Where those differences occur in a workable fashion, varied application of fertilizer is recommended. Computer technology has advanced the mapping and fertilizer spreading capabilities. Many manufacturers of fertilizer truck spreaders now have the capability to vary fertilizer application on the go with a computer on board the truck. No doubt you will hear more of this technology in the future. You should take soil samples for fertilizer and limestone recommendations to a depth of 6 to 7 inches or to tillage depth if deeper.
Nutrients accumulate at the surface because of fertilizer application.
The surface soil is not, however, a good indicator of fertility requirements. Soil pH may drop rapidly in the surface soil and reduce some herbicides' activities. A lower rate of limestone to reduce the acidity of the surface two inches of soil is necessary if acidity becomes a problem. Be sure to record sampling depth on the information form when you take depths of less than six inches. Where to submit the samples Soil samples are tested for acidity, phosphorus, potassium, calcium, magnesium, and organic matter to provide recommendations for limestone, nitrogen, phosphate and potash on your crop.