Measure Bioavailable Phosphate On-Site. These kits require the use of NECi’s Handheld Photometer, results are not colorimetric. Quick and Reliable Results, Easy to Use, Environmentally Benign. This reagent refill test kit will measure 0 ppm - 20 ppm Phosphate in soil and sediment samples to be analyzed with our handheld photometer.  If you do not yet have a handheld photometer, please view our introductory photometer package where you can complete the bundle with a test kit pack size of your choice. This method is based on the Methods X article published in April 2015, Determination of phosphate in soil extracts in the field: A green chemistry enzymatic method.