NIRS: What Is It? How Can It Benefit You?

Grady Miller
University of Florida, Gainesville
Institute of Food and Agricultural Sciences

You have probably been hearing the word NIRS (pronounced so that it rhymes with EARS) mentioned in superintendents' meetings the last year or so and wondered what was being talked about. NIRS is actually an acronym for near infrared reflectance spectroscopy. NIRS is a relatively new approach for turfgrass tissue testing. NIRS equipment used for tissue testing turfgrasses is similar to equipment used to analyze agricultural crops and livestock feed for the last 15 to 20 years. The objective to using the equipment is to identify nutrient deficiencies well before they are visually apparent. NIRS analysis is rapid because the sample preparation involves no chemicals. A downside is the cost of the equipment -- over $30,000 without a computer. This seems expensive until you compare it to traditional wet chemistry laboratory instruments that can easily cost over $300,000. Currently, the primary supplier of NIRS instruments for turfgrass evaluation is through Karsten Turf, Inc located in Phoenix, Arizona. Toro Company's BioPro Division is also actively involved with NIRS technology development and offers tissue analysis to their Turf/Irrigation customers.

How It Works

To perform NIRS analysis, grass leaf tissue is dried in a microwave, ground into small particles, then carefully loaded into the testing instrument via a small metal and glass cell. The instrument passes light in the near infrared wavelength spectrum onto the samples. The light interacts with the sample by absorption, with the resulting frequency relating to the molecular bond in the sample. The instrument and attached computer records the reflected spectra for element calculation. Due the complexity of interpreting the reflected light, there are some weaknesses in the technology. For example, the accuracy that elements can be detected differs for each element. The strength of using this technology is cost savings and faster turn-around time than wet chemistry analysis. People have asked about the portability of the NIRS instrument. There are companies that have mounted the instruments inside vans for mobility, the equipment works best stationary in an office or at a lab work station.

How It Can Help You

Currently, research is being conducted at the Turfgrass Envirotron to investigate the use of NIRS technology for nitrogen (N) scheduling on dwarf bermudagrass. Fertilizer N is relatively inexpensive, and deficiencies can result in low quality turf. Turf managers are inclined to manage fertilizer N to minimize the risk of deficiency, which can lead to excessive fertilizer applications. Although a turf manager understands that fertilizer applied at excessive rates costs money and may lead to contamination of the environment, managers also want assurance that applying less fertilizer N will not reduce turf quality. Graduate student Ian Rodriguez and I have initiated a study this spring using NIRS technology. These studies are designed to investigate NIRS technology to see how accurately it can predict tissue concentration levels of various nutrients and if it can be used to predict when additional fertilizer N is needed to maintain high quality turf. These studies will be conducted on the new Envirogreen located adjacent to the Turfgrass Envirotron. NIRS equipment was made available through the generosity of the Toro Company and the Florida Turfgrass Association.