Improving Soil Health and Increasing Rotation Options for Organic High Tunnel Vegetable Production.

Continued use of manure compost as a nutrient source for crop grown under high tunnels can lead to salt build up in the soil leading to decreased vegetable production. This study evaluated the effects of compost, crop species, and crop rotation on soil fertility and produce yield when cropped in organically certified high tunnels at the University of Minnesota SWROC in Lamberton, MN.  The soil treatments included beef manure compost, alfalfa tissue compost, and granulated turkey manure compost applied at 112 kg N ha^-1 plus a no-fertility control.  Crop species included cucumber, pepper, tomato, potato, and sweet potato.  A second double crop of table beets and cauliflower followed the potato harvest and broccoli and Brussels sprouts followed sweet potato harvest. The nutrient sources did not seem to effect cucumber or table beets yield as no significant differences were observed.  Tomato and pepper yields were significantly lower in the no-fertility treatment and similar in the compost treatments. Potato yield varied depending on the variety, red potatoes had no significant yield variation across all grades, while yellow potatoes had significant yield variation across grades.  Sweet potato yields varied by variety and grade, with Georgia Jet yields greater than Beauregard.  Soil nitrogen levels decreased after potato (from 88 kg to 45 kg N ha^-1) and sweet potato (from 71 kg to 27 kg N ha^-1) harvest.  Phosphorus and potassium did not decrease suggesting the crop was able to remove what was applied and didn’t need to use the nutrients in reserve.  In summary, the research conducted showed that different nutrient sources and crop species can be used to manage soil fertility in high tunnel organic cropping systems.