Figure 3.Oil Bottle Floats. Barley straw of good quality was the only effective material for unsupported covers. To be considered of good quality, barley straw should be fresh, unweathered, relatively dry, with as many whole stalks as possible. The tubular stalks act as flotation devices, and surface life is reduced if stalks are shredded or shattered excessively. Barley straw can give effective odour control over the entire season with only one or two reapplications to small areas of the lagoon surface to recover areas of straw sinkage.
Flax straw forms a mat which is too porous for odour control purposes.
Also, flax straw sinks quickly and may cause pump-out problems. Oat straw also sinks quickly. Durum straw is better than oat or flax straw but is similar to wheat straw which floats approximately one third the time of barley straw. Any type of cereal straw and even poor quality straw may work effectively when float systems are used to support the cover. The damp areas will have effective, although not excellent, odour control, while open liquid areas will provide no odour control.