Deep connections: Studying deep recharge and healthy soil management practices in California

Summary:

California has one of the most diverse and productive agricultural economies in the world and we rely on the use of surface water deliveries as well as groundwater pumping to meet the water use needs of our crops. To maintain the agricultural economy of California and sustain it far into the future, we must take steps to increase the sustainable use of groundwater resources and protect the health and viability of our soil. For this project, we investigate links between soil and agricultural management practices and the movement of water deep into the profile that will ultimately recharge the aquifer below.

Investigator:

Nathaniel Bogie
Assistant Professor, Geology
San Jose State University

Project description:

To maintain the agricultural economy of California and sustain it far into the future, we must take steps to increase the sustainable use of groundwater resources and protect the health and viability of our soil. In this project, we investigate links between soil and agricultural management practices and the movement of water deep into the profile that will ultimately recharge the aquifer below. California has one of the most diverse and productive agricultural economies in the world and we rely on the use of surface water deliveries as well as groundwater pumping to meet the water use needs of our crops. If groundwater sustainability is not implemented, however, over-pumping will continue to lead to problems of water availability, water quality, and, in some areas, subsidence and problems with surface infrastructure.

In addition to the need to sustainably manage groundwater, we must maintain the viability of our precious soil resources. One way to do this is to use a framework of soil health, or the maintenance of the soil as a complex biophysical system through the use of conservation and regenerative agricultural practices such as winter cover cropping, reduced tillage, and increased input of manures, composts, and mulches. There has been a significant amount of work in a number of diverse cropping systems into these soil health management practices, however, the links between soil health and deep movement of winter precipitation to recharge aquifers is not well understood. Furthermore, much of the work to understand these linkages has been carried out in cropping systems elsewhere in the country and the world that don’t encounter the same water availability constraints as we do here in California.

The goal of this project is to train a master’s and an undergraduate student at San José State University to conduct soils research to quantify the impact of organic (with winter cover crop), conventional, and low-input (pasture) management on soil properties and soil moisture during the winter and spring months when rainfall occurs and water drains below the root zone. Some of the specific questions we answer are whether the growth of cover crops increases the deep percolation compared to the other treatments. The intent of this research is to better quantify changes to the field-scale water cycle as a result of these management techniques so we may be able to confidently approach our challenges to water availability.