Quantifying Water Use of Cover Crops in Rotation with Rice, 2021

 

Kosana Suvocarev, Dept. of Land, Air and Water Resources, UC Davis

California rice fields are highly productive agricultural systems, showing the integration of highly intensive agriculture with valuable ecosystem services. These systems also provide valuable habitat for a wide range of wildlife, including migratory and resident waterfowl.

The creation of seasonal habitat can be done by establishing cover crops in fallow rice fields and maintaining them through the waterfowl breeding season. The cover crops provide a win-win solution for utilizing fallowed lands by providing both soil health benefits and nesting habitat on agricultural lands. Cover crops in Sacramento Valley grown in rice fields rely mostly on rain and water storage in the soil for their growth.

After two years of experimental measurements, the project has looked at fallow filed, vetch, mix of cover crops, and winter wheat. Most of the water use was supplied from winter precipitation and soil moisture storage. Since both winters were very dry, winter wheat was irrigated multiple times.

Water use during the time when water transfers are made, after May 1, cover crops are responsible for 4 – 5.5 inches of water use. Despite not having any crop grown, the fallow field had quite high water use. Non-irrigated cover crops depleted the soil water profile more than fallowed land by drawing water from lower depths of the soil profile.