Das Projekt "B 3.1: Efficient water use of mixed cropping systems in watersheds of Northern Thailand highlands" wird vom Umweltbundesamt gefördert und von Universität Hohenheim, Institut für Kulturpflanzenwissenschaften (340), Fachgebiet Düngung und Bodenstoffhaushalt (340i) durchgeführt. Worldwide an important part of agricultural added value is produced under irrigation. By irrigation unproductive areas can be cultivated, additional harvests can be obtained or different crops can be planted. Since its introduction into Northern Thailand lychee has developed as one of the dominating cash crops. Lychee is produced in the hillside areas and has to be irrigated during the dry season, which is the main yield-forming period. Water therefore is mainly taken from sources or streams in the mountain forests. As nowadays all the available resources are being used do to increased production, a further increase in production can only be achieved by increasing the water use efficiency. In recent years, partial root-zone drying has become a well-established irrigation technique in wine growing areas. In a ten to fifteen days rhythm one part of the root system is irrigated while the other dries out and produces abscisic acid (ABA) a drought stress hormone. While the vegetative growth and thus labor for pruning is reduced, the generative growth remains widely unaffected. Thereby water-use efficiency can be increased by more than 40Prozent. In this sub-project the PRD-technique as well as other deficit irrigation strategies shall be applied in lychee and mango orchards and its effects on plant growth and yield shall be analyzed. Especially effects of this water-saving technology on the nutrient balance shall be considered, in order to develop an optimized fertigation strategy with respect to yield and fruit quality. As shown in preliminary studies, the nutrient supply is low in soils and fruit trees in Northern Thailand (e.g. phosphate) and even deficient for both micronutrients boron (B) and zinc (Zn). Additionally, non-adapted supply of nitrogen (mineralization, fertilization) can induce uneven flowering and fruit set. Therefore, improvement is necessary. For a better understanding of possible influence of low B and Zn supply on flowering and fruit set, mobility and retranslocation of both micronutrients shall be investigated for mango and lychee. Finally, the intended system of partial root-zone fertigation (PRF) shall guarantee an even flowering and a better yield formation under improved use of the limited resource water. As this modern technique, which requires a higher level of irrigation-technology, cannot be immediately spread among the farmers in the region, in a parallel approach potential users shall be integrated in a participative process for adaptation and development. Water transport and irrigation shall be considered, as both factors offer a tremendous potential for water saving. Local knowledge shall be integrated in the participatory process (supported by subproject A1.2, Participatory Research) in order to finally offer adapted technologies for application within PRF systems for the different conditions of farmers in the hillsides of Northern Thailand.
Das Projekt "D 1.2: Reducing alternation and production of off-season fruits in Lychee, Longan and Mango" wird vom Umweltbundesamt gefördert und von Universität Hohenheim, Institut für Kulturpflanzenwissenschaften (340), Fachgebiet Düngung und Bodenstoffhaushalt (340i) durchgeführt. The aim and vision of sub-project D1.2 was and is to encourage hillside farmers to plant erosion resistant fruit trees instead of erosion susceptible annual plants. For that reason, experiments to overcome the irregular bearing behaviour of the three most common fruit tree species in Northern Thailand (Litchi, Longan and Mango) from the first SFB period will be continued in order to make their planting more attractive to the farmers. Considerable progress has been made in D1 during the past 3 years to induce flowers and fruit in Longan trees by the application of KClO3 . With this technique, it was not only possible to induce year around flowers and fruit (off season fruit) but also to overcome the generally rather irregular fruiting behaviour of these trees. A similar technique is now being developed for Mango by using an inhibitor of the bio-synthesis of the plant hormone gibberellin. Only Litchi still resist this kind of manipulation by an 'off season technique' (OST). Great effort will therefore be devoted establishing a similar system for this species as well. Reliably, this can only be done by gaining a much better knowledge of the - most certainly hormonal - regulatory system that governs flower induction in trees. Investigations into the hormonal changes taking place during natural and induced flower induction is, therefore, one of the central objectives in this sub-project, with the goal to better understand the process of flower induction. Until now most of the progress in this area is entirely empirical in nature and a more specific manipulation therefore difficult. While the ability to produce off season fruit all year around and under various weather conditions has brought about a great number of new possibilities, new challenges will still be faced with regard to these methods. These circumstances will affect the whole production chain from the orchard to the market and consumer. In order to better investigate and understand these new situations, a large model experiment with Mango will be set up and problems like tree pruning, water and nutrient demand, phytopathological problems, demand on work force, fruit processing and drying etc. will be investigated by the interdisciplinary co-operation of 8 sub-projects within the SFB. The results obtained during these investigations will be shared with hillside farmers enabling them to take advantage of these new possibilities, which will provide for more reliable yields and allow them to market fruit year around. In general, these new opportunities should encourage farmers to plant more trees and thus reduce erosion. However, to make this system not only reliable and economic but also ecologically and socially beneficial to the society all potential benefits as well as risks have to be evaluated carefully from all different aspects.
Das Projekt "D 1.3: Regulation of flowering in tropical fruit crops on erosion prone sites in Northern Thailand" wird vom Umweltbundesamt gefördert und von Universität Hohenheim, Institut für Kulturpflanzenwissenschaften, Fachgebiet Ertragsphysiologie der Sonderkulturen (340f) durchgeführt. NRCT component: Assoc.Prof.Dr. Sruamsiri, Pittaya - Development of Clean Technology for Off-season Fruit Production: A Case Study of Mango, Longan, Litchi and Tangerine. Specific basic and applied science activities for each crop will be carried out in an attempt to solve the following issues. Longan: Previous research work has shown that flower induction can successfully be manipulated by application of KClO3. This crop is therefore an ideal model plant to investigate the regulatory mechanisms of flowering by: 1. determining acquisition and distribution of KClO3 using isotope labelling techniques and measuring enzyme activities in leaves to decide whether nitrate reductase is involved in the conversion and flower inducing activity of KClO3; 2. identifying mutual influences between hormones including their time-dependent changes brought about by manipulation of hormone biosynthesis through exogenously applied plant growth regulators (PGRs); 3. investigating the effect of off-season production systems on carbohydrate distribution and reserves. Mango: Paclobutrazol (PBZ) is already commercially used to manipulated flower induction in mango, however, the technique may not be sustainable due to its persistence in plant and soil. Prohexadione-Ca (Pro-Ca), another gibberellin biosynthesis inhibiting compound, and specific crop management techniques may prove to be successful and more sustainable alternatives to PBZ and warrant detailed investigation by: 1. evaluating appropriate time-of-season, concentration and application procedure (injection or spray) of Pro-Ca as possible alternative of PBZ and subsequent effects on hormonal status; 2. pruning or defoliation techniques which may induce a secondary flower through an altered hormonal status in the bud tissue. Litchi: There are still no proven orchard management practices for inducing off-season flowering in litchi. The main research objective is to study the significance of plant stress (pruning, girdling shoot tipping techniques, water and nutrient deficiency) on flowering signals by determining carbohydrate changes and hormonal status.
Das Projekt "Guiding early silvicultural interventions through predicting canopy and crown dynamics in plantations of sub-tropical eucalypts" wird vom Umweltbundesamt gefördert und von Universität Freiburg, Waldbau-Institut durchgeführt. This project aims to establish the scientific basis for silvicultural treatments of eucalypt plantations for clear wood production. While eucalypt plantations in north-eastern NSW have dramatically increased in recent times, the knowledge base for the production of clear, branch-free wood from the tree species used does not exist. A physiological, mechanistic understanding of crown and canopy dynamics as well as branch shedding will form the scientific foundation for stand manipulations such as pruning and thinning to enhance wood quality. Project outcomes will provide the basis for a stand management simulation model for the most important eucalypt species. Specifically the project is testing the following three management related hypotheses: 1. The plasticity of green crowns (length, shape, number and size of branches) in response to stand density and spatial arrangement is greater in the more shade-tolerant eucalypts than in the intolerant eucalypts. 2. The effect of green crown pruning on biomass production in eucalypts can be related to the amount of foliage removed, the nutrient status of the pruned foliage, the water status of pruned trees and the shade tolerance of the species. 3. Leaf area index and thus green crown length is more closely related to site quality, water and nutrient availability, in the more shade-tolerant eucalypts than in shade intolerant species.
Das Projekt "Steuerung des Waldwachstums - Astentwicklung und Astreinigung in Abhängigkeit vom Dickenwachstum bei Eichen und Buchen" wird vom Umweltbundesamt gefördert und von Universität Freiburg, Professur für Waldwachstum durchgeführt. Astentwicklung und Astreinigung werden von verschiedenen standörtlichen und ökophysiologischen Faktoren gesteuert. Sie bestimmt die Architektur der Krone, die für das Baumwachstum von großer Bedeutung ist. Bestimmend für die Astausprägungen und die Kronenlänge ist die Konkurrenz. Die Anzahl und die Ausprägungen von Grün- und Totästen haben einen großen Einfluss auf mechanische und ästhetische Eigenschaften des Holzes und beeinflussen deshalb die Holzqualitätssortierung. Zentrale Frage dieser Arbeit ist, wie Dickenwachstum einerseits und Astentwicklung andererseits als wertbestimmende Faktoren zueinander in Relation stehen. Kenntnisse über diese Zusammenhänge sind eine Voraussetzung für eine gezielte, auf einen hohen Wertholzanteil bei zugleich begrenztem Risiko, ausgerichtete Waldpflege. Bei dieser Untersuchung werden Astcharakteristiken und Astreinigungsprozesse der Buche als ausgesprochen konkurrenzstarke und schattenertragende Baumart, die im Jugendalter einen vergleichbar geringen jährlichen Höhenzuwachs aufweist der Baumart Eiche gegenübergestellt, die als langlebige lichtbedürftigere Baumart einen vergleichbar großen jährlichen Höhenzuwachs im Jugendstadium aufweist, der jedoch sehr bald zur Kulmination gebracht wird.