What You Do This Fall and Winter Affects 2023 High Tunnel Productivity

Plant parasitic nematodes are being observed more frequently in high tunnels. Nematode assays should be taken this fall in any high tunnel that has been cropped for more than one year. Nematode assays are best taken before the onset of colder weather and should be shipped overnight to the laboratory of your choice. The North Carolina Department of Agriculture nematology lab is a very affordable option for Pennsylvania growers at $13 per sample (out-of-state). If your nematode assay reveals that plant parasitic nematodes are a problem, you may need to consider biofumigation, moving your tunnel, or using resistant cultivars or grafted plants (nematode-resistant rootstocks).

Most growers routinely test their high tunnel soils at the end of the growing season. When filling out the paperwork for these soil tests, make sure that you request that the soil soluble salt levels and organic matter levels be measured as well. These tests are not always part of a routine soil test, and you may have to pay an extra fee to have these tests conducted, but these tests are essential.

High tunnels that have been cropped for several years will see both elevated soil soluble salt levels and elevated organic matter levels in their soils. High soluble salt levels will cause a reduction in crop yield which means lower returns per square foot for growers (reduced profitability). If high soluble levels are detected in the soil, prescriptive leaching with clear water can reduce the soil soluble salt levels. As per the California Fertilizer Association (1985), 6 inches of clear water will leach about 50% salts, 12 inches of clear water will leach about 80% salts, and 24 inches of clear water will leach about 90% salts. Soil texture, organic matter levels, and the presence of hardpans can impact the effectiveness of leaching in high tunnels. The quality of the water used for leaching is also critical.

Do not leach soils with water that has an EC (Electrical Conductivity) level of 0.6 mS or higher (Penn State University Ag-Analytical Lab).

Elevated organic matter levels are also being observed in many high tunnels due to the incorporation of manure-based composts into these soils. Organic matter contributes to a soil's overall fertility, but when the organic matter levels are high, growers must consider this reserve fertility when developing their fertility program for the coming year. Researchers indicate that for each percent above 2 that 20 pounds of Nitrogen per acre is realized. In some high tunnels, we have observed organic matter levels at 8%, which means that 120 pounds of nitrogen is being contributed by the organic matter. If this reserve fertility is not considered when developing the 2023 fertility program, nutrient imbalances in the crop will be observed (like green shoulders in tomatoes).