An impact sensor is located in a distribution tower which divides the seed and/or nutrient flow into individual rows, and a second sensor provides a compensation signal dependent upon one or more variables such as the velocity of the air in the conveying system, implement vibrations. As the seed/fertilizer bounces off of the impact sensor and flows into the individual row air streams, the impact sensor provides a force signal to a processor which calculates the total particulate mass flow rate from the force signal and the air velocity signal. To determine individual seed and fertilizer rates, a rate controller temporarily changes the metering rate of one of the materials, and the processor then calculates the desired information from the mass flow change and meter speed change. Another embodiment includes seed sensor structure at the meter output for achieving or confirming accuracy.