The normal frequent irrigations will replace soil gradually around the stems. Varieties Open pollinated varieties such as Elephant have been the mainstays of the leek industry for many years. However, these varieties are prone to bolting and hybrid varieties such as Rhino and Harpoon are now being more widely planted. Check with the suppliers for new varieties. Red varieties are also occasionally planted.
Some growers maintain seed stocks of their own open-pollinated varieties.
Fertilisers Apply the following rates of magnesium and trace elements to the soil before planting. This will add organic matter to the soil, supply nutrients for the first weeks and retain moisture in the soil. Levels of superphosphate may be reduced if a soil test shows that phosphorus levels are more than 80 ppm or if compost is used. Double superphosphate is preferred to single superphosphate as it contains less cadmium, which is a toxic heavy metal. Reduce the rates for nitrogen if the irrigation water contains more than 10 ppm of nitrate nitrogen.