Distribution of NO3, P, K, Cl, pH and conductance through the soil profile were measured on two soil types after 4 yr of crop production using zero tillage (ZT) or conventional tillage (CT), with or without addition of KCl. All plots received N and P fertilizer each year as banded applications. Surface concentrations of NO3-N were higher under ZT than CT, particularly on the fine sandy loam soil. Accumulation of NO3-N also occurred in the 60- to 120-cm zone, under both tillage systems in both soils. Carryover of NO3-N was substantially greater on the silty clay than the fine sandy loam soil. Phosphate accumulated at the depth of band application in both soils under both tillage systems. Potassium concentration was generally higher under ZT than CT in the surface 15 cm of both soils, presumably due to surface retention of K from fertilizer applications and crop residues. Chloride was higher under ZT than CT in the surface 5 cm of both soils, but was higher under CT than ZT in the 30- to 60-cm and 60- to 120-cm depths in the silty clay soil, if KCl had been applied. The pH on both soils under both tillage systems was reduced in the 10- to 12.5-cm soil depth, corresponding to the zone of fertilizer application. On the silty clay soil, pH was higher under ZT than CT in the 10- to 15-cm depth and tended to be higher under ZT than CT at all depths below 15 cm. Conductance was not influenced by tillage in either soil. Application of KCl increased K and Cl concentrations in the surface 15 cm on both soils. Concentration of Cl was increased to 120 cm in both soils, indicating the mobility and leaching potential of this anion. Conductance and pH were increased in the 2.5- to 5.0-cm and 10- to 12.5-cm depths by KCl application in the fine sandy loam soil, but on the silty clay soil, only conductance was increased. Key words: Zero tillage, nutrient stratification, pH stratification
The effects of tillage systems on soil physical properties and water conservation in a sandy loam soil in Eastern Kenya
