Hoop houses are a great way to extend the growing season. They offer protection from frost and allow farmers and gardeners the luxury of control over the elements. This level of control comes at a price. Without exposure to rainfall, our hoop houses are at risk of toxic nutrient buildups. Keeping your hoop house soil healthy and productive is not complicated. It just requires a little foresight.
Nutrient Salt Build Up
Hoop house soil health is crucial to maintaining crop yields. Just like your uncovered garden beds, hoop house soil requires maintenance. Unlike those garden beds, hoop houses do not have access to the natural processes that flush out toxic buildups of salts. Nutrient salts (nitrates) are essential minerals in appropriate quantities. In large quantities, these nitrates cause root rot and prevent the growth of plants.
Excess salts are naturally washed away by rainfall. Irrigation alone is not enough to flush away the salts. In a hoop house, this is a problem. There are two ways to determine if your hoop house has a nitrate problem. Root rot and stunted growth are good indicators of a nutrient deficiency or salt overload, but by the time we realize there is a problem it is too late for the crop. A more accurate method is an annual SME (Saturated Media Extract) soil test.
SME soil tests determine the level of nitrates in the soil as well as other vital nutrients. Soil experts at university extensions across the U.S. recommend the SME test, especially for hoop house soil. Take an SME test two years into hoop house production, as this is typically when nitrates start to build up.
The best way to flush the soil of nitrates is to open the hoop house up by removing all or part of the plastic. Leaving the plastic off for a month, or for at least four major rainfalls, removes the nutrient buildups without depleting the soil of its nutrient reserves. Intense irrigation mimics this effect but requires significant amounts of water. Some hoop houses can be moved. Building a hoop house on runners or tracks allows growers to easily expose soil to rain while also opening up more possibilities for crop rotation.
Importance Of Regular Soil Tests
Regular soil testing does more than monitor salt build ups. Soil tests are inexpensive and well worth it for both the hobby and market gardener. Aside from telling us vital information about our soil, they prevent us from dumping expensive supplements where they are not needed.
A regular soil test is all that is required the first year of production in your hoop house. During this time, the hoop house soil is very similar to the soil outside. Things change after the first year. The increased evaporation caused by the micro-climate contributes to nitrate accumulation. This is when SME soil tests are helpful.
Soil tests take very little time to collect and send off. They tell you vital information about the nutrients you need to add to your soil to keep your plants healthy and productive. Don't wait until the plants start presenting signs of deficiencies to add supplements or deal with nitrates. Test your soil annually and save yourself time, money, and unhealthy plantings.
Maintaining Soil Fertility
Once you have your soil test in hand, you know what you need to add. Take care to add the appropriate amount of each supplement. Your soil test should give you the information you need to calculate the exact quantity of the supplements needed.
Supplements only go so far without additional organic material. Compost is key to soil health. Adding the organic material in high-quality compost supplies some of the same nutrients as your supplements at a lower cost, especially if you produce the compost yourself. High-quality compost does wonders for hoop house soil health. Compost made with nutrient deficient materials, or compost that is not sufficiently mature is less effective.
The use of organic mulches like straw also improves soil fertility. Mulches protect exposed soil and prevent weeds while also adding organic matter to your beds. Mulch decreases evaporation, helping to reduce nitrate buildups and lowering your irrigation costs. Straw and cardboard attract earthworms. Earthworms aerate, mix, fertilize, and distribute important microbes through the soil, aiding plant growth and increasing soil fertility.
The easiest way to deplete soil fertility is planting vegetables from the same family in the same place season after season. Rotate your crops to prevent the depletion of specific nutrients from the soil. Rotation also reduces the risk of disease and pests in your hoop house.
Planting cover crops is another way to promote soil fertility. Cover crops add organic material and legume cover crops fix nitrogen, making it more accessible to other crops.
With proper management, the soil in your hoop house yields abundant fruits and vegetables while also extending your season.