Further information on Hopi Corn
How the Hopi grow corn in an arid landscape.
The area the hopi grow their corn in has an average of 20.5 - 29.5cm of precipitation a year (auckland has 125cm a year). This rainfall comes in 2 short bursts of snow in winter and what falls as downpours during thunder storms in late summer. This pattern of precipitation arrives at unfortunate times as winter is too cold to grow anything and in summer the rain is too intense to percolate into the soil.
To get around the harsh climate the Hopi plant corn in arroyos which are a sandy loamdeposited by flash floods covered by a layer of sand. Below this topsoil is an impermeable layer of shale which water cannot move through. Winter snowmelt flows down these arroyos and is trapped by the shale. During spring the sand forms a crust which prevents the winter snowmelt from evaporating.
The Hopi plant the corn during late spring 18 - 25cm deep holes which gives the seeds enough moisture to germinate and develop until the intense summer rains begin. To best use the summer rains a system of dams and ditches are built protecting the corn from flash floods and spreading the floods into a sheet allowing slowing it and allowing it to enter the soil. This management provides enough moisture for the corn to mature and deposits new soil every year. The newly deposited soil also produces a hard crust protecting the moisture from the summer rains from evaporation.
The local Hopi corn variety is a short variety so it does not blow over in high winds and it has a deep tap root to access moisture deep in the soil.