RHS: Endorsed by the Royal Horticultural Society. Gardening: Get a 50 litre bag of RHS SylvaGrow farmyard manure. Enhances fertility: A rich source of organic matter which enhances fertility increases yields and aids the water-holding capacity of soils. Improve your soil: Well-rotted and can be used all around the garden for adding essential organic matter, nutrients to soils. 50L Rhs Sylvagrow Farmyard Manure | Living Social