Development of a mobile robot-based combined sensor platform to determine the correlation between soil penetration resistance and electrical conductivity

Open-field farming involves successive major processes such as preparation of soil, planting the seed, adding pesticides and fertilizers, irrigation, cultivation, and harvest. The main aim of all processes is to achieve maximum yield out of the available agricultural landscape. It is necessary to collect geo-referenced descriptive data on soil characteristics, such as soil penetration resistance and electrical conductivity before starting all these processes. In this context, agricultural robots offer highly promising technologies providing valuable soil data, lower production costs, reduced manual labour, and maximum crop efficiency. The aim of this study is to design and develop a combined sensor platform and a GPS-guided 4WD agricultural autonomous robot to provide rapid measurement and mapping of the soil penetration resistance and the electrical conductivity for precision farming applications. The agricultural robot is a nonholonomic mobile robot, which has a differential steering mechanism and can be forwarded to stable-target points. The combined sensor platform, which is a y-axis shifter driven by a DC motor with reducer, consists of the Wenner array probes and load cell-based penetration rod. AutoCAD software was used for designing and drawing of the robot and measurement platform. All software was coded in Microsoft Visual Basic.NET programming language. Field studies were conducted to measure the soil penetration resistance, electrical conductivity, and determine the correlation between soil penetration resistance and electrical conductivity. As a result, the ranges of the soil measurement were observed between 1.13 MPa-2.14 MPa for penetration resistance and 0.14-0.33 dS/m for electrical conductivity. Results showed that there is a fairly strong negative relationship between the soil penetration resistance and the electrical conductivity (R-2 = -0.78).