A grass sports ground is produced by mixing man-made vitreous fibres into soil having relatively high loam levels at a rate in the range 0.5 to 50 parts by weight per 100 parts soil (dry weight), preferably in the presence of moisture to separate the fibres and distribute them among soil particles, and then growing grass. The soil/fibre mixture has desirable moisture management properties as well as good mechanical characteristics providing extended use characteristics even in cold, wet or hot and dry conditions.