Organic matter measurements on sand‐based putting greens using a portable near‐infrared spectrometer

Abstract

Organic matter management is critical on golf course putting greens; however, current methods for measuring organic matter require extensive laboratory preparation, substantial energy inputs, and long turnaround times. The objectives of this study were to (1) develop and evaluate near‐infrared (NIR) spectroscopic models using spectra acquired from a portable NIR spectrometer to predict total organic matter (TOM) content on sand‐based putting greens and (2) compare NIR model performance from samples subjected to three different preparation methods to maximize processing efficiency. Samples were collected from six putting greens that had a wide range of TOM content and divided into three depth increments (0–2, 2–4, and 4–6 cm). Prior to NIR scanning, samples underwent three sequential preparation methods: (1) fresh samples collected from the field and immediately ground with a mortar and pestle, (2) samples dried at 105°C for 48 h, and (3) dried samples finely ground with a ball mill. For each preparation method, the number of scans per sample (one scan vs. three scans with sample remixing between scans) was also evaluated. Models were the least accurate for fresh samples; however, at the 0‐ to 2‐cm depth, models achieved r ² ≥ 0.88, standard error of prediction ≤ 4.42%, and bias ≤ 1.81%. Model accuracy improved when scanning samples three times for the fresh and dried preparation methods. Our findings demonstrate that the NIR models developed with a portable spectrometer can provide rapid TOM measurements on sand‐based putting greens.