. . . the popular mind is still fixed on the idea that a fertilizer is the panacea.
—J.L. HILLS, C.H. JONES, AND C. CUTLER, 1908
Although fertilizers and other amendments purchased from off the farm are not a panacea to cure all soil problems, they play an important role in maintaining soil productivity. Soil testing is the farmer’s best means for determining which amendments or fertilizers are needed and how much should be used.
The soil test report provides the soil’s nutrient and pH levels and, in arid climates, the salt and sodium levels. Recommendations for application of nutrients and amendments accompany most reports. They are based on soil nutrient levels, past cropping, and manure management and should be a customized recommendation based on the crop you plan to grow.
Soil tests—and proper interpretation of results—are an important tool for developing a farm nutrient management program. However, deciding how much fertilizer to apply—or the total amount of nutrients needed from various sources—is part science, part philosophy, and part art. Understanding soil tests and how to interpret them can help farmers better customize the test’s recommendations. In this chapter, we’ll go over sources of confusion about soil tests, discuss N and P soil tests, and then examine a number of soil tests to see how the information they provide can help you make decisions about fertilizer application.