Development of a Subsoiler with Two Tandem Shanks Arranged for Directional Movement and Automated Depth Adjustment

Abstract

Subsoiling is essential for farmers to rectify soil compaction that reduces crop yields, but it requires high drawbar pull, often exceeding the capabilities of farmers' tractors and increasing costs. This study aimed to develop a tandem-type subsoiler with a front shank equipped with automatic depth adjustment to minimize drawbar pull during subsoiling operations. The front subsoiler shank (FSS) can autonomously adjust its depth, controlled by an automatic depth control system utilizing an Arduino UNO microcontroller. Moreover, the distance between the FSS and the rear subsoiler shank (RSS) is adjustable. Field tests were conducted in Kampheang Sean, Nakhon Pathom, where the soil exhibited a moisture content of 5.4±1.92%, a bulk density of 1.5±0.14 g/cm3, and a soil penetration resistance ranging from 0 to 50 cm depth, with an average of 1.88±0.41 MPa. Four key factors were considered during testing: 1) type of FSS point (winged point and fin point), 2) Motor systems for adjusting the depth of the front subsoiler shank (fixed displacement control system and immediate response system), 3) Motor sensitivity (10, 20 and 30%), and 4) Distance between the FSS and RSS (40, 50 and 60 cm). The subsoiling depth during the test was 50 cm. Results demonstrated that the control system facilitated automatic up and down movement of the FSS to determine the optimal drawbar pull. Specifically, the FSS equipped with a fin point exhibited significantly lower drawbar pull compared to the winged point, with values of 14.84±3.30 kN and 17.66±2.87 kN, respectively. Additionally, a distance of 40 cm between the FSS and RSS resulted in the least drawbar pull of 14.42±3.00 kN. Notably, the tandem-type subsoiler with automatic depth adjustment achieved the lowest drawbar pull of 12.65±1.33 kN, representing a reduction of over 10% compared to a conventional single shank subsoiler, which exhibited a drawbar pull of 14.00±2.01 kN under similar test conditions. Motor systems for adjusting the depth of the front subsoiler shank and sensitivity did not significantly affected drawbar pull. Research results indicate that using a subsoiler with two tandem shanks, where the front shank automatically adjusts its depth, allows farmers to perform subsoiling more efficiently, resulting in better crop yields and reduced costs.