Nitrate is essential for the healthy growth of plants. However, a high level of nitrate and nitrite in the diet has been inconclusively linked to an increased risk of serious illnesses, such as methaemoglobinaemia and gastric cancer. As a consequence, growers are under increasing pressure to reduce the levels of these compounds in their crops. Leavy vegetables such as lettuce, spinach, and leafy Asian vegetables, have the greatest potential to accumulate nitrate. Research indicates that in Australia, the main contributor to excessive nitrate levels in crops is the inefficient use of organic or mineral nitrogen-based fertilisers.