EVALUATION OF COASTAL SANDY LAND IN THANH HOA PROVINCE FOR AGRICULTURAL DEVELOPMENT WITH CASE STUDY OF QUANG XUONG DISTRICT I n a u g u r a l d i s s e r t a t i o n zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Ernst-Moritz-Arndt-Universität Greifswald vorgelegt von Hao Huu Nguyen geboren am 02.03.1981 in Thanh Hoa, Vietnam Greifswald, 2017 i Dekan: Prof. Dr. rer. nat. Werner Weitschies 1. Gutachter: Prof. Dr. rer. nat. Reinhard Zölitz 2. Gutachter: Prof. Dr. rer. nat. Ing Ralf Bill Tag der Promotion: 18th of October, 2017 ii Summary Quang Xuong is considered as one of the most developed districts in Thanh Hoa Province in terms of agricultural. The major purpose of this research is to find good places to suggest for annual crops production in the case study. Therefore, the assessment of land potential productivity, land suitability, and land cover/land use change in different periods is essential for making strategies of sustainable agricultural development as this will help land-users and land managers to discover the potential and limitations of the current existing land conditions to make appropriate policies and plans for future land use. Its results will provide basic information to make reasonable decisions for investments and rational reclamations of cultivated land before and after each crop season in order to meet the objectives of sustainable development in terms of economic efficiency, social acceptability, and environmental protection. The research site is located at latitudes 19034‘N - 19047‘N and at longitudes 105046‘E - 105053‘E. The total area is about 227km2; in which 128km2 is in use for agricultural activities. Based on soil classification methods by FAO-UNESCO (1988), the agricultural land is classified into six main soil groups, including Arenosols, Salic Fluvisols, Fluvisols, Gleysols, Acrisols, and Leptosols, 12 soil units and 18 sub-units. The largest area belongs to the Fluvisols group with 9358.29ha and the smallest area is identified as the Leptosol group with 219.33ha. Most of the soil in this district has low to moderate nutrition, but in general, they are still suitable for agricultural production. There are 42 land units defined in the land mapping, which can be different from each other by one or more land characteristics. The land mapping unit is created from the overlay of all thematic maps of soil chemicals, soil physical characteristics, and relative topography together by application of GIS techniques. It presents land characteristics and properties in this case study and will be used in comparasion with a particular crop requirement for growth in land suitability evaluation process. A certain land unit may be suitable for one or more types of different land use. It is also classified as highly suitable for a specific land utilization type, but less suitable or unsuitable for other crops. For example, in this study, land unit 26 is determined as highly suitable (S1) for growing paddy rice and maize, but it falls into moderately suitability (S2) for groundnut crop by using parametric (square root) method used in this thesis. Depending on the kind of crops need to be evaluated and its requirement for development compared with each land unit characteristics, land-users will determine the best suitable place for crop production. i Identification of land use change in different periods of time has become a central key to monitoring of land resources. It is relatively important for effective land management to protect the land resources, especially the land used for agricultural production from overuse and environmental changes. The sprawl of inhabitant areas, development of rural infrastructures, and industrialization are responsible for serious losses of agricultural land. In this study, remote sensing techniques were applied to studying the trends of land cover change in the abovementioned district in a period of about 24 years from 1989 to 2013. ArcGIS software was adopted to develop the land cover and the change of land use maps from 1989 to 2013. Two satellite images with moderate resolution were collected from USGS Earth Explorer website, Landsat5 TM for 1989 and Landsat8 OLI & TIRS for 2013. After image geo-processing, the images were classified into six land cover categories by applying supervised classification method (Maximum Likelihood). The six main obtained land cover types were built-up areas, agricultural land, forest land, water surface area, salty land, and unused land. The overall accuracies of land cover maps for 1989 and 2013 were 94.08% and 92.91%, respectively. The results of change detection analysis indicate that the cultivated, water surface and unused lands decreased by 22%, 17%, and 91%, respectively. In other side, the built-up and salty land increased by 78%, 58%, respectively and forest land increased from 52.69ha in 1989 to 395.76ha in 2013. The assessment of land potential productivity for agricultural production and land suitability for selected annual crops was based on FAO guidelines for land evaluation (FAO, 1976, 1985, and 1993) which were adopted and slightly modified for compatibility with Vietnamese conditions. All related data were stored, analyzed, mapped and presented in ArcGIS software. Weighted Linear Combination Method developed by Hopkins (1977) and GIS techniques were used to analyze and determine the land potential for agricultural use in the study area. The results show that 5.26%, 83.10%, 10.06%, and 1.57% of the investigated areas were assessed as high potential, moderate potential, low potential and very low potential for growing crops. Regarding land suitability evaluation, the simple limitation, parametric (square root), and AHP methods were used to evaluate the suitability levels for selected crops, including paddy rice, sweet potato, groundnut, maize, potato, sesame, soybean, and green pepper. The obtained results indicate that each applied method provides different results of land suitability level for a specific crop in certain land units compared to the other two methods, and OM, soil pH, soil texture, and relative topography were found out as the main limitation factors which affected land suitability level. The study also suggests that three different methods as abovementioned can be expanded and applied in other places with the appropriate factors used for land suitability evaluation according to particular area conditions. ii Zusammenfassung Quang Xuong gilt als einer der wichtigsten Distrikte für die landwirtschaftliche Entwicklung in der Provinz Thanh Hoa. Hauptzweck der vorliegenden Arbeit ist es, für den Anbau einjähriger Kulturen am besten geeignete Flächen im Untersuchungsgebiet zu finden. Für eine nachhaltige landwirtschaftliche Bewirtschaftung ist es notwendig, die potentielle landwirtschaftliche Leistungsfähigkeit, die Landeignung, die Oberflächenbedeckung und die Landnutzungsänderung in verschiedenen Perioden zubetrachten. Die Arbeit soll Landwirte und Landmanager dabei unterstützen, Potenziale und Grenzen der gegenwärtigen bestehenden Bewirtschaftung zu bestimmen, um in der Zukunft gesetzeskonforme Richtlinien und sinnvolle Pläne der Bewirtschaftung zu erstellen. Die Ergebnisse sollen grundlegende Informationen liefern, um angemessene Entscheidungen für Investitionen und Rekultivierungen von Anbauflächen vor und nach jeder Pflanzsaison zu treffen, um das Ziel einer nachhaltigen Entwicklung im Hinblick auf wirtschaftliche Effizienz, soziale Akzeptanz und Umweltschutz zu erfüllen. Das Untersuchungsgebiet befindet sich zwischen den Breitengraden 19034'N- 19047'N und den Längengraden 105046'E - 105053'E. Die Gesamtfläche beträgt etwa 227km2; In welcher 128km2 für landwirtschaftliche Aktivitäten genutzt wird. Auf der Grundlage der Bodenklassifikation der FAO-UNESCO (1988) werden die landwirtschaftlichen Flächen in sechs Hauptbodengruppen, bestehend aus Arenosols, Salic Fluvisols, Fluvisols, Gleysols, Acrisols und Leptosole, 12 Bodeneinheiten und 18 Untereinheiten eingeteilt. Die größte Fläche nimmt die Gruppe der Fluvisole mit 9358,29ha ein, die kleine Fläche wird von der Gruppe der Leptosole Gruppe mit 219,33ha gebildet. Die meisten Böden im Distrikt haben einen niedrigen bis mäßigen Nährstoffgehalt, sind aber generell noch für die landwirtschaftliche Produktion geeignet. Es können 42 Landeinheiten unterschieden werden. Jede Landeinheit kann sich durch eine oder mehrere Eigenschaften voneinander unterscheiden. Eine solche Einheit entsteht aus der Überlagerung aller thematischen Karten von bodenchemischen und bodenphysikalischen Eigenschaften und relative Topographie (relative topography), durch die Anwendung von GIS-Techniken. Diese beschreibt Charakteristiken und Eigenschaften der untersuchten Gebiete und wird verglichen mit Wachstumsanforderungen und Landeignung. Eine bestimmte Landeinheit kann für unterschiedliche Landnutzungen geeignet sein. Sie kann für eine bestimmte Art der Landnutzung präferiert sein, jedoch weniger oder ungeeignet für andere Anbauarten. Beispielsweise wird in dieser Studie die Landeinheit 26 als sehr geeignet (S1) zum Anbau iii von Paddy Reis und Mais eingestuft, aber nur moderat geeignet (S2) für den Erdnussanbau klassifiziert, nach dem in der Arbeit vorgestellten parametrischen (Quadratwurzel) Verfahren. In Abhängigkeit der untersuchten Anbauart und ihrer Ansprüche und der zur Verfügung stehenden Landeinheiten, kann der Landwirt den am besten geeigneten Platz für diese Feldfrucht bestimmen.