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Search results on 06/19/13
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.
10864. Fitch, B.C., S.K. Chong, J. Arosemena, and G.W. Theseira. 1989. Effects of a conditioner on soil physical properties.. Soil Sci. Soc. Amer. J. 53:1536-1539.
Agri-SC, a soil conditioner, was applied at four rates to a silt loam in Illinois for two successive years. There were no effects of the treatments, but the various physical parameters measured all declined the second year, probably due to the detrimental effects of fallow the land during the study.
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.
1273. Chang, C. and C.W. Lindwall. 1989. Long-term minimum tillage practices affect soil physical properties of chernozemic clay loam.. Can. J. Soil Sci. 69:443-449.
1782. Dutt, A.K.. 1948. Earthworms and soil aggregation.. J. Am. Soc. Agron. 40:407-410.
Earthworms increased water-stable aggregates; addition of alfalfa hay had the largest effect; better than straw or forest leaves; earthworm casts were 3 times as stable as 0-3" soil, for field, pasture, and forest; aggregation with straw additions was increased, with no effect of earthworms. T: water, stable aggregates and organic additions.
1810. Elliott, E.T.. 1986. Aggregate structure and carbon, nitrogen, and phosphorus in native and cultivated soils.. Soil Sci. Soc. Am. J., vol.50, p. 627.
Native sod soil had the same general structural characteristics as cultivated soil but the macroaggregates were more stable. The macroaggregate-microaggregate conceptual model is applied to help explain accumulation of soil organic matter under native conditions and its loss upon cultivation. Losses of organic C and N correlated with the reduction of soil structure and increases in erodability.
1854. Emmond, G.S.. 1971. Effect of rotations, tillage treatment and fertilizers on the aggregation of a clay soil.. Canadian J. Soil Science, 51:235-241.
Soil aggregation was lowest in a wheat-fallow rotation and increased in other fallow-grain rotations with the second, third and forth crops after the fallow year. The best aggregation was under continuous wheat. Rotations containing hay crops increased aggregation significantly. Tillage treatments affected soil aggregation in the following order: green manure crop plowed under> cultivated with trash cover> crop residue plowed under > cultivated with crop residue burned off = crop residue disked in. Fertilizer (11-48-0) increased aggregation except where crop residue had been removed. Barn manure increased soil aggregation. T: Effect of barn manure and crop sequence on soil aggregation. Effect of 5 tillage treatments on soil aggregation.
2211. Goldstein, Walter. 1989. Thoughts on drought-proofing your farm: a biodynamic approach. Working paper No. 2, Michael Fields Agr. Institute.
Describes the influence of soil aggregate size on moisture retention and crop growth. Discusses the benefits of perennial grasses in the rotation to improve soil structure. Discusses management of sweetclover for grazing and green manure. Discusses stubble mulch tillage.
2274. Greenland, D.J.. 1977. Soil structure and erosion hazard.. Soil Conserv. and Management in the Humid Tropics..
The structure of surface soil is usually given most attention in relation to soil erosion, because it is most subject to deterioration under raindrop impact, and due to agricultural practices its contition can be readily altered. However, subsoil structure is also important, as infiltration in a water-saturated profile is determined by the horizon of lowest conductivity.
2284. Greenland, D.J.. 1971. Changes in the N status and physical condition of soils under pastures.. Soils and fertilizers, 34(3): 237-251.
In the U.S. continuous cropping with inorganic N and herbicide use results in high yields. Would such practices work in Australia or would they result in soil degredation? This paper examines the role of pastures in maintaining soil quality. The study concludes that legume pastures are needed to maintain soil fertility in wheat growing areas. This is due to the high silt/fine sand content of the soil and the relationship between organic matter polysaccharides and soil structure necessary for maintaining soil porosity and water infiltration. T: Effects of a nitrification inhibitor (N-serve) on loss of N from soils during incubation. Mean annual soil N incements in soils under pasture. Changes in N content of soil under continuous fallow-wheat pasture and pasture-wheat rotations.