Measuring the spatial performance of chemical applicators

This chapter focuses on variability attributable to driving precision and presents the theory, methodology and practical testing for a single disk mounted fertilizer spreader. The theory is applicable to sprayer and dry chemical applicators. The chapter presents a list of sources of variation that may account for spatial variability in an overall model. It provides insight into how the quality of material distribution may be evaluated for spreaders used in site specific application of materials. When operating at the effective swath width the range of application rates indicated poor spreader performance as they frequently were >120% or <80% of the mean rate. The chapter aims to develop a statistically sound model that explains the spatial variability of materials applied with a field applicator. The variability determined by either the differential or the integral method are 50% > the variability determined using the ASAE Standard.