Sheep grazing a green crop of mustard, in Norfolk, UK, sown by direct drilling in August after harvest of the previous (cereal) crop. The sheep were introduced as the mustard flowers faded in December. Used in this way, sheep were traditionally called "the golden hoof". As they graze the green crop, their dung fertilises the soil. Intensive farming of cereals may, after harvest, involve a passage of a plough, followed by harrowing and sowing the ensuing (winter) cereal crop