Browsing by Subject "Bio-Effektoren"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    Bio-effectors for improved growth, nutrient acquisition and disease resistance of crops
    (2017) Weinmann, Markus; Neumann, Günter
    Recent scientific approaches to sustain agricultural production in face of a growing world food demand, limited natural resources, and ecological concerns have been focusing on biological processes to support soil fertility and healthy plant growth. In this context, the use of “bio-effectors”, comprising living (micro-) organisms and active natural compounds, has been receiving increasing attention. In contrast to conventional fertilizers and pesticides, the effectiveness of “bio-effectors” is essentially not based on the substantial direct input of mineral plant nutrients, neither in inorganic nor organic forms, nor of a-priori toxic compounds. Their direct or indirect effects on plant performance are rather based on the functional implementation or activation of biological mechanisms, in particular those interfering with soil-plant-microbe interactions. The general objective of the present research work was to improve the empirical and conceptual understanding concerning the utilization of bio-effectors in agricultural practice, following the principles of plant growth stimulation, bio-fertilization and bio-control. One main aspect of investigation was the application of bio-effectors to improve the efficiency of phosphorus (P) acquisition by the plant. Promising bio-preparations based on microbial inoculants (e.g. Bacillus, Pseudomonas, Trichoderma species) as well as natural compounds (e.g. algae extracts, humic acids) were tested in screening assays, greenhouse, and field experiments to characterize their potential effectiveness under varying environmental conditions. The most significant effects on plants appeared under severely low phosphate availability, but even under controlled conditions, bio-effectors required a narrow range of conductive environmental settings to reveal their potential effectiveness. Another focus of research was the application of bio-effectors to control soil borne pathogens, which typically appear in unsound crop rotations. Emphasis was set on take-all disease in wheat induced by the fungus Gaeumannomyces graminis. While the effectiveness of oat precrops to control take-all in subsequent wheat has been attributed to microbial changes and enhanced manganese (Mn) availability in soils, the take-all fungus is known to decrease the availability of Mn by oxidation. Against this background, the effectiveness of oat precrops and alternative crop management strategies to improve the Mn status and suppress the severity of take-all in wheat was investigated under controlled and field conditions. In conclusion, none of the tested supplemental treatments, such the application of microbial bio-effectors, stabilized ammonium or manganese fertilizers, could fully substitute for the multiple effectiveness of oat precrops, which was further confirmed by the results of a field experiment. Finally, some general conclusions and perspectives are summarized. Selected bio-effectors showed a strong capacity to improve the nutrient acquisition and healthy growth of crop plants under controlled conditions, but not in field experiments. However, even under controlled conditions the strongest effects occurred when plants were exposed to abiotic or biotic stresses, such as severely limited P availability or pathogen infestation of the soil substrate, still restricting plant growth to unproductive levels. Facing this situation, there is no perspective to improve the field efficiency of promising bio-effectors applications as a stand-alone approach. The only chance to develop viable alternatives to the conventional use of fertilizers or pesticides, for an ecological intensification of agriculture that maintains high yield levels, seems to be a reasonable integration of bio-effectors into the whole crop management of sound agricultural practice.
  • Thumbnail Image
    Publication
    Bio-effectors for improved growth, nutrient acquisition and disease resistance of crops.- 2nd unrevised edition
    (2019) Weinmann, Markus; Madora GmbH, Luckestr.1, D-79539 Lörrach; Raupp, Manfred G.
    Recent scientific approaches to sustain agricultural production in face of a growing world food demand, limited natural resources, and ecological concerns have been focusing on biological processes to support soil fertility and healthy plant growth. In this context, the use of “bio-effectors”, comprising living (micro-) organisms and active natural compounds, has been receiving increasing attention. In contrast to conventional fertilizers and pesticides, the effectiveness of “bio-effectors” is essentially not based on the substantial direct input of mineral plant nutrients, neither in inorganic nor organic forms, nor of a-priori toxic compounds. Their direct or indirect effects on plant performance are rather based on the functional implementation or activation of biological mechanisms, in particular those interfering with soil-plant-microbe interactions. The general objective of the present research work was to improve the empirical and conceptual understanding concerning the utilization of bio-effectors in agricultural practice, following the principles of plant growth stimulation, bio-fertilization and bio-control. One main aspect of investigation was the application of bio-effectors to improve the efficiency of phosphorus (P) acquisition by the plant. Promising bio-preparations based on microbial inoculants (e.g. Bacillus, Pseudomonas, Trichoderma species) as well as natural compounds (e.g. algae extracts, humic acids) were tested in screening assays, greenhouse, and field experiments to characterize their potential effectiveness under varying environmental conditions. The most significant effects on plants appeared under severely low phosphate availability, but even under controlled conditions, bio-effectors required a narrow range of conductive environmental settings to reveal their potential effectiveness. Another focus of research was the application of bio-effectors to control soil borne pathogens, which typically appear in unsound crop rotations. Emphasis was set on take-all disease in wheat induced by the fungus Gaeumannomyces graminis. While the effectiveness of oat precrops to control take-all in subsequent wheat has been attributed to microbial changes and enhanced manganese (Mn) availability in soils, the take-all fungus is known to decrease the availability of Mn by oxidation. Against this background, the effectiveness of oat precrops and alternative crop management strategies to improve the Mn status and suppress the severity of take-all in wheat was investigated under controlled and field conditions. In conclusion, none of the tested supplemental treatments, such the application of microbial bio-effectors, stabilized ammonium or manganese fertilizers, could fully substitute for the multiple effectiveness of oat precrops, which was further confirmed by the results of a field experiment. Finally, some general conclusions and perspectives are summarized. Selected bio-effectors showed a strong capacity to improve the nutrient acquisition and healthy growth of crop plants under controlled conditions, but not in field experiments. However, even under controlled conditions the strongest effects occurred when plants were exposed to abiotic or biotic stresses, such as severely limited P availability or pathogen infestation of the soil substrate, still restricting plant growth to unproductive levels. Facing this situation, there is no perspective to improve the field efficiency of promising bio-effectors applications as a stand-alone approach. The only chance to develop viable alternatives to the conventional use of fertilizers or pesticides, for an ecological intensification of agriculture that maintains high yield levels, seems to be a reasonable integration of bio-effectors into the whole crop management of sound agricultural practice.
  • Thumbnail Image
    Publication
    Fertilizer placement and the potential for its combination with bio-effectors to improve crop nutrient acquisition and yield
    (2016) Nkebiwe, Peteh Mehdi; Müller, Torsten
    Even when total nitrogen (N) and phosphorus (P) concentrations in most agricultural soils are high, the concentrations of plant-available N and P fractions are often inadequate for acceptable yield. In comparison to conventional fertilizer application by homogenous broadcast over the soil surface (with or without subsequent incorporation), fertilizer placement in defined soil areas/volumes close to seeds or crop roots is a more effective application method to enhance the plant-availability of applied fertilizers. Nevertheless, considerable root growth in subsurface nutrient patches or around concentrated fertilizer-depots (and/or improved nutrient influx rates in roots) is a prerequisite for improved uptake of placed nutrients. Furthermore, zones with intense rooting around placed fertilizer depots (“rhizosphere hotspots”) with high concentrations of organic nutrients released as root exudates may be favorable for the survival and establishment of inoculated plant-growth-promoting microorganisms (PGPMs), which mobilize nutrients in soil to favor plant growth. In the last three decades, several published field studies comparing fertilizer placement to fertilizer broadcast arrived at different and often conflicting results regarding their effects on yield and nutrient status of various crops. For this reason, the first task was to conduct a Meta-analysis on data in published peer-reviewed field studies on fertilizer placement that met a set of pre-defined criteria for inclusion. We investigated the relative effect of fertilizer placement for specific fertilizer formulations (e.g. NH4+ and CO(NH2)2 without or in combination with soluble P (HPO42-; H2PO4-); soluble K; solid or liquid manure) in a precise restricted area on surface or subsurface soil in comparison to fertilizer broadcast on yield, nutrient concentration and content in above-ground plant parts. We utilized data from a total of 40 field studies published between 1982 and 2015 (85% of studies published from 2000) that met our criteria. We used the method of “baseline contrasts” to compare different fertilizer placement treatments to fertilizer broadcast as a common control or baseline treatment. Results showed that overall, fertilizer placement led to +3.7% higher yields, +3.7% higher concentrations of nutrients in above-ground plant parts and +11.9% higher contents of nutrients also in above-ground plant parts than fertilizer broadcast application. Placement depth had a strong effect of the outcome of fertilizer placement because relative placement effects increased with increasing fertilizer placement depth. Composition of fertilizer formulations was also an important factor. High yields of fertilizer placement relative to fertilizer broadcast application were obtained for CO(NH2)2 in combination with soluble P (HPO42-; H2PO4-) (+27%) or NH4+ in combination with HPO42-; H2PO4- (+15%) (Nkebiwe et al., 2016 a: Field Crops Research 196: 389–401). The next aim was to investigate the effect of fertilizer placement in subsurface soil in combination with application of bio-effectors (BEs) (PGPMs and natural active substances such as humic acids and seaweed extracts) on root growth of crop plants, establishment of inoculated PGPM in the rhizosphere, grain and biomass production as well as plant nutrient status for maize (Zea mays L) and wheat (Triticum aestivum L) cultures. Through various pot and rhizobox experiments, we observed that placement of a subsurface concentrated NH4+-fertilizer depot stabilized with the nitrification inhibitor DMPP (3,4-di-methylpyrazolphosphate) induced dense rooting around the depot contributing to more efficient exploitation of the depot. For this, it was crucial the N persisted in the depot mainly as poorly mobile NH4+, in order to induce localized depot-zone root-growth as well as favorable chemical and biological changes in the rhizosphere to improve N and P uptake by crop plants. Through in vitro culture experiments on solid and liquid media, we could show that via acidification of the growth media, several selected microbial BEs were capable to solubilize sparingly soluble inorganic phosphates and also that these BEs showed considerable tolerance to high concentrations of NH4+ und DMPP. The latter indicated a potential for the BEs to colonize plant roots in NH4+-rich well rooted soil zones around a subsurface NH4+-fertilizer depot (Nkebiwe et al., 2016 c: Manuscript submitted). Through further pot experiments and four others experiments as Bachelor and Master theses conduction under my supervision, we observed that certain BEs that readily solubilized tri-calcium phosphates in vitro were able to mobilize rock phosphate (RP) applied in soil-based substrates when N was supplied as stabilized NH4++DMPP, thereby contributing to enhanced P uptake and growth of maize and wheat plants. The bacterial BE Pseudomonas sp. DSMZ 13134 and BE consortia products containing bacteria and fungi such as CombiFectorA were good candidates. BE-induced RP-solubilzation occurred mainly in substrates with low CaCO3 contents indicating low P sorption capacity for neutral and moderately alkaline soils. With CombiFectorA, maize P-acquisition from sewage sludge ash could be enhanced, thus increasing the efficiency of a sparingly soluble fertilizer based of recycled wastes. Possible explanations for the beneficial effects of best performing BEs to improve plant growth were enhanced solubility of sparingly soluble P fertilizers via acidification of the rhizosphere and release of nutrient-chelating substances as well as improvement of root growth for better spatial interception of nutrients (Nkebiwe et al., 2016 d: Manuscript in preparation). Alongside, more greenhouse and two field experiments (grain maize 2014 and maize silage 2015) were designed, planned, conducted and evaluated. A peer-reviewed paper from this work has already been published (Nkebiwe et al., 2016 b: Chemical and Biological Technologies in Agriculture 3:15). In the greenhouse and experiments, placement of a concentrated stabilized NH4+-fertilizer depot led to improved root and shoot growth, and increased shoot N and P contents. Through intense root growth of maize around the NH4+-depot, increased root-colonization by Pseudomonas sp. DSMZ 13134 close to seeds could be observed. In the field, many weeks after subsurface placement of the concentrated stabilized NH4+-depot, it could be shown that N considerably persisted in the depot-zone as NH4+, which strongly induced depot-zone root growth. Placement of the NH4+-depot led to +7.4 % increase in grain yield of maize (2014) and +5.8% increase in maize silage yield (2015) in comparison to fertilizer broadcast. Placement of Pseudomonas sp. DSMZ 13134 inoculum in the sowing row let to +7.1% increase in yield of maize silage (2015) in comparison to the non-inoculated control. In total, these results showed that precise placement of specific fertilizer formulations in combination with the application of selected PGPMs can lead to improved plant growth, improved N and P uptake with a potential to save resources.