12.1: Introduction

The quickest way to rebuild a poor soil is to practice dairy farming, growing forage crops, buying ... grain rich in protein, handling the manure properly, and returning it to the soil promptly.

—J. L. Hills, C. H. Jones and C. Cutler, 1908

There are good reasons why farmers tend to specialize in a few crops or in raising just one species of livestock; it provides economies of scale and fits into the regional agricultural system with its support infrastructure and established marketing channels. A substantial portion of the U.S. poultry, beef and hogs is raised in huge factory-size operations (concentrated animal feeding operations, or CAFOs), but there are many problems associated with these systems. Most such farms import some or all of their feed, sometimes from far away, requiring the supplying crop farms to use large amounts of fertilizers to replace nutrients exported to the animal operations. At the same time the large amounts of manure that accumulate on the animal farms—relative to their land base—may lead to applying quantities of manure that contain more nutrients than needed by crops, resulting in pollution of ground and/or surface waters. (see Chapter 7, “Nutrient Cycles and Flows” for a discussion of patterns of nutrient movement into and out of farms.) Storing large amounts of manure for periodic spreading (as occurs on CAFOs) creates a potential pollution problem and under certain conditions direct contamination of surface waters. The flooding in North Carolina caused by Hurricane Florence in September 2018 was not the first time that hog manure lagoons in that state were breached and surface water was contaminated.

When crops are fed to animals, most nitrogen, phosphorus and potassium contained in the feeds are excreted as waste products. Thus, when animal products are the main sales from the farm, relatively few nutrients (relative to what animals ate) leave the farm. On the other hand, farms that exclusively produce annual grain crops, such as corn, soybeans, wheat and sorghum, or even vegetables, export a lot of nutrients contained in their crops. Another issue is that farms concentrating on production of annual crops usually have no reason to include perennial forage crops in their rotations. Additional equipment is needed to manage the crop, and the sale of forages, bulky by nature, is sometimes difficult. Occasionally there may be a local demand for hay, but most commonly there is little market for it in the wide expanse of regions growing annual crops. Exclusively growing annuals, especially only one or two crops, makes weed control more challenging, deprives the land of the improved soil health of multi-year grasses and legumes, allows disease and insect pests to flourish, and requires large amounts of nitrogen fertilizer to be applied for most crops. Integrating livestock into the farm operation can make it more sustainable but also makes it more complex. If not implemented in the right way it can also increase environmental problems.