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1.  Introduction

Heterogeneity is a common phenomenon in nature. The vast majority of agricultural fields are heterogen and have large variations in parameters such as soil type, nutrient availability, slope, crop height, tiller density, plant mass and others within a single field. Spatial and temporal processes are causing this variability resulting in spatial variability (variability in space) and temporal variability (variability in time). Variability may be random or correlated, may be over a long distance or short distance, and may have a small or large magnitude. Arable crops respond to this variability to different extends that produce variations in quantity and quality of the cultivated crop and is finally visible by different yields. In general, the current practice of farmers is to treat fields uniformily regarding the applied inputs such as fertilizers and agrochemicals. It is obvious that this uniform application of treatments to an arable crop is not only inefficient in terms of costs, but also has a negative environmental result.

The pressures of environmental constraints and efficient use of treatments are driving farmers towards precision in arable crop operations. To reduce environmental damage and optimise the use of agrochemicals, it is necessary to take into account the spatial variability in above and below ground environments, which is inherent in almost every agricultural field.

This management is variously known as site-specific, precision, spatially-variable, soil-specific agriculture or farming. The concept of site-specific agriculture or precision farming is the use of local soil and crop parameters, to target inputs more accurately according to locally determined requirements of field crops. It is a developing technology that modifies existing techniques and incorporates new ones, to produce a new set of tools for the manager to use. The variation of crop and soil properties within the fields leads to attempts to understand these variations and to manage production accordingly.

Technological advance in other areas such as sensing and control systems is enabling precision agriculture systems to be implemented, though agronomic and decision support systems lag behind. Locating these differences within a large field is impossible without the access to positioning systems, and an increased use of electronics and computers in agriculture. The whole concept depends on the acquisition and interpretation of data on spatial variability although there are only a few existing sensing systems. Adequate utilisation of appropriate sensors will offer major opportunities for precise targeting of inputs.


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