With fertilizer prices doubling and even tripling, there has never been a more opportune time to invest in soil testing. With total phosphorus and potassium crop removal maintenance in the range of $75 to $125 per acre, it makes good sense to have accurate soil test information.

Soil tests will give you a basis for fine-tuning fertilizer and manure inputs to make sure these inputs are used cost-effectively on your farm.

Sampling Approaches

Soil sampling should be done to a uniform depth of 6 inches (Table 1). If you vary the depth of your samples, the parts per million of the nutrients for which you are testing will vary as you change the sampling depth. Thus, you must sample a consistent depth.

There are several approaches to soil sampling. Whole field sampling, grid sampling and zone sampling are all common approaches to soil sampling. Each of these approaches is acceptable; the one you use is dependent upon the following factors:

• Expected fertilizer management approach — variable rate or fixed;

• Sampling history – recent or long overdue sampling;

• Existing fertility level – low and need to know and/or high and ready to fly.

With fertilizer prices high, re-evaluate your testing program and consider using a more intensive sampling and application program. Grid sampling and variable-rate technology may not be as expensive as you think if you can improve the efficiency of fertilizer dollars.

Figure 1 is an example of an unaligned systematic grid point method. This grid system…