On a soggy Saturday afternoon in mid-December, we hosted a small meeting before the American Geophysical Union meeting in San Francisco to discuss water infiltration with staff from the Union of Concerned Scientists (UCS), Point Blue Conservation Science, and TKREF. The goal of the meeting was to share information on water infiltration as a soil health indicator, different methodologies, and a meta analysis of water infiltration studies as it pertains to regenerative agriculture.
Mel Preston onsite rangeland ecologist from Point Blue opened the day with a presentation describing the new TomKat Ranch data map that you can find here. Over the last couple of years, Mel and her field team have been collecting soil samples, in addition to bird and vegetation data on TomKat Ranch. This map is incredibly useful and easy to use. As you click on each point, you get the corresponding data to the category selected. Sharing this information in an open source way is crucial toward helping others understand the potential benefits regenerative grazing can bring to rangelands.
Next up, Point Blue Senior Ecologist Libby Porzig presented the Rangeland Monitoring Network and the extraordinary task of soil sampling throughout California rangelands. In 2014, Point Blue started the Rangeland Monitoring Network to measure the ecological function of rangelands across California, to establish baselines for monitoring change and to observe the effects of grazing and management practices. The idea was that providing land owners with this information could help landowners understand the relationships between ecological metrics and the ecological functions that support life and guide decision making.
The soil dynamic properties that RMN researchers observe include bulk density, which measures compaction, water infiltration, which measures the ability of the rain or irrigation to soak into the ground, and organic carbon, which is the source of life in the soil and what helps maintain good water holding capacity. Libby pointed out that water infiltration is the only one of those three tests that you can do in the field and get an answer for the land owner immediately. Seeing the test firsthand helps them think about what is happening in the field.
Continuing after lunch, Marcia DeLonge and Andrea Basche from Union of Concerned Scientists presented preliminary results (link https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/157921 )
from a meta -analysis that includes 85 crop studies and 36 grazing studies and explores how agricultural practices in crops and grazing lands impact soil water infiltration. Looking at a range of agricultural practices – including no-till, crop rotations, perennial grasses, , cover crops, and agroforestry – their meta-analysis showed that the greatest increases in infiltration came from constant cover of the soil or continuous living cover practices. Results are showing that cover crops and perennially-based practices can lead to the largest increase in infiltration rates over other practices in annual crop systems where bare ground is prevalent.
By the end of the day, we were saturated with water infiltration studies and perspectives. It was interesting to find that the data supports what we see on the ground and in the pasture. In addition to assisting infiltration, continuous living cover protects the soil from erosion while helping it to retain moisture and provide nutrients for microbes and forage. It is a critical component of regenerative agriculture.