Advanced Mapping and Passive Sampling Techniques for Studies in Environmental Agriculture = Advanced Mapping and Passive Sampling Techniques for Studies in Environmental Agriculture

다국어 초록 (Multilingual Abstract)

The development in environmental agriculture requires “appropriate” spatial mapping and “appropriate” measurements of the chemicals in soils. This presentation focuses on some “problems” in these two main areas which are very different and have seldom been considered together. While the GIS techniques have been widely applied to produce spatial distribution maps, little attention has been paid to the assessment of whether the maps are produced appropriately or not. Specifically any spatial interpolation methods require the spatial correlation which is the primary pre-condition. This condition could be often breached in environmental agriculture. The examples from Ireland demonstrated that the plant available fractions of P showed poor spatial patterns at the national level, with a poor spatial structure revealed by variogram in geostatistics, implying the strong influences of agricultural activities. Intensive soil sampling at the farmland level has also revealed strong spatial variations of available P and other nutrients at the in-field level, with nutrient index advice level ranging from the lowest to the highest. These results provide strong challenges to the sampling strategy and the resulting advisory services in agriculture. On the other hand, regarding the measurements of the plant available forms of chemicals in soils, conventional extraction methods cannot provide the in-situ conditions of soils. The recent development of a passive sampling technology of diffusive gradients in thin films (DGT) provides a promising way forward. The DGT can be applied to provide bioavailability assessment of phosphorus and metals in sediments and soils. Compared with conventional methods, DGT, as a passive sampling method, has significant advantages: in situ measurement, time averaged concentrations and high spatial resolution. In summary, the appropriate spatial mapping requires spatial correlation and assessment for bioavailable chemicals in soils requires in situ measurements.