Internationally recognized food and farming activist Gary Paul Nabhan says Tucson gardeners do a good job recognizing the importance of harvesting rainwater to grow crops in the desert climate.
But on the heels of Tucson’s warmest year on record, Nabhan feels more can be done.
“There’s been a lot of emphasis on things like harvesting water, but not much on the other ways that deal with scarce water and cooling crops,” says Nabhan.
He describes what more there is to do in “Growing Food in a Hotter, Drier Land, Lessons from Desert Farmers on Adapting to Climate Uncertainty,” which won two awards in 2014.
The book combines farmers’ stories, personal experiences from Nabhan’s 4.5-acre farm in Patagonia and technical details on how to garden in deserts and other drought-ridden places.
Rainwater harvesting is a good, but merely first, step, he says.
“I really tried to emphasize not just where we get our water from, but all the stages in using and delivering it.”
For instance, Tucson gardeners can do much better in creating moisture-holding soil.
“A lot of people mulch, but don’t build up water-storing soil beneath the mulch,” he says.
Rain downpours and flood irrigation are often wasted on crops because the water is pushed below the root zone.
Moisture-holding soil at the root zone keeps that water where it’s needed for growing.
“It may be time that we replace the term water harvesting with harvesting water and organic matter,” Nabhan writes in his book.
Compost from food and landscape waste is one source for creating moisture-holding soil. Another, more natural source is compost washed from the desert during the rainy season.
This “flood-washed detritus” is full of organic material – leaves, twigs, flower spikes and animal droppings from wild flora and fauna.
Instead of hauling it away, such material ought to be dug into gardens, he argues.
“Where these organic materials accumulate on your own land or in public spaces nearby,” he writes, “you can rescue them from being dismissed as a nuisance or disposed of as trash, and provide nutrients as well as enhance the moisture-holding capacity of your soils.”
This practice is one of many that Nabhan talks about in his book, which gathers techniques from farmers in the Sahara, Arabian, Central Asian and Arizonan deserts, including the Sonoran.
He praises Tucson for leading in finding farming practices for a drier future.
“Tucson is a proving ground for techniques and crop varieties that will need to be used over half the area of the United States.”