Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 11, 2004
Publication Date: December 1, 2005
Citation: Wuest, S.B., Caesar-TonThat, T.C., Wright, S.F., Williams, J.D. 2005. Organic matter addition, N, and residue burning effects on infiltration, biological, and physical properties of an intensively tilled silt-loam soil. Soil & Tillage Research 84 (2005) 154-167. Interpretive Summary: Soil management such as tillage and the addition or removal of residues affects surface soil properties. These properties are critical in the infiltration of water, and therefore critical in determining whether water is stored in the soil or runs off, creating the potential for erosion. No-till farming practices have often proven effective in improving water infiltration, but it is not clear which soil property changes are responsible. We analyzed 22 soil properties in a 70-year-old winter wheat experiment and found that, despite a high degree of tillage in all treatments, measures of water-stable soil aggregation, soil carbon, and the fungal residue glomalin were well correlated with water infiltration. Two new measures of aggregate stability, water stable whole soil and percolation stability, proved to be better predictors of infiltration than a traditional measure, water stable aggregates of 1- to 2- mm size. This proves that relatively small differences in soil aggregation are sufficient to produce environmentally significant differences in infiltration, even under conventional tillage practices in this weakly aggregated silt-loam soil. It may be possible to develop farming systems with improved water infiltration that allow for tillage when economically necessary, as long as care is taken to maintain water stable aggregation.
Technical Abstract: Seventy years of residue management treatments have produced significant differences in runoff, erosion, and ponded infiltration rate in a winter wheat (Triticum aestivum L.)- summer fallow experiment in Oregon, USA. All plots received the same tillage (plow and summer rod-weeding). Manure (containing 111 kg N ha^-1), pea (Pisum sativum L.) vine (containing 34 kg N ha^-1), or N additions of 0, 45 and 90 kg ha-1 were treatment variables with burning of residue as an additional factor within N-treatments. The hypothesis tested was that differences in infiltration are due to changes in soil structure related to treatment-induced biological changes. We measured soil organic C and N, water stability of whole soil, water stable aggregates, percolation through soil columns, glomalin, basidiomycete-produced glue, earthworm populations, and dry sieve aggregate fractions. Infiltration was correlated to C, N, stability of whole soil, percolation, and glomalin. Basidiomycete extracellular carbohydrate assay values and earthworm populations did not follow soil C concentration, but appeared to be more sensitive to residue burning and to the addition of pea vine residue and manure. Dry sieve fractions were not well correlated to the other variables. We conclude that differences in infiltration measured in the field are related to relatively small differences in aggregate stability, even though the size of aggregates differed little.