Relationships of Dense Tillage Pans, Soil Properties, and Subsoiling To Tobacco Root Growth
1986
Vepraskas, M. J. | Miner, G. S. | Peedin, G. F.
Deep tillage with subsoilers can fracture tillage pans and increase root development in some soils, but little is known about the precise soil conditions for which subsoiling works best. This study evaluated relationships of soil physical properties, chemical properties, and subsoiling to root distributions in 10 Ultisols. Five sites had dense tillage pans in their E-B horizons with bulk densities (ρb) ≥1.66 Mg m⁻³. At each location flue-cured tobacco (Nicotiana tabacum L.) was grown in subsoiled and nonsubsoiled (moldboard plow/disk) tillage treatments. At approximately 100 d from transplanting, root distributions were described by the trench-profile method. Soil properties evaluated included bulk density, texture, ped mean weight-diameter, cone index (CI), Ca and Al saturation ratios, base saturation, and pH. Subsoiling significantly increased the proportion of roots below the E-B horizon (0.15 m below the Ap), in three of the five sites with E-B ρb's ≥1.66 Mg m⁻³, while it had no significant effect on proportion of roots below the E-B horizon in any of the five sites whose E-B ρb's were <1.66 Mg⁻³. A regression analysis showed that ρb of the E-B horizon, B horizon sand content, and cummulative rainfall accounted for 96% of the observed variation in subsoil root development for the nonsubsoiled treatment across the 10 sites. Soil chemical properties had little effect on variation in subsoil root development across sites.
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