bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plant Density and Nitrogen Rate Effects on Sugar Beet Yield and Quality Early in Harvest
Authors: Lauer Joseph G. 
Published: July 2010

AbstractThe sugar beet (Beta vulgaris L.) industry has adopted an early harvest option that lengthens the processing campaign by 15 to 30 d. Field experiments were conducted near Powell, WY, from 1989 to 1991, to determine whether plant density and N rate should be adjusted for earlier harvests. Main plots were N application rates of 0, 112, 168, 224, 280, and 336 kg N ha−1; split plots were target plant densities of 37 100, 61 800, 86 500, and 111 200 plants ha−1. Harvests were at regular intervals beginning 13 September and ending 25 October. During the harvest season, root yield increased 8.0 Mg ha−1, sucrose content increased 29 g kg−1, and recoverable sucrose increased 2.44 Mg ha−1. The first 112 kg N ha−1 increased root yield 11.8 Mg ha−1, while the next 56 kg N ha−1 increased root yield 5.2 Mg ha−1. Sucrose content decreased from 164 to 157 g kg−1 as N rate increased from 0 to 336 kg ha−1. The first 168 kg N ha−1 increased recoverable sucrose 2.48 Mg ha−1. Plant density had no effect on root yield. Sucrose content increased 5 g kg−1 as plant density increased from 42 000 to 112 000 plants ha−1. Recoverable sucrose increased from 7.40 Mg ha−1 at 42 700 plants ha−1 to a maximum of 7.79 Mg ha−1 at 88 600 plants ha−1. No consistent harvest date ✕ plant density interactions were observed for yield and quality measurements, suggesting that no adjustments in plant density were needed for earlier harvest dates. A harvest date ✕ N rate interaction for recoverable sucrose implies that N rate should be decreased for earlier harvest dates.
Differences in Autotoxicity among Seven Alfalfa Cultivars
Authors: Chung Ill‐Min , Miller Darrell A. 
Published: July 2010

AbstractThere is a need to determine if alfalfa (Medicago sativa L. subsp. sativa) can be selected for low concentrations of allelopathic compounds. The objective of this study was to evaluate alfalfa cultivar differences in autotoxic traits in relation to various concentrations of aqueous extracts. Plant extracts from seven alfalfa cultivars (Apollo‐Supreme, Arrow, Vernal, DK‐125, Dawn, Pioneer 5472, and Magnum III) were evaluated in the laboratory for autotoxic effects on the same cultivar at four levels of extract solution (10, 20, 30, and 40% w/v). Double‐distilled water was used as a control. Germination percentage, seedling length, and seedling dry weight were measured to determine the effect of the same cultivar extracts on alfalfa growth. These parameters were significantly reduced as the extract concentration increased. The highest concentration (40%) caused the greatest reduction in hypocotyl and radicle length, seedling dry weight, germination percentage, and seedling vigor in all cultivars. It also significantly increased the time required for germination. Autotoxicity effects were significantly different among the various cultivars. Cultivars may be classified in the following order of decreasing inhibition: Pioneer 5472, Arrow, Magnum III, Vernal, Apollo‐Supreme, DK‐125 and Dawn. The results indicate that there may be genetic differences among cultivars for resistance to alfalfa autotoxicity, and that selection for low autotoxicity may be possible.
Soybean Effects on Soil Nitrogen Availability in Crop Rotations
Authors: Vanotti Matias B. , Bundy Larry G. 
Published: July 2010

AbstractSoybean [Glycine max (L.) Merr.] production contributes significantly to the N supply for a following corn (Zea mays L.) crop, even though soybean N budget studies indicate that N removed in grain may substantially exceed biological fixation. Information on the N status of cereal crops during the 2nd yr following soybean may help resolve this issue. This study reports on N effects of soybean on yield response of succeeding cereal crops and soil N availability based on data from a 15‐yr crop rotation experiment (1977–1991) on a Rozetta silt loam soil (Typic Hapludalfs) at Lancaster, WI. We evaluated the yields of corn and oat (Avena sativa L.) succeeding soybean and alfalfa (Medicago sativa L.) in corn‐soybean‐corn‐oat‐alfalfa (CSCOM) and corn‐corn‐oat‐alfalfa‐alfalfa (CCOMM) crop rotations. Fertilizer N (0, 56, ll2, and 224 kg ha−1) was applied only to corn, but NO3‐N carryover usually affected oat yields as well. The legume fertilizer N replacement values based on check plot yields and the response function of 3rd‐yr corn in a corn‐corn‐corn‐alfalfa‐alfalfa sequence, were equivalent to 153 and 36 kg N ha−1 for the 1st and 2nd yr after alfalfa, respectively, and 75 kg N ha−1 for the 1st yr after soybean. In the 2nd yr after soybean (CSCOM), oat yields were significantly lower than following corn in the CCOMM rotation. Preplant soil NO3 and oat N uptake (1987–1991) indicated that oat yield differences were due to lower soil N availability in the CSCOM rotation. The average soybean effect on soil N availability in the 2nd yr was equal to a soil N debit of 36 kg N ha−1. This indicates that part of the N contribution of soybean to 1st‐yr corn is realized at the expense of subsequent reductions in soil N availability.
Water Stress and Clipping Management Effects on Guineagrass: II. Photosynthesis and Water Relations
Authors: Páez Alejandra , González O. María E. 
Published: July 2010

AbstractGrowth and biomass production and allocation in guineagrass are affected by clipping and water stress, but little is known about the mechanisms responsible. This study was undertaken to determine the short‐term interacting effects of clipping management and water stress on photosynthesis and water relations of guineagrass (Panicum maximum Jacq.). The experiments were conducted outdoors in pots in Maracaibo, Venezuela. After seedling emergence and establishment, plants were clipped at four frequencies and three heights for 3 mo, followed by exposure to water stress. After a stress cycle of 15 d, a group of plants was reirrigated for 21 d, to observe recovery. Photosynthesis and transpiration rates, stomatal conductance, leaf water potential, and water use efficiency (WUE) were measured. During the stress period, the most closely clipped plants had greater photosynthesis, but not increased stomatal conductance. Photosynthesis was also greater in more frequently clipped plants, and both photosynthesis and conductance were reduced by water stress. Upon rewatering, photosynthesis increased sharply. Leaf transpiration rates were not affected by clipping height or frequency during water stress. A linear decrease in WUE occurred as cutting height increased, but clipping frequency did not alter WUE. Water stress reduced leaf water potential, and this effect occurred sooner in plants clipped less frequently and to greater heights. After reirrigation, highest photosynthesis in closely clipped plants was associated with increased stomatal conductance; leaf transpiration rate, WUE, and water potential were not altered by clipping height or frequency. Partial defoliation may relieve water stress to some degree. The increase in photosynthesis caused by close clipping is not fully related to higher stomatal conductance as previously reported, so other factors must also be involved.
Evaluation of Four Intermediate Wheatgrass Populations under Grazing
Authors: Moore Kenneth J. , Vogel Kenneth P. , Klopfenstein T. J. , Masters Robert A. , Anderson Bruce E. 
Published: July 2010

AbstractThe grazing season in the central and northern Great Plains could be extended by use of adapted cool‐season grass pastures for spring and fall grazing to augment the native warm‐season range. A grazing trial was conducted to evaluate the forage quality of four intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey] populations for use in forage‐livestock systems. The cultivars Slate and Oahe and two populations selected for improved IVDMD, ‘Manska’ and NE TI 1, were evaluated. Each population was seeded in the fall of 1987 in three replicated 0.4‐ha pastures arranged in a randomized complete block design. Pastures were stocked with three beef yearlings for 28 d in spring 1989 and 42 d in spring 1990 to provide a stocking rate of 7.5 steers ha−1. Duration of grazing was shorter in 1989 because of inadequate soil moisture. Average daily gain (ADG) and gain per hectare were higher (P ≤ 0.10) in 1989 than 1990, despite the lower (P ≤ 0.10) forage availability and lesser number of grazing days in 1989. Steers grazing Manska in 1989 gained 1.59 kg d−1, compared with 1.42, 1.27, and 1.43 for Oahe, Slate, and NE TI 1, respectively. There were no differences (P > 0.10) in ADG or gain per hectare among populations in 1990. The improvement in ADG resulted in 30 to 65 kg more gain per hectare from Manska compared with the other populations in 1989. These results demonstrate the excellent quality of intermediate wheatgrass for grazing livestock and the impact that modest improvements in forage quality can have on animal performance.
Straw Color for Altering Soil Temperature and Heat Flux in the Subarctic
Authors: Sharratt Brenton S. , Flerchinger Gerald N. 
Published: July 2010

AbstractIn the Subarctic, straw management methods are needed that improve the early season soil thermal environment of conservation tillage systems. This study determined whether soil heat and water flux are influenced by barley (Hordeum vulgare L.) straw color. Surface temperatures, thaw depth, and latent, sensible, and soil heat flux were ascertained for soil‐black straw, soil‐white straw, and soil‐natural straw surfaces during the spring of 1988 to 1990 at Fairbanks, AK. Daily soil temperatures at 0.05 m, soil surface heat flux, and thaw depth were as much as 0.5°C, 0.5 MJ m−2, and 10 mm greater, respectively, for the black straw than for the other straw color treatments. An atmosphere‐snow‐straw‐soil system model predicted greater absorption of radiation by the soil‐black straw surface, although the percentage of net radiation partitioned to soil heat was lower for the soil‐black straw surface than for the soil‐natural straw and soil‐white straw surfaces. Simulation indicated that straw color did not influence the proportion of absorbed radiation utilized in latent heat flux, but the black straw treatment had the greatest percentage of net radiation partitioned into sensible heat flux. Although the soil thermal environment was slightly altered by changing straw color, managing straw color in conservation tillage systems may aid little in optimizing the thermal regime of subarctic soils unless methods are employed to minimize sensible heat loss from the soil‐straw surface.
Plant Density and Soybean Maturity in a Soybean‐Maize Intercrop
Authors: Hiebsch C. K. , Tetio‐Kagho F. , Chirembo A. M. , Gardner F. P. 
Published: July 2010

AbstractLong, warm seasons that are inadequately filled by sole crops can be more productive when more fully utilized by intercrops. The effect of plant densities and plant maturity on the magnitude of this increased productivity is not well documented. During two seasons of ≥ 190 d at 29°38′ N lat, maize (Zea mays L.) at 12 densities (from 1.0 to 10.0 plants m−2) and two soybean [Glycine max (L.) Merr.] cultivars, representing Maturity Groups VIII (Cobb) and VI (Davis), at three densities (3.0, 8.5, and 24.0 plants m−2) were grown in intercrop and sole crop in fan designs. Soybean was planted 56 d (1985) and 31 d (1986) after maize. Soybean density did not affect maize yield (P ≤ 0.05). Although predicted sole‐crop Cobb and Davis seed yields were not different (P ≤ 0.05), averaging 336 g m‐2, the two cultivars were differentially affected by maize density. Each unit increase in maize density (plants m‐2), reduced soybean seed yield 20% for Cobb and 47% for Davis at 3.0 soybean plants m−2 and 7% for Cobb and 35% for Davis at 24.0 soybean plants m−2. Cobb had two to three trifoliolates expand after maize removal, while Davis had all leaves fully developed at maize harvest. Land equivalency ratios (LER) were <1.1 for Davis‐maize and peaked at 1.4 for Cobb‐maize. Area‐time equivalency ratios (ATER) were <0.8 for Davis‐maize and peaked at 0.9 for Cobb‐maize. Davis‐maize was not a viable intercrop. The Cobb‐maize intercrop at 24 soybean plants m−2 over a range of maize densities utilized the long growing season more productively (LER = 1.4) than in sole crop; the increased productivity was due to increased season use (ATER < 1.0).
A Chilling Response Test for Early Growth Phase Maize
Authors: Hodges D. Mark , Hamilton Robert I. , Charest Christiane 
Published: July 2010

AbstractResults from a new laboratory screening technique for the determination of chilling responses in maize (Zea mays L.) at the early growth phase were compared with those obtained from the field. This laboratory technique consisted of growing plants hydroponically in Styrofoam rafts floated on Hoagland's solution at a constant low temperature. Seedlings of eight inbred maize lines were pinned into the rafts and placed in controlled environment chambers at 11°C and 98% relative humidity for 28 d until the four‐leaf stage. A control test used a constant 25°C for 7 d, at which point all lines were at the four‐leaf growth stage. Total, shoot, and root dry mass, and the shoot and root water content were the responses measured. Comparisons between the chilling and the chilling/control ratios showed that they were good indicators of chilling tolerance. Field trials of the same eight inbreds were sown in Ottawa (45°24′ N, 75°43′ W) in the early spring of 1992 and 1993 and the shoot dry mass recorded at the four‐leaf stage. The chill/control ratios of the shoot dry mass of seven of the eight lines from the laboratory were correlated with the averaged field shoot dry mass (r = 0.780, P = 0.032). Thus, this laboratory screening procedure was successful in that the lines indicated by shoot dry mass to be the most chilling resistant or the most sensitive in the laboratory responded similarly in the field.
Yield and Soil Water Uptake of Sunflower Sown in Spring and Summer
Authors: D'Andria Riccardo , Chiarandà Fabrizio Quaglietta , Magliulo Vincenzo , Mori Mauro 
Published: July 2010

AbstractSunflower (Helianthus annuus L.) is both tolerant to water deficits and capable of bearing high yield in response to irrigation inputs. In both situations, knowledge of the seasonal distribution of water uptake and the quantification of water extracted in deeper soil layers are required for irrigation scheduling. In a 2‐yr field study in southern Italy, we determined water consumption in relation to seed yield of ‘Romsun HS90’ sunflower with early (spring; mid‐April) and late (summer; mid‐June) sowing dates under five irrigation regimes: a rainfed control; periodic replacement of calculated crop evapotranspiration (a meteorological approach); and one, two, or three irrigation applications at selected growth stages assumed critical for yield expression (a phenological approach). Spring‐sown crops provided significantly higher yields (3.15 vs. 1.75 t ha−1). Irrigation was necessary to achieve high production, especially for the summer crop. Three waterings gave best results in 1989 only. The treatment providing two waterings always showed similar yield and more efficient use of water with respect to the treatment irrigated according to the meteorological approach and performed better than the single irrigation. The ratio between actual and reference crop evapotranspiration was 20% higher in the period between R1 and R6 for the summer crop and 30% higher for the spring crop, with respect to the adopted crop coefficients (Kc). All the yield components were positively affected by irrigation; the most important one was found to be the diameter of calathide. Oil concentration in the achenes was always lower in the summer crop and increased when adequate irrigation was provided, especially in the grain‐filling stage.
Changes in Maize Hybrid Photosynthetic Response to Leaf Nitrogen, from Pre‐Anthesis to Grain Fill
Authors: Dwyer Lianne M. , Anderson Anne M. , Stewart Douglas W. , Ma B. L. , Tollenaar Matthijs 
Published: July 2010

AbstractImprovement of nitrogen use efficiency in maize production requires quantifying genotypic variability in response to soil N. The objective of this field study was to quantify the relationship between leaf N concentration and leaf photosynthetic rate from pre‐anthesis to grain fill for six maize (Zea mays L.) hybrids. Maize hybrids were grown at the Central Experimental Farm at Ottawa in Ontario (45°23′ N, 75°43′ W) in 1991, 1992, and 1993 at three N fertilizer rates (0, 100, and 200 kg N ha−1). A method of analysis was developed to relate leaf photosynthesis measurements at comparable irradiance levels to leaf N concentration measurements. Photosynthetic response to leaf N was characterized by two fitted coefficients, N0, threshold leaf N concentration for photosynthesis, and P3, photosynthetic rate at high (30 g N kg−1 dry weight) leaf N concentration. There were no hybrid differences in N0 (P > 0.05). There were differences in P3, notably a significantly lower P3 value at anthesis for an old hybrid compared with recent commercial hybrids. In 1992, a recent commercial hybrid, Pioneer 3902, had the highest P3 value, the second highest crop growth rate (CGR) and the highest grain yield, but hybrid differences in P3 were not generally correlated with CGR or grain yield (P > 0.05). Growth stage had a significant effect on both N0 and P3; both declined at later growth stages (P ≤ 0.05). The decline in P3 was greatest in Pride 5 in 1993. Photosynthate production during grain fill was potentially limited in all hybrids by a decline in P3 as the season progressed, although the degree of decline varied with year and hybrid. This analysis quantified the relationships between leaf N concentration and leaf photosynthetic rate for different growth stages and hybrids for evaluation of hybrid N use efficiency.
Chemistry and Mechanisms of Allelopathic Interactions
Authors: Seigler David S. 
Published: July 2010

AbstractAllelopathy, originally defined as chemically elicited interactions between plants or fungi, is mediated by many types of compounds with different sites and modes of biochemical action. Although it is possible to measure a generalized effect, it is unlikely that deeper insight into the basic mechanisms of of this phenomenon will be obtained until problems are more clearly and specifically delineated. Future work should include identification of the compounds found in specific interactions and their evaluation in bioassay systems that use organisms actually involved in the response. A broader range of compounds and test organisms must be considered, and the biochemical sites and mechanisms of interaction must be evaluated, even for compounds that appear to be inactive. Once active compounds have been identified, their release, movement, uptake, and effects on source and target species in the allelopathic system should be examined. The effects of plant density require additional investigation. Studies in which plants are grown in various combinations and ratios can ultimately provide information about the major sources of allelopathic interaction in communities, the role of allelopathy in succession, and the nature and extent of coadaptation of organisms. Understanding the role of allelopathy in succession will require information about the chemistry and biology of interactions, and a better understanding of the ecological factors involved. Agricultural systems can supply much needed information, as they are similar to natural systems but usually are simpler and better defined. In turn, a better understanding of allelopathy is important in many phases of modern agriculture, especially in the tropics. By attacking allelopathic interactions at several organizational levels, the effects collectively known as allelopathy can be understood, even in complex natural communities. Major advancement in understanding allelopathy will be accomplished only by the combined effort of investigators from many disciplines.
Limited Applicability of the CENTURY Model to Highly Weathered Tropical Soils
Authors: Gijsman Arjan J. , Oberson Astrid , Tiessen Holm , Friesen Dennis K. 
Published: July 2010

AbstractThe CENTURY soil organic matter model was developed to describe nutrient dynamics for soils of the North American Great Plains, but is now applied to other soil types and climates. Phosphorus transformations in CENTURY are based on empirical relationships, developed for soils where N is the most limiting nutrient. This restricts the model's applicability in P‐limited soils, particularly those that differ in reactivity to P and in organic matter stabilization. Moreover, nutrient ratios in plant litter from nutrient‐poor tropical soils may be much wider (e.g., C:P ratios up to 3000) than those commonly found in liter from temperate zones. Equations used in the model to partition incoming litter into slowly and rapidly cycling organic matter may not be suited for such litter. A problem in validating the model is achieving congruence between nutrient fractions that can be measured in the soil and the conceptual pools (state variables) that represent such fractions in the model. Work on P in tropical soils indicates that parameterizing CENTURY may require the use of different P fractions than those of the original version. State variables thus will change. The lack of experimental data on P fractionation in relation to P availability in highly weathered P‐deficient soils is a major restriction in formulating an adequate theoretical framework on P dynamics in tropical soils. The CENTURY model therefore has limited applicability to highly weathered low‐P soils. Various improvements in the P submodel of CENTURY are recommended.
Multinutrient Fertilization and Placement to Improve Yield and Nutrient Concentration of Tall Fescue
Authors: Sweeney Daniel W. , Moyer Joseph L. , Havlin John L. 
Published: July 2010

AbstractAlthough tall fescue (Festuca arundinacea Schreb.) is one of the major cool‐season grasses used for animal feed in the USA, it often is unfertilized or is top‐dressed with N alone. Additional fertilizer nutrients applied with N may improve yield and quality. Subsurface placement of N has been shown to improve cool‐season grass production, but data are limited regarding effects of placement of different fertilizer combinations on elemental composition and yield of tall fescue. Thus, a field study was conducted from 1984 to 1986 to determine the effects of multinutrient fertilization (N‐only, NP, NPK, NPKSBZn, and PKSBZn without N) and placement method [broadcast, dribble (surface banding), and knifing (subsurface banding)] on nutrient concentrations and yield of tall fescue. Nitrogen was the primary nutrient limiting fescue growth. Adding N doubled yields of samples that estimated early‐grazing potential and tripled yields of hay. Supplementing N fertilization with additional nutrients increased tissue concentrations of the added nutrient, but increases in yield were small and often not significant. Broadcasting fertilizers resulted in greater yields of early‐grazing samples and higher P and K concentrations than knifing; however, by hay harvest, knifing resulted in about 10% greater yields and 20% greater N concentrations. Dribble applications generally resulted in responses intermediate between those of broadcast and knifing.