Topsoil thickness effects on soil properties and maize (Zea mays) yield in three ecoregions of Tanzania

Erosion-productivity experiments were conducted in the Kilimanjaro, Tanga, and Morogoro ecoregions for seven predominant soils of these areas. Decrease in topsoil thickness adversely affected a number of soil properties and reduced maize grain yield. Among the most important effects were diminution of soil organic carbon (SOC), cation exchange capacity (CEC), pH, total soil N (TSN), available P, available water capacity (AWC), and water saturation percentage. The magnitude of effects differed between soils and ecoregions. Maize grain yield was positively and significantly correlated with topsoil thickness, SOC, total N, CEC, and AWC. Maize grain yield declined at the rate of 38.5, 55.0 and 87.7 kg per cm decrease in topsoil thickness in the Kilimanjaro, Tanga and Morogoro ecoregions, respectively.