Ancien regime

The ancient Anasazis in Southwest America used an ingenious method to irrigate their crops in a water-starved region. They would bury an unglazed earthenware pot up to its neck in the ground, fill it with water, place a lid on it and plant maize and beans around it. Fed by the slow seepage of water from the pot the plants would grow, their leaves in turn sheltering the pot from the sun. Water could be replenished in the pot every week.

A similar experiment has been undertaken by a farmer in the Arizona desert in the US. Howard Wuertz has buried drip lines 20-25 cm deep in the soil which release small amounts of water very close to the plant's roots. The soil surface stays dry, reducing surface evaporation, while soil around the roots is never saturated, reducing water logging.

An attendant advantage is that since water loss is reduced, less herbicide and fertiliser are lost, decreasing herbicide use by 50 per cent and nitrogen fertiliser use by 25-50 per cent. Crop yield also increases by 15-50 per cent due to greater uniformity in water application.

The system also reduces tillage operations, replacing ploughing, floating and land planning with simple, shallow surface tillage. A University of Arizona study concluded that tillage energy use was reduced by 50 per cent using the system. Simplified tillage also made possible quicker post-harvest turnaround of fields, enabling more crops to be reaped in a year.