Extensive development of dairy farming in the dairy belt of North America has been possible due to the presence of a combination of physical and economic factors. The region receives a rainfall varying between 55 and 125 cm. The rainfall efficiency is further increased by relatively lower temperature ranging between 18° and 24°C. The cattle yield more milk in a cool climate and the milk can also be kept for a longer time at lower temperature.
Salinity is directly positively related to seawater density.On an average, seawater density increases with increasing salinity and vice versa.E.g. Density of pure water is 1.00 g/cm3 and density of water with 35% salinity is 1.028 g/cm3.