Discrete element simulation and experimental verification: Effect of spray position in rotary tillage on the spatial redistribution of liquid soil amendments

Rotary tillage is a common cultivation for mixing cultivated soils with various dopants, including liquid amendments. The mixing performance of rotary tillage should be understood quantitatively. This study aimed to further validate the added value of the discrete element method (DEM) for spray-location selection in rotary tillage with the application of liquid amendments. A normalized amendment mixing index (AMI) was defined to describe the mixing of liquid amendments with soils. The AMI was used to quantify the mixing situations of the horizontally sliced subspace (HSS) and the vertically sliced subspace (VSS). The effect of spray position on the AMI of the slices was statistically analyzed. A field experiment was conducted using a spray position configuration that yielded the highest AMI in the simulation. The experimental AMIs were captured by processing images of vertical soil profiles. Simulated results show that spray position significantly affects the AMI, and spraying in the front of the tillage obtained the highest AMI. The experimental average AMI of VSS had an error of 7.08 % related to the simulation. Statistical analysis showed no significant difference between the simulation and experimental results. These results indicate that the AMI can distinguish between soil spaces containing only impregnated components and those containing only unimpregnated components, and can quantitatively describe the mixing situation in experiments and simulations. DEM simulation can provide reliable insights on spray-location selection to apply amendments with a rotary tiller. These are expected to support the DEM simulation of solid–liquid mixing to investigate the mixing situation.