Understanding and Identifying Variability

In precision farming, variability is the measure of dissimilarity or difference in soil, crops, management, pests, varieties, yields, elevation, soil water and soil nutrients in space and time across a field. The first step in managing variability is understanding the root causes and extent. If little variability exists, the use of variable rate technology will have a minimal ability to improve yields. If variability is high, then the opposite is true. Therefore, key goals in precision farming is the ability to identify spatial and temporal variability and then tailor the appropriate management to that variability. The purpose of this chapter is to help describe sources of variability typically found in crop production systems. It includes descriptions and examples of both spatial and temporal variability, and contrasts biotic versus abiotic factors. Included are explanations of how weather and soil interact to create variability. Variability in crop production fields also is influenced by management, such as through increased erosion, compaction, rotations, and uneven application of fertilizer, lime, manure and irrigation. By managing for variability with precision farming, farmers can increase profitability and improve environmental services