Described herein is a method of analyzing nutrient content in soil, the method comprising a) obtaining a soil sample, b) adding a liquid to the soil sample to form a soil slurry, c) flowing the soil slurry through a filter, whereby the filter is oriented such that the soil slurry flows downward through the filter at least partially under the effects of gravity, d) blending a reagent composition with the soil slurry to form a soil mixture, and e) measuring an absorbance of the soil mixture.