The effect of soil compaction on wheat during early tillering: I. Growth, development and root structure

Wheat (Triticum aestivum L. cv. Eradu) was grown in the field on a deep loamy sand which had either a compact soil layer (compact soil) between 10 and 55 cm depth or a deep‐tilled profile (loosened soil). Between 33 and 62 d after sowing, shoots grew more slowly and had fewer tillers on the compact soil. Nitrogen and K (but not P) concentrations were 12–14% lower in shoots grown on the compact soil, suggesting that nutrient deficiencies might have contributed to impaired shoot growth. Seminal root axes elongated at 0.60 and 1.78 cm d⁻¹ in compact and loosened soil, respectively. At 47 d after sowing, roots in compact soil were short, thick and contorted; cortical cells expanded radially in response to high soil strength but were 66 % shorter, causing cortical cell volumes to be smaller than in roots from loosened soil. The diameter of the stele was not affected by soil compaction. In addition the zone of elongation was much nearer the apex and shorter in roots from compact soil. Overall, seminal roots in compact soil grew slowly and explored the soil profile inefficiently.