In various embodiments of an analytics system, a spike-in including synthetic constructs of nucleic acid is added to soil samples for processing. The analytics system determines sequence reads classified to a microbe in the soil sample. The analytics system determines one or more measures of soil texture of the soil sample, for example, indicating percentages of sand, silt, and clay. The analytics system determines a measure of the microbe as a function of at least the classified sequence reads, the one or more measures of soil texture, and a mass of the spike-in. The analytics system can transmit the measure of the microbe to a client device for display on a user interface. A field where the soil sample was obtained can be treated according to the measure of the microbe.