Why might a rancher plant several varieties of grass fro grazing on the same ranch

The reasons why a rancher may plant several varieties of grass for grazing on the same ranch are for making hay where some horse owners may prefer to feed their animals with a feeding mixture of alfafa hay and timothy hay.  Secondly, they plant the grasses for grazing their animals since the grasses may be having different soil conditions in different fields. lastly, the farmers may be raising different animals with varying nutritional needs.  

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.