| dc.description.abstract | Four proximal soil sensors were tested at four smallholder farms in Embu County, Kenya:
a portable X-ray fluorescence sensor (PXRF), a mobile phone application for soil color determination
by photography, a dual-depth electromagnetic induction (EMI) sensor, and a LED-based soil optical
reflectance sensor. Measurements were made at 32–43 locations at each site. Topsoil samples
were analyzed for plant-available nutrients (N, P, K, Mg, Ca, S, B, Mn, Zn, Cu, and Fe), pH, total
nitrogen (TN) and total carbon (TC), soil texture, cation exchange capacity (CEC), and exchangeable
aluminum (Al). Multivariate prediction models of each of the lab-analyzed soil properties were
parameterized for 576 sensor-variable combinations. Prediction models for K, N, Ca and S, B,
Zn, Mn, Fe, TC, Al, and CEC met the setup criteria for functional, robust, and accurate models.
The PXRF sensor was the sensor most often included in successful models. We concluded that the
combination of a PXRF and a portable soil reflectance sensor is a promising combination of handheld
soil sensors for the development of in situ soil assessments as a field-based alternative or complement
to laboratory measurements. | en_US |
