Nutrient Management: An Introduction

Of the eighteen elements needed by plants, only three—nitrogen (N), phosphorus (P), and potassium (K)—are commonly deficient in soils. Deficiencies of other nutrients, such as magnesium (Mg), sulfur (S), zinc (Zn), boron (B), and manganese (Mn), certainly occur, but they are not as widespread. Deficiencies of sulfur, magnesium, and some micronutrients may be more common in regions with highly weathered minerals, such as the southeastern states, or those with high rainfall, such as portions of the Pacific Northwest. On higher-pH calcareous soils, especially in drier regions, keep an eye out for deficiencies of iron, zinc, copper, and manganese. In contrast, in locations with relatively young soil that contains minerals that haven’t been weathered much by nature— such as glaciated areas with moderate to low rainfall like the Dakotas—K deficiencies are less common.

Environmental concerns have resulted in more emphasis on better management of N and P over the past few decades. While these nutrients are critical to soil fertility management, they also cause widespread environmental problems. Poor soil and crop management; overuse of fertilizers; misuse of manures, sewage sludges (biosolids), and composts; and high animal numbers on limited land area have contributed to surface and groundwater pollution in many regions of the U.S. Because both N and P are used in large quantities and their overuse has potential environmental implications, we’ll discuss them together in chapter 19. Other nutrients, cation exchange, soil acidity (low pH) and liming, and arid and semiarid region problems with sodium, alkalinity (high pH), and excess salts are covered in chapter 20.