The C&SF established 470,000 acres (1,900 km2) for the Everglades Agricultural Area—27 percent of the Everglades prior to development.[136] In the late 1920s, agricultural experiments indicated that adding large amounts of manganese sulfate to Everglades muck produced a profitable harvest for vegetables.[137] The primary cash crop in the EAA is sugarcane, though sod, beans, lettuce, celery, and rice are also grown. Fields in the EAA are typically 40 acres (160,000 m2), bordered by canals on two sides, that are connected to larger canals where water is pumped in or out depending on the needs of the crops.[138] The fertilizers used on vegetables, along with high concentrations of nitrogen and phosphorus that are the byproduct of decayed soil necessary for sugarcane production, were pumped into WCAs south of the EAA. The introduction of large amounts of these chemicals provided opportunities for exotic plants to take hold in the Everglades.[139] One of the defining characteristics of natural Everglades ecology is its ability to support itself in a nutrient-poor environment, and the introduction of fertilizers began to alter the plant life in the region.[140]