Characterizing Changes in Aggregate Stability Subsequent to Introduction of Forages
1994
Rasiah, V. | Kay, B. D.
Limited information exists on the methods used to compute the changes in wet aggregate stability, WAS, with time subsequent to changes in management practices. The objectives of this study were to: (i) develop a model to compute the net gain in WAS, WASₙₑₜ, with time subsequent to the introduction of forages, (ii) assess the model using data from different soils, and (iii) determine the influence of soil properties on the regeneration of WAS. Stability measurements were made at monthly intervals during the 1989, 1990, and 1991 growing seasons from seven different soils under continuous conventional corn (Zea mays L.) and forage treatments established in 1989. The interaction of cropping treatment, time of sampling, and gravimetric soil water content, θ, at sampling was significant for six out of seven soils at P = 0.05. Using the relation between WAS and θ and the changes in WAS with time, a semiempirical model was developed to predict WASₙₑₜ. The model parameters described (i) the duration of delay before any observable changes in WAS occurred, (ii) the rate at which WAS increased from an initial to a maximum value, and (iii) the maximum potential change in WAS. The R² for the best fit of the model ranged from 0.31 to 0.72 for the seven soils. The projected half-life for WASₙₑₜ, computed using the 3-yr data, ranged from 4.52 yr for a clay loam to 7.75 yr for a sandy loam. Pedotransfer function analysis indicated that WASₙₑₜ increased with increasing clay and organic matter contents and pH of soil. The model parameters and the associated pedotransfer functions were useful in assessing the influence of soil properties on stability following changes in management practices. Contribution from the Dep. of Land Resource Science, University of Guelph, Guelph.
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