www.sare.org publications building-soils-for-better-crops-3 biological-diversity-abundance-and-balance Biological Diversity, Abundance, and Balance The soil population must be considered from the point of view of a biological complex it is not sufficient to separate it into different constituent groups. —S.A. WAKSMAN, 1923 A diverse biological community in soils is essential to maintaining a healthy environment for plant roots. There may be over 100,000 different types of organisms living in soils. Most […]
www.sare.org publications building-soils-for-better-crops-3 plant-roots Plant Roots Healthy plant roots are essential for good crop yields. Roots are clearly influenced by the soil in which they live and are good indicators of soil quality. If the soil is compact, is low in nutrients or water, includes high populations of root pathogens, or has other problems, plants will not grow well. On the […]
www.sare.org publications building-soils-for-better-crops-3 very-large-soil-animals Very Large Soil Animals Very large soil animals, such as moles, rabbits, woodchucks, snakes, prairie dogs, and badgers, burrow in the soil and spend at least some of their lives below ground. Moles are secondary consumers, their diet consisting mainly of earthworms. Most of the other animals exist on vegetation. In many cases, their presence is considered a nuisance […]
www.sare.org publications building-soils-for-better-crops-3 small-and-medium-size-soil-animals Small and Medium-Size Soil Animals Nematodes Nematodes are simple multicellular soil animals that resemble tiny worms but are non-segmented. They tend to live in the water films around soil aggregates. Some types of nematodes feed on plant roots and are well-known plant pests. Fungi such as Pythium and Fusarium, which may enter nematode-feeding wounds on the root, sometimes cause greater disease […]
www.sare.org publications building-soils-for-better-crops-3 soil-microorganisms Soil Microorganisms Microorganisms are very small forms of life that can sometimes live as single cells, although many also form colonies of cells. A microscope is usually needed to see individual cells of these organisms. Many more microorganisms exist in topsoil, where food sources are plentiful, than in subsoil. They are especially abundant in the area immediately […]
www.sare.org publications building-soils-for-better-crops-3 appendix-and-sources Appendix and Sources Calculations for Table 3.2 and Figure 3.7 Using a Simple Equilibrium Model The amount of organic matter in soils is a result of the balance between the gains and losses of organic materials. Let’s use the abbreviation SOM as shorthand for soil organic matter. Then the change in soil organic matter during one year (the […]
www.sare.org publications building-soils-for-better-crops-3 the-dynamics-of-raising-and-maintaining-soil-organic-matter-levels The Dynamics of Raising and Maintaining Soil Organic Matter Levels It is not easy to dramatically increase the organic matter content of soils or to maintain elevated levels once they are reached. It requires a sustained effort that includes a number of approaches that add organic materials to soils and minimize losses. It is especially difficult to raise the organic matter content of soils that […]
www.sare.org publications building-soils-for-better-crops-3 how-much-organic-matter-is-enough How Much Organic Matter Is Enough? As mentioned earlier, soils with higher levels of fine silt and clay usually have higher levels of organic matter than those with a sandier texture. However, unlike plant nutrients or pH levels, there are few accepted guidelines for adequate organic matter content in particular agricultural soils. We do know some general guidelines. For example, 2% […]
www.sare.org publications building-soils-for-better-crops-3 amounts-of-living-organic-matter Amounts of Living Organic Matter In chapter 4, we discuss the various types of organisms that live in soils. The weight of fungi present in forest soils is much greater than the weight of bacteria. In grasslands, however, there are about equal weights of the two. In agricultural soils that are routinely tilled, the weight of fungi is less than […]
www.sare.org publications building-soils-for-better-crops-3 active-organic-matter Active Organic Matter Most of the discussion in this chapter so far has been about the factors that control the quantity and location of total organic matter in soils. However, we should keep in mind that we are also interested in balancing the different types of organic matter in soils—the living, the dead (active), and the very dead […]