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Neue Forschungsergebnisse über die Klimawirkung von Dachbegrünung

Medienbeitrag, . (2022)


September: Beobachten, vorbeugen, bekämpfen

Lohrer, T. (2022)

DEGA GALABAU 76 (9), S. 94-97.

New approaches to assess stability of wood fiber

Beuth, E.; Schreiner, M.; Lohr, D.; Meinken, E. (2022)

31. International Horticultural Congress (IHC2022); International symposium on innovative technologies and production strategies for sustainable controlled environment horticulture.


In the wake of the decarbonisation of the entire economy, the use of peat in horticulture is under increasing pressure. In Germany, wood fibre is by far the most important substitute in growing media for professional horticulture. However, due to readily microbial degradability and a wide C:N ratio, nitrogen immobilization is a major problem of wood fibre products and considerably limits their use. Concurrently, stability of wood fibre is assessed by incubation experiments in which the change of mineral nitrogen is measured. However, these experiments have three shortcomings: First, they are quite labour and time-consuming as incubation period is up to 21 days. Second, if long-term fertilizers – especially urea-aldehyde condensation products – are applied by the manufacturer, the experiments only provide information about the stability of the N balance, but not about the stability of the material itself. Third, comparability and repeatability of the incubation experiments are rather poor. To overcome these shortcomings new approaches to evaluate stability of wood fibre were tested.

The setup of the first approach is similar to the currently used incubation experiments. However, the incubation period is only five days and additionally to change in mineral nitrogen from the beginning to the end of the experiment, carbon mineralization is analysed continuously by Oxitop®-C measuring heads. The second approach focusses on the characterization of readily decomposable nitrogen and carbon fractions in the wood fibre. On the one hand, hydrolysable nitrogen and carbon is measured and on the other hand, a stepwise thermal fractionation of carbon under pyrolytic conditions is done.

The results of the two approaches are compared to nitrogen immobilization measured in common incubation experiments and further validated by nitrogen balances deduced form short-term pot experiments with Chinese cabbage.


Development of an adaptive and sensor-based water management for extensive green roofs

Lohr, D.; Schmitz, H.; Meinken, E. (2022)

31. International Horticultural Congress (IHC2022); II International symposium on greener cities: improving ecosystem services in a climate-changing world (greencities2022).


Green roofs play a crucial role in climate change mitigation strategies. On the one hand, they should reduce the risk of urban floods after heavy rainfalls. On the other hand, they should cool the city by evapotranspiration and avoid the formation of urban heat islands. However, concurrently most green roofs in Germany are extensive ones. They are designed as dry sites, with shallow and well-drained vegetation layers, no additional irrigation and greened with highly drought-adapted plants - mainly sedum. Indeed, during the last years a new kind of extensive green roofs – still with shallow vegetation layers – but equipped with sub-surface irrigation and voluminous retention elements as temporary water storage beneath the vegetation layer as well as greened with plants with high transpiration, were developed. But also these new kind of green roofs are facing a conflict of objectives between storm water retention and cooling performance.

To solve this conflict of objectives an adaptive and sensor based water management system was developed. It consists of two main components: Irrigation management of the plants and management of storm water runoff, especially the control of the retention element. For the irrigation management a decision matrix was developed which adapts the irrigation strategy, depending if cooling performance or water retention has higher priority. Prioritization is based on thermal discomfort and rain forecast. The decision matrix uses environmental data, data of the weather forecast and information about water resources (e.g. grey water, water supply in the retention element). For management of storm water, run-off is actively controlled and the vegetation layer used as temporary water storage. In combination with a retention element, this can quadruple water retention capacity of green roofs. The amount of water stored in the green roof system – especially the retention element – is mainly controlled on basis of real-time, radar-based precipitation data.


Effect of co-composted biochar on nitrogen availability to spinach

Görl, J.; Lohr, D.; Meinken, E. (2022)

31. International Horticultural Congress (IHC2022); International symposium on plant nutrition, fertilization, soil management .


Co-composted biochar is suspected to be an effective sorbent for nitrate and thus might reduce nitrate leaching from agricultural soils. However, the underlying mechanism is unknown now and the effect on nitrogen availability is under discussion. In the current study, a pot trial with spinach was conducted to evaluate the influence of two co-composted biochars on nitrogen availability. Two wood-based biochars were co-composted with grass clippings and woody scrap material from landscaping activities. Additionally, a compost without biochar was prepared. Composts were mixed to an arable soil at rates of 30, 60 and 120 t ha-1 and nitrate was applied on basis of 100 kg N per hectare. Afterwards, mixtures were filled in balcony boxes, moisturized and placed in a greenhouse for 40 days. As control the soil without compost was treated in the same way. Furthermore, additional treatments without and with the highest application rate, but without nitrogen fertilization, were prepared. After the 40 days these balcony boxes were also fertilized with 100 kg ha-1 of nitrogen and spinach – pre-cultivated in press pots – was planted in all balcony boxes.

Irrespectively of application rates and – in case of the highest application rate – of date of nitrogen fertilization, no negative effect of co-composted biochar on N uptake was observed. In addition, the nitrogen balance for treatments with co-composted biochar was not significantly different from the control. However, for treatments with compost without biochar an increasing balance shortfall with increasing amounts of compost was observed. This might due to a nitrogen immobilization of woody residues. In view of the fact, that N uptake by plants was comparable and significant amounts of easily extractable nitrate were found in the soil at the end of the experiment, we assume that the co-composted biochars used in this experiment had no adsorption capacity for nitrate.

Estimation of plant availability of different phosphates by the CaCl2/DTPA and CAL method

Lohr, D.; Babel, B.; Lau, C.; Levaillant, N.; Prell, F.; Hauck, D. (2022)

31. International Horticultural Congress (IHC2022); International symposium on innovative technologies and production strategies for sustainable controlled environment horticulture .


Due to depletion of global phosphorus resources, there is an increasing interest in phosphorus recycling products as fertilizer for growing media. However, in contrast to currently used fertilizers, which are almost completely based on calcium phosphates, at least in sewage-sludge based recycling products a remarkably amounts of phosphorus can be bound to iron or aluminum. In previous studies, the CaCl2/DTPA (CAT) and CAL method partly underestimated plant availability of such sewage-sludge based recycling products, which might be due to a low solubility of iron- and aluminium-bound phosphorus in these two extractants. Thus, a pot trial with marigold was done: plants were fertilized with mono-calcium phosphate (MCaP), di-calcium phosphate (DCaP), tri-calcium phosphate (TCaP), aluminium phosphate (AlP) or iron phosphate (FeP) at growing media pH of 5.5 and 6.5, respectively. No effect on plant growth was observed for the three calcium phosphates irrespectively of pH. However, plant fresh weight was reduced if P was applied as FeP and AlP, whereby no effect of pH was found for AlP but for FeP. Against expectations, plant availability was poorer at the higher pH. In contrary to fresh weight, P uptake of plants decreases from mono- to tri-calcium phosphate and with increasing pH. For aluminium and iron phosphates results for P uptake was comparable to those reported for fresh weight. Whereas plant availability of the three calcium phosphates was well reflected by CAT and overestimated by CAL, P uptake from iron phosphate was strongly underestimated by CAT but matches CAL soluble P. Availability of aluminum phosphate was strongly underestimated by both extractants as well as by the combination of CAT and CAL soluble phosphorus. This supports previous findings for various sewage-sludge based products and raises the question of the need of other extractants.


Suitability of dielectric soil moisture sensors for measuring the water supply status of green roofs

Schmitz, H.; Jüttner, I.; Lohr, D.; Meinken, E. (2022)

31. International Horticultural Congress (IHC2022); II International symposium on greener cities: improving ecosystem services in a climate-changing world (greencities2022).


Extensive green roofs are a key component of urban water management in the future. On the one hand, they should mitigate urban heat islands, for which evapotranspiration has to be maximized, and on the other hand, they are supposed to reduce the risk of urban floods after heavy precipitation events. To achieve these goals, an exact measurement of the water supply status is necessary. In arable soils as well as in organic growing media, dielectric sensors are widely common. However, there is only little knowledge about the suitability of this kind of sensors for mineral and coarse-textured substrates used for extensive green roofs. In the current research four dielectric sensors (EC-5, 10 HS, SMT 100 and Aquaflex TR) were tested using five different green roof substrates. The five substrates were filled in plastic boxes of 80 x 60 cm. Substrate height was 15 cm and the four sensors were placed at half height. Afterwards, white lupine was sown and cultivated up to a height of about 30 cm. For testing the sensors, the substrates were saturated with water and then they have been left to dry out until plants show severe signs of wilt. During dry out, the sensor signals as well as the weight of the boxes were recorded automatically every five minutes. For each substrate six consecutive drying cycles were done. With exception of the Aquaflex TR, for all sensors output signals were closely linear correlated to the weight loss and signal ranges were comparable for the six drying cycles. However, significant differences in output signals of the sensors between the five tested substrates were observed. This indicates a need for substrate specific calibrations. The relation between the output signal of the Aquaflex TR and the weight loss was not linear, but also reproducible and suitable to assess water supply status of plants.


Klimawandel im Garten. Teil VII: Gestaltet: entsiegeln und pflanzen

Fröhler, L.; Bucher, A. (2022)

Gartenpraxis 08/2022, S. 38-42.


Simplified energy modeling to investigate the effect of lighting strategies on the energy efficiency of container indoor farms

Wittmann, S.; Jüttner, I.; Mempel, H. (2022)

DGG-Proceedings 2021/10, 2, S. 1-7.
DOI: 10.5288/dgg-pr-10-02-sw-2021

Open Access

Predicting shelf life along horticultural supply chains: Evaluation of applicable quality parameters using near-infrared scanner

Huneck, L.; Kulko, R.; Wittmann, S.; Elser, B.; Mempel, H. (2022)

DGG Proceedings 2021/10, 5, S. 1-8.
DOI: 10.5288/dgg-pr-10-05-lh-2021

Open Access

Visible-Near-Infrared Scanners enable a noninvasive prediction of quality properties of fruit and vegetable based on previously created models. A combination of NIR scanners and
machine learning methods can lead to economic improvements and reduction of food waste by strategies like "first expired, first out" and dynamic pricing. In order to identify parameters
capable of showing dynamic postharvest development, three horticultural products with different postharvest behavior (e. g. strawberry, table grape and mango) were chosen for
morphological and statictical analysis. According to the results, a graduation of spectra in correspondence to the day of measurement was noticeable for strawberry regarding the a-
value as well as presumingly mass loss for both mango and table grape. Furthermore, a PLS model for the a-values r2cv = 0.80 was developed for strawberries.


Klimawandel im Garten. Teil VI: Kostbar: Wasser und Bewässerung

Fröhler, L.; Bucher, A. (2022)

Gartenpraxis 07/2022, S. 34-38.


Vom Westallgäu bis zum Bodensee – 23. Juni 2022

Medienbeitrag, . (2022)



Mächtiges Grünzeug: So hilfreich und genial sind Pflanzen

Medienbeitrag, . (2022)

odysso - Wissen im SWR (Fernsehbeitrag des SWR), 23.06.2022.


TorfFrie - Modell-und Demonstrationsvorhaben zum Einsatz torfreduzierter Substrate im Friedhofsgartenbau

Lohr, D. (2022)

Tagung „Torfminderungskonzepte“ des BMEL.


Energieeffiziente Regelstrategie in der Gewächshausproduktion

Medienbeitrag, . (2022)

Gärtner + Florist 06/2022.

Klimawandel im Garten. Teil V: Gefährdet: kontrollieren und ernten

Fröhler, L.; Bucher, A. (2022)

Gartenpraxis 06/2022, S. 54-59.


Risiko Starkregen: Wie können wir uns vor Sturzfluten schützen?

Medienbeitrag, .; Meinken, E.; Schmitz, H. (2022)

UNKRAUT - Umweltmagazin des BR Fernsehen, Stand: 23.05.2022.


HSWT: Heizkosten sparen mit dem "Weihenstephaner Modell"

Medienbeitrag, .; Stiele, V. (2022) - Internet-Portal für den Erwerbsgartenbau. Online erschienen am 06.05.2022.


Klimawandel im Garten. Teil IV: Gegessen: säen und ernten

Fröhler, L.; Bucher, A. (2022)

Gartenpraxis 05/2022, S. 48-53.


Controlled deficit irrigation – effects on growth and water relations of Daucus carota L. roots

Herppich, W.; Mempel, H.; Schreiner, M.; Huyskens-Keil, S. (2022)

Acta Horticulturae ISHS2022, 1335, S. 681-686.
DOI: https://doi/org/10.17660/ActaHortic.2022.1335.86


Regulated deficit irrigation (RDI) comprises controlled reduction of irrigation during certain phases of plant development, accepting minor yield reduction but maximising net returns. To optimise RDI, plant response-based irrigation scheduling may be essential. For this, the knowledge of plant reactions to soil water regimes is indispensable. In field trials (randomized block design, 3 repetitions), ‘Nanthya’ carrots (F1-hybrid) were grown at 20, 40, 60 and 80% field capacity (determined by TDR sensors), yielding soil water contents of 5.1±0.2, 6.2±0.8, 10.1±0.5 and 11.2±0.2% (controls). To guarantee constant controlled soil water contents, plastic rain shelter (76% transparency) were applied. Plots were irrigated if necessary. Treatments started 23 d after sowing (DAS), first sampling was 91 DAS, while final harvest was 106 DAS. On each date, fresh and dry mass, water content, water potential, osmotic potential, turgor and stiffness of carrot tubers were analyzed. Root fresh mass (n=20 carrots per treatment) was higher at high water availability only at the 1st sampling but not at the final harvest. Here, water regime did not affect yield. At this time, root tuber water potential was lower than at the 1st sampling and it was also lower at low soil water availability (20%, 40%). Similar results were obtained for the mean osmotic potential. These variations partially resulted from osmotic adjustment (at 1st harvest) and from a lower root tuber water content at the final sampling. The generally higher modulus of elasticity at this date indicated water volume-independent cell wall-stiffening, i.e. elastic adjustment. The presented results point out that moderately reduced (by 20%) irrigation of carrots does not affect their yield, while pronounced water shortage may induce physiological adjustment.


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