Effects of shallow tillage on physical properties of clay soil and growth of spring cereals in dry and moist summers in southern Finland

Abstract

Field experiments under Nordic conditions have shown that on clay and silty clay soils, shallow tillage gives higher yields than ploughing if the early summer is dry. A long-term field experiment was carried out with spring wheat ( Triticum aestivum L.) during 1986–1990 and with spring oats ( Avena sativa L.) during 1991–1995 on a clay soil (Vertic Cambisol) in southern Finland. The objective of the study was to clarify the factors making soil shallow-cultivated (6 cm) in spring (SH) more drought-resistant than soil conventionally ploughed (25 cm) in autumn and cultivated in spring (CN). Between treatments, the differences in the macropore (equivalent diam. > 30 and 300 μm) volumes of the 0–20 and 20–40 cm layers were slight. At a depth of 20 cm the SH tillage increased the biopore (diam. 0.2–1 and > 1 mm) number, associated with earthworms and made by roots and root density. Shallow tillage favoured the deep growth of root systems during the early summer. No clear differences were found between the SH and CN treatments in root clustering in the soil. Just after sowing, the soil was markedly moister under SH treatment than under CN treatment. Spring shallow cultivation may substantially increase the yields (1.9 Mg ha −1) and N uptake by grains (48 kg ha −1) if the early summer is dry.