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Search results on 12/14/18
1729. Douglas, C.L., R.R. Allmaras and N.C. Roager. 1984. Silicic acid and oxidizable carbon movement in a Walla Walla silt loam.. Soil Sci. Soc. Amer. J. 48:156-162.
Leachate concentrations and net transfers of silicic acid decreased as long term C additions and soil pH increased; liming reversed this; results in adverse physical properties below the plow layer - decreased hydraulic conductivity, increased cementation.
3392. Johnson, E.C.. 1952. Emphasis on conservation.. WA Agr. Expt. Sta. Cric. #186.
A narrative on historical efforts in soil conservation at Washington State College, including establishment of the Soil Erosion Station near Pullman, WA.
261. Allmaras, R.R., K. Ward, C.L. Douglas and L.G. Ekin.. 1982. Long-term cultivation effects on hydraulic properties of a Walla Walla silt loam.. Soil Tillage Research, 2:265-279.
Hydraulic properties were significantly changed by 50 years of wheat-pea and/or wheat-fallow rotations. pH was reduced, dry bulk density was increased, more smaller soil pores were produced at the expense of larger pores, in the upper 30 cm soil hydraulic conductivity was reduced 10-fold increasing water runoff and denitrification.
906. Blake, J.. 1989. Reading the soil.. Seattle Times p. F1, 7/24/89.
Describes in popular style the highlights of the long-term plots at Pendleton, OR. The importance of organic matter is stressed.
1024. Boyle, M., W. Frankenberger, L. Stolzy. 1989. The influence of organic matter on soil aggregation and water infiltration.. J. Production Agric. 2:290-299.
Describes a conceptual model for soil aggregate formation and stability. Soil organic matter contributes to improvement of soil structure in a number of ways. It enhances microbial action which produces more polysaccharides. Aggregation is the product of such forces as mechanical binding by roots and fungal hyphae, temporary adhesive properties by products of microbial synthesis and decay, and persistent cementing action by resistent humus components. Organic materials that decompose quickly (low C:N) had a rapid but ephemeral effect on soil structure. Plant materials that are more resistant to decomposition are slower but more persistent in changing structure. Soil polysaccharides are more complex and diverse than those derived from plants and microbes. Long-term pastures are ideal for aggregation. Good distribution of OM in soil is achieved from the fine roots of grasses, which can translocate as much as 50% of their photosynthate below ground. Green manuring rarely increases aggregate formation, but may inhibit its destruction. Cereals are similar to perennials in increasing % water stable aggregates formed during vegetative growth, but perennials are superior in maintaining the structure after the growing season. A grass-legume mixture is most effective at maintaining soil aggregation, while cereals and root crops are least effective.
1042. Bradfield, R.. 1954. Organic farming with chemical fertilizers.. J. Agric. Food Chem., 2:1216-1220.
An excellent discussion of soil organic matter and the question of fertilizer use. T: Comparative direct residual effects of manure and chemical fertilizers.
1266. Chandra, P., W.B. Bollen, and L.T. Kadry. 1962. Microbial studies of two Iraqi soils representative of an ancient site.. Soil Sci. 94:251-257.
Alluvial soils cultivated for 4-5000 years. No fertilizer, crop residues removed. Low OM, N, and total bacteria and fungi. After 5 days incubation, micorbial levels increased to values similar to more humid, fertile soils. Azotobacter was present. Decomposition of native and added organic matter was relatively slow. Measured soil properties, microbial levels, ammonification, nitrification, denitrification, S oxidation, P mineralization, decomposition of various added organic materials.
1378. Conacher, A. and J. Conacher. 1983. A survey of organic farming in Australia.. Biol. Agr. Hort. 1:241-254.
Describes a survey that sought to determine whether there were any farmers applying organic methods on a commercial basis in Australia, and what their motivations, practices, and success and problems were. Farms were identified, with 24 being grain/sheep operations. Results are similar to U.S. surveys. Farmers felt they had improved soil fertility, reduced erosion, and improved crop and livestock health. The environmental costs of modern agriculture are considerable in Australia. A 1975 estimate places land remediation for cropland and pasture at $675 million for that one year. Annual production losses were estimated in western Australia at $94 million.
1511. Davidson, J.M., G. Fenton and D.I. Pinson. 1967. Changes in organic matter and bulk density with depth under two cropping systems.. Agron. J. 59(4):375-378.
Measurement of BD and OM with depth after 24 years of continuous cotton and lespedeza were significantly different. The maximum compaction that could be given to a Reddish Prairie soil was directly related to its OM. Compaction was extremely sensitive to small changes in OM, caused by different cropping practices. This experiment should be repeated under wheat and alfalfa cropping in the Palouse. T: Average BD at 4 depth following 24 years continuous cotton and continuous lespedeza. Average OM at 4 depths following 24 years cotton vs. lespedeza. BD vs. soil water following a given load application. Maximum BD vs. OM.
1521. Davies, D.B.. 1977. Soil management. 3rd edition.. Farming Press Ltd., Suffolk..
Soil compaction increased chances of root disease (take-all, foot rot); problems of loss of soil structure; leads to reduced fertilizer use efficiency, especially N & P; winter cereals less sensitive to poor structure than spring cereals; 2-3 yr grass/alfalfa stand helps restore structure; benifits of subsoiling on silt soils; best time is when soil is dry.