| Soil nutrients and crop yields have spatial within-field variability, changing with the time. However, agricultural production has been taking based on field unit for a long time past and same quantities of agricultural materials are applied to the whole field or all the fields in the area from year to year, so the spatial and temporal variability within fields is ignored, which wastes the natural resource and exerts a harmful impact on the environment. The aim of Precision Agriculture (PA) is to change this status, matching resource application and agronomic practices with soil and crop requirements as they vary in space and time within individual field units. An understanding of both the temporal and the spatial components of variability is essential, therefore, before decisions can be made about the feasibility of site-specific management. Thus, the research on spatial and temporal variability of soil properties and crop yields is the key topic which has being attracted the attention of scholars in the world.In present, much of the research done has concentrated on quantifying and understanding the spatial components of soil nutrients and crop yields variability; less attention has been given to the effects of time and season on the spatial patterns. Relatively little is known about the nature, extent or temporal stability of 'within-field' variability of soilnutrients in paddy field, and whether or not it would be feasible to manage it in a site-specific way. Actually, the crop yield is an integrate effect of a lot of factors, and soil nutrient variability is the main cause of the crop yield variability. In this present study, the spatial and the temporal components of variability of certain key soil properties and sward yields in a grassland field and their correlations, the spatial components of variability of certain key soil properties in three paddy fields were evaluated to assess the likely feasibility of adopting a site-specific approach to fertilization management. A 7.9 ha grassland field managed by the Agricultural Research Institute at Hillsborough, Co. Down, Northern Ireland and three paddy fields in Jiashan and Huzhou were selected for the study. Then a scheme of classed management and fertilization for the sward field was put forwarded, and soil sampling strategy and nutrient management mode adapt to the fields under the family responsibility system in southern China were explored. The main results obtained in this paper are as follows: Soil available nutrients, such as available P and available K, had the greatest within-field variability and the highest degree of temporal instability, whereas, soil total N and total C had the least within-field variability and were much more stable over time in the sward field. Soil available nutrients had good correlation with sward yields, their variability could influenced the sward yields more, therefore, available soil nutrients ought to be managed in a site-specific way. At cut 1, the spatial patterns of sward dry matter (DM) and N yield (N offtake) proved to be well defined and temporally stable. In contrast, at cut 2 and cut 3, the patterns of DM production were temporally unstable. Itwas concluded that site-specific management approach to fertilization according to the classified management map, in spring, ought to be feasible. It was also concluded that the spatial and temporal within-field variability of soil nutrients, sward DM and N yield (offtake) were influenced each other. In other words, the difference of soil, management way etc. can cause the crop yield variability, which enhances the soil variability again. The variability in the sward field was related with the topography, so three zones which ought to be managed in different site-specific ways were divided by elevation. Further work should be done to make fertilizer management scheme later. However, some fertilizer suggestion for the field was put forward especially for fertilizer N.Characteristics of soil properties of paddy field are different with those of sward fiel...
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