Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2005
Publication Date: 6/1/2006
Citation: Fuentes, J.P., Bezdicek, D.F., Flury, M., Albrecht, S.L., Smith, J.L. 2006. Microbial activity affected by lime in a long term no-till soil. Soil & Tillage Research. Vol. 88 (2006) Pgs. 123-131.
Interpretive Summary: The gradual acidification of soils from nitrogen fertilization can limit crop productivity in the dryland cereal-growing areas of the Pacific Northwest. Under normal farming practices, lime is usually applied on the surface and then worked into the soil to correct acidity. In no-till systems, where surface-applied lime is not worked into the soil, lime will likely not move to where it is required and the lime may have to be mixed the soil by mechanical means. The objective of this research was to characterize the effect of lime, placed at different depths, on chemical and biological properties in a long-term, no-till soil. Soil samples taken from the several depths were analyzed for acidity, nitrogen (as nitrate) content, microbial activity (as carbon dioxide flux), and the quantity of soil microbes. Lime was applied to soil at low, medium, and high rates and decreased soil acidity in direct proportion to the amount of lime added. Soil nitrogen, in the form of nitrate, increased over time and in proportion to liming rate. Greater microbial activity and greater quantities of soil microorganisms were found in the lime-treated than in non-limed soils. This was attributed to reduced soil acidification. Faster turnover rates of soil organic matter were also found in lime-treated than in non-limed soils. These studies show that below-surface lime placement can enhance soil microbial activity and is effective for correcting soil acidity in this region.
Technical Abstract: Under conventional farming practices, lime is usually applied on the soil surface and then incorporated into the soil to correct soil acidity. In no-till (NT) systems, where surface-applied lime is not incorporated into the soil, lime will likely not move to where it is required. Consequently, lime may have to be incorporated into the soil by mechanical means. The objective of this laboratory study was to characterize the effect of lime, incorporated at different depths, on chemical and biological soil properties in a long-term NT soil. Soil samples taken from the 0-5, 0-10, and 0-20 cm depths were analyzed in incubation studies for soil pH, nitrate, CO2 respiration, and microbial biomass-C (MBC). Lime (CaCO3) was applied at rates equivalent to 0, 4.4, 8.8, and 17.6 Mg ha^-1. Application of lime to 0-10 and 0-20 cm depths increased soil pH from 4.9 by 0.9, 1.7, and 2.7 units for the low, medium, and high liming rates, respectively. Soil nitrate increased over time and in proportion to liming rate, suggesting that conditions were favorable for N-mineralization and nitrification. Greater respiration rates and greater MBC found in lime-treated than in non-limed soils were attributed to higher soil pH. Faster turnover rates and increased mineralization of organic matter were found in lime-treated than in non-limed soils. These studies show that below-surface lime placement is effective for correcting soil acidity under NT and that microbial activity and nitrification can be enhanced.