AN AUTOMATED SAMPLING SYSTEM FOR MEASURING SOIL pH

TLDR

Precision farming requires better methods to assess soil variability, and site‑specific soil‑pH management can improve crop production, but existing grid sampling and mapping techniques may be inadequate. The authors developed an automated, on‑the‑go soil‑sampling system to measure soil pH. The system combines a computer‑controlled shank sampler, GPS, and flat‑surface pH electrode, sampling 0–20 cm every 8 s and calibrating the electrode output to laboratory pH via linear regression. Field tests achieved an r² of 0.83 with a prediction error of 0.45 pH units.

Abstract

Within the scope of precision farming there is a need for improved methods of assessing and managing soilvariability. The site-specific management of soil pH is one application that has potential benefits for crop production.However, current grid sampling and mapping techniques to estimate lime requirement may not be adequate. For thisreason, an automated soil sampling system for measuring soil pH on-the-go has been created. The system includes acomputer-operated soil sampling mechanism mounted in a shank, a global positioning unit, and a pH meter with a flatsurface electrode. The system measures soil pH directly on a sample. The automated soil sampling system can determinepH while taking soil samples at a selected depth (0-20 cm) every 8 s. A simple linear regression was used to calibrate theelectrode mV output against soil pH obtained via a standard laboratory method. Field testing yielded an r2of 0.83 and astandard error of prediction of 0.45 pH.