Humans, animals and plants rely on a safe, healthy supply of food and nutrients like nitrogen (N), phosphorus (P) and potassium (K) for proper growth and development. Fertiliser is the 'food' that plants need to produce a healthy and bountiful crop. Experts estimate that without commercial Fertilisers, the world would be without one-third of its food supply.  So why is fertiliser so important?  And what are those numbers on the bags or tubs mean?  We at Scotplantsdirect.co.uk have devised a short summary of what it all means