Effect of Soil Compaction on Carrot Roots1

Abstract

Effects of soil compaction on early root growth of carrot ( Daucus carota L.) growing in organic soil contained in specially constructed pots were studied under controlled environmental conditions. Screened and steamed mucky peat soil was artificially compacted with an applied pressure of 0.45 — 2.23 bars to produce soil densities of 0.7 — 1.1 g/cm3. Soil strength, measured as penetrometer resistance was directly related to applied compacting pressure and highly dependent upon soil moisture. Highest soil strengths were produced when the soil contained 52-58% moisture. Taproot lengths 16 days after seeding were significantly shorter at each increase in soil strength produced by applied compacting pressures of 0.45, 1.12, 1.51, and 2.23 bars. Rates of early taproot growth measured at 2-day intervals for 18 days were similarly decreased with increasing soil strength. Young taproots grew normally through compaction zones produced by 0.45 bars but were severely impeded when compaction zones produced by 1.12, 1.51, and 2.23 bars were encountered. Roots impeded by high soil strength were frequently thickened and convoluted with increased branching but no significant differences between treatments could be detected. Effects of soil compaction on mature roots were evidenced by abnormally short, blunt, and abruptly tapered roots. Mature root weight, diameter, and length decreased with increasing soil compaction.