Browsing by Subject "CROPGRO"

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Grasping the complexity of intercropping - developing and testing an integrated decision support system for vegetable production in the North China Plain
(2010) Feike, Til; Claupein, Wilhelm
This cumulative dissertation consists of six papers published, accepted or submitted to international high standard journals or books. To detect and describe the status quo of vegetable intercropping in the North China Plain (NCP), a survey was conducted from autumn 2007 to spring 2008. The results of the interviews with researchers, extensionists and farmers embedded in the first article revealed a huge variety of intercropping systems being practiced by farmers in the region. The first article furthermore elaborated farmers? underlying motives and concepts and described the knowledge transfer systems involved. When evaluating the prevailing systems against the background of the rapidly changing socio-economic frame conditions for farming in rural China, it became obvious that a great proportion of the systems practiced nowadays are prone to extinction in a long run. Therefore the second article discussed possible adjustments of the intercropping systems to fit the demands of modern agriculture, while maintaining their potential agronomic and environmental benefits. To enable mechanization, it was suggested to either adjust the machinery to the traditional row intercropping systems, or adjust the cropping system to the prevailing and available machinery. The latter approach was then followed throughout the thesis, using an agronomic modeling approach. The combination of Chinese cabbage and maize was selected, as it is a traditional intercropping system, with strong interspecific effects. In the course of this study, the two crops were strip intercropped in four field experiments at three sites in Germany and in China in 2008 and 2009. To understand, explain and predict plant behavior under the impact of complex cropping structures, crop growth models present a viable and powerful tool. However, two constrains had to be overcome within the framework of this thesis i) Chinese cabbage is not integrated in the common process-oriented crop growth models, ii) a method had to be developed to quantify resource competition and simulate intercropping. Therefore the integration of Chinese cabbage, the number one field vegetable of China, into the CROPGRO model constituted the first step for the simulation of intercropping systems in China. Two greenhouse experiments, testing crop growth and development under different temperature regimes, served as the data base for the accurate parameterization of Chinese cabbage and built the baseline for the third article. Cardinal temperatures of Chinese cabbage were identified by correlating mean relative growth rates and mean leaf appearance rates to temperature. Minimum growth temperature was identified at 0 °C, optimum temperature ranges between 14 °C and 24 °C, and maximum temperature is 34 °C. The further adjustment and testing of the model, which was executed on up to six independent data sets, is presented in the fourth article. The key to successfully simulate intercropping systems is the knowledge on changes in resource availability compared to monocropping. Therefore, a method was developed to quantify the availability of the most crucial growth factor solar radiation at any location within a Chinese cabbage strip, presented in the fifth article. The method was extended in the sixth and final article to enable the estimation of available radiation in Chinese cabbage strips of different widths. The ?environmental modifications? option of CROPGRO was employed to simulate the effects of the estimated reduction in incoming radiation in Chinese cabbage strips of different width. Simulations were conducted over up to thirty years of weather data of 12 locations throughout the NCP, and were additionally tested on different soil texture types. The results were extended over the entire NCP by linking them to a GIS-system. The developed approach constitutes a reliable decision support for the optimization of the spatial arrangements in Chinese cabbage strip intercropping systems, according to local soil and climate conditions. The described approach can be extended to develop a comprehensive decision support system that allows testing of various intercrop combinations under a wide range of climate and especially radiation environments. The presented thesis is a valuable contribution to the development of sustainable vegetable production systems in the NCP. A new method to quantify availability of solar radiation in strip intercropping was developed, which can be applied in various other intercropping systems. The integration of Chinese cabbage into CROPGRO, offers great opportunities not only for studying intercropping systems, but also for improving input levels and resource use efficiency in Chinese cabbage production in China and throughout the world. Understanding farmers? concepts and estimating the production potential of intercropped Chinese cabbage created additional value, which substantially contributes to realizing the potential of intercropping in the NCP.