SCBG Sweet Potato Soil Improvement Project

As part of a Specialty Crop Block Grant through Missouri Department of Agriculture, Cultivate KC has partnered with three local farmers to test a new technique. Developed by Dan Krull, Ag Systems Design Consultant and Board Member at Manheim Community Garden, this technique utilizes the growth habit of the common sweet potato, and free materials such as leaves, woodchips and other waste streams to quickly improve soil organic matter. The result is increased nutrient cycling, improved water infiltration, enhanced beneficial organisms, and decreased costly inputs, while at the same time growing a profitable and nutritious cash crop.

Cultivate KC had tested this procedure at the Westport Commons Farm for three seasons with excellent results, and this grant project created an opportunity to test the method at three local farms to obtain more data, and to educate local farmers on this new technique. Thanks to Jameson Hubbard of Dirt Beast Farm, Jackie Palmer of Jackie and the Beanstalk Farm, and Amelia McDaniel, Homesteader Extraordinaire & Executive Director of The Pilgrim Center for their collaboration. At the end of the first year, we hosted a workshop on Zoom to learn from project leaders and participating farmers about their experience using the technique. All reported positive results in the first season.

In the second year of the project, participants planted a crop of their choice. The Jackie and Beanstalk Farm has stepped away from farming, so the following results are from Dirt Beast Farm and Amelia’s homestead. One participant planted all tomatoes and another planted beds with eggplant, tomatoes, and ground cherries, each with basil interplanted. Jameson of Dirt Beast Farm reported, “I like using the leaves. Before this experiment I had been using leaves as a winter mulch in some areas. From what I’ve seen it definitely improves the soil, and I think it’s better than cover cropping or using straw if the purpose is to build organic matter in the first couple years on a clay-heavy plot.” Amelia reported on her tomatoes in early August, “They are doing splendidly! It is interesting compared to the tomatoes in my high tunnel. I took the plastic off the roof in June, but they still are dying off. We had a house fire, so I had my water shut off for two months. I couldn’t water any of the tomato plants very well. But the ones out front in the soil improvement plot clearly are thriving despite the same disadvantage.” This was reported in an extremely hot and dry summer.

The observations of improved soil quality are backed up by soil tests showing significant improvements in soil organic matter. In December of 2020, all of the test plots had low levels of soil organic matter – Jameson’s test plot had 2.4% and Amelia’s had 2.3%. By October of 2022, Jameson’s soil organic matter increased to 11.2% which is very high, and Amelia’s increased to 4%, which is also considered high. Soil organic matter is the foundation of healthy soils and is essentially what makes soil fertile. Learn more about soil organic matter in Building Soils for Better Crops from Sustainable Agriculture Research and Education (SARE).

So don’t bag your leaves this winter! Mulch them and pile them high on your current or future growing spaces, gather your neighbors’ leaf bags, and get ready to plant sweet potatoes next summer and enjoy healthier soil for years to come.

Watch Using Low-Cost Materials to Improve Urban Soils here.