Farms grow <b>crops</b>, which can be used in various places but primarily to feed your people. However, crops don’t grow for free, they consume both <b>water</b> and <b>fertility</b>.
Soil water levels are replenished by rain, which is usually sufficient for crops with low water demands, such as potatoes. However, rain is not a reliable water source and crops may yield less or even dry out if they don't get enough water.
Having an external water source is vital for reliable farming. This requires upgrading farms with irrigation systems (unlocked through research). <b>Irrigated Farms</b> only consume water when the soil is dry so externally supplied water does not get wasted.