Submitted to: Journal of Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2008
Publication Date: 10/30/2008
Citation: Chung, S.O., Jung, I.K., Sung, J.H., Sudduth, K.A., Drummond, S.T. 2008. Analysis of Spatial Variability in a Korean Paddy Field Using Median Polish Detrending. Journal of Biosystems Engineering. 33(5):362-369. Interpretive Summary: Precision agriculture is a crop management strategy which seeks to address within-field variability. Already well-established in North America, Europe, and Australia, precision agriculture is now being adopted in other places, including the Republic of Korea. The application of precision management principles and techniques to the diverse crops and small-scale farming systems in Korea presents new challenges. Describing within-field variability in typical Korean production settings is a fundamental first step toward the application of precision agriculture in Korea. In this study, we measured rice yield, chlorophyll content, and soil properties in a typical (approximately 0.75 acre) Korean rice paddy field. Data analysis showed that there was significant variation in yield, chlorophyll content, and several soil properties, even within this small area. This finding is significant, because some scientists have assumed that variability would be negligible in these small, flood-irrigated fields. Scientists working to apply precision agriculture in Korea or other Asian countries with similar cropping systems will benefit from this research, as it provides them with information on the level of yield and soil variability present in typical rice production systems.
Technical Abstract: There is developing interest in precision agriculture in Korea, despite the fact that typical fields are less than 1 ha in size. Describing within-field variability in typical Korean production settings is a fundamental first step toward determining the size of management zones and the inter-relationships between limiting factors, for establishment of site-specific management strategies. Measurements of rice (Oriza Sativa L) yield, chlorophyll content, and soil properties were obtained in a small (100-m by 30-m) Korean rice paddy field. Yield data were manually collected on 10-m by 5-m grids (180 samples with 3 samples in each of 60 grid cells) and chlorophyll content was measured using a Minolta SPAD 502 in 2-m by 2-m grids. Soil samples were collected at 275 points to compare results from sampling at different scales. Ten soil properties important for rice production in Korea were determined through laboratory analyses. Variogram analysis and point kriging with and without median polishing were conducted to determine the variability of the measured parameters. Influence of variogram model selection and other parameters on the interpretation of the data was investigated. For many of the data, maximum values were greater than double the minimum values, indicating considerable spatial variability in the small paddy field, and large-scale spatial trends were present. When variograms were fit to the original data, the limits of spatial dependency for rice yield and SPAD reading were 11.5 m and 6.5 m, respectively, and after detrending the limits were reduced to 7.4 m and 3.9 m. The range of spatial dependency for soil properties was variable, with several having ranges as short as 2 m and others having ranges greater than 30 m. Kriged maps of the variables clearly showed the presence of both large-scale (trend) variability and small-scale variability in this small field where it would be reasonable to expect uniformity. These findings indicate the potential for applying the principles and technology of precision agriculture for Korean paddy fields. Additional research is needed to confirm the results with data from other fields and crops.