THE EFFECTS OF TILLAGE, DIRECT DRILLING AND NITROGEN FERTILISER ON SOIL TEMPERATURE UNDER A BARLEY CROP

Abstract

Summary: Continuous hourly records of soil temperature were collected at 1, 5 and 20 cm, throughout two growing seasons, 1973 and 1974, under crops of spring barley in the east of Scotland. Measurements were obtained from three cultivation treatments, deep ploughing, normal ploughing and direct drilling, at two nitrogen fertiliser levels, 0 and 150kg/ha. Compared with ploughed soil, direct‐drilled soil had a higher surface reflection coefficient and a higher thermal diffusivity between 5 and 20 cm; overall, this resulted in lower heat sums (°C hours/day over 5 °C and 10 °C) in direct‐drilled soil at 1 cm and 5 cm during the first 20 days after sowing. The thermal regimes of normally and deeply ploughed plots were very similar. Nitrogen fertiliser caused significant lowering of soil temperature at all three depths in the latter half of the growing season, due to increased shading of the soil surface by the crop canopy. Some implications of these findings for cultivations for cereals are discussed.