Remediation of Stratified Soil Acidity through Surface Application of Lime in No-till Cropping Systems.

Reduced crop yield and vigor, resulting from soil acidification, are of increasing concern in the Palouse region of Eastern Washington and Northern Idaho. Soil pH has been decreasing at an accelerated rate, primarily due to long-term inputs of ammoniacal fertilizers. The soils of the Palouse region used for agriculture are primarily derived from native forest land as well as prairie that originally were not acidic and will likely have different responses to liming. Lime is traditionally incorporated using tillage and surface applications of lime in no-tillage systems have not been effective for remediating acidic subsurface zones that result from deep banding fertilizer. Recently, however, a 98% CaCO₃ fluid lime with ultra-fine particle size (1 to 2 microns) has become commercially available. The fine particles may increase the physical mobility of the lime and more effectively address subsurface acidity in no-tillage systems. Additionally, sugar lime, a byproduct of the sugar beet industry, is also commercially broadcast-applied in the region. We surface applied fluid lime and sugar lime at two sites under long-term no-tillage management. The sites represent soils derived from native vegetation of forest or prairie and had subsurface, stratified soil acidification with pH (1:1 water) values as low as 4.2. The lime was applied in the fall with treatments ranging from 448 kg/ha to 2240 kg/ha prior to the no-till planting of spring crops. Lime treatment effectiveness in remediating acidic subsurface zones and crop responses to lime are being evaluated. Parallel studies are underway to update soil pH buffer tests and corresponding lime requirement recommendations for the region and to assess how different liming materials react in the soil over time.