High Tunnel Technical Paper 1 

1. Exploring Overwintered Cover Crops as a Soil Management Tool in Upper-midwest High Tunnels.  Perkus et al. 2022. 9pp.

Click here to link to study

At three different sites in Minnesota (Grand Rapids, Morris, and Rosemount), the authors used in-production organic high tunnels to winter test aboveground biomass of different legume mixtures and their effect on soil health indicators during 2015-2017.  An early and late planting date were set for August 24-September 2 and September 14-September 22, respectively which were 2-3 weeks apart.  Three different cover crop scenarios were employed: red clover monoculture, winter pea/rye biculture, hairy vetch/tillage radish/rye 4:1:15 mix against a bare ground weeded control.  Cover crops were grown into the winter and terminated the following spring using a flail or riding mower.  Soil samples were taken throughout four intervals the subsequent summer after incorporation and in conjunction with a cash crop of peppers.  Extractable nitrogen, potentially mineralizable nitrogen, microbial biomass, and microbial biomass carbon were several of the soil health metrics evaluated.  Mixes were also evaluated for their potential to increase marketable and unmarketable pepper yield.  

The authors found that the later planting date resulted in greater biomass accumulation across cover crop scenarios.  Red clover monoculture was a reliable cover crop for high biomass at both planting dates but was better at weed suppression in earlier planting dates.  Including rye in the cover crop mix helped with weed suppression either through allelopathic or canopy cover effects.   Soil nitrogen increased with cover crop planting but this was influenced by the species of cover crop and soil sample interval.  Overall, planting cover crops helped to store available nitrogen that could have been lost in bare ground situations, particularly when the high tunnel is left uncovered for the winter.  There were not appreciable effects of planting cover crops on pepper yield; however, the short duration of the study may not have captured the long-term benefits to soil health that ultimately result in greater crop yields.