Researchers at the University of Arizona’s Yuma Agricultural Center are testing an annual summer cover crop called Sesbania, or summer hemp, to improve soil health and water-use efficiency for winter iceberg lettuce. The multi-year study is funded by a two-year grant from the Arizona Department of Agriculture’s Soil Health and Water Efficiency Program.
Unlike commercial crops, the dense summer hemp will not leave the farm. It is cut and tilled into the soil to decompose, enriching it for the winter growing season. Mitch McClaran, a University of Arizona professor of range management, said the plant requires minimal water, needing only two waterings to reach full height.
The study compares Sesbania with traditional cover crops like Sudan grass. Sudan grass does not fix nitrogen, while Sesbania naturally adds nitrogen to the soil through its foliage and stems. This improves soil fertility, which helps the soil retain moisture and allows lettuce to produce higher yields per watering.
Researchers are cutting the Sesbania before it seeds to prevent it from becoming invasive. The trial uses three fields: one in its second year of Sesbania, one planted for the first time, and a control field without it. All fields will be planted with iceberg lettuce in September and harvested in December.
The project aims to provide a roadmap for more sustainable, water-conscious desert farming. By tracking soil properties and crop yields across the fields, the team hopes to demonstrate the benefits of summer hemp for Arizona agriculture.
Source: yumasun.com
