TILLAGE AND FERTILIZER EFFECTS ON WATER INFILTRATION

Tillage techniques have been linked to the formation of tillage pans, which cause reduced infiltration capacity and increased runoff and erosion. Reduced infiltration is especially detrimental on steeply sloping agricultural lands, which are common in many areas of the Pacific Northwest and elsewhere. Infiltration rates in three long-term tillage treatments with two fertilizer levels were measured using a rainfall simulator. Surface sealing by raindrop impact and soil frost are probably more important than the tillage pan in controlling the infiltration capacity. Analysis of the infiltration-rate curves strongly indicates that, if surface sealing is prevented by a complete residue cover, the type of tillages does not have a significant effect on infiltration and is not a major factor in reducing the infiltration capacity of this soil. Conversely, fertility level is an important determinant of infiltration capacity, apparently because of the additional biomass produced by the crop. -from Authors