Die chronologische Liste zeigt aktuelle Veröffentlichungen aus dem Forschungsbetrieb der Hochschule Weihenstephan-Triesdorf. Zuständig ist das Zentrum für Forschung und Wissenstransfer (ZFW).
Forecasting future demand is of high importance for many companies as it affects operational decisions. This is especially relevant for products with a short shelf life due to the potential disposal of unsold items. Horticultural products are highly influenced by this, however with limited attention in forecasting research so far. Beyond that, many forecasting competitions show a competitive performance of classical forecasting methods. For the first time, we empirically compared the performance of nine state-of-the-art machine learning and three classical forecasting algorithms for horticultural sales predictions. We show that machine learning methods were superior in all our experiments, with the gradient boosted ensemble learner XGBoost being the top performer in 14 out of 15 comparisons. This advantage over classical forecasting approaches increased for datasets with multiple seasons. Further, we show that including additional external factors, such as weather and holiday information, as well as meta-features led to a boost in predictive performance. In addition, we investigated whether the algorithms can capture the sudden increase in demand of horticultural products during the SARS-CoV-2 pandemic in 2020. For this special case, XGBoost was also superior. All code and data is publicly available on GitHub: https://github.com/grimmlab/HorticulturalSalesPredictions.
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Ronja Fritzsche
Projekt TerZ - Substrate
Tagung der Zierpflanzenproduktionsbetriebe des BGV (2021)
Dr. Agnes Emberger-Klein,
Dr. rer. pol. Johanna Schöps,
Prof. Dr. Klaus Menrad
Traditionally in Germany, chopped hop bines are returned to hop gardens after the harvest season in late autumn. However, due to more stringent legal regulations addressing the application of manure, this common practice is banned. Furthermore, the return of hop residues bears phytopathological risks, such as the spreading of Verticillium spores. Aerobic composting of hop bines might solve both problems. Nitrogen is conserved over winter, and pathogens are killed due to high temperatures during composting. However, nitrogen release from mature composts is relatively poor. Thus, in a pot trial, the nitrogen fertilizing effect of aerobically composted hop bines was compared to that of fresh hop bines (air-dried directly after harvest), aged hop bines (stored on a heap for four weeks according to common practice) as well as mature green waste compost and green manure (Phacelia). Lamb's lettuce was cultivated in balcony boxes filled with topsoil used for arable crops. The plant density was 116 plants m-2, and nitrogen was applied on a basis of 130 kg ha‑1. Nitrogen from hop bines, green waste compost, and green manure was estimated to become plant available at rates of 100, 75, 50, and 25%, respectively. The control was fertilized with ammonium nitrate. With the exceptions of composted hop bines and green manure, plant growth in organic fertilized treatments was significantly less compared to the control, even if only 25% of the nitrogen was estimated to become plant available. The fertilizing effect of composted hop bines was comparable to that of fresh hop bines and higher than aged ones. However, nitrogen release of all kinds of hop bines was significantly less compared to Phacelia. The results indicate that nitrogen in hop bines can be conserved over winter by aerobic composting, but due to remarkable gaseous N losses during the composting process, the overall efficiency is relatively poor.
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Dr. Dieter Lohr,
Johannes Görl,
Prof. Dr. Elke Meinken
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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Betreuung der Publikationsseiten
Gerhard Radlmayr
Referent für Wissenstransfer und Forschungskommunikation
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