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

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200 = z `.A NTE, and HOOPER ter may enhance infiltration and percolation to facilitate leaching of Na ca- tions and prevent the formation of a claypan caused by excessive Na. In revegetated spoil areas without topsoil, organic matter can play an im- portant role in nutrient supply. In spoil material minor elements usually are adequate for plant growth, but there may be N and P deficiencies. As men- tioned, organic matter is a viable nutrient source enhancing revegetation ef- forts. Furthermore, applications of organic matter increase microbial growth, creating a more fertile environment for plants that can enhance reclamation of relatively infertile, biologically inactive spoil or subsoil material. Determining the soil organic matter content needed to mitigate undesir- able characteristics in plant growth media or site conditions varies with the undesirable characteristic or degree to which such characteristics are ex- pressed. Following are the organic matter levels achievable through organic matter application that may mitigate adverse soil properties or site condi- tions. Texture. Increased water - holding capacity is the dominant positive influ- ence that organic matter has on sandy, skeletal, and loamy particle size classes. In one study the water - holding capacities of a 50 percent sand and 50 percent peat mix and 100 percent peat mix was 36 percent and 82 percent, respectively, greater than that of sand (38). In addition, research shows that organic matter with high C/N ratios reduced permeability in sand, while low C/N ratios caused reduced permeability for only short periods of time. In another study a 20 percent addition of peat raised the water- holding capacity of a clay loam and loamy fine sand about 30 and 51 percent, re- spectively (13). A thin layer of peat or organic matter on the surface may preclude surface crusting, thus facilitating better seedling emergence (4). Such a layer is also beneficial from an infiltration perspective (74). On the other hand, minimizing organic matter build -up in the surface layer benefits plants because it promotes increased N availability through enhanced nutri- ent cycling (68). In summary, sandy, loamy, and skeletal particle size classes benefit most from the standpoint of water - holding capacity because of higher organic matter levels. Clayey textured soils benefit more from increased infiltration and percolation rates and reduced crusting. Reaction. Organic matter indirectly and directly benefits very high or very low pH materials. In soil and /or spoil materials that have high pH levels (> 8.4) organic matter applications may indirectly reduce the pH one unit or more by increasing infiltration and percolation. This assumes that adequate precipitation causes leaching and the proper types of organic mat- ter are applied. In an Ohio study mulch treatments in sandy loam spoils having a pH from 2.4 to 4.9 produced survival rates among Ponderosa pine (Pinus ponderosa), jack pine (Pinus banksiana), pitch pine (Pinus rigida), and SOIL ORGANIC MATTER white pine (Pinus strobus) that we areas (45). The mulch no doubt ex properties. But a pH of 2.4 is pro eluding these four tree species. Th effect on pH as well. On sandy soils with a pH of 5.( the pH about 0.3 unit after 18 mo tain region and elsewhere in the neutral —where the organic matte tion of an increased or higher cati saturation (55) and higher hydro Sodicity. Organic matter appl than or equal to 13) spoil used as the effects of Na. Applying orga cultivated or mixed into the top 1 ing (repelling) effect Na has on claypan, organic matter will facili or in higher rainfall areas, the Na of the Na cation if suitable amen added. Salinity. In reclaimed areas from saline spoil organic matter the desert Southwest a 1 percent applications, reduced infiltration rates — saturated hydraulic condu infiltration rates lasted only one y for a more frequent and complet' ers of the spoil, thereby reducing management in the desert Southl duce salinity problems and flood Nutrient levels. Organic ma ing nutrients when revegetating United States. In spoil material plant growth. But N and usually matter is a nutrient source and a But organic matter is an ineffici■ cow manure contains about 5 g Organic amendments, such as of energy for soil microorganism in the soil. As a result, soil nutr and compounds available to plat tity of organic matter to the soil the nutrient reserves of the soil Undesirable organic matter k