In other words, the plans must be site-specific. If within-field variability is substantial, profitability and environmental soundness may be improved by considering the variability existing within the field boundaries. Site-specific precision management involves recording yield, soil test, soil properties and other observations along with a precise description of the location within the field where the data were collected. Input applications are varied based on maps that are created from geo-referenced records of soil test values, soil yield potential, previous yield histories, and nutrient applications that can be coded in the computerized record keeping system. New computer software allows the geo-referenced records to be analyzed and displayed as management maps.
Computers use the maps to automatically change input rates and blends during application.
Site-specific nutrient management attempts to capitalize on the inherent variability of soils by avoiding over fertilization of less productive areas and under fertilization of the more productive areas. Ultimately that should lead to the most agronomically sound, economically efficient, and environmentally responsible nutrient management plan for each field. The quantity of a nutrient to apply is obviously a critical part of any management plan and impacts greatly the profitability and environmental impact of the practice. Other nutrients may be utilized less efficiently and if crop growth is decreased significantly, soil erosion increases due to reduced soil cover. If too much of a nutrient is applied, profitability is again reduced and the excess may contribute to water quality problems.