The Influence of Selected Soil Conservation Practices on Soil Properties and Crop Yieldsin the Usambara Mountains, Tanzania

The Usambara Mountains in Tanzania are severely affected by soil erosion which has led to deterioration of soil properties and reduced crop productivity. Indigenous soil erosion control measures such as miraba which are widely practised in the area have yielded little success. Field plot experiments were laid down in Majulai and Migambo villages from 2011 – 2014 on typical soils of the area (Acrisols). The aim was to single out soil properties developed under the studied soil conservation practices and their impact on crop productivity with reference to maize (Zea mays) and beans (Phaseolus vulgaris). Results showed that total N, OC, available P, Ca2+, Mg2+, K+ and Ph were powerful (P = .05) attributes that discriminated conservation measures. Magnitudes of the discriminating attributes followed the trend: miraba with Tughutu (Vernonia myriantha) mulching >miraba with Tithonia (Tithonia diversifolia) mulching > miraba sole > cropl and with no ‘Soil and Water Conservation’ (SWC) measures (control). Contents ofmicro-nutrients did not differ significantly with SWC measures except for Zn which was significantly (P = .05) lowin the control. Bulk density and available moisture content (AMC) were also strong discriminators of conservation measures. Maize and bean grain yields differed significantly (P = .05)with the trend: miraba with Tughutu > miraba with Tithonia > miraba sole > control in both villages. Crop yields under miraba were a function of AMC and pH (R2= 0.71); AMC, available P, Ca2+ and K+ (R2= 0.89) under miraba with Tithonia mulching; AMC, available P, Ca2+ and K+ (R2= 0.90) under miraba with Tughutu mulching. These findings imply that miraba with Tughutu mulching had greater potential in improving soil properties and crop yields than miraba with Tithonia mulching and miraba sole.