Managing soil sustainably on small‐scale vegetable farms: Lessons learned from 100 Minnesota high tunnels and vegetable fields

Small‐scale vegetable farms are increasingly important to local food systems, but their soils are not well understood, particularly in high tunnels. We sampled soil in 100 Minnesota vegetable farm fields and high tunnels with three objectives: (1) Compare soil nutrients and soil health metrics in high tunnels and nearby open fields. (2) Document soil nutrient accumulation and assess loss potential. (3) Explore the impacts of specific management practices (input use, cover crops, tillage, and soil testing) and demographics on soil health and soil nutrients. Overall, vegetable farms had high organic matter in both high tunnels and fields (average 6.34% and 4.7%, respectively), and soil phosphorus levels were “very high” in 87% of high tunnels and 84% of fields. Just under half of the high tunnels studied had slightly to moderately saline soil (sufficiently saline to impact sensitive crops), and soluble salts were associated with higher soil nitrate concentrations. The pH of many high tunnel soils was above the optimal range for crop production, which correlated with irrigation water alkalinity. Some high tunnel soils had rapid water infiltration rates, with implications for irrigation management. Our preliminary risk assessment suggested a high to medium risk of nitrate leaching in two thirds of the fields and three quarters of the high tunnels studied. Farmer experience and more years in vegetable production were negatively associated with soil health metrics like aggregate stability and organic matter, but reduced tillage, organic management, and application of plant‐based compost were weakly positively associated with soil health indicators.