Spatial and temporal variability of some soil physical properties following tillage of a Nigerian Paleustult

The objective of this study was to evaluate quantitatively the magnitude of the spatial and temporal variation for 7 soil physical properties on a conventionally-tilled Nigerian Paleustult. A 0.4-ha plot was disc-ploughed, disc-harrowed twice, subjected to tractor-wheel traffic at regular space intervals and then seeded to maize (Zea mays, L.). There were significant differences in the physical properties owing to tillage position (spatial variability) and date of sampling (temporal variability), more so in the 0–10-cm layer than in the 10–20-cm layer. In the surface layer, bulk density (Db) and penetrometer resistance (PR) were significantly higher (P ⩽ 0.01) along the tyre marks (maximum Db = 1.76 Mg m⁻³) than in the uncompacted crop row (maximum Db = 1.35 Mg m⁻³) and interrow positions (maximum Db = 1.46 Mg m⁻³). Saturated hydraulic conductivity (K_sat), total porosity (TP) and macroporosity (M) were significantly lower along the tyre mark than in the crop row and interrow positions. K_sat ranged from 0.6 to 42.8 cm h⁻¹, TP, from 0.34 to 0.50 cm³ cm⁻³ and M from 0.06 to 0.25 cm³ cm⁻³ along the tyre mark and crop row positions, respectively. Significant temporal changes were noticed only in K_sat, soil moisture content (MC) and PR. K_sat increased steadily with time along the tyre mark, but showed an irregular trend in the other two positions. PR did not change with time along the tyre marks but it increased significantly with time along the other two positions. MC changed according to the periodicity of rainfall. Only TP varied, owing to tillage position × date interaction. The 10–20-cm layer was spatially less variable but temporally more viarable than the surface layer. Only K_sat and PR showed significant changes owing to the tillage positions, but Db, K_sat, PR and moisture retained at 10 kPa suction (τv10) showed significant temporal changes. Only τv110 varied owing to position × date interaction in this layer.