Soil sampling is the key to effective nutrient management because it provides the grower with an estimate of the capacity of the soil to provide adequate nutrients to meet crop demand. The three most common questions on soil sampling are:
1. How long are the answers good for?
2. Why take soil samples?
3. How should a soil sample be taken?
An old saying is “Take care of the land and the land will take care of the cattle.” The problem with this saying for alfalfa production is that most hay growers are not growing for themselves and are not getting paid for the nutrient value of their crop. Most growers are getting paid for color and tonnage with protein and ADF being taken into account once in awhile.
The future for agriculture-related businesses will be a quality product with documentation. This emphasis will be driven by buyers – until the buyers demand quality and nutrient value in the alfalfa crop, soil testing in the forage industry will never take off.
Western Laboratories commonly receives soil samples from alfalfa fields from people who are buying land, have land that is not producing well or are participating in federal programs that require soil testing.
We have found that alfalfa growers are under-producing on good ground and overspending on poor ground. The best-producing ground has not reached its best potential and poor ground never will unless it’s a fertility- related problem. In both cases, proper use of soil testing allows the grower to obtain optimum return from nutrient inputs.
A soil test should be taken with a probe 12 inches deep at 9 to 15 locations throughout the field. The sub-samples should be thoroughly mixed in a plastic bucket and placed into a double-lined paper bag. Always collect samples from the best growing area and never mix soil from a good growing area with that from a poor area. The relationship between sampling areas for alfalfa production can be described as follows:
A + B = C
A=soil in a good area
B=soil in a poor area
C=soil from a petunia in Mrs. Smith’s front room in Pasadena, California
The poor growing areas are commonly found in “hog wallows,” steep slopes and on ridges with gravelly sands. We recommend that the grower not sample soil in poor areas unless there is a known fertility or moisture problem. Fertilizer crop advisers, county agents and the NRCS all have probes to lend. In alfalfa, the test results are good for three to five years.
The soil test report provides valuable information for management of the alfalfa crop, but many hay growers don’t look at the numbers. In order to help growers interpret soil report data, Western Laboratories has a tutorial on the company website: www.westernlaboratories.com FG
John P. Taberna
Soil Scientist
Western Laboratories
