"People will plant the same crops, leave their pumps running, not fertilize, and it doesn't matter how long they've been farming," he said. If the acidity is not high enough, then essential nutrients cannot be dissolved and processed by the crops. Farmers should take 15 to 20 samples each from 6 inches deep, mix all the samples into a bucket and fill a soil box provided by a county extension office, he said. Arkansas is one of several states that offer the service for free at the division of agriculture soil testing and research laboratory in Marianna. Target application rates for nitrogen will also be included based upon what crop was indicated by the farmer.