Introduction
Romaine or Cos lettuce (Lactuca sativa L. var. longifolia) is a variety of lettuce that belongs to Asteraceae or sunflower family. The characteristics are non heading and semi heading (Wikipedia, 2014). The thick ribs, especially on the older outer leaves, should have milky fluids which give the romaine the typically fine-bitter herb taste. Dark greens leaf contain the antioxidants that prevent cancer, reduce levels of colon and liver cancer carcinogens (Lavelle and Christine, 2010).
Liquid fertilizer is popular for leaf vegetable and easy for absorption. Therefore, almost farmer apply directly to their crops (Wikipedia, 2014). The aim of this study focusing on the growth of Baby Cos after applied liquid fertilizers combined ammonium sulfate fertilizer.