988 and 1989, the effect of grazing management on rhizoma peanut canopy light interception (LI) and the role of rhizome reserves in regrowth were studied on a Sparr fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudults). Treatments were replicated twice and included all combinations of three levels of residual dry matter (RDM; 500, 1500, and 2500 kg ha−1) and four grazing cycle lengths (GC; 7, 21, 42, and 63 d between grazings, including a 0.5 to 2‐d grazing period). Data were analyzed by fitting multiple regression equations starting with a second order polynomial model. Canopy LI before grazing ranged from 24 to more than 90% and was lowest for low RDM and short GC treatments, while canopy LI after grazing ranged from 9 to 79% and increased at a decreasing rate as RDM increased. When grazed to 500, 1500, and 2500 kg ha−1, RP required an average of 49, 24, and 12 d to reach 85% LI. At season‐end 1989, rhizome mass (range of 450‐4100 kg ha−1) and total nonstructural carbohydrate (TNC; range of 58‐210 g kg−) concentration were lowest at low RDM and short GC, increased with increasing GC when RDM was low, and changed only slightly with changes in GC at RDM above 1700 kg ha−1. Low postgraze light interception and depletion of rhizome mass and total nonstructural carbohydrate with close grazing suggest that reserves were mobilized for rhizoma peanut regrowth. In contrast, postgraze light interception and rhizome mass and reserve status remained high when residual dry matter was 1700 kg ha−1 or greater suggesting that residual leaf area was primarily responsible for regrowth under more lenient grazing.
Development of Soybean Fresh and Dry Weight Relationships for Real Time Model Calibration
Authors: Kenig A. , Mishoe J. W. , Boote K. J. , Cook P. W. , Reicosky D. C. , Pettigrew W. T. , Hodges H. F.
Published: July 2010

Measurements of dry weight and crop phenology are normally used to validate comprehensive growth models. To reduce this requirement in applications such as large area yield forecasting, the present research was conducted to study the change of dry matter concentration (ratio of dry weight to fresh weight) of the vegetative and reproductive plant components of soybean (Glycine max (L.) Merr.]. The paper evaluates the usefulness of simple statistical equations that relate dry matter concentration to developmental stages for the specific purpose of growth model calibration. During the 1984 through 1985 seasons, five cultivars of soybean were grown in five locations throughout the soybean producing regions of the U.S. Soil type, planting date, plant population, and irrigation management varied from site to site. Plant samples were taken at 1‐ to 2‐wk intervals during the growing season for fresh weight and dry weight of vegetative parts and pods, and counts of reproductive sites. In most of the field locations, dry matter concentration of different soybean parts was found to follow a predictable pattern. The pattern was explained for most locations by a simple relation of developmental stage and vegetative dry matter concentration, using data collected until the beginning of pod fill. A second model explained the course of pod dry matter concentration over developmental stage, using data collected after the beginning of seed growth. Insignificant differences among regression lines of extreme locations suggest that the course of dry matter concentration may be of an inherent nature, with minor impact due to differences of cultivar, or weather. The equations developed in this paper to estimate dry weight data will reduce the effort of calibrating and/or validating soybean comprehensive growth models by requiring only the collection of fresh weight samples at known phenological events.
Frequency of Plant Growth Regulator and Mowing Treatments: Effects on Injury and Suppression of Centipedegrass
Authors: Johnson B. Jack.
Published: July 2010

Centipedegrass [Eremochloa ophiuroides (Munro) Hack.] is a popular low maintenance turfgrass that produces seedheads from midsummer until early fall, Since regular mowing is needed to maintain a quality turf, experiments on rate and frequency of plant growth regulator applications and mowing frequencies were initiated to assess their effect on suppression of vegetative and reproductive growth of centipedegrass. Various rates of imazethapyr {2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐ethyl‐3‐pyridinecarboxylic acid}, mefluidide {N‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)sulfonyl]amino]phenyl]‐acetamide}, and CGA 163935 [4(cyclopropyl)‐α‐hydroxy‐methylene)‐3,5‐dioxocyclohexanecarboxylic acid ethylester] were evaluated as sequential applications and in combination with mowing on suppression of centipedegrass. Imazethapyr applied initially at 0.3 kg ha−1 and then followed by 0.15 kg ha−1 4‐wk later suppressed a higher percentage of centipedegrass seedheads without causing undesirable injury than when the second application was made at a 2‐or 3‐wk interval. Seedhead suppression was similar when imazethapyr was applied at 0.3 kg ha−1 and then followed by two mowings (6 + 8 wk) in 1990 and one mowing (6 wk) in 1991. Mefluidide applied initially at 0.6 kg ha−1 and followed by 0.6 kg ha−1 2‐wk later injured centipedegrass less than when the second application was made at a 3‐ or 4‐wk interval. Seedhead suppression was not consistent each year regardless of the time of the second mefluidide application. However, seedhead suppression was acceptable for 10 wk when mefluidide was applied to 0.6 kg ha−1 and followed by two mowings (4 + 7 wk) in 1990 and three mowings (2 + 4 + 8 wk) in 1991, or when 0.6 kg ha−1 was followed by 0.3 kg ha−1 and one mowing at 6 wk in 1990 and 2 wk in 1991. CGA 163935 injured centipedegrass more and suppressed seedheads less than either imazethapyr or mefluidide.
Nutrient Accumulation and Removal by Sugarcane Grown on Everglades Histosols
Authors: Coale F. J. , Sanchez C. A. , Izuno F. T. , Bottcher A. B.
Published: July 2010

Sugarcane (interspecific hybrids of Saccharum spp.) is Florida's most valuable agronomic crop. Recently, sugarcane production has come under scrutiny because of concerns regarding the impact of nutrient‐rich drainage water on the ecology of adjoining bodies of water and wetlands. The objective of our research was to define the N, P, K, Ca, and Mg seasonal accumulation patterns in the aerial portion of sugarcane grown on organic soils of the Everglades Agricultural Area. Sugarcane fields were sampled on 30 to 60 d intervals during the plant‐cane and first‐ratoon crops. Dry weight, N, P, K, Ca, and Mg accumulation were determined and characterized by logistic growth models. Dry weight accumulation averaged 0.15 t ha−1 d−1 during the grand growth period. The period of most rapid nutrient uptake was shown to correspond with the grand growth period and the rates of nutrient uptake during different phases of crop development were defined. At harvest, 71% of total dry matter and 55, 63, 64, 25, and 38% of total accumulated N, P, K, Ca, and Mg, respectively, were removed from the field as millable sugarcane. Phosphorus and K removal from the field by crop harvest was equivalent to 179 and 201%, respectively, of added fertilizer P and K. Apparently, fertilizer P and K were minor contributors to the total soil pool of plant available P and K. Nutrient accumulation patterns should be incorporated into future management plans designed to minimize the impact of sugarcane production on the surrounding environment.
Predicting Grain Sorghum Canopy Structure for Soil Erosion Modeling
Authors: Armbrust D. V. , Bilbro J. D.
Published: July 2010

Development of modern water and wind erosion prediction technology requires information on the canopy structure of various plant species to accurately predict the canopy effect on the falling raindrop or the erosive force of the wind. The objective of this study was to develop equations to predict grain sorghum [Sorghum bicolor (L.) Moench] canopy structure characteristics. Grain sorghum plants were sampled weekly from emergence to maturity at Big Spring, TX (1986–1987), and Manhattan, KS (1987), to measure the following crop canopy parameters: plant height, stem length, leaf area, stem area, and canopy cover. Manhattan data were used to develop equations that relate canopy structure parameters of grain sorghum to the total above‐groundry weight, and Big Spring data were used to validate those equations. Leaf and stem area distributions with height also were determined. Coefficients of determination of predicted values using the Manhattan equations and Big Spring above‐ground dry weight and the measured Big Spring data ranged from 0.987 for leaf area to 0.922 for stem length. Distribution of leaf and stem area with height remained essentially constant with plant age through the first 7 wk after planting. The equations can be used to supply canopy structure information needed by wind and water erosion prediction models currently under development.
Evaluation of Statistical Methods for Determining Differences between Samples from Lognormal Populations
Authors: Parkin T. B.
Published: July 2010

Soil variables often exhibit frequency distributions that are positively skewed. When this situation exists, the assumption of normality associated with analysis‐of‐variance procedures is violated, and two common recommendations are given: (i) perform a normalizing transformation, or (ii) apply nonparametric statistical methods. Information regarding the relative efficacy of these two procedures with regard to power to detect differences between batches of samples is lacking. This study evaluates five statistical procedures for detecting differences between samples drawn from lognormal populations. The tests evaluated were (i) two‐tailed t‐test on untransformed data, (ii) twotailed t‐test on natural log‐transformed data, (iii) nonparametric Mann‐Whitney test, (iv) median confidence interval overlap method, and (v) a mean confidence interval overlap method. The tests were evaluated with regard to Type I error rate by comparing batches of samples drawn from the same lognormal population. Also, the power of the statistical tests to detect differences between two batches of samples drawn from different lognormal populations was evaluated over a range of population variances and sample sizes (n = 4 to 100). It was found that three of the tests (Tests 2, 3, and 4) were sensitive to sample differences when the underlying populations differed with regard to their medians. The other two tests (Tests 1 and 5) were sensitive to differences in population means. Test 2 is recommended when the median is the location parameter of interest; however, Test 5 should be used to detect differences in means.
Baling System for Making Laboratory‐Scale Hay Bales
Authors: Coblentz W. K. , Fritz J. O. , Bolsen K. K.
Published: July 2010

Research on the preservation of moist hay has long been an area of intense interest; however, such research has often been hampered by the difficulty in controlling experimental conditions luring field hay trials. The development of a laboratory‐scale baling system that would allow researchers to impose a baling treatment on a small quantity of forage would reduce the need for expensive field trials and, to a large degree, minimize weather as a factor in hay experiments. A simple system that utilizes a hinged metal baling unit and a hydraulic press to make 10.3‐ by 10.8‐ by 13.4‐cm wire‐tied hay tales over a wide range of densities (150 to 800 kg m−3) is described. The system was inexpensive to build, easy to use, and could easily be reproduced.
Residue Management Effects on Sugarcane Yield and Soil Properties in Northeastern Brazil
Authors: Ball‐Coelho B. , Tiessen H. , Stewart J. W. B. , Salcedo I. H. , Sampaio E. V. S. B.
Published: July 2010

Sugarcane (Saccharum spp.) production systems commonly include preharvest or postharvest burning to dispose of residue. In northeastern Brazil, no‐burn mulching practices are being introduced as a labor‐intensive but environmentally more friendly alternative. We examined the effect of burning crop residues on sugarcane yield and C, N, and P cycles. Carbon, N, and P losses during preharvest burning were measured for a sugarcane first ratoon crop. Postharvest burn and mulch treatments were compared for a plant crop grown on an Oxic Haplustult soil. During the preharvest burn of the first ratoon crop, 2600 kg C ha−1, 17 kg N ha−1 and 1 kg P ha−1 were lost by convection. The postharvest burn of the plant crop residue resulted in losses of 4800 kg C ha−1 and 42 kg N ha−1; P losses were undetectable in the burn. The postharvest burn of the plant crop residue had no significant effect on total C or NH4‐N plus organic N in soil during the first ratoon crop cycle. Soil pH in the top 7.5 cm layer of soil did not change after the postharvest burn, but increased 1.1 units in the top 1‐cm layer. In the unburned mulch treatment, the litter layer did not reduce tillering or N and P uptake. Harvestable cane yield of the first ratoon crop was 17 Mg ha−1 (wet wt.) greater in the mulch than the burn treatment (54 vs. 37 Mg ha−1). This yield response was attributed to increased soil water retention and reduced weed growth under the mulch. In this short‐term trial, mulching proved to be an alternative to the traditional burn system.
Simultaneous Determination of Total Sodium, Potassium, Magnesium, and Calcium in Plant Tissues Using Acid Digestion and Ion Chromatography
Authors: Goyal Sham S. , Hafez Ahmed A. R , Rains Donald W.
Published: July 2010

Sodium, K, Mg, and Ca in plant tissue were measured by single column ion chromatography (SCIC) as an alternative to traditional methods such as atomic absorption spectrophotometry (AAS) or inductively coupled plasma–atomic emission spectrophotometry (ICPAES). Interference of the NH4 peak on the Na peak in SCIC was eliminated by removal of NH4 ions by drying the nitric‐perchloric acid plant digest at 350 °C. Cations were separated using an IC‐Pack CM/D column with 0.1 mM EDTA + 3 mM HNO3 as eluent. Inclusion of 10% (v/v, = 1.89 M) acetonitrile in the eluent shortened the retention time of divalent cations by 22% compared with the time without acetonitrile. The Na, K, Mg, and Ca content of plant samples analyzed with this technique agreed closely with certified values provided by the National Institute of Standards and Technology (NIST). The lower limit of detection of SCIC for Na, K, Mg, and Ca were 0.05, 0.2, 0.025, and 0.05 mg L−1, respectively, using a 100‐μL sample. The response of peak areas as a function of solute concentration was linear up to 10 mg L−1 of each cation. The SCIC method was cheaper than AAS or ICP, and faster than AAS, mainly due to simultaneous analyses of all four cations. SCIC did not generate hazardous and toxic waste and thus did not require special disposal procedures.
WAS: Computer Software for Wheat Quality Data Management
Authors: Morris Craig F. , Raykowski James A.
Published: July 2010

Wheat (Triticum aestivum L.) cultivar development programs benefit from the efficient assessment of end‐use quality of experimental lines. Efficiency of assessment is enhanced when quality testing data are accurately collected, recorded, interpreted, and reported. The Wheat Analysis System (WAS) software specifically addresses this management need by providing a user‐friendly, menu‐driven system that generates data collection forms and reports, structures data entry, and maintains a cumulative database which is amenable to statistical analysis and interpretation. Data are managed in two master files according to a nursery‐sample system of organization. Quality tests and analyses are grouped into processes that accommodate all of the common methodologies used for soft and hard wheat evaluation, including grain and flour analyses, milling, and baking. A supplemental process, in addition to user‐defined variables, provides flexibility and broad applicability. The WAS software is compiled in Borland C, version 3.0, and operates on DOS‐based computers with 640K RAM, hard and floppy disk drives, and a printer. A color monitor, though not required, greatly enhances the use of the menu‐driven features. WAS is simple to use, requires no programming, and directly and specifically addresses the needs of wheat quality testing and evaluation programs—thereby aiding the overall cultivar development process.
Nitrogen and Carbon Dynamics in No‐Till and Stubble Mulch Tillage Systems
Authors: Christensen Neal B. , Lindemann William C. , Salazar‐Sosa Enrique , Gill L. R.
Published: July 2010

Soil nitrogen and organic carbon differences between no‐till and conventional tillage systems are often dramatic and well documented, but these differences between no‐till and stubble mulch tillage systems are more subtle. Our objective was to evaluate changes in soil inorganic N, organic N, organic C, surface soil moisture and grain yield on the southern High Plains as affected by stubble mulch and no‐till tillage systems from 1988 to 1992. The cropping system was a sorghum (Sorghum bicolor (L.) Moench)‐sorghum‐fallow‐wheat (Triticum aestivum L.) rotation conducted on a Pullman sandy clay loam (fine, mixed, thermic Torrertic Paleustoll) under dryland conditions near Clovis, NM. Tillage treatments were main plots and N fertilization treatments were subplots. Averaged over 5 yr and 37 sampling dates, the no‐till treatment had 2.0 mg kg−1 less inorganic N, 40 mg kg−1 more organic N, and 617 mg kg−1 more organic C than the stubble mulch treatment. Although differences between tillage systems were generally small, they were most noticeable during sorghum planting and development. No‐till unfertilized treatments often showed N deficiency symptoms during development. Nitrogen fertilization was more important than tillage system in determining sorghum and wheat yields in wet years. In dry years, N‐fertilized stubble mulch treatments had the lowest yields. Since conversion to either stubble mulch or no‐till in 1987, organic C levels under both systems have continually increased.
Growth Regulator and Seed Storage Effects on Switchgrass Germination
Authors: Zarnstorff Mark E. , Keys Robert D. , Chamblee Douglas S.
Published: July 2010

Switchgrass (Panicum virgatum L.) is a warm season perennial grass that shows potential as a forage in the southeastern USA. Problems with switchgrass establishment from seed are often due to inherent seed dormancy from seeds harvested in fall and seeded the following spring. The objectives of this study were to determine (i) the effects of wet prechill (PC) treatment (5°C for 14 d) and scarification (8 M H2SO4 for 5 min) on germination of five switchgrass cultivars and (ii) the effect of plant growth regulators (ethylene, gibberellin, and kinetin), CO2, PC, and influence of storage temperature and duration on germination of four selected lots of Blackwell (BW) and Cave‐in‐Rock (CIR) seeds. Storage treatments were initiated 1 February using seeds harvested the previous fall. Early germination percentage (7 d) was increased between 22 and 73 by PC, while final germination percentage (28 d) was increased between 2 and 40. Germination of BW 6086 was increased from 60 to 63% by ethylene, and from 59 to 65% by gibberellin (ɑ = 0.05). Seeds stored at −8°C showed little change in early or final germination with time of storage (90 d to 4 yr). Dormancy of BW 1198, BW 6086, and CIR 6012 was largely broken after 90 d of storage at 23°C. Germination of seeds stored at 23°C generally started to decline after 180 d to 2 yr. Postharvest storage of seeds at 23°C from January to April (90 d) should ensure adequate germination at time of seeding.
Floral Asynchrony and Kernel Set in Maize Quantified by Image Analysis
Authors: Bassetti Paolo , Westgate Mark E.
Published: July 2010

A delay in the onset of silk emergence relative to pollen shed often decreases kernel set in maize (Zea mays L.). Lack of pollen, failure of silks to emerge, and loss of silk receptivity all are probable causes for kernel loss. To date, it has not been possible to distinguish between these possibilities, due to the lack of quantitative information on the intensity of pollen shed and progress of silk emergence under field conditions. Using a computer‐aided image analysis system, we measured the daily progress of silk emergence and the intensity of pollen shed in the field. Kernel set also was measured on plants whose silk emergence varied from 8 d before to 13 d after anthesis (DAA). About 200 silks emerged on the first day silks appeared and >90% of the florets had silks exposed within 3d. Pollen shed followed a normal distribution with time, peaked 3 DAA, and ended 13 DAA. On ears with silks exposed to pollen for only one d, nearly all florets set kernels when pollen was shed at intensities greater than ≈ 100 grains cm−2 d−1mm; however, percent set in apical floret positions decreased when the onset of silk emergence was delayed >3 DAA, despite pollen shed at a rate sufficient to ensure high kernel set. These results indicate that asynchrony between silk emergence and pollen shed decreases kernel set because silks emerge after pollen amount becomes limiting. In the current experiment, the intensity of pollen shed limited kernel set only beyond 7 DAA. Also, silks emerged prior to anthesis remained receptive to pollen for at least 5 d. This finding suggests that selection for silk emergence prior to pollen shed (protogyny) may improve kernel set in maize under conditions known to delay silk emergence.
Nitrogen Utilization of Selected Cropping Systems in the U.S. Northeast: II. Soil Profile Nitrate Distribution and Accumulation
Authors: Guillard Karl , Griffin Gary F. , Allinson Derek W. , Yamartino William R. , Rafey M. Moosa , Pietrzyk Stephen W.
Published: July 2010

High rates of N fertilizers and limited crop uptake of N during the growing season can result in excessive accumulation of soil nitrate (NO−3). Soil NO−3 can be decreased with efficient cropping systems. Experiments were conducted in Connecticut from 1987 through 1990 on a Paxton fine sandy loam soil (coarse‐loamy, mixed, mesic Typic Dystrochrept) to determine the effects of N rate and cropping system on soil NO−3. Orchardgrass (Dactylis glomerata L.), red clover (Trifolium pratense L.), a double‐crop system of oat (Avena sativa L.) followed by tyfon [Brassica rapa L. × B. pekinensis (Lour.) Rupr.], maize (Zea mays L.) followed by a cover crop of winter rye (Secale cereale L.), and a fallow system received preplant N at 0, 112, 224, 336, and 448 kg ha−1. Each system was evaluated for two consecutive growing seasons and repeated three times. Nitrogen was applied only in the first growing season. Soil NO−3 at the first autumn sampling generally increased for all systems as N rate increased. Mean spring soil NO−3 levels were only 23% of previous autumn NO−3 levels. By the second autumn sampling, soil NO−3 values were near background levels except in the fertilized fallow system. At the two highest N rates, oat‐tyfon produced the smallest overwinter change in soil NO−3 storage. An oat‐tyfon double crop, orchardgrass, or red clover system should decrease soil NO−3 more effectively than maize or a noncropped fallow when soil NO−3 accumulations are greater than those produced from N inputs equivalent to 224 kg ha−1.
Rhizobia1 Inoculation and Phosphorus and Zinc Nutrition for Annual Medics Adapted to Mediterranean Environments
Authors: Materon Luis A. , Ryan John
Published: July 2010

Cereal production in the Mediterranean region (where rainfall averages 200 to 600 mm yr−1) has traditionally used fallowing in alternate years to conserve crop‐limiting soil moisture. Self‐regenerating pasture medics (Medicago spp.) were introduced to provide forage for livestock in the alternate year and to reduce the cereal's need for fertilizer N; their adaptation depends on compatible Rhizobium meliloti bacteria for N2 fixation and on climatic conditions. In addition, nutrients such as P and Zn are potentially limiting factors. Therefore, in a greenhouse experiment (60 d) using a P‐deficient, air‐dried, nonsterilized clay soil (Calcixerollic Xerochrept) treated with P (0, 15, 45, and 135 mg kg−1) and Zn (0 and 5 mg kg−1, we assessed growth of four annual medic species with and without rhizobial inoculation and fertilizer N: Medicago polymorpha L., M. rotata Boiss., M. rigidula (L.) All., and M. noeana Boiss. Except for M. noeana, growth of all species responded significantly to applied P and to Zn only with adequate P and N levels (or rhizobial inoculation). Pod number and root biomass were also increased by P application, with differences occurring between species. Thus, when a medic species is newly introduced, inoculation has a role to play where no compatible rhizobia exist. Phosphorus fertilization and medic seed inoculation can easily be done, while the use of adapted biotypes in low‐Zn soils is more problematic
An Algorithm for Predicting Crown Root Axes of Annual Grasses
Authors: Rickman Ronald W. , Klepper Betty , Ball Daniel A.
Published: July 2010

Root formation by any plant determines its success or failure for creating seed for its next generation. Those interested in managing plants for optimum harvestable yield require information about effects of their practices on root growth. Crop growth models can be convenient summarizations of such knowledge. Models of plants and environment currently describe the plant shoot more completely than they describe the root. The morphologically based root formation algorithm presented in this paper provides opportunities for improving both the description of root formation and the response of roots to their environment. The equation relating shoot and root development will be convenient for crop modeling. It can also be used as a standard for comparison of field rooting observations, as environmental effects on rooting are quantified. The equation predicts the number of root axes on a plant from the plant phyllochron interval, the timing of nodal root appearance relative to leaf appearance, and the effect of environmental stresses that reduce tillering. A comparison of algorithm predictions with observed root formation by wheat (Triticum aestivum L.) from a warm, dry seedbed revealed that fewer roots were formed during the early tillering stage of development than predicted for unstressed plants. Correction for observed tillering did not reduce predicted root numbers to those observed. Observed early‐season root observations were matched by using one‐half of possible tillering as a stress correction.
Allelopathy in Forage Crop Systems
Authors: Miller Darrell A.
Published: July 2010

Secondary plant metabolites and their degradation products are important in all agroecosystems including those with forage crops. Allelopathy affects cropping systems and interseeding of one species into established sods of another. Autotoxicity and heterotoxicity are types of allelopathy. Alfalfa (Medicago sativa L.) has been investigated as both an autotoxic and heterotoxic species. Reestablishment of alfalfa immediately after alfalfa has usually resulted in poor stands due to autotoxicity, and several other forage species also exhibit autotoxicity. Many forage species have shown heterotoxicity, both between forage species and weed species. Several investigators have identified various allelochemicals and/or families of allelochemicals as being responsible for allelopathic reactions. Identifying such chemicals would aid in developing resistant forage cultivars and in maintaining a productive and profitable crop. Crop rotation, cover‐crop management, interplanting, double cropping, no‐till planting, and nonrotational cropping systems are involved with allelopathic effects. Some alfalfa cultivars possess some resistance to these allelochemicals. Therefore, a breeding program could provide resistant germplasms. Various forage grasses and some weed species have demonstrated allelopathic effects on alfalfa, and alfalfa has allelopathic effects on some weed species. This alone may provide an insight for herbicide studies in alfalfa production.
Canopy Light Reflectance and Field Greenness to Assess Nitrogen Fertilization and Yield of Maize
Authors: Ma B. L. , Morrison Malcolm J. , Dwyer Lianne M.
Published: July 2010

Assessment of crop N requirements is necessary to develop production systems with optimal N input. A field experiment with six maize (Zea mays L.) hybrids grown at three N fertilizer rates (0, 100, and 200 kg N ha−1) was conducted on a well‐drained sandy loam of the Grenville series (coarse‐loamy, mixed, mesic Typic Eutrochrepts) on the Central Experimental Farm at Ottawa, ON, in Canada (45°23' N, 75°43' W) for 3 yr (from 1991 to 1993) to evaluate whether canopy reflectance and greenness can measure changes in maize yield response to N fertility. Canopy reflectance, leaf area and greenness were measured on 11 dates from 4 wk before to 4 wk after anthesis. Grain yield at harvest was also measured. Direct radiometer readings at the 600‐ and 800‐nm wavelengths or a derived normalized difference vegetation index [NDVI = (800 nm − 600 nm)/(800 nm + 600 nm)] best differentiated N and hybrid treatments at most sampling dates. Canopy light reflectance was strongly correlated with field greenness at almost all growth stages (field greenness being a product of plant leaf area and leaf greenness measured with a chlorophyll meter, in this case a SPAD‐502). Both canopy light reflectance and field greenness measured preanthesis were correlated with yield at harvest. Light reflectance measured after anthesis differentiated hybrid differences in leaf senescence. Our data suggest that light reflectance measurements prior to anthesis may predict grain yield response and provide in‐season indications of N deficiency.
Ammonia Transport in a Temperate Grassland: II. Diurnal Fluctuations in Response to Weather and Management Conditions
Authors: Bussink D. Wim , Harper Lowry A. , Corré Wim J.
Published: July 2010

Ammonia emission into the atmosphere is of concern because of its potential impact on atmospheric aerosol chemistry and fertilizer N use efficiency. The purpose of this study was to evaluate the effects of N surplus and deficit on soil‐plant‐atmosphere NH3 exchange in a temperate humid grassland. Plant and soil N measurements were made along with NH3 fluxes using flux‐gradient techniques. Ammonia flux was related to the plant ammonia compensation point (NH3 CP), which was controlled by plant N concentration and management practices (such as harvest and fertilization). The measured fluxes were generally much larger during daytime than during nighttime. The daily variation in flux was apparently caused by higher diffusive resistance at night. Generally, there were no significant differences between daytime and nighttime NH3 CP. Ammonia was absorbed in dew and released during dew evaporation; however, nighttime absorption exceeded daytime release, with some of the N apparently being captured by the crop.
Simulating Forage Sorghum Yields with SORKAM
Authors: Fritz John O. , Vanderlip Richard L. , Heiniger Ronnie W. , Abelhalim Ahmed Z.
Published: July 2010

A validated crop model can be a valuable tool for evaluating new production and management practices, particularly for crops routinely grown in environments that produce large variation in field performance tests. Previous work has been done to validate SORKAM a crop growth model for grain sorghum [Sorghum bicolor (L.) Moench]. The purpose of this study was to determine the ability of SORKAM to simulate forage sorghum yields for a wide range of environmental conditions. Data for the simulations used in the validation process were taken from performance tests for four cultivars (‘Early Sumac’, ‘Atlas’, ‘Sugar Drip’, and ‘Canex’) conducted at two sites in Kansas over 25 yr. Simulated bloom date, grain, stover, and total dry matter yields were regressed on measured data. The SORKAM model simulated bloom dates without bias; however, the root mean square error (RMSE) was 8 d, and the model tended to overestimate bloom date under conditions of water deficit. The model generally overpredicted yields of the four cultivars for grain (bias = 3.2 Mg ha−1), stover (bias = 2.0 Mg ha−1), and total dry matter (bias = 5.2 Mg ha−1). In addition to overestimation of total dry matter production, weaknesses in the SORKAM model in simulating forage sorghum growth included inability to simulate phenological development accurately under moisture deficit stress and to partition dry matter into grain and stover. These problems must be resolved before SORKAM can be used to address management decisions.
Sugar Beet Performance and Interactions with Planting Date, Genotype, and Harvest Date
Authors: Lauer Joseph G.
Published: July 2010

Producers and processors have lengthened the sugar beet (Beta vulgaris L.) factory campaign by beginning harvest about 1 mo earlier. Agronomic practices may need to be adjusted to maximize yield and quality of sugar beet harvested earlier. The objective was to describe yield and quality relationships between dates of planting and harvest among 18 sugar beet genotypes. The experiment was conducted at the University of Wyoming Research and Extension Center near Powell, WY, during 1992 and 1993 on a Garland clay loam (fine‐loamy over sandy or sandy‐skeletal, mixed, mesic Typic Haplargids). Treatments consisted of five planting dates between 30 March and 8 June, and four harvest dates every 2 wk beginning 10 September. When averaged across all years, genotypes, and harvest dates, a delay in emergence of 46 d decreased root yield 38% (from 52.5 to 32.3 Mg ha−1), sugar content 4% (183 to 175 g kg−1), and recoverable sucrose 42% (9.25 to 5.34 Mg ha−1). Delaying planting 46 d increased loss to molasses by 21% (7.75 to 9.41 g kg−1). Root yield varied 18% among sugar beet genotypes (40.9–50.1 Mg ha−1), sugar content varied 6% (173–185 g kg−1), loss to molasses varied 13% (7.90–9.10 g kg−1), and recoverable sucrose varied 14% (7.14–8.33 Mg ha−1). Over the 43‐d harvest period, root yield increased 22% (from 41.1 to 50.2 Mg ha−1), sugar content 15% (165 to 190 g kg−1), and recoverable sucrose 45% (6.41 to 9.28 Mg ha−1). Over the harvest period, loss to molasses decreased 21% (from 9.10 to 7.12 g kg−1). The relationships for both yield and quality between planting and harvest dates was linear and nearly parallel. Genotypic differences for yield and quality were greatest on early planting dates as compared with later planting dates. Recoverable sucrose ranking of genotypes at the beginning of harvest was similar at the end of harvest. Producers should consider planting high root yield genotypes in early planted fields that are harvested late, thereby taking advantage of the entire growing season, and genotypes with average root yield and above‐average sugar content should be used for late planted or early harvested fields.
Phosphorus Nutrition Affects Wheat Response to Water Deficit
Authors: Gutiérrez‐Boem Flavio H. , Thomas Grant W.
Published: July 2010

Plant leaf area affects both plant growth and yield. Although the effects of phosphorus and water availability on leaf area development have been studied as isolated factors, little work has been done on their possible interactions. A pot experiment was conducted to investigate the effects of both P and water availability on early leaf appearance and expansion in soft red winter wheat (Triticum aestivum L.), and to determine whether the effect of water deficit changes at each level of P nutrition and whether the soil water content affects plant P uptake. The soil was a Lonewood loam (fine‐loamy, siliceous, mesic Typic Hapludult), which had an available P level of 8.2 mg P kg−1 (Mehlich III). Additional P was applied at 0, 10 and 20 mg P kg−1 soil. Water treatments consisted of keeping soil‐water content at 80% (well watered) and 53% (stressed) of the 10 kPa soil‐water content. Plant development, leaf appearance and expansion, and stomatal resistance were measured during the experiment. At harvest (38 d after emergence), leaf area, aboveground biomass, and P concentration were measured. Phosphorus and water availability exhibited a significant interaction on tiller and leaf appearance, which were reduced by water stress but only at 0 applied P. As individual factors, P and water influenced different plant features. Lack of applied P decreased the rate of leaf appearance and, therefore, the final number of leaves and leaf area per plant. Water deficit reduced individual leaf area and, at 0 applied P, reduced rate of leaf appearance, number of simultaneously expanding leaves, and final number of leaves. Phosphorus uptake was increased only with added soil P, and not by water stress. The ability of plants to cope with mild water stress was enhanced by adequate P nutrition.
Efficacy of Treatments for Delaying Senescence of Wheat Leaves: I. Senescence under Controlled Conditions
Authors: Benbella Mohamed , Paulsen Gary M.
Published: July 2010

Senescence of wheat (Triticum aestivum L.) leaves is accelerated by high temperature during the critical grain filling period. Loss of leaf viability decreases grain yields and the response to production inputs. Studies were conducted under controlled conditions to identify treatments that might delay the rapid senescence induced by high temperature. Shoots of 30‐d‐old seedlings of ‘Nesma’ wheat were immersed in 0.1 mM solutions of kinetin, abscisic acid, or one of six mineral salts [0.1 mM Ca(NO3)2, NaH2PO4, K2SO4, KH2PO4, KNO3, or NH4H2PO4] and incubated at 20 and 30°C with continuous irradiance of 150 μmol m−2 s−1. Chlorophyll and free amino acid concentrations and crude protease enzyme activity were monitored over an 8‐d period as measures of shoot senescence. High temperature and abscisic acid generally increased all senescence processes, whereas kinetin and several mineral salts reduced the loss of chlorophyll and slowed the increases in amino acid concentration and protease activity compared with amounts in shoots incubated in distilled water. Mineral salts that contained N or P were usually most effective, particularly in countering rapid senescence at 30°C relative to 20°C. We conclude that senescence processes induced by high temperatures in detached shoots resemble those in whole plants and that the feasibility of delaying senescence by foliar application of selected compounds under field conditions merits investigation.
Golf Green Soil and Crown‐Level Temperatures under Winter Protective Covers
Authors: Dionne Julie , Dubé Pierre‐André , Laganière Marc , Desjardins Yves
Published: July 2010

Winter protective covers are currently used in northern climates to mitigate winter damages on golf greens. Despite the critical importance of soil temperature on winter survival of golf greens, little information exists on the effects of commercially available protective covers on soil temperatures regimes during winter. This 3‐yr (1993–1996) field study was conducted to determine the influence of different winter protective covers on golf green soil temperature under two northern climate conditions (thick or thin snow cover). Six winter protection treatments were tested: permeable covers; impermeable covers; curled wood shavings mat, straw mulch, and 5 cm air space (each under an impermeable cover); and a control treatment without any protection. Daily climatological data and soil temperatures under protective covers were recorded at two experimental sites (Quebec City and St‐Lambert, Montreal, Canada). Throughout the winter seasons, soil temperatures under protective covers and control plots remained around 0°C under a thick and stable snow cover (average of 42 cm during experiment). Under .thin snow cover (average of 6 cm during experiment), minimum crown temperatures were markedly influenced by winter covers and reached a minimum over all years of −20.6, −19.5, −18.2, −11.1, −6.6,and −1.0°C for control, impermeable, permeable, curled wood mat, air space, and straw treatments, respectively. The insulating material covers (curled wood mat, air space, and straw) reduced soil temperature variation ranges, minimized the impact of freezing air temperature and thin snow cover, and consequently enhanced winter survival of golf greens under thin snow cover. Thus, depending on local conditions, and particularly on snow cover, the characteristics of specific protective covers can influence golf green soil temperatures and turfgrass survival during the overwintering period.
Soybean Weed Communities: Relationships with Cultural History and Crop Yield
Authors: de la Fuente Elba B. , Suárez Susana A. , Ghersa Claudio M. , León Rolando J. C.
Published: July 2010

Cultural history and cropping systems create an environmental heterogeneity that determines variability in both crop yield and weed communities. Describing relationships between environmental heterogeneity, crop yield, and weed communities may be useful for making agricultural management decisions. We studied the weed communities of soybean [Glycine max (L.) Merr.] fields in the Rolling Pampa, Argentina, to identify floristic and functional (life cycles, origin, and morphotypes) structure in fields with different management practices, and to explore the association between weed species, cultural history, and crop yield. We surveyed 18 and 42 different fields in 1994 and 1995, respectively, in soybean cropped with conventional and notillage practices. In 1994, we recorded presence of weed species and in 1995 we recorded weed presence and abundance, and management information (type of tillage, number of agricultural cycles, grain yield, planting date, and weed control). We used multivariate analysis to examine relationships among variables. We distinguished four communities and eight floristic groups, related to crop yield and tillage system. The presence of Floristic Groups II [Oxalis chrysantha (Kunth) Prog., Sonchus oleraceus L., and Veronica persica Poir.], VII [Carduus acanthoides L., Stellaria media (L.) Vill., Physalis viscosa L., Taraxacum officinale Weber, and Coronopus didymus (L.) Sm.], and IV [Bidens subalternuns DC., Cirsium vulgare (Savi) Ten., and Cyperus sp. L.] may be an indicator of high potential crop yield (low soil degradation), and their absence may be an indicator of low potential crop yield (increasing soil degradation). Functional structure (life cycles, origin, and morphotypes) was similar between communities, indicating that agroecosystems preserve function, despite management practices. The main variables explaining weed distribution in the surveyed region were tillage system, crop yield, planting date, and the number of agricultural cycles.
GUICS: A Generic User Interface for On‐Farm Crop Simulations
Authors: Acock Basil , Pachepsky Yakov A. , Mironenko Eugene V. , Whisler Frank D. , Reddy Vangimalla R.
Published: July 2010

As knowledge of crop growth and development is quantified, it can be included in the computer code of crop simulators that mimic the essential features of plant–soil–atmosphere–management interactions. The next step necessary is to provide tools to simplify operation of the crop simulator by end users. Our objectives were to (i) develop a graphical user interface (GUI) specifically oriented to on‐farm use and (ii) research the possibility of building a generic GUI that could be used with many crop simulators not necessarily having the same structure of input data. We call the interface GUICS (standing for Graphical User Interface for Crop Simulations). GUICS is built on the usability paradigm developed by software designers and has a user‐centered design based on results of human–computer interaction studies. The usability of the interface is facilitated with special features that enhance the directness, user‐in‐control, consistency, forgiveness, feedback, and simplicity of the interface. Including a simulator in GUICS is a straightforward operation that does not require changes in the simulator code. The GUICS prototype was evaluated by its future users in interviews during which they had hands‐on experience. Two years of on‐farm use of GUICS has proved the usability of the interface.
Summer Accumulation of Tall Fescue at Low Elevations in the Humid Piedmont: II. Fall and Winter Changes in Nutritive Value
Authors: Burns Joseph C. , Chamblee Douglas S.
Published: July 2010

The mild but variable temperatures and predominant rainfall during the winter could reduce the nutritive value in the winter of summer‐accumulated tall fescue (Festuca arundinacea Schreb.). The objective of our 3‐yr study was to determine the nutritive value of tall fescue accumulated from 1 June, 1 July, 1 July + N (67 kg N ha−1), 1 August, and 1 September and sampled from October to March. The treatments were arranged in a randomized complete block design with four replicates. Delaying accumulation from 1 June to 1 September increased in vitro dry matter disappearance (IVDMD) linearly (P ≤ 0.05) at each monthly sampling from October to March. Highest IVDMD (717 g kg−1) was obtained from the 1 September accumulation sampled in October and declined to 623 g kg−1 in March. Forage accumulated from 1 June and 1 July was lowest in IVDMD and averaged 590 g kg−1 in October and declined to 539 g kg−1 in March. Crude protein (CP) concentrations showed little change from November to March (mean = 121 g kg−1). Green tissue in accumulated forage retained high IVDMD (mean = 714 g kg−1) throughout the winter, but the proportion shifted from about 73% green in November to 36% in January. Dead tissue, consistently low in IVDMD (mean = 393 g kg−1), reduced canopy IVDMD from 26 to 55 g kg−1 for each 10 percentage unit increase. Tall fescue can be accumulated during the summer in the Piedmont and can provide forage of high nutritive value until January or until dead tissue dominates in the forage.