Experimental research on mechanised strip application process based on DEM of compressed granulated straw

Returning the entire straw to the field can lead to excessive buildup, obstructing the seeding process and reducing quality. To address this, technologies like straw granulation and strip application enhance straw decomposition and soil organic matter. However, differing sizes of granulated straw can impact seeding quality. This paper presents a straw-crushing device with a differential counter roller that breaks long straw particles during rotation. It also includes trenching shovels, covering discs, and compaction wheels for practical mechanised application. The discrete element method (DEM) was used to simulate the straw crushing capacity and analyse the factors affecting the crushing rate. The work determined that the centre distance between the two rollers is 99 mm, the teeth height H is 15 mm, teeth width b₁ is 10 mm, and teeth thickness b₂ is 10 mm. It was found that the minimal variation in the straw crushing rate varied between 0.77 and 1.77 kg s⁻¹. Optimal crushing rates are achieved when the upper roller's rotation speed ranges from 100 to 200 r·min⁻¹ and the lower roller's speed ranges from 300 to 400 r·min⁻¹. A simulation model is also developed to analyse the mechanised strip application process. Through single-factor tests and orthogonal test methods, the operational parameters were optimised. The findings indicated that an upper roller speed of 150 r·min⁻¹, a lower roller speed of 300 r·min⁻¹, a strip application depth of 150 mm, and a forward speed of 5 km h⁻¹ resulted in a straw crushing rate of 33.6 %. The uniformity variation coefficient of strip application is determined to be 14.4 %, which complies with the strip application requirements. Field validation of the test parameters yielded an average coefficient of variation of 14.9 %; the average crushing rate of granulated straw is 41.5 %, with an error margin of 0.5 % and 7.9 % compared to field tests. The optimised parameters achieve the necessary standards for mechanised strip application, providing valuable technical support for developing new granulated straw strip application methodologies.