Die chronologische Liste zeigt aktuelle Veröffentlichungen aus dem Forschungsbetrieb der Hochschule Weihenstephan-Triesdorf. Zuständig ist das Zentrum für Forschung und Wissenstransfer (ZFW).
Due to high nitrate loads in ground water, the German government tightened up legal regulations addressing the application of green manure crops during the last years. Among others, the current practice of putting back chopped hop bines to hop gardens after harvest was banned. However, there is a lack of knowledge about the nitrogen dynamics of chopped hop bines and their contribution to nitrate leaching. Indeed, pot trials revealed a fertilization effect of chopped hop bines, but in incubation experiments, no increase of mineral nitrogen was found. This might be due to the heterogeneity of hop bines, which consist of N rich, “green” parts (leaves, small branches) as well as the “woody” main stem. To test this hypothesis a pot trial with Italian ryegrass and an incubation experiment were conducted using “green” and “woody” hop material at various ratios. Therefore, entire hop bines were cut off and after removal of the cones divided into leaves, petioles, residues of cones and small side shoots (“green”) as well as into the lignified parts of the stem (“woody”). The two fractions were applied to an arable soil with ratios of 100:0, 70:30, 50:50, 30:70, 10:90 and 0:100 on a mass base, respectively. N uptake of ryegrass as well as net mineralization in unplanted Mitscherlich vessels were measured. Results confirmed the hypothesis: N uptake by plants was significantly higher than net mineralization in unplanted pots. For the woody material a nitrogen immobilization potential of about 4 to 5 g kg‑1 dry matter was found, whereas for green material a mineral fertilizer equivalent of 18% was calculated. Overall, the results indicate that application of chopped hop bines is not part of the nitrate problem but might be - in combination with catch crops - a good strategy to preserve the bounded nitrogen available for the next growing season.
Due to coarse textured, fast-draining growing media with poor buffer capacity, nitrogen leaching after heavy rainfall is a major concern in container nurseries. The amendment of growing media with Chabazite – a natural zeolite with high ammonium (NH4+) exchange capacity – in combination with NH4+ fertilization might reduce nitrogen losses significantly. This was tested in a pot trial with Photinia fraseri. Growing media amended with Chabazite were compared with a pumice containing growing medium as control. Chabazite was used on the one hand untreated and on the other hand it was charged with ammonium sulfate ((NH4)2SO4) with loads of 1 and 5 g ammonium nitrogen (NH4-N) pot‑1. During the first part of the trial, pots with untreated Chabazite were repeatedly fertilized with NH4+ and leached after each fertilizer application. Pots with charged Chabazite were also leached on the same dates. In the second part, pots with untreated Chabazite received an excessive NH4+ supply and were leached several times afterwards. In both parts of the trial, NH4+ was adsorbed by Chabazite after fertilization. Higher amounts of NH4+ were leached from growing media with pumice than from those with untreated Chabazite. In leachates from growing media with NH4+-charged Chabazite, higher amounts of nitrate (NO3-) were only found in the case of charging with 5 g N pot‑1. Whereas after excessive NH4+ fertilization leaching of NH4+ remained low in presence of Chabazite, summing up to 5% of the applied N, in the control leached NH4+ was 28% of fertilized NH4+. Thus, it can be concluded that fertilized NH4+ was adsorbed to Chabazite and thus protected from direct leaching as well as from nitrification and subsequent leaching as NO3-. This protection decreased with increasing NH4+ charging of Chabazite. Hence, the combination of Chabazite with repeated NH4+ fertilization is a promising approach to reduce nitrogen leaching from container nurseries.
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Dr. Annette Bucher,
Dr. Dieter Lohr,
Prof. Dr. Elke Meinken
Amendment of growing media with Chabazite, a natural zeolite with a high ammonium sorption capacity, in combination with ammonium fertilization might be a promising approach to reduce nitrogen leaching in container nurseries. However, it is unclear if ammonium, which is adsorbed to Chabazite is still plant-available. Thus, a pot trial with Photinia fraseri was conducted with growing media containing 25 vol % of either pumice or Chabazite. Chabazite firstly was used as received and secondly was charged with two levels of ammonium resulting in nitrogen loads of 1 and 5 g N pot‑1, respectively. The untreated Chabazite was fertilized with 1 g N pot‑1 as ammonium sulfate divided in repeated applications in accordance with the control (pumice). In these two treatments plant growth and nitrogen uptake was more or less the same. Plants in the growing media with NH4-charged Chabazite receiving also 1 g N pot‑1 produced a significantly lower fresh mass compared to the untreated Chabazite and pumice and suffered from slight nitrogen deficiency. If 5 g N pot‑1 were applied with charged Chabazite, plants grew better and took up more nitrogen. The results indicate that Chabazite did not influence negatively plant availability of fertilized ammonium. However, ammonium from charged Chabazite is only partly plant-available. With increasing NH4 charging of Chabazite, ammonium and nitrate accumulated in the growing media.
The value chain of flowering potted plants (FPP) is associated with environmental, social and economic sus-tainability challenges. Indicator-based assessment methods can provide insights into sustainability performanceof agricultural value chains. The FPP value chain is not comparable to other agricultural systems and thereforecannot be assessed with existing indicator-based tools. In this study, a framework was developed for sustain-ability assessment of the FPP value chain, from breeding to distribution. The development of the frameworkinvolved defining sustainability themes and subthemes based on the characterization of the value chain and theinvestigation of social, environmental and economic sustainability challenges. The generic sustainabilityassessment tools, Sustainability Assessment of Food and Agriculture Systems (SAFA) and Response-InducingSustainability Evaluation (RISE), provided the foundation for indicator selection and development. The cur-rent study emphasized the need for a system-specific view, especially in unique systems such as the FPP valuechain, because generic assessment tools, such as SAFA and RISE, do not cover all sustainability subthemes. Mostof the indicators missing from generic assessment tools were environmental indicators. Environmental assess-ment is closely related to value chain stages and product-specific processes, therefore indicators were allocatedaccording to the value chain stages, breeding, production and distribution. Social sustainability themes areinfluenced by national and regional socio-economic conditions, such as government provision of healthcare and asocial safety net. Therefore, indicators are allocated based on geographical regions and stakeholder groups. Theeconomic subthemes are determined by industry structure and sector-specific conditions. The ornamental sectoris characterized by low margins and high uncertainty, related to profitability and vulnerability. Despite the initialevaluation performed in the current study, in the next step, industry actors need to determine the feasibility ofthe indicators. The implementation of the framework developed in the current study will provide further insightsinto the value chain, which will guide actors in taking actions for performance improvement and provideguidance for policy-makers in setting sustainability targets.
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Betreuung der Publikationsseiten
Gerhard Radlmayr
Referent für Wissenstransfer und Forschungskommunikation
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