Development of an image-based system to assess agricultural fertilizer spreader pattern.

• An image processing system for agricultural spreader calibration was developed. • This automatic tool uses a specific mat that simulates calibration standards rules. • Tests were performed with several image acquisition conditions and 2 types of granules. • The average accuracy was 0.75 ± 0.75% for fertilizer and 2.12 ± 1.68% for wheat. • The accuracy and robustness justify its use to support spreader pattern calibration. An Automatic Calibration of Fertilizers (ACFert) system was developed, for use with centrifugal, pendulum or other types of broadcast spreaders which distribute dry granular agricultural materials on the top of the soil. The ACfert is based on image processing techniques and includes a specially designed mat, which should be placed in the ground for spreaders calibration. A set of images acquired outdoor by a standard device (simple camera) is used to extract information about the spreader distribution pattern. Each image is processed independently, providing as output two numerical values for each grid element present in the image – the number of fertilizers/seeds counted, and its numerical label. The performance of ACFert was evaluated for automatic granules detection using a set of manual counting measurements of nitrate fertilizer and wheat seeds. A total of 185 images acquired with two mobiles devices were used with a total of 498 quadrilateral elements observed and analysed. The overall mean absolute relative error between counting and computed by the ACFert system, were 0.75 ± 0.75% for fertilizer and 2.12 ± 1.68% for wheat. This near real-time calibration tool is a very low cost system that can be easily used on field, providing results to support accurate spreader calibration in near real time for different types of fertilizers or seeds. [ABSTRACT FROM AUTHOR]