The majority of irrigation systems do not use a consistent irrigation scheduling method. Typically, irrigation is the last "crop need" met following nutrients and pest control. Many crops are not receiving as much water as the crop actually needs, or irrigation may be started late. Often crop yields are lowered before the onset of wilting symptoms. In some cases, the crops are being over-irrigated to reduce the potential for drought-related stress (high value crops in particular). Effective timing of water maximizes return on investments in seed, fertilizers, land and other inputs.