Building Soils for Better Crops, 2nd Edition

	Introduction Used to be anybody could farm. All you needed was a strong back. . . but nowadays you need a good education to understand all the advice you get so you can pick out what'll do you the least harm. Vermont saying, mid-1900s One of our truly modern miracles is our agricultural system, which produces abundant, affordable food. High yields come from the use of improved crop varieties, fertilizers, pest control products, and irrigation. At the same time, mechanization and the ever-increasing capacity of field equipment allows farmers to work increasing acreage. Despite the high productivity per acre and per person, many farmers, agricultural scientists, and extension specialists see severe problems associated with our intensive agricultural production systems. Examples abound: Too much nitrogen fertilizer or animal manure sometimes causes high nitrate concentrations in groundwater. These concentrations can become high enough to pose a human health hazard. Phosphate in runoff water enters water bodies and degrades their waters by stimulating algae growth. Antibiotics used to fight diseases in farm animals can enter the food chain and may be found in the meat we eat. Their overuse has resulted in outbreaks of human illness from strains of disease-causing bacteria that have become resistant to antibiotics. Erosion associated with conventional tillage and lack of good rotations degrades our precious soil and, at the same time, causes the silting up of reservoirs, ponds, and lakes. The food we eat and our surface and ground waters are sometimes contaminated with disease-causing organisms and chemicals used in agriculture. Pesticides used to control insects and plant diseases can be found in foods, animal feeds, groundwater, and in surface water running off agricultural fields. Farmers and farm workers are at special risk. Studies have shown higher cancer rates among those who work with or near certain pesticides. The general public is increasingly demanding safe, high quality food that is produced without excessive damage to the environment and many are willing to pay a premium to obtain it. Farmers are also in a perpetual struggle to maintain a decent standard of living. As consolidations and other changes occur in the agriculture input, food processing, and marketing sectors, the farmer's bargaining position weakens. The high cost of purchased inputs and the low prices of many agricultural commodities, such as wheat, corn, cotton, and milk, have caught farmers in a cost-price squeeze that makes it hard to run a profitable farm. Given these problems, you might wonder if we should continue to farm in the same way. A major effort is underway to develop and implement practices that are both more environmentally sound than conventional practices and at the same time more economically rewarding for farmers. As farmers use management skills and better knowledge to work more closely with the biological world, they frequently find that there are ways to decrease use of products purchased off the farm. With the new emphasis on sustainable agriculture comes a reawakening of interest in soil health. Early scientists, farmers, and gardeners were well aware of the importance of soil quality and organic matter to the productivity of soil. The significance of soil organic matter, including living organisms in the soil, was understood by scientists at least as far back as the 17th century. John Evelyn, writing in England during the 1670s, described the importance of topsoil and explained that the productivity of soils tended to be lost with time. He noted that their fertility could be maintained by adding organic residues. Charles Darwin, the great natural scientist of the 19th century who developed the modern theory of evolution, studied and wrote about the importance of earthworms to the cycling of nutrients and the general fertility of the soil. Around the turn of the 20th century, there was again an appreciation of the importance of soil health. Scientists had realized that "worn out" soils, where productivity had drastically declined, resulted mainly from the depletion of soil organic matter. At the same time, they could see a transformation coming: although organic matter was "once extolled as the essential soil ingredient, the bright particular star in the firmament of the plant grower, it fell like Lucifer" under the weight of "modern" agricultural ideas (Hills, Jones, and Cutler, 1908). With the availability of inexpensive fertilizers and larger farm equipment after World War II, and of cheap water for irrigation in some parts of the western United States, many people working with soils forgot or ignored the importance of organic matter in promoting high quality soils. As farmers and scientists placed less emphasis on soil organic matter during the last half of the 20th century, farm machinery was getting larger. More horse power for tractors allowed more land to be worked by fewer people. Large 4-wheel drive tractors allowed farmers to do field work when the soil was wet, creating severe compaction and sometimes leaving the soil in a cloddy condition, requiring more harrowing than otherwise would be needed. The use of the moldboard plow, followed by harrowing, broke down soil structure and left no residues on the surface. Soils were left bare and very susceptible to wind and water erosion. New harvesting machinery was developed, replacing hand-harvesting of crops. As dairy herd size increased, farmers needed bigger spreaders to handle the manure. The use of larger equipment created new problems. Making many passes through the field with heavy equipment for spreading fertilizer and manure, preparing a seedbed, planting, spraying pesticides, and harvesting created the potential for significant amounts of soil compaction. A new logic developed that most soil-related problems could be dealt with by increasing external inputs. This is a reactive way of dealing with soil issues you react after seeing a "problem" in the field. If a soil is deficient in some nutrient, you buy a fertilizer and spread it on the soil. If a soil doesn't store enough rainfall, all you need is irrigation. If a soil becomes too compacted and water or roots can't easily penetrate, you use an implement, such as a subsoiler, to tear it open. If a plant disease or insect infestation occurs, you apply a pesticide. Are low nutrient status, poor water-holding capacity, soil compaction, susceptibility to erosion, and disease, nematode, or insect damage really individual and unrelated problems? Perhaps they are better viewed as only symptoms of a deeper, underlying problem. The ability to tell the difference between what is the underlying problem and what is only a symptom of a problem is essential to deciding on the best course of action. For example, if you are hitting your head against a wall and you get a headache is the problem the headache, and aspirin the best remedy? Clearly, the real problem is your behavior and not the headache, and the best solution is to stop banging your head on the wall! What many people think are individual problems may just be symptoms of a degraded, poor quality soil. These symptoms are usually directly related to depletion of soil organic matter, lack of a thriving and diverse population of soil organisms, and compaction caused by use of heavy field equipment. Farmers have been encouraged to react to individual symptoms instead of focusing their attention on general soil health management. A new approach is needed to help develop farming practices that take advantage of the inherent strengths of natural systems. In this way, we can prevent the many symptoms of unhealthy soils from developing instead of reacting after they develop. If we are to work together with nature, instead of attempting to overwhelm and dominate it, the buildup and maintenance of good levels of organic matter in our soils is as critical as management of physical conditions, pH and nutrient levels. This book has three parts. Part One provides background information about soil health and organic matter: what it is, why it is so important to general soil health and why some soils are of higher quality than others. Also included are discussions of soil physical properties, soil water storage, and nutrient cycles and flows. Part Two deals with practices that promote building better soils with a lot of emphasis on promoting organic matter buildup and maintenance. Following practices that build and maintain organic matter may be the key to soil fertility and may help solve many problems. However, other soil-management practices also are needed to supplement soil organic matter management. Practices for enhancing soil quality include the use of animal manures and cover crops; good residue management; appropriate selection of rotation crops; use of composts; reduced tillage; minimizing soil compaction and enhancing aeration; better nutrient and amendment management; and adapting specific conservation practices for erosion control. Part Three deals with how to combine soil-building management strategies that actually work on the farm and how to evaluate soil to tell if its health is improving. Source Hills, J.L., C.H. Jones, and C. Cutler. 1908. Soil deterioration and soil humus. pp. 142­177. In Vermont Agricultural Experiment Station Bulletin 135. College of Agriculture, University of Vermont. Burlington, Vermont. Top