Many growers establish cash and non-cash rotation or cover crops each main season with the percentage of land in cash and non-cash crops varying farm to farm and year to year. Non-cash rotation crops are established to help maintain or improve soil health and nutrient levels, suppress weed growth, break pest and disease cycles, and provide other benefits. Despite these benefits, typically, high tunnel vegetable growers can be understandably reluctant to devote high tunnel space to non-cash crops in summer (main season). Perhaps as a partial consequence, soil health challenges (e.g., declines in organic matter and increases in nutrient imbalances, salt accumulation, compaction, and disease and pest pressure) are increasing in high tunnel soils. Anecdotal reports mention declines in crop yield and/or quality and increases in costs to maintain productivity. It is reasonable to expect that these trends could be be slowed or reversed through the consistent use of non-vegetable rotation crops in high tunnel production much like they have in open field production. However, few conclusive high tunnel-based experiments have been completed on farms or research stations.
This situation was not necessarily front of mind when the VPSL established cowpea, pearl millet, and sorghum sudangrass in many of its high tunnels at the OARDC in Wooster in early summer. Rather, the decision was primarily pandemic-related as vegetable experiments planned for the tunnels were suspended. That said, a summer including non-cash rotation crops is providing us with the opportunity to observe and learn about them and their potential value going forward. Currently, we consider cowpea, pearl millet, and sorghum sudangrass as just three of many potentially useful ‘alternative’ high tunnel crops for main season plantings, regardless of whether their use is planned or unplanned. The pictures below are examples of what we have observed to date. Please contact us (firstname.lastname@example.org; 330.263.3810) if you would like to discuss the plantings or the “high tunnel rotation” question further.