The contract represents approximately 75 per cent of all of Sainsbury's compost requirements.
J.Arthur Bowers is a potting compost for all gardening uses including seed-sowing, pricking out, houseplants, hanging baskets and patio containers.
William Sinclair will begin delivering its compost to Sainsbury's on 15 February 2011 and the J.Arthur Bowers product will be available to Sainsbury's customers from 23 February 2011.
William Sinclair Retail MD Danny Adamson said:
"Sainsbury's has some of the most demanding quality standards and product performance criteria in the horticulture industry and it is reassuring to see that they, like us, believe the quality of the J.Arthur Bowers brand to be unsurpassed."