2002-07-08_GENERAL DOCUMENTS - M2002004 (3)

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190 SMITH, REDENTE, and HOOPER translocating microorganisms, fragmenting plant material (4), and releasing such plant nutrients as C, N, and S (47). Earthworms in arid and semiarid agricultural and riparian soils frequently comprise half a soil's biomass. They can digest 49 to 861 t /ha of soil per year. Beetle grubs and other soil invertebrates that inhabit most arid and semiarid soils in the West do not completely replace the function of earthworms (24). Bacteria grow best in moist, but aerobic, warm, and slightly alkaline to moderately acid soils. Actinomycetes grow better in drier soils with a neu- tral pH and in warmer climates (2). Optimum soil conditions for fungi range from very low to very high pH and moist and warm soils. Yeasts, however, do well in anaerobic conditions of stockpiled topsoil (E. Allen, Utah State Univerity, Logan, personal communication). Vesicular - arbuscular mycorrhiza are soil -borne fungi that invade the roots of vascular plants and establish a symbiotic relationship. The mycorr- hiza hyphae, extending from plant roots, increase the surface area for ab- sorption of nutrients and water. In the symbiosis the mycorrhiza fungus provides nutrients to the plant, while the plant provides favorable growth mileu and carbohydrates for metabolism by the fungi (21). Surface mining can disrupt mycorrhiza populations in soil because plant communities are temporarily destroyed and soils are either stored for long periods of time or mixed or diluted with spoil and subsoil material (44). Such disruptions usually lead to lower propagule numbers and infection levels in mined land relative to adjacent, undisturbed areas (3, 23, 78). Repopulation by mycorrhiza in such areas can be very slow because the fungi do not readily adapt to chemical and physical changes in soils caused by disturbance, especially when topsoil is diluted with chemically undesir- able material (54). Types of applied organic matter. Soil organic matter derives from plant and animal tissue. Under natural conditions, plants supply large amounts of residue annually. These plant materials are decomposed by soil organisms and become part of the underlying horizons, either by leaching or physical incorporation (9). Machinery operations usually mix crop remains with the soil. If incorpo- rated into the soil, crop remains facilitate greater water infiltration and ero- sion control. Also, decomposition rates are greater when crop remains are mixed with soil rather than left on the soil surface. Root remains are superior to top remains, such as stubble. Roots are better sources of C, with the exception of leguminous residues, and as roots decompose they build better soil structure (4). Manure, which supplies numerous micronutrients, is an excellent source of organic matter. It helps maintain good soil tilth, improve water infiltra- tion, increase CO2 release, and increase organic matter content in some soils (82). Manure contains 50 to 80 percent water and 20 to 50 percent volatile SOIL ORGANIC MATTER solids. Thus, an application of 1 matter. Aged manure and comp ually well rotted already. Aged n influencing the growth and dev But applications of green man mination and development (73). Peat and mineral fertilizers c conditions and plant growth. ( posed organic matter accumulat Adding peat to a soil can impro' and water infiltration in fine -te absorbing and retaining plant n penetration, and increase a soil Sewage sludge contains abou fore, be used to build and mail Municipal sewage sludge can be quantity to rebuild disturbed sc cerns about using sewage sludg the sludge can be toxic to plant the applied sludge can increase retard plant growth (83). Man) plication guidelines exist (33). Wood wastes can be effective ing wood wastes to soil may because N may be immobilize scarce. It may be necessary to a, N for plant growth. Addition c fects on the physical properties composition, which improves (72). Methods of analyzing organi in soil organic matter (passing ganic C often is used to estima ed by multiplying organic C tir tor should be 1.9 and 2.5 for (11). Other researchers recomr mined experimentally for each gested that reporting only labo than estimating organic matter organic matter values. But Alli tor to estimate organic matter not required." There are three methods fo]