This commentary was published in The Fresno Bee on July 29, 2022.
Change is coming to farming in the San Joaquin Valley. Because of the need to reduce groundwater pumping to comply with the 2014 Sustainable Groundwater Management Act, we’ve estimated that at least 500,000 acres of farmland will need to come out of irrigated production in the coming years.
This is a major shift for California’s agricultural heartland, and one that will have profound impacts on the region’s residents, workers, economy, and environment.
With such major change looming, it’s in everyone’s interest to find ways to help these land use transitions cause as little harm as possible—and ideally bring benefits. If the transition is haphazard, or not managed well, it could lead to increased problems, including weeds, pests, and dust. To avoid negative outcomes, the region may need to look to the past for inspiration.
Looking to the San Joaquin Valley’s past
Crops that can survive mostly on rainfall, such as winter wheat, were once common on the San Joaquin Valley floor, but they fell out of favor with the advent of irrigation. Now, as SGMA and drought force land fallowing, these old farming practices may gain new currency.
In our new report, we looked at whether crops could grow in the valley without irrigation. Our models told us that if a farm gets less than 10 inches of rainfall in a year, a grower won’t have much success. And much of the valley falls into this low-rainfall category.
But modern-day California grain growers can use other tactics to give their crops a leg up. Adding 4 to 8 inches of irrigation in a season can help to establish a crop that might fail to even germinate without it. Such “water-limited” crops are likely to have reduced yields compared to a fully irrigated crop, but they may provide other benefits, including forage for grazing animals—for which there is potentially a large local market.
Why grow water-limited crops?
While water-limited crops may not provide a financial windfall, growing them might be preferable to fallowing. Fallowed land must be tilled multiple times a year to tamp down noxious weeds, at a cost to both the landowner and air quality (tillage operations can be large sources of dust). Water-limited crops could generate some revenue while keeping agricultural land operational should water conditions become more favorable.
Growing winter cereals also helps with soil conservation. Leaving standing residue in the field after harvest can reduce dust emissions and conserve soil water during the hot, dry summer months. A winter crop also improves rainfall capture by aiding water infiltration. This directly benefits both the grower and the broader public.
That said, these benefits don’t pay for themselves: Water-limited crops may need external support to make them worth growers’ while. Public funding has supported major transitions in the valley’s past—for example, to eliminate agricultural burning. But the longevity of such programs is a concern, and demand can often outstrip the funds.
Our research looked at whether water-limited farming could be a feasible alternative to fallow. And while the results are promising, more research is needed, particularly into the risk of salt accumulation in soils and increasing weed pressure over time. Furthermore, other winter and drought-adapted crops deserve investigation, including canola, safflower, chickpeas, prickly pear cactus, agave, and others.
Priorities for research and development include:
- Field testing water-limited crops and management approaches
- Exploring market opportunities and economic constraints for water-limited winter forage
- Improving our understanding of other biophysical, social, and economic tradeoffs
And planners and decision-makers should consider water demand reduction programs that incentivize the public benefits of water-limited crops. Keeping crops in the ground could improve air quality and soil structure, provide forage for grazing animals, and even provide surrogate habitat for wildlife. This is a direction California’s farmers and policymakers should seriously investigate. Fallowing is coming—the valley needs to be ready.