bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonparametric Analysis of Cultivar Performance Trials: Experimental Results and Comparison of Different Procedures Based on Ranks
Authors: Hühn Manfred , Léon Jens
Published: July 2010

Cultivar performance trials are usually analyzed by analysis of variance techniques. In the field of practical applications, the required simplifying assumptions may often not be fulfilled. Nonparametric methods based on ranks avoid this difficulty and provide a viable alternative to parametric procedures. The objective of this study was to compare four nonparametric procedures (Bredenkamp, Hildebrand, Kubinger, and van der Laan‐de Kroon) and the parametric analysis of variance with each other for extensive data sets from German official registration trials (1985–1989) with winter oilseed rape (Brassica napus L.), fababean (Vicia faba L.), oat (Avena sativa L.), fodder beet (Beta vulgaris L.), and sugar beet (B. vulgaris). The van der Laan‐de Kroon method is based on the crossover concept of interaction (different rank orders), while the other methods are based on the concept of deviations from additivity of main effects. The methods were compared using the numerical values of the test statistics. For the sources cultivars, locations, and interactions one obtains these relationships: ANOVA ≥ Hildebrand ≅ Kubinger > van der Laan‐de Kroon > Bredenkamp. If the assumptions for parametric methods cannot be accepted, the van der Laan‐de Kroon method is recommended for the crossover interaction concept, while the Hildebrand or Kubinger method (both of which are approximately equivalent) should be applied for the usual interaction concept. The Bredenkamp method cannot be recommended.
Inheritance of Potassium‐Sodium Nutritional Traits in Alfalfa
Authors: James David W. , Dhumal Suresh S. , Rumbaugh Melvin D. , Tindall Terry A.
Published: July 2010

Alfalfa (Medicago sativa L.) growing on K‐depleted, semiarid, calcareous soil displays three K‐deficiency symptoms: (i) white spots on leaflets W, (ii) marginal chlorosis M, and (iii) normal leaflets on stunted plants (N). In a greenhouse study, we examined partitioning and heritability of K and Na nutritional traits in three alfalfa clones and their crosses, and also how K and Na soil fertility levels affected biomass production, genetic dependence of K and Na uptake and partitioning, and K use efficiency. Mother plants were propagated vegetatively and by seed from phenotype crosses in a low‐K, low‐Na, calcareous soil rooting medium. One trial used K‐ and Na‐amended soil. Harvests were at early bloom. Leaves contained more K than stems, with no difference among phenotypes; Na was uniform in stems, but leaves of M contained much more Na than leaves of N and W. With nonamended soil, K and Na uptake and partitioning among leaves, stems, and roots were significantly affected by cross. The Na:K ratio in leaves, stems, and roots was strongly influenced by phenotype and cross. Biomass production of leaves and stems differed among crosses and was increased by K fertilization; Na fertilization affected biomass only of leaves, and only in crosses M ✕ M and N ✕ N (Na may have partially replaced K). The shoot:root ratio was affected only by cross. Potassium use efficiency was affected by cross and by Na fertilization. Broad‐sense heritability for K and Na concentration was high, especially for Na in leaves and stems. Uptake and partitioning of Na and K in phenotype crosses supported narrow‐sense heritability as well. Genetics, rather than soil K‐Na competition, governed Na uptake, translocation, and utilization by phenotypes. Accordingly, characterization of K nutrition in alfalfa must consider Na levels. As phenotypes of alfalfa cultivars range widely in K‐Na nutritional traits, it should be possible to select for high yield and K use efficiency.
Potato Leafhopper Management: Effects on Production and Quality of Alfalfa‐Timothy Mixtures
Authors: Davis Paula M. , Fick Gary W.
Published: July 2010

Alfalfa (Medicago sativa L.) mixtures with grasses, especially timothy (Phleum pratense L.), are widely planted in the Great Lakes Region, but most information on potato leafhopper [Empoasca fabae (Harris)] (PLH) management for new stands is based on alfalfa monocultures. Field research was conducted in 1991 and 1992 to evaluate the ability of alfalfa to recover from PLH injury following insecticide application and to compare the effect of injury on yield and quality of first‐year monocultures or mixtures. Four replicates of alfalfa monoculture and alfalfa‐timothy mixtures were established each year. One week after the first harvest in early July, eight split‐plot treatments were established in each main plot: an uncaged check, a caged check, and six combinations of two PLH infestation densities (25 or 50 PLH adults m−2) and three insecticide application dates (1 wk after infesting plots, 3 wk after infesting plots, and unsprayed). Crop mixture had no effect on PLH nymphal populations on a per stem basis. Although differences between years were noted, delaying insecticide application generally reduced forage yield and quality, delayed crop maturity, and increased weed content, particularly in forage mixtures. There was little evidence that seedling timothy could compensate for PLH injury to alfalfa. Data on stem elongation and dry matter accumulation indicated that alfalfa can recover from leafhopper injury; however, dry matter production did not increase for at least 2 to 3 wk following a spray application. Reductions in forage crude protein due to PLH injury were a result of both reduced crude protein content in the alfalfa and an increase in the proportion of weed biomass in the forage. Early detection and rapid response to economically significant populations are necessary to realize the greatest benefit from treatment. The presence of timothy in the mixture does not alter PLH management recommendations for new stands.
Evaluation of Video Image Analysis and Line‐Intercept Methods for Measuring Root Systems of Alfalfa and Ryegrass
Authors: Murphy Stephanie L. , Smucker A. J. M.
Published: July 2010

Improved quantification of plant root systems is essential for determining the functional efficiencies of plant roots. The objective of this study was to evaluate the video image analysis procedure of quantifying roots of different species and compare it with more traditional measurements. Three methods were used to quantify roots of alfalfa (Medicago sativa L.) and perennial ryegrass (Lolium perenne L.) from a greenhouse experiment: (i) root length by video image analysis, (ii) root length by the line‐intercept method, and (iii) dry root weight. Estimates of root length by image analysis and line‐intercept methods were comparable for alfalfa and were positively correlated with root weight. In contrast, the correlation between image analysis and line‐intercept estimates of ryegrass root length was poor (r2 = 0.090), and no significant relationship was found between ryegrass root length and root weight. Difficulty in the quantification of ryegrass roots was related to the large numbers of very fine roots, which resulted in extremely large root lengths and excessive error. Root data of ryegrass (and species with similar root morphology) obtained by the line‐intercept method may provide only relative values to be compared among these species. The image analysis method of root measurement is bound to improve root data with increased magnification and resolution of the video images when the root density in the image (cm cm−2) is sufficiently low.
Laboratory Freeze Tolerance of Field‐Grown Forage Bermudagrass Cultivars
Authors: Anderson Jeffrey A. , Taliaferro Charles M.
Published: July 2010

Freeze tolerance is a limiting factor in production of many bermudagrasses (Cynodon spp.) in the transition zone between warm‐ and cool‐season grasses. Our objective was to evaluate the seasonal patterns of freeze tolerance in five forage bermudagrass cultivars. Midland, Hardie, Tifton 44, World Feeder, and Gordon's Gift were grown in field plots and acclimated under natural conditions, then subjected to laboratory freeze tolerance evaluations. Lowest survival temperatures (LSTs) were determined at monthly intervals from November through May in 1992‐1993 and 1993‐1994. LSTs were between −5 and −7°C for all cultivars in early November. Gordon's Gift had the greatest freeze tolerance in midwinter, surviving exposure to ≈ −11°C in 1992‐93 and ≈ −10°C in 1993‐94. Gordon's Gift was significantly more freeze tolerant than the other cultivars on most dates. The differences in freeze tolerance among the cultivars tested indicates substantial variation in the species that may be used for breeding improvement.
CPM: Software for Cotton Final Plant Mapping
Authors: Plant Richard E. , Kerby Thomas A.
Published: July 2010

Final plant mapping in cotton (Gossypium hirsutum L.) is the practice of recording from a sample of plants the location of every retained boll on the plant, together with ancillary whole‐plant information. We have developed an easy‐to‐use computer program called CPM (Cotton Plant Mapper) for efficient entry and statistical analysis of final plant map data. It takes plant‐by‐plant data as input and generates statistical information on the sample. It also permits samples to be merged into an aggregate so that summary statistics may be computed. The program is intended primarily for use on a palmtop computer, permitting direct data entry. It features a sequential sampling procedure that indicates when a sufficiently precise estimate of whole‐plant data has been obtained and sampling may be stopped.
Yield and Botanical Composition of Legume‐Interseeded vs. Nitrogen‐fertilized Switchgrass
Authors: George J. Ronald , Blanchet Kevin M. , Gettle Randall M. , Buxton Dwayne R. , Moore Kenneth J.
Published: July 2010

Switchgrass (Panicum virgatum L.) has a relatively high N requirement for high yields of quality forage. It is not clear what role legumes can play in supplying this N and in improving herbage yield when grown in association with switchgrass. To evaluate cool‐season legume renovation vs. N fertilization of established switchgrass, 10 forage legumes and a legume mixture were compared with 0, 60, 120, and 240 kg N ha−1. Forage yield and botanical composition of basal (<20 cm) and upper (>20 cm) canopy were compared at Ames, IA, on a Webster silty clay loam (mesic Typic Haplaquoll). Legumes were no‐till interseeded in early April; N was applied before mid‐May. Legume renovation did not affect June yield during the establishment year (Yl), but produced 9% greater yields than 0‐N grass in July. N fertilization increased uppercanopy grass yield 2.4‐fold compared with 0 N and legume renovation during Yl. During the second year (Y2) of 1991 seedings, all legume treatments except crownvetch (Coronilla varia L.) produced more totalseason upper‐canopy yield than grass fertilized with 240 kg N. For 1992 seedings, birdsfoot trefoil (Lotus corniculatus L.), Mammoth red clover (Trifolium pratense L.), and trefoil‐red clover mixture had Y2 yields that equaled or exceeded yield for 240 kg N. Mean legume composition of Y2 upper canopy for June, July, and August was 84, 70, and 51%, respectively, in 1991 seedings and 53, 28, and 27% in weather‐damaged stands of 1992 seedings. Y2 yields for interseeded legumes provided significant improvement over 120 or 240 kg ha−1 N, so cool‐season legumes can substitute for N fertilization after the seeding year. Adequate defoliation in early June is important to minimize legume competition to established switchgrass. Livestock producers should renovate only a portion of switchgrass pastures in a single year, because of a shortfall in forage supply during legume establishment compared with that of N‐fertilized grass.
Foliar Methanol Applications to Cotton in the Southeastern United States: Leaf Physiology, Growth, and Yield Components
Authors: van Iersel Marc W. , Heitholt James J. , Wells Randy , Oosterhuis Derrick M.
Published: July 2010

Foliar methanol applications have previously been reported to dramatically increase yields of a variety of crops under arid conditions, including cotton (Gossypium hirsutum L.). Whether methanol is effective in the southeastern USA is not known. In addition, the agronomic and physiological events contributing to the increase are not understood. Therefore, we conducted a series of experiments in 1993 to study the effects of methanol on the gas exchange, water relations, development, growth, and yield of field‐grown cotton at three locations in the southeastern USA. Conventional management and irrigation procedures were used. Methanol solutions in water, with and without urea and iron, were applied over the top at midday to cotton. Four to eight applications were made from flowering to late boll filling. Both single‐leaf and canopy photosynthesis rates taken 2 h to 6 d after treatment were unaffected by methanol or the nutrients. At one site, CO2 compensation point was determined, but did not differ among treatments. This finding does not support previous claims that methanol reduces photorespiration. Transpiration and water potential also were not affected by foliar applications of 15 or 30% methanol (v/v). Foliar methanol applications also did not result in faster development of the crop and did not increase yield at any of the locations. Our results do not indicate any positive effect of foliar methanol applications on cotton in the southeastern USA.
Performance of Buffelgrass Germplasm with Improved Winter Survival
Authors: Hussey Mark A. , Bashaw Elexis C.
Published: July 2010

Lack of winter hardiness in buffelgrass [Cenchrus ciliaris L.; syn. Pennisetum ciliare (L.) Link] currently limits the utilization of this species in Texas and northern Mexico. This study was conducted to assess differences in field survival and yield potential of buffelgrass germplasm believed to have increased levels of winter hardiness. To document differences in field winter survival seedlings of five buffelgrass genotypes (‘Common’, ‘Llano’, ‘Nueces’, PI 409704, and T‐7040) were established at six locations in Texas ranging from 28 to 34°N latitude. The winter‐hardy species Pennisetum orientale L. cv. Cowboy was included as a check. The buffelgrass entries PI 409704 and T‐7040 (a 2n + n hybrid between 409704 and an unknown male parent) had greater field survival than the cultivars Common, Llano, and Nueces, but were less winter hardy than Cowboy at the three locations (Knox City, Stephenville, and Vernon) north of College Station. All entries survived the winter at Beeville, College Station, and Uvalde. Yield at two cutting heights was evaluated over a 3‐yr period at College Station. The rhizomatous cultivars Llano and Nueces had the greatest yield when harvested at 50 mm, while no significant differences existed among Llano, Nueces, PI 409704, and T‐7040 when harvested at 150 mm. Defoliation height influenced winter survival of Common buffelgrass at College Station. During the winter of 1987–1988, 60 and 20% of the Common plants failed to survive at the 50‐ and 150‐mm defoliation heights, respectively. Defoliation height did not affect crown nonstructural carbohydrate concentration (CHO). The most winter‐hardy entry, Cowboy, had the highest CHO; the least winter‐hardy entry, Common, had the lowest. These results suggest that winter‐hardy pentaploid buffelgrass germplasm such as PI 409704 have the potential to expand the current range of buffelgrass.
Plant Analysis with Standardized Scores Combines DRIS and Sufficiency Range Approaches for Corn
Authors: Baldock Jon O. , Schulte Emmett E.
Published: July 2010

The Sufficiency Range (SR) system and the Diagnosis and Recommendation Integrated System (DRIS) represent two competing approaches to interpreting plant analyses. Our objectives were (i) to show that the two approaches are complementary and (ii) to introduce a new plant analysis system that combines them, called Plant Analysis with Standardized Scores (PASS). The SR provides discrete, easily computed independent nutrient indices (INI). The DRIS determines continuous, difficult to calculate, but easily interpreted dependent nutrient indices (DNI), plus an overall balance index and a ranking of the relative deficiencies. Those differences are complementary; that is, the strengths of the one are the weaknesses of the other, and vice versa. The PASS system combines the strengths of the SR and DRIS by including an INI section and a DNI section, in which both types of indices are on the convenient DRIS scale. When we compared the ability to diagnose deficiencies and sufficiencies in 24 corn (Zea mays L.) dry matter or grain yield comparisons, PASS had a higher efficiency rating (82%) than the SR (41%) and DRIS (33%). The PASS system had a significantly higher proportion of correct diagnoses of deficient nutrients than the DRIS and a significantly greater proportion of correct diagnoses of sufficient nutrients than the SR. Furthermore, the PASS overall index, but not the DRIS, was significantly correlated with relative corn grain yield in 10 comparisons showing a yield response.
Spatiotemporal Variability of Corn and Soybean Yield
Authors: Jaynes Dan B. , Colvin Thomas S.
Published: July 2010

Little is known about the spatial structure of yield across fields, nor of the temporal stability of this structure. We determined the spatial structures of grain yield for 6 yr of data and examined the stability of these structures over time. Yields were measured each year at 224 locations on an 8 × 24 grid within a 16‐ha field, using plot combines. The field was planted either to corn (Zea mays L.) or soybean [Glycine max (L.) Merr.] in an alternate‐year rotation. Soybean yields averaged 3.16, 3.14, and 3.12 Mg ha−1 in 1990, 1992, and 1994. Corn yields averaged 9.30, 9.34, and 5.02 Mg ha−1 in 1989, 1991, and 1993 with the lower yield in 1993 a result of excessive rainfall that year. The large‐scale deterministic structure of the spatial yield data was constructed for each year by median polishing. The trend surfaces were different for each year, indicating a lack of temporal stability in large‐scale structure, although the trend surfaces shared some similar features. Overall, the deterministic structure accounted for about 25% of the overall yield variance. The small‐scale stochastic spatial structure was determined by computing variograms of the yield residuals after subtracting the trends. Variograms showed strong spatial structure of the yield residuals, with zero nugget and correlation ranges approaching 150 m. Variograms differed from year to year and were not related to the crop being grown. The range was significantly correlated to precipitation, increasing with increasing total growing‐season rainfall. Long‐term monitoring of yield will be necessary to fully characterize its spatial‐temporal pattern.
Performance and Stability of Brachytic and Normal‐Stemmed Isolines of Soybean
Authors: Lee Suk Ha , Boerma Roger H. , Raymer Paul L. , Ashley Doyle A.
Published: July 2010

Plant lodging is a problem in soybean [Glycine max (L.) Merr.] production, particularly in high‐yield environments. The brachytic stem trait (sb1 sb2) reduces plant stature while maintaining the number of nodes for fruiting and may be desirable in the development of lodging‐resistant cultivars. To determine the effects of brachytic stem on seed yield, plant height, and other agronomic traits across a range of environments, this trait was backcrossed into ‘Wright’ and ‘GaSoy 17’, and the near‐isogenic lines (isolines) were evaluated in 57 (Wright) and 36 (GaSoy 17) environments. Averaged across environments, the height of brachytic Wright (B‐Wright) was 56% of its normal‐stemmed isoline and that of brachytic GaSoy 17 (B‐GaSoy 17) was 66% of its isoline. In a combined analysis over environments, brachytic genotypes averaged 37% shorter internode length, 5% fewer nodes, and 7% smaller seed weight than normal‐stemmed isolines. Brachytic and normal‐stemmed isolines did not differ in yield, seed protein concentration, or seed oil concentration. There was a genotype x environment interaction (P < 0.01) for yield for both isoline pairs. Regression analysis of yield stability indicated that the GaSoy 17 isolines were equally stable across environments (similar coefficients and R2 values). For B‐Wright, however, a smaller regression coefficient (b = 0.82 ± 0.07) than Wright (b = 1.07 ± 0.05) and a lower R2 value (70 vs. 89%) suggest that Wright yielded higher in favorable environments and was more stable in yield performance. Plant height of brachytic lines was much less stable than for normal‐stemmed lines. Genotypes with the brachytic stem trait produced yields similar to normal‐stemmed genotypes in environments not highly conducive to lodging. The reduced stability of yield and plant height for brachytic‐stemmed genotypes must be considered (along with the expected increase in yield in lodging‐prone environments) prior to commercial acceptance.
Modified No‐Till Systems for Corn Following Wheat on Clay Soils
Authors: Opoku George , Vyn Tony J. , Swanton Clarence J.
Published: July 2010

Concerns about corn (Zea mays L.) grain yield reduction with notill following winter wheat (Triticum aestivum L.) in rotation on clay soils has been a major factor in slowing the rate of adoption of no‐till systems in Ontario. Our objective was to determine conservation tillage and wheat residue management systems that provide favorable seedbed conditions for emergence, growth, and yield of corn following winter wheat on clay soils. Seven tillage and residue management systems (fall moldboard plow, chisel plow, tandem disk, and zonetill, and no‐till bare and with straw baled and not baled) were evaluated in 1994 and 1995 at two locations in Ontario. Fall zone‐till reduced the amount of wheat residues on the soil surface. Wheat residues remaining in late fall with zone‐till, no‐till (baled), and no‐till (not baled) treatments were 3.1, 4.0, and 7.1 Mg ha−1. Volumetric soil moisture levels in the top 15 cm early in the season did not differ among fall tillage treatments, but were all lower than for no‐till with wheat residue. Modifying the no‐till system by adopting fall zonetill or fall tandem disk produced grain yields no different from fall moldboard plow or fall chisel plow treatments, and greater by 5 to 10% than for no‐till with wheat residue. No‐till yield potential was affected by the level of wheat residue present. Completely removing all wheat residue increased no‐till corn grain yields by 0.5 and 0.9 Mg ha−1 compared with baling and not baling straw, respectively. The baled and not‐baled no‐till treatments had the lowest proportion of finer soil aggregates in the seedbed, greatest penetrometer resistance up to the 20‐cm soil depth, slowest corn growth, and lowest grain yield. We recommend zone‐till or tandem disk in the fall for corn production on clay soils following wheat.
Effectiveness of Soil‐Applied Herbicides with Mechanical Weed Control for Conservation Tillage Systems in Soybean
Authors: Hooker David C. , Vyn Tony J. , Swanton Clarence J.
Published: July 2010

Producers who adopt conservation tillage systems need information on effective weed control strategies. In 1991 and 1992, various weed control strategies were evaluated in soybean [Glycine max (L.) Merr.] grown with three tillage systems at two locations in southern Ontario. Primary tillage treatments were fall moldboard plowing (MB), fall chisel plowing (CP), and first‐year no‐till (NT). Combinations of mechanical weeding, residual herbicides broadcast at two rates, and a band application of metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide) plus linuron (N'‐(3,4‐dichlorophenyl)‐N‐methoxy‐N‐methylurea) were investigated as treatments within each tillage system. Timely rotary hoeing reduced weed numbers in MB and CP treatments, but was not effective in NT. In general, weeds were controlled by residual herbicide plus mechanical treatments (one pass with rotary hoe and two interrow cultivations) regardless of tillage system, or whether herbicides were applied in a band, or broadcast at either reduced or full rates. Herbicides broadcast at reduced rates with no subsequent mechanical weeding controlled weeds in NT; the degree of weed control was inconsistent with location with this weed treatment in MB and CP systems. In general, tillage did not appear to influence the relative proportion of one annual broadleaf weed species over another. However, overall weed populations were lower in first‐year NT than MB or CP tillage systems. Annual broadleaf weeds were effectively managed with reduced herbicide inputs in newly established conservation tillage systems.
Determination of Pasture Biomass Using Four Indirect Methods
Authors: Harmoney Keith R. , Moore Kenneth J. , George J. Ronald , Brummer E. Charles , Russell James R.
Published: July 2010

The most accurate method for determining canopy biomass of pastures for forage availability is by cutting and weighing forage from known areas. Faster methods that require less time and labor would help producers to monitor forage availability in pastures on a daily or weekly basis. Indirect methods rely on calibrations performed on pure or evenly distributed plant compositions to determine forage biomass. However, microclimates developed by varying landscape positions and soil morphological characteristics of pastures may cause uneven plant and species distributions. This study was performed to compare the ability of a modified Robel pole, rising plate meter, canopy height stick, and Li‐Cor LAI 2000 leaf canopy analyzer to determine forage availability in pastures with varying species composition from four areas. Swards consisted of pure warm‐season grass stands, cool‐season grass stands, legume stands, and grass‐legume mixtures. Instrument readings were compared with forage availability determined by clipping and were measured for accuracy, or closeness to clipped weight. For all observations, coefficients of determination (r2), were 0.63, 0.59, 0.55, and 0.32 for the modified Robel pole, rising plate meter, canopy height stick, and leaf canopy analyzer, respectively. For modified Robel pole readings, r2 was highest for observations in red clover (Trifolium pratense L.) (r2 = 0.83), smooth bromegrass (Bromus inermis Leyss.) (r2 = 0.82), and alfalfa (Medicago sativa L. (r2 = 0.76) swards, whereas the rising plate meter r2 values were highest for observations in tall fescue (Festuca arundinacea Schreb.) (r2 = 0.85), alfalfa (r2 = 0.84), and red clover (r2 = 0.73) swards. Grass observations also had their highest r2 values with the modified Robel pole and rising plate meter at 0.63 and 0.59, respectively. The modified Robel pole proved to be the most accurate method used over a variety of species.
Digital Image Correlation Procedure to Characterize Soil Surface Layer Cracking
Authors: Caárdenas‐García Jaime F. , Yao Haigen , Zheng Siding , Zartman Richard E
Published: July 2010

This study was conducted to characterize surface layer cracking in Vertisols by determining surface displacement trends. A disturbed sample from the Ap horizon of a Randall clay (fine, smectitic, thermic Ustic Epiaquerts) was evaluated. Digital image correlation (DIC) used to track the movement of points on the surface as the soil dried and to assess the development of soil surface cracking. Displacement fields among a group of images were obtained by using a cross‐correlation algorithm. The displacement vectors resulting from the analysis of the displaced fields can be used to show cracking patterns on a ground‐up soil sample from a Vertisol before they become visually apparent. Digital image correlation may be used to calculate the deformation of the surface layer with relatively high precision.
Estimating Root Mass in Maize Using a Portable Capacitance Meter
Authors: van Beem Janny , Smith Margaret E. , Zobel Rich W.
Published: July 2010

Time and expense are major constraints limiting the detection of genotypic differences in the length, structure, and growth rate of root systems in the soil. Recent development of a hand‐held capacitance meter could enable the routine quantification of root mass. The objective of this study was to determine the accuracy with which a BK Precision 810A capacitance meter can estimate root fresh mass in maize (Zea mays L.) using a technique that allows a rapid and noninvasive capacitance reading. The capacitance meter measured root capacitance of maize grown under greenhouse (8 genotypes) and field (6 genotypes) conditions. After the capacitance readings, 14 plants per genotype were uprooted, roots were washed thoroughly, and root fresh mass was obtained. The statistical relationship between capacitance and root fresh mass in greenhouse experiments was significant early in the growth season for all genotypes (r2 = 0.73, P < 0.001), and significant only late in the growth season for inbreds (r2 = 0.56, P < 0.001). Field studies showed that capacitance and root fresh mass were statistically correlated for all genotypes at flowering (r2 = 0.69, P < 0.001). In conclusion, capacitance meters equipped with a clamp for rapid attachment to the plant may facilitate the nondestructive identification of genotypes with root characteristics that confer adaptation to various environments. Conditions for accurate capacitance measurements included a moist medium around the plant's root system and a consistent placement of the electrode at 6 cm above the crown.
Establishment of Switchgrass and Big Bluestem in Corn with Atrazine
Authors: Hintz Roger L. , Harmoney Keith R. , Moore Kenneth J. , George J. Ronald , Brummer Edward C.
Published: July 2010

Switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) provide abundant forage for livestock and wildlife during hot summer months when cool‐season grass species may decline in production. Little biomass production for grazing may result during warm‐season grass establishment because of weed competition. Chemical methods of weed control are now limited, because application of atrazine [6‐chloro‐N‐ethyI‐N'‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] to switchgrass and big bluestem is no longer allowed according to the label. Using corn (Zea mays L.) as a companion crop could provide potential for high biomass production during warm‐season grass establishment, and allow the use of atrazine for weed control. This study investigated the ability of switchgrass and big bluestem to establish in a corn companion crop. The effects of corn hybrid (short‐ vs. long‐season), population density, row spacing, and harvest date on switchgrass and big bluestem stands and on corn production were quantified. Establishment of switchgrass and big bluestem in corn was successful. Switchgrass mean stands were 26.3 plants m−2 in 1995 and 46.4 plants m−2 in 1996. Big bluestem stands were similar to switchgrass in 1995 (31.7 plants m−2), but were much lower in 1996 (5.2 plants m−2). Long‐season corn hybrids and higherdensity corn populations increased corn silage and grain yield without reducing warm‐season grass stands. Within a season, no difference existed between corn grain yields when grown with either switchgrass (6.7 Mg ha−1 in 1995, 5.3 Mg ha−1 in 1996) or big bluestem (6.9 Mg ha−1 in 1995, 5.7 Mg ha−1 in 1996). Silage dry matter yield was not different between corn grown with switchgrass (12.6 Mg ha−1 in 1995, 16.1 Mg ha−1 in 1996) and corn grown with big bluestem (13.1 ha−1 in 1995, and 16.6 Mg ha−1 in 1996) for a given year. Switchgrass and big bluestem grown in corn with atrazine reduced land production losses during the establishment year, yet allowed adequate establishment of these grasses for future forage production.
Apparatus for Dissecting Stalks to Evaluate Stem Borer Insect Resistance in Maize
Authors: Kreps Ralph C. , Klein Dietrich , Melchinger Albrecht E.
Published: July 2010

Measuring tunnel length in stalks is a common method for evaluating resistance against European corn borer (Ostrinia nubilalis Hübner) in maize (Zea mays L.). Infested plants are dissected and tunnel length, attributed to feeding of corn borer larvae, is measured. This is laborious and time‐consuming, thus restricting the number of genotypes that can be evaluated for resistance in breeding programs. An apparatus built mostly of polyvinylchloride (PVC) and spring steel was constructed for dissecting maize stalks. Stalks are pushed by hand through the apparatus and are thus split apart. This apparatus dissects the stalk into two equal parts for measuring stem borer resistance in maize and reduces the time spent for splitting a stalk by =50% compared with conventional methods. The cutter ensures no escapes in investigating tunnel lengths.
Response of Spring Wheat to Nitrogen Fertilizers of Different Nitrification Rates
Authors: Goos R. Jay , Schimelfenig Julie A. , Bock Bert R. , Johnson Brian E.
Published: July 2010

Hydroponic and greenhouse studies have shown that grain yields of wheat (Triticum aestivum L.) are maximized when the N supply contains a mixture of NH4 and NO3. Tillers per plant is the yield component most commonly increased by mixed N nutrition in greenhouse studies. The objective of this study was to evaluate, under field conditions, the response of ‘Butte 86’ spring wheat to N sources differing greatly in nitrification rate. Nitrogen was applied at 0 or 112 kg N ha‐1; the N sources were calcium nitrate (CN), urea, ureadicyandiamide (DCD), 0.1‐g urea granules, and 0.1‐g urea–DCD granules. Six field trials were performed. Topsoil (0–15 cm) analysis of fertilized plots during tillering indicated a wide range of mineral N contents (19–101 mg N kg‐1) and of NH4:NO3 mole ratios (0.04–2.06). Correlation analyses suggested that tillering was sensitive to the total mineral N supply, but quite insensitive to the NH4:NO3 ratio in the topsoil. Vegetative growth and N uptake were generally lower for CN than for the other N sources. At some locations, more heads per square meter at harvest were observed with the slower‐nitrifying N sources. Grain yields were increased by N fertilization, but significant differences between N sources were not generally observed. For both years of the study, the 0.1‐g urea‐DCD granules gave the highest N uptake efficiency. However, the dramatic responses in growth, tillering, or grain yield routinely observed with mixed N nutrition in hydroponic or greenhouse studies could not be duplicated in the field.
Fertility Gradients in Naturally Formed Terraces on Honduran Hillside Farms
Authors: Walle Robert J. , Sims Brian G.
Published: July 2010

Deposition of eroded sediment within soil conservation barriers may create a gradient of soil properties. Our objective was to determine the presence of soil fertility gradients in the naturally formed terraces of two representative conservation practices; contour grass barriers and stone walls. Soil samples were taken at five slope positions to depth of 20 cm, divided into 5‐cm sections, with three replicates (60 samples per location). Samples were analyzed for texture, total Kjeldahl N, organic matter, and extractable P, K, Ca, and Mg. For both sites, the upper slope positions were lower in soil organic matter, nutrients, and silt than the lower positions. Within stone barriers, the silt fraction and extractable P contents showed gradients, with three of five positions different. Within grass barriers, a gradient was present for clay, with three of five positions different. Organic matter and Ca showed distinct gradients, with all positions different, increasing downslope. A position × depth interaction for organic matter was detected, showing surface removal and deposition along the lower slope positions. Identification of fertility gradients may lead to improved cropping systems and fertilizer management and to refinement of agronomic research on hillside farms.
Management Effects on Herbage Yield and Botanical Composition of Rhizoma Peanut–Mixed Grass Associations
Authors: Valencia E. , Sollenberger L.E. , Kunkle W.E. , Williams M. J. , Chase C. C. , Hammond A. C. , Kalmbacher R.S.
Published: July 2010

Broadleaf weeds invade rhizoma peanut (Arachis glabrata Benth.) (RP) stands as they age, possibly because of decline in associated grasses, particularly bahiagrass (Paspalum notatum Flügge). Our objective was to assess the effect of spring N fertilization and summer stocking rate (1.5 vs. 2.5 animals ha−1; Exp. 1) or spring N fertilization and presence or absence (no grazing until July) of spring grazing (Exp. 2) on the herbage yield and botanical composition of mixed RP‐grass swards. In both experiments, pastures were fertilized with either no N (N‐0) or 35 kg ha−1 of N (N‐35) in March or early April for 3 yr. Sward herbage mass (Mg ha−1) and botanical composition were assessed in spring (April), summer (July), and fall (October) of 1995 and 1996 and spring of 1997. In Exp. 1, stocking rate did not affect herbage mass or botanical composition, but N fertilization did. By spring 1997, there was an eight percentage unit increase in grass contribution (0.30 Mg ha−1 increase in dry matter) and a trend for greater decline in RP (five percentage units, but no change in RP dry matter) for N‐35 vs. N‐0. Other forbs, Mexican tea (Chenopodium ambrosoides L.), and cogongrass [Imperata cylindrica (L.) Räusch.] were not affected by N rate. Similar changes in herbage mass and RP percentage were noted for Exp. 2, but there was a stocking rate × N fertilization interaction for grasses because the percentage increase in grass was greatest when N was applied and grazing deferred in the spring. Forb content of the sward was not affected by N fertilization or spring grazing. Our results show that grass yield and content of RP‐grass swards can be manipulated by N fertilization and deferral of spring grazing, but for the limited time period studied (3 yr), increased grass presence was not sufficient to inhibit encroachment of weedy forbs.
Productivity, Botanical Composition, and Nutritive Value of Swards Including Forage Chicory
Authors: Belesky David P. , Fedders James M. , Turner Kenneth E. , Ruckle Joyce M.
Published: July 2010

Pure stands of ‘Grasslands Puna’ chicory (Cichorium intybus L.) are productive and responsive to N fertilization in the eastern USA. We conducted a field experiment for 3 yr to investigate productivity and nutritive value of swards including chicory, orchardgrass (Dactylis glomerata L.), and birdsfoot trefoil (Lotus corniculatus L.) as a function of clipping frequency (3‐ and 6‐wk intervals). Each treatment was replicated three times on an upland site of Dekalb series soil (loamy‐skeletal, mixed, subactive, mesic Typic Dystrochrept). Modest rates of N, P, and K were applied annually. Herbage mass, botanical composition, in vitro organic matter disappearance (IVOMD), and crude protein (CP) were determined. Cumulative herbage yield was not influenced by initial sward composition with chicory, chicory‐orchardgrass, and chicory–orchardgrass–trefoil averaging 6.8 Mg ha−1 during a growing season. Clipping frequency influenced yield with canopies clipped at 6‐wk intervals producing 26% more herbage than those clipped at 3‐wk intervals. Growth rates of canopies clipped at 6‐wk intervals averaged 51 kg ha−1 d−1 early in the growing season, suggesting that swards including chicory would be responsive to nutrient inputs and where rapid herbage regrowth and nutrient use by the growing crop are needed. Chicory declined in swards with time, regardless of initial sward composition or clipping frequency. Fluctuations in IVOMD and CP were related to changes in sward composition arising from the interaction of time and clipping frequency. Including orchardgrass and trefoil retarded invasion of less desirable species and so provided a means to control overall sward productivity and herbage composition.
Switchgrass Morphological Development Predicted from Day of the Year or Degree Day Models
Authors: Sanderson Matt A. , Moore Kenneth J.
Published: July 2010

We tested recently published linear equations for predicting developmental morphology of warm‐season perennial grasses on three cultivars of switchgrass (Panicum virgatum L.). Mean stage count (MSC, based on the Nebraska system) of ‘Cave‐in‐Rock’ and ‘Kanlow’ switchgrass was measured at Ames, IA, and MSC of Cave‐in‐Rock and ‘Alamo’ switchgrass was measured at Stephenville, TX, during 1995. Measured MSC was compared with MSC estimated from day of the year (DOY) or growing degree day (GDD; base of 10°C) equations. The DOY equation more closely estimated MSC for switchgrass grown at Ames than at Stephenville. The GDD equation did not work well for any cultivar at either location. The equations did not work as well in Texas, probably because of genotypic interactions with daylength and climate for developmental morphology. These results indicate that the DOY equation may be useful with some varieties of switchgrass in the central Great Plains.
Timing, Defoliation Management, and Nitrogen Effects on Seed Yield of ‘Argentine’ Bahiagrass
Authors: Adjei Martin B. , Mislevy Paul , Chason Wallace
Published: July 2010

Seed yield of bahiagrass (Paspalum notatum Flugge) can be increased by burning the sward and applying N fertilizer at the proper time during the growing season. Our objective was to determine the optimum calendar month (photoperiod) for managing ‘Argentine’ bahiagrass pasture for seed production. Triplicate paddocks of a 10‐yr‐old Argentine bahiagrass pasture established on a Pomona fine sand (sandy, siliceous, hyperthermic, Ultic Alaquods) were grazed or not grazed (main plots) from October–February, 1988–89 and 1989–90, in a randomized complete‐block design. Cattle were removed from the area on 25 February. Then, on the 25th of February, March, April, and May (subplots) each year, portions of residue (sub‐subplots) were burned or mowed in both grazed and ungrazed fields. The residue removal dates corresponded with day lengths of 11.5, 12.3, 13.1, and 13.7 h, respectively. Immediately after residue removal, sub‐sub‐subplots (2.4 by 6.1 m) were fertilized with 0, 100, or 200 kg N ha−1. Mature raceme density, seed yield, and seed germination (1989 only) were determined in 1989 and 1990. Grazing did not affect any measured trait. Burning increased seed yield only for the 25 May 1990 treatment. Date of residue removal and N rate influenced (P < 0.0001) the number of mature racemes and seed yield interactively (P < 0.05). Nitrogen rate increased (P < 0.05) all measured traits in a quadratic manner when applied only during late‐April to late‐May. Results suggest that seed production from Argentine bahiagrass pasture in the subtropics could be enhanced with management implemented at day lengths >13.0 h.
Leaf and Stem Area Relationships to Masses and Their Height Distributions in Native Grasses
Authors: Retta Amare , Armbrust Dean V. , Hagen Lawrence J. , Skidmore Edward L.
Published: July 2010

A recently developed wind erosion model (wind erosion prediction system, WEPS) for crop lands is being extended for estimating soil erosion from rangelands, military lands, and desert ecosystems. Wind velocity near the soil surface is calculated as a function of the aerial distribution of stem silhouette area and leaf area of both live plants and standing residue. Grasses either dominate or form a significant part of the plant species growing in the noncrop lands of the world. Several grass species were studied to determine the aerial distribution of stem and leaf masses and areas. Plant samples were taken weekly from pure stands of big bluestem (Andropogon gerardii Vitman), switch grass (Panicum virgatum L.), little bluestem [Schizachyrium scoparium (Michx.) Nash], Indian grass [Sorghastrum nutans (L.) Nash], gamagrass (Tripsacum dactyloides L.), blue grama [Bouteloua gracilis (Kunth) Lag. ex Griffiths), and sideoats grama [Bouteloua curtipendula (Michx.) Torr.]. Plants were cut from a 0.2 m2 area and five tillers were randomly selected and cut into five equal segments. Leaves and stems were separated and their areas and dry weights were measured. For each species a straight line with a zero intercept fit the data of leaf area vs. leaf mass with r2 ≥ 0.87. Stem area vs. stem mass data fit a power function with r2 ≥ 0.92. Normalized leaf and stem masses were fit to a hyperbolic tangent (r2 ≥ 0.96) and exponential (r2 ≥ 0.98) functions, respectively. The empirical regression coefficients obtained for each species will be included in the WEPS plant growth data base.
Corn Response to Fertilizer Placement Treatments in an Irrigated No‐Till System
Authors: Riedell Walter E. , Beck Dwayne L. , Schumacher Thomas E.
Published: July 2010

Corn (Zea mays L.) plants express unexpected K‐deficiency symptoms when grown under certain conservation tillage production systems on high‐K‐testing soils. This field study was conducted to determine if K fertilizer treatments interact with P and N planting‐time fertilizer placement treatments to affect crop growth, nutrient composition, and yield in an irrigated no‐till corn production system on high‐K‐testing soil. The 3‐yr study was conducted on Lowry silt loam soils (coarse‐silty, mixed, superactive, mesic Typic Haplustolls) near Pierre, SD. Fertilizer placement (main plot) treatments consisted of P and N fertilizers that were applied with the corn planter to (i) the soil surface, (ii) the seed furrow, or (iii) a band 5 cm to the side of the seed furrow and 5 cm deep. Fertilizer products containing K, also applied at planting time, provided a with‐K subplot comparison with subplots that received no added K fertilizer. Corn plants were sampled for root pull resistance, shoot dry weight, and shoot mineral nutrient composition at the tassel stage of development and grain yield. Data combined over the 3 yr of the study revealed that added K fertilizer had no effect on grain yield and did not interact with P and N fertilizer placement treatments to affect grain yield. When P fertilizer was placed with the seed and N fertilizer was placed in a 5‐ by 5‐cm band, corn plants had 185 kg root−1 pull resistance, 0.26 g shoot−1 P accumulation, and 10.5 Mg ha−1 grain yield. However, when P and N fertilizers were applied to the soil surface, corn plants had significantly less root pull resistance (151 kg root−1), P accumulation (0.22 g P shoot−1) and grain yield (10.1 Mg ha−1). Added K fertilizer decreased shoot dry weight (added K = 97 g shoot−1, no K = 103 g), decreased P accumulation (added K = 0.22 g P plant−1, no K = 0.25 g), increased shoot N concentration (added K = 19.3 mg N g−1, no K = 19.0 mg), and had no significant effect on K concentration or accumulation. We conclude that, although planting‐time fertilizer placement was important for optimum corn growth and yield production in irrigated no‐till systems, added K fertilizer did not interact with fertilizer placement to improve yield on the high‐K‐testing soils used in this study.
Genetically Modified Crops and the Environment
Authors: Barton Joanne E. , Dracup Miles
Published: July 2010

Genetic modification (GM) of crops provides new crop management options (production traits) and crops with industrial, pharmaceutical, and neutraceutical applications are likely to follow. The environmental benefits and risks of growing GM crops have drawn considerable, often polarized debate. This review seeks a balanced appraisal of environmental issues, and looks at principles associated with several GM production traits. Environmental assessment needs to consider the nature of the introduced trait, in the context of the biology of the plant and the environment it will be grown in (e.g., prospects of gene flow into other species). Interactions with the target ecosystem, including the possibility of cummulative impacts from organisms already released into the ecosystem (e.g., prospects for gene pyramiding) need to also be included in assessments. Current agricultural management practices and ecosystems have their own impacts on the environment, and it is against this background that the benefits and risks of releasing GM organisms should be judged. Before release, data collection on impacts of GMOs is temporally and spatially constrained, so caution must be exercised in decision making. Potential impacts also need to be monitored after release and the post‐release monitoring framework needs scope to identify unforeseen impacts. The environmental sustainability of using GMOs will depend largely on wise management practices and monitoring must provide appropriate data to support continuing adaptation of management and regulation of GMOs.