Spatial variability of soil physical properties as affected by different tillage systems

Penetration resistance (PR), soil bulk density (BD), and volumetric water content (VWC) are important determinants of crop production. The objectives of this study were to: (1) evaluate the effect of conventional (S-1), conservation (S-2), and reduced tillage (S-3) systems on BD, PR, and VWC shortly after soil tillage; and (2) characterise the spatial variations of these soil properties before the seedbed preparation for the second crop in Tasliciftlik clay loam (medium, mixed, mesic Ustic Fluvents) located in north-central Anatolia, Turkey. Tillage effect was evaluated at two different soil depths (0-10cm and 10-20cm). Soil BD and VWC measurements were conducted on undisturbed soil samples and PR was measured with a hand-pushing penetrometer. All three tillage systems increased the variation in the PR; S-2 and S-3 decreased and S-2 increased the variation in BD; and S-2 and S-3 increased, and S-1 decreased the variation in soil VWC in 0-10cm depth. Spatial structure of PR in 0-10cm was not affected by the tillage systems. Slight changes occurred in spatial structure of PR in 10-20cm after the tillage. Spatial structure of BD in 0-10cm was considerably affected by S-1 compared to both S-2 and S-3. In 10-20cm depth, chiseling considerably altered the BD as indicated by semivariograms. However, tillage effect on BD was negligible in S-1 and S-3 in the same depth. Although the spatial structure of VWC in 0-10cm depth was highly altered in S-1, S-2 and S-3 had smaller effects on VWC in 0-10cm. Both S-1 and S-3 resulted in more uniform volumetric water content in 10-20 cm depth.