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- ItemMethoden für die präzise obstbauliche Produktion(Darmstadt : KTBL, 2012) Zude, Manuela; Peeters, Aviva; Selbeck, Jörn; Käthner, Jana; Gebbers, Robin; Bengal, Alon; Hetzroni, Amots; Jaeger-Hansen, Claes; Griepentrog, Hans-Werner; Pforte, Florian; Rozzi, Paolo; Torricelli, Alessandro; Spinelli, Lorenzo; Ünlü, Mustafa; Kanber, RizaDer Ansatz von Precision Horticulture im Obstbau lehnt sich an das aus dem Ackerbau stammende Konzept der Präzisionslandwirtschaft bzw. der teilflächenspezifischen Bewirtschaftung an. Hierbei sollen präzise an das individuelle Gehölzwachstum angepasste Pflegemaßnahmen die bislang praktizierte einheitliche Behandlung aller Bäume in einer Anlage ablösen. Voraussetzungen hierfür sind u. a. Bodenkarten und Informationen zum Pflanzenwachstum. Das Ziel ist es, den informationsgestützten Obstbau voranzutreiben und durch ein räumlich und zeitlich differenziertes Management eine effizientere und nachhaltigere Bewirtschaftung zu erreichen.
- ItemEvaluating spatially resolved influence of soil and tree water status on quality of European plum grown in semi-humid climate(Lausanne : Frontiers Media, 2017) Käthner, Jana; Ben-Gal, Alon; Gebbers, Robin; Peeters, Aviva; Herppich, Werner B.; Zude-Sasse, ManuelaIn orchards, the variations of fruit quality and its determinants are crucial for resource effective measures. In the present study, a drip-irrigated plum production (Prunus domestica L. “Tophit plus”/Wavit) located in a semi-humid climate was studied. Analysis of the apparent electrical conductivity (ECa) of soil showed spatial patterns of sand lenses in the orchard. Water status of sample trees was measured instantaneously by means of leaf water potential, Ψleaf [MPa], and for all trees by thermal imaging of canopies and calculation of the crop water stress index (CWSI). Methods for determining CWSI were evaluated. A CWSI approach calculating canopy and reference temperatures from the histogram of pixels from each image itself was found to suit the experimental conditions. Soil ECa showed no correlation with specific leaf area ratio and cumulative water use efficiency (WUEc) derived from the crop load. The fruit quality, however, was influenced by physiological drought stress in trees with high crop load and, resulting (too) high WUEc, when fruit driven water demand was not met. As indicated by analysis of variance, neither ECa nor the instantaneous CWSI could be used as predictors of fruit quality, while the interaction of CWSI and WUEc did succeed in indicating significant differences. Consequently, both WUEc and CWSI should be integrated in irrigation scheduling for positive impact on fruit quality.
- ItemEffects of Interrow Maintenance on Microclimate Parameters in Black Currant (Ribes nigrum L.)(Berlin ; Heidelberg [u.a.] : SpringerOpen, 2022) Nagler, Linda; Schwefler, Jana; Käthner, Jana; Giebel, Antje; Kramer, EckartThe aim of the study was to determine the influence of tramline maintenance frequency on air temperature and relative humidity in blackcurrant (Ribes nigrum) plantations. In practice, keeping tramline vegetation short serves as an applied and preventative technique to improve aeration in the crop and reduce disease pressure. The on-farm trials took place on two ecological shrub berry farms in Brandenburg (Weggun and Schöneiche) over a period from March to June 2021. The effects of maintenance frequency on the microclimate in the tramlines were determined for normal mowing frequency (business as usual, BAU) and increased mowing frequency (TEST). The results show that continuous short keeping of the tramlines has a demonstrable influence on the air temperature and humidity in the currant stand. In some cases, an increased mowing frequency (TEST) led to a significantly higher mean air temperature than under usual management (BAU), whereas the mean relative humidity was significantly lower. The effects were dependent on timing and site. Over the experimental period, maximum mean air temperature differences of 1.14 °C (Weggun site) and 1.96 °C (Schöneiche site) and maximum mean relative humidity differences of 3.69% (Weggun site) and 3.90% (Schöneiche site) were observed between the TEST and BAU variants. Especially in the plantation with the smaller row distance, this effect occurs more clearly. The results suggest that the plantation structure has an influence on these effects, which should be investigated in further trials.
- ItemA computational model for path loss in wireless sensor networks in orchard environments(Basel : MDPI, 2014) Anastassiu, Hristos T.; Vougioukas, Stavros; Fronimos, Theodoros; Regen, Christian; Petrou, Loukas; Zude, Manuela; Käthner, JanaA computational model for radio wave propagation through tree orchards is presented. Trees are modeled as collections of branches, geometrically approximated by cylinders, whose dimensions are determined on the basis of measurements in a cherry orchard. Tree canopies are modeled as dielectric spheres of appropriate size. A single row of trees was modeled by creating copies of a representative tree model positioned on top of a rectangular, lossy dielectric slab that simulated the ground. The complete scattering model, including soil and trees, enhanced by periodicity conditions corresponding to the array, was characterized via a commercial computational software tool for simulating the wave propagation by means of the Finite Element Method. The attenuation of the simulated signal was compared to measurements taken in the cherry orchard, using two ZigBee receiver-transmitter modules. Near the top of the tree canopies (at 3 m), the predicted attenuation was close to the measured one—just slightly underestimated. However, at 1.5 m the solver underestimated the measured attenuation significantly, especially when leaves were present and, as distances grew longer. This suggests that the effects of scattering from neighboring tree rows need to be incorporated into the model. However, complex geometries result in ill conditioned linear systems that affect the solver’s convergence.