Investigation of the impact of short-term tillage practices on soil properties at various depths in light soils of the highlands of Central Ethiopia

Soil degradation caused by repeated shallow tillage had remained a major challenge in Ethiopian highland farming systems. Traditional tillage often resulted in shallow disturbance, compaction, and poor residue incorporation, which reduced soil fertility and crop productivity. This study investigates the comparative effects of traditional and modified plow practices on soil properties in Chefa Kebele, Central Ethiopia, focusing on physical, mechanical, and chemical characteristics at varying soil depths (0-5, 5-10, 10-15, 15-20, and 20-25 cm), wheat-based light soils. Traditional tillage, employing the oxen-drawn 'Maresha' plow, was evaluated against a modified plow designed to enhance soil structure and fertility. A randomized complete block design with three replications was used, and data were analyzed using ANOVA with significance (p < 0.05) and a paired t-test. The analysis of soil physical properties with depth revealed significant variations, with the surface layer (0-25 cm) exhibiting the highest values for liquid limit, plastic limit, plastic index, bulk density, and dry density. In contrast, moisture content was significantly lowest at the surface and peaked in the 10-15 cm layer. Subsurface layers (5-20 cm) showed lower strength-related properties (PL, PI, BD, DD) and higher porosity and moisture. Soil mechanical properties showed significant variation with depth, particularly for dynamic cone penetration (DCP) resistance and cohesion, while the friction angle remains relatively consistent. The DCP resistance varies significantly, with the highest strength observed in the 5-10 cm layer and the lowest in the 20-25 cm layer. Cohesion is significantly highest in the top two layers (0-10 cm) and decreases to 1.1 kPa in the 10-20 cm depth. Soil chemical properties exhibit significant differences between the upper (0-15 cm) and lower (15-25 cm) soil layers. The topsoil has significantly higher levels of total nitrogen, phosphorus, potassium, and cation exchange capacity compared to the subsoil. The modified plow significantly improved soil physical properties by reducing specific gravity, increasing plastic limit, and decreasing plastic index, promoting better root penetration and water retention. Soil moisture content was increased by 10.52% under the modified plow, indicating enhanced water-holding capacity. In terms of mechanical properties, modified tillage reduced penetration resistance and friction by 15.59% and 4.76% respectively, and mitigating compaction risks. The modified plow increased soil organic carbon (10.75%), total nitrogen (35.71%), and available phosphorus (17.93%), while maintaining stable pH levels. These improvements suggested enhanced nutrient cycling and microbial activity. The modified plow optimizes soil health by improving structure, reducing compaction, and boosting fertility, thereby supporting sustainable wheat production in light-textured soils. Future research should focus on promoting modified tillage adoption among smallholder farmers, integrating it with organic amendments, and providing training for effective implementation. This research underscores the potential of tailored tillage innovations to enhance agricultural productivity and soil sustainability in Ethiopia's highlands.