Design and experiment of the variable rate fertilization system for soybean and maize strip compound planting

In view of the existing composite planting, which cannot independently control the fertilizer rate for each row, fertilizer is prone to moisture solidification caking and relies on a single way to measure the speed of inaccurate problems, a split-drive variable fertilizer application system was designed for soybean and maize strip cropping composites. It includes roller crushing bi-directional spiral fertilizer discharger, split-drive variable fertilizer application system and ‘GNSS + encoder’ dual speed measurement system. By modeling agglomerated fertilizer particles, a discrete element simulation was carried out to analyze the crushing effect. The speed measurement error variation folds of both GNSS and encoder under different speed conditions were obtained through field speed measurement tests. Finally, 4.5 km/h was identified as the switching point between the two speed measurements. Through bench testing, a mathematical relationship model was developed for the soybean and maize belts in terms of ‘Fertilizer Application Rate - Operating Travel Speed - Metering Mechanism Rotor Speed’, and the results are presented in the table below. Fertilizer discharge consistency was verified for fertilizer dischargers. Field trials were conducted, and the results show: The soybean belt had a maximum error of 4.81% at a fertilizer application rate of 150 kg/hm² and an operating speed of 5 km/h; the maximum error in the corn belt was 4.67% at a fertilizer application rate of 600 kg/hm² and operating speed of 4 km/h. Both have a maximum error of less than 5%, which meets the requirements for variable fertilizer application.