Using the NIRS for analyzes of soil clay content

REQUASUD network (based in Wallonia, Belgium) consists of laboratories working directly with farmers, giving them soil fertility diagnostics and advice for a good management of soils and cultures. Therefore, the laboratories analyze, among others, available nutrients. But they need more information to correctly interpret the results and give fertility advice, like the cationic exchange capacity (CEC) and the clay content. However, analyzing CEC and clay content is expensive, time-consuming and requires the use of chemicals. To overpass this problem, the near-infrared reflectance spectroscopy (NIRS) has been developed and is now used routinely in the laboratories. This method is rapid, non-destructive and allows the simultaneous estimation of soil characteristics. Nowadays, the REQUASUD NIR database performances for clay content are the followings : RPD = 2,22% for cultures and RPD = 1,72% for grasslands. This method of analysis can be used for other purposes than fertility advice.