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Vienna, Austria

Vollmann J.,University of Natural Resources and Life Sciences, Vienna | Wagentristl H.,University of Natural Resources and Life Sciences, Vienna | Hartl W.,Bio Forschung Austria
European Journal of Agronomy | Year: 2010

Breeding for increased weed suppression would be a sustainable contribution to improved soybean weed management, because weed infestation is a major constraint to soybean production world-wide and in organic farming in particular. However, genetic variation in the soybean-weed interaction would be necessary to enable plant breeders to select soybean genotypes based on a superior weed suppression behavior. As there is a lack of information on variation between soybean cultivars in their competitive ability against weeds, the effects of weed pressure on ten early maturity soybean genotypes were studied in a controlled field experiment over three years in Austria. Winter oilseed rape was sown into the soybean stand to simulate pressure from a seed-propagated type of weed. Weed pressure significantly affected soybean yield as well as other agronomic, phenologic and seed quality characters. In two seasons, strong competition from weeds caused a soybean yield reduction of 370 and 560 kg/ha, respectively. In a third season a significant yield increase over weed-free controls was observed at relatively low levels of weed pressure which is explained by non-competition effects of a weak weed ground cover on soybean growth. Yield loss due to weed pressure was lower in early than in late maturity genotypes which appears to be the effect of a better weed tolerance rather than weed suppression. Genotype by weed treatment interaction was not significant, and genetic variation in ground cover development or leaf area was low or not significant in the early maturity soybean cultivars investigated. As such characters are considered important for weed suppression, their variation needs to be increased to enable selection for improved weed suppressive ability. © 2010 Elsevier B.V. All rights reserved. Source

Vollmann J.,University of Natural Resources and Life Sciences, Vienna | Walter H.,University of Natural Resources and Life Sciences, Vienna | Sato T.,University of Natural Resources and Life Sciences, Vienna | Schweiger P.,Bio Forschung Austria
Computers and Electronics in Agriculture | Year: 2011

Leaf photosynthesis and rhizobial nitrogen fixation are the two metabolic processes of utmost importance to legume growth and development. As these processes are closely related to each other, measuring of leaf chlorophyll content can provide information on the nodulation and nitrogen fixation status of crop plants. In the present investigation, a number of soybean breeding lines consisting of near-isogenic families which are genetically segregating for the nodulation trait were utilized in field experiments carried out across three growing seasons at Vienna, Austria. For phenotyping leaf chlorophyll content, the Minolta SPAD spectrometer was applied in parallel to a simple leaf digital image analysis procedure based on a commercial digital still camera. The main objectives of the research included the comparison of SPAD metering and image analysis for determination of chlorophyll content, phenotyping of the soybean nodulation vs. non-nodulation characteristic with respect to leaf, agronomic and seed traits, and relating both chlorophyll and image analysis data to seed quality characteristics. Nodulating and non-nodulating soybean lines significantly differed in chlorophyll content from the V5 (five leaves fully developed) soybean developmental stage onwards. Apart from chlorophyll content, leaf size, plant height, number of pods per plant, 1000-seed weight, and seed protein and oil content were also affected by nodulation type. The chlorophyll content of soybean leaves as determined by SPAD metering was significantly correlated (r = -0.937) to the green color value (RGB color model) of leaf image analysis at the R3 (beginning of pod growth) soybean developmental stage. Both chlorophyll content and leaf image analysis parameters were correlated to 1000-seed weight, seed protein and seed oil content. Thus, it appears that these leaf parameters related to photosynthesis and nitrogen fixation could be utilized to determine the nitrogen status of a soybean crop and subsequently in forecasting seed quality parameters of the harvest product. © 2010 Elsevier B.V. Source

Schweiger P.,Bio Forschung Austria | Hofer M.,Bio Forschung Austria | Vollmann J.,University of Natural Resources and Life Sciences, Vienna | Wanek W.,University of Vienna
Physiologia Plantarum | Year: 2014

The contribution of N2 fixation to overall soybean N uptake has most commonly been quantified by N isotope-based methods, which rely on isotopic differences in plant N between legumes and non-fixing reference plants. The choice of non-fixing reference plants is critical for the accuracy of isotope-based methods, and mismatched reference plants remain a potential source of error. Accurate estimates of soybean N2 fixation also require information on N isotopic fractionation within soybean. On the basis of a previous observation of a close correlation between an expression of N fractionation within soybean and the proportion of plant N derived from atmosphere (%Ndfa) determined by 15N natural abundance, this field study aimed at assessing the relationship between various expressions describing intraplant 15N or N partitioning and %Ndfa during soybean development. Starting from a late vegetative stage until beginning senescence, the N content and N isotopic composition of shoots, roots and nodules of nodulated and non-nodulated soybeans was determined at eight different developmental stages. Regression analysis showed that %Ndfa most closely correlated with the difference in the N isotopic composition of shoot N minus that of root including nodule N, and that this relationship was similar to that obtained in a previous multi-site field study. We therefore consider this expression to hold promise as a means of quantifying %Ndfa independent of a reference plant, which would avoid some of the external sources of error introduced by the use of reference plants in determining %Ndfa. © 2014 Scandinavian Plant Physiology Society. Source

Zaller J.G.,University of Natural Resources and Life Sciences, Vienna | Wechselberger K.F.,University of Natural Resources and Life Sciences, Vienna | Gorfer M.,University of Natural Resources and Life Sciences, Vienna | Hann P.,Bio Forschung Austria | And 4 more authors.
Biology and Fertility of Soils | Year: 2013

Earthworms (Annelida: Oligochaeta) deposit several tons per hectare of casts enriched in nutrients and/or arbuscular mycorrhizal fungi (AMF) and create a spatial and temporal soil heterogeneity that can play a role in structuring plant communities. However, while we begin to understand the role of surface casts, it is still unclear to what extent plants utilize subsurface casts. We conducted a greenhouse experiment using large mesocosms (volume 45 l) to test whether (1) soil microsites consisting of earthworm casts with or without AMF (four Glomus taxa) affect the biomass production of 11 grassland plant species comprising the three functional groups grasses, forbs, and legumes, (2) different ecological groups of earthworms (soil dwellers-Aporrectodea caliginosa vs. vertical burrowers-Lumbricus terrestris) alter potential influences of soil microsites (i.e., four earthworms × two subsurface microsites × two AMF treatments). Soil microsites were artificially inserted in a 25-cm depth, and afterwards, plant species were sown in a regular pattern; the experiment ran for 6 months. Our results show that minute amounts of subsurface casts (0.89 g kg-1 soil) decreased the shoot and root production of forbs and legumes, but not that of grasses. The presence of earthworms reduced root biomass of grasses only. Our data also suggest that subsurface casts provide microsites from which root AMF colonization can start. Ecological groups of earthworms did not differ in their effects on plant production or AMF distribution. Taken together, these findings suggest that subsurface earthworm casts might play a role in structuring plant communities by specifically affecting the growth of certain functional groups of plants. © 2013 The Author(s). Source

Schweiger P.,Bio Forschung Austria | Hofer M.,Bio Forschung Austria | Hartl W.,Bio Forschung Austria | Wanek W.,University of Vienna | Vollmann J.,University of Natural Resources and Life Sciences, Vienna
European Journal of Agronomy | Year: 2012

The purpose of this study was to quantify the impact of effective nodulation on yield and quality of organically produced soybean and to assess three methods for the quantification of symbiotic N2 fixation. We used (i) the natural abundance (NA) method which relies on isotopic differences in shoot N between the N-fixing legume and non-fixing reference plants, (ii) a method independent of reference plants that is based on within-soybean N isotopic fractionation and (iii) the xylem solute method, in which the proportion of N transported into shoot material in the form of ureides that are specific to N-fixing soybeans is quantified. Effectively nodulated soybeans produced greater yields of better quality than non-nodulated soybeans in three separate experiments conducted on fertile, organically managed fields. Employing the NA method with non-nodulated soybeans as reference plants, symbiotic N2 fixation contributed 40-52% to overall N uptake by nodulated soybeans. These estimates for the percentage of soybean N derived from atmosphere (%Ndfa) were significantly increased when isotopic data from naturally occurring weeds were used in the calculation. Xylem ureide concentrations were not correlated with %Ndfa determined by the NA method. NA-determined %Ndfa were closely correlated with differences in the isotopic composition between soybean shoot N and root including nodule N (Δδ15N=δ15N shoot-δ15N root). Further studies are required to assess the potential suitability of Δδ15N to quantify soybean %Ndfa independent of reference plants. © 2012 Elsevier B.V. Source

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