Soil salts · EC test · leach · not a kit

High-tunnel soil salinity / soluble salts / EC testing — why salts build and how to leach (sourced)

Growers search high-tunnel soil salt buildup, soluble salts, soil testing EC, and leaching after a year under plastic with drip and compost. Rain never hits the bed. This page is the salt sibling — why salts sit, how labs and handheld meters measure them, which EC ranges a named extension page actually printed, and what to do (uncover, sprinkler leach, cut manure). Full film rolls and uncover timing stay on high-tunnel plastic replacement. Drip hardware stays on high-tunnel drip irrigation. Floor fabric stays on high-tunnel ground cover / weed barrier. It is not a commercially manufactured high-tunnel kit and not a USDA payment schedule.

Extension quotes copied 17 October 2026, about 03:30 UTC from UMN Extension, Penn State Extension, UMass Extension, UVM Extension, and UKY CCD-FS-24. Featured Amazon prices copied the same night. A missing featured price stays an em dash. Ratings are not copied. EC ranges stay with the method named on that page — 1:2 is not 1:1 is not saturated paste. EQIP language below is the structure-only wording already on what EQIP will not pay for. Meters, lab fees, and leaching water are grower expense. No USDA payment dollar is invented here.

Kit index: commercially manufactured kits. Replacement-parts directory: high-tunnel replacement parts. Size map: high-tunnel sizes. Film rolls: 6-mil plastic replacement. Drip: drip irrigation. Double poly: double-poly inflation. Tomatoes: high-tunnel tomatoes. Winter lettuce: high-tunnel winter lettuce. Affiliate method: about / disclosure. County inspection: EQIP checklist.

No rain, drip-only water, and extra fertilizer

Open-field rain and snow push salts below the root zone. A year-round plastic roof does not. Drip puts just enough water in a strip. Compost and fertigation add more dissolved ions.

High tunnels exclude rain and snow which lead to leaching and may result in a build-up of salts that can negatively affect plant growth. In addition, most high tunnels are equipped with drip irrigation, which also limits leaching.

Source: Penn State Extension — Elsa Sánchez, Dealing with High Soluble Salt Levels in High Tunnels (updated 16 December 2025).

Nutrient salts can easily build up in high tunnels since there’s no natural rainfall to flush out excess salts in the soil, and evaporation from the soil surface can bring dissolved nutrient salts to the soil surface, which can cause damage to plants. To avoid reaching damaging levels of soluble salts, test for them every year in high tunnels.

Source: University of Minnesota Extension — Natalie Hoidal, Spring soil testing: which tests are right for your vegetable farm? (30 March 2020).

Salts can build up in a high tunnel over time from over-application of inputs, use of irrigation water with high alkalinity, and fertigation. These salts can limit plant growth and damage seedlings.

Source: University of Minnesota Extension — Soil health and nutrient management in high tunnels.

In high tunnels, soluble salts can accumulate to excessive levels because leaching is minimal. Composted manure is generally higher in salts than composted vegetative matter. Raw manure can be very high in salts and ammonium and is not recommended for use in high tunnels.

Source: University of Minnesota Extension — How to correct problems caused by using too much compost and manure (Hoidal / Rosen / Pagliari; reviewed 2021).

Elevated soil-soluble salts are the second most commonly observed production problem associated with high tunnels. Soil soluble salt levels can increase as a direct result of over-fertilization, overapplication of manure-based compost, and poor water quality.

Source: Penn State Extension — Thomas Ford, Did Common High Tunnel Production Issues Impact Your Yields? (updated 23 April 2024).

UKY CCD-FS-24: tunnels are typically covered year-round, so rain never moves salts the way a field does. Rudolph, Lark, and Jacobsen — Soil Salinity in High Tunnel Production (University of Kentucky Center for Crop Diversification CCD-FS-24, March 2022).

What salt stress looks like

Salt-sensitive crops show it first. Tomatoes and winter lettuce are named on those crop pages; this page only repeats the salt sentences.

In addition to affecting yields, salt injury symptoms include necrosis (burning) of leaf margins, stunted plants, wilting, and in severe cases, plant death.

Source: Penn State Extension — Elsa Sánchez, Saline Soils and Plant Growth (updated 16 December 2025).

A common symptom of salt damage is dead tissue (black or brown in color) on leaf margins. Yield will also be reduced. When salt levels are too high, most plants have difficulty taking up water. This is known as a chemical-induced drought.

Source: Penn State Extension — High Tunnel Soil Test Report: Soluble Salts Levels (updated 16 December 2025).

High tunnel crops respond differently to soluble salts levels. For example, beets are considered salt-tolerant, while peppers are moderately salt-sensitive. Tomatoes are considered moderately salt sensitive, but with more tolerance than peppers and potatoes.

Source: Penn State Extension — High Tunnel Soil Test Report: Soluble Salts Levels (updated 16 December 2025). Tomato crop notes stay on high-tunnel tomatoes. Lettuce notes stay on high-tunnel winter lettuce.

Soluble salts above the normal range for a prolonged period may cause root injury, leaf chlorosis, marginal burn and sometimes wilting.

Source: UMass Extension Greenhouse Crops and Floriculture — Soluble Salts and Electrical Conductivity (EC) for Greenhouse Crops (last updated 27 October 2016).

Lab soluble-salts test vs a handheld meter

Ask the state extension soil lab for a soluble-salts add-on. Handheld EC/pH pens are a screen. The number only means what the extraction method means.

Soils should be tested more frequently in a high tunnel than in open fields (every year vs. every few years), and growers should include a variety of analyses in their annual tests.

Source: University of Minnesota Extension — Soil health and nutrient management in high tunnels.

Collect at least 10-15 sub-samples per tunnel to a depth of 5-8 inches, where most roots grow. Do not mix samples from areas that have had significantly different rates of fertilizers or soil amendments applied previously – keep these areas separate. A soil augur is best for collecting an equal amount of soil from top to bottom of the sampling depth.

Source: Becky Maden and Vern Grubinger, UVM Extension — Soil Testing in High Tunnels (10 May 2023). UMN nitrate-N: sample the upper one foot, not the usual six-inch depth.

Soluble salts may accumulate due to lack of rain and snowfall in tunnels and can damage plant roots. Salts usually accumulate near the soil surface so tillage prior to sampling may provide a more accurate measurement.

Source: Becky Maden and Vern Grubinger, UVM Extension — Soil Testing in High Tunnels (10 May 2023). UMaine basic vs long-term high-tunnel packages are named on that 2023 factsheet. Tonight’s page does not copy those 2023 lab dollars.

Penn State Extension’s Agricultural Analytical Laboratory uses a 1:2 soil-to-water dilution to determine soil-soluble salt levels. Soils testing <0.40 mmhos/cm are considered to have negligible salinity.

Source: Penn State Extension — Thomas Ford, Did Common High Tunnel Production Issues Impact Your Yields? (updated 23 April 2024). Optional soluble-salts test currently $5 on Penn State Extension — Elsa Sánchez, Saline Soils and Plant Growth (updated 16 December 2025) — that is a lab fee on the page opened tonight, not EQIP money and not an Amazon price.

Soil samples are evaluated for salinity by first determining the electrical conductivity (E.C.) of a 1:1 suspension. Two 10 gram scoops are mixed with 20 milliliters deionized water to form a slurry, which is stirred intermittently for 30 minutes. The E.C. is determined by the Orion Star A212 conductivity meter, and is reported in units of millimhos per centimeter (mmohs/cm).

Source: University of Minnesota Soil Testing Laboratory — Soluble Salts method page. UMN starts with a 1:1 slurry; above 0.9 millimhos they run a saturated paste. That is not PSU’s 1:2 table.

In this test an air-dried sample of soil and water are mixed together in the volume ratio of 1 part soil to 2 parts water (e.g., using a measuring cup, 1 fl. oz. of soil + 2 fl. oz. of water). The liquid extract is then separated from the solids using laboratory grade filter paper or a common coffee filter. The extract is then ready for analysis. This is a very easy test to master and quite suitable for on-site greenhouse testing of pH and soluble salt using the so-called pH and EC "pens" available from greenhouse suppliers.

Source: UMass Extension Greenhouse Crops and Floriculture — Soluble Salts and Electrical Conductivity (EC) for Greenhouse Crops (last updated 27 October 2016). Pour-through is for containers, not ground beds.

Always use the interpretative data that match the test you made otherwise you could make an incorrect interpretation of the results. For example, a result of 2.6 for soilless media would be "extreme" (too high) for the 1:2 method, "normal" for SME, and "low" for leachate pourthru.

Source: UMass Extension Greenhouse Crops and Floriculture — Soluble Salts and Electrical Conductivity (EC) for Greenhouse Crops (last updated 27 October 2016). Units on that page: 1.0 mmhos/cm = 1.0 dS/m = 1.0 mS/cm = 1000 EC (µS/cm). PSU: 0.40 dS/m equals 0.40 mmhos/cm.

Irrigation water: Test your irrigation water at least once to determine its pH and alkalinity. Also, test for nitrate in your water regularly.

Source: University of Minnesota Extension — Soil health and nutrient management in high tunnels.

Interpretation ranges — only as the source printed them

Do not average these tables. PSU 1:2 is one lab. UMN’s 2023 farm-study bands do not name 1:2 on that page. UKY Table 1 is another EC1:2 vegetable guide with a different 0–0.40 row.

Source: Penn State Extension — Elsa Sánchez, Saline Soils and Plant Growth (updated 16 December 2025) / Penn State Extension — Thomas Ford, Did Common High Tunnel Production Issues Impact Your Yields? (updated 23 April 2024). Growers can expect to observe some reduction in yield on salt-sensitive crops when the EC exceeds 0.40 mmhos/cm.

In the same study, just under half of the high tunnels had some salt accumulation. Slightly saline soils (2-4 mmhos/cm) can stress very sensitive crops like carrots, onions, strawberries, and raspberries. Moderately saline soils (4-8 mmhos/cm) can stress a wider variety of crops, including cabbage, celery, lettuce, peppers, and sweet potatoes.

Source: University of Minnesota Extension — Soil health and nutrient management in high tunnels, 2023 study of 100 Minnesota farms. Those 2–4 and 4–8 mmhos/cm bands are printed there; that page does not call them 1:2. Do not line them up with PSU 0.40.

Requesting a soluble salts test on the soil test form is recommended. Many testing laboratories, including the University of Kentucky (UK) Regulatory Services Soil Testing Laboratory, measure soluble salts by measuring the electrical conductivity (EC) of a water extract from a mixture of 1 part soil and 2 parts water. This is referred to as EC1:2.

Source: Rudolph, Lark, and Jacobsen — Soil Salinity in High Tunnel Production (University of Kentucky Center for Crop Diversification CCD-FS-24, March 2022). UKY Table 1 EC1:2 prints 0–0.40 as “very low / nutrient levels too low for normal growth” — a different sentence than PSU’s negligible-salinity row at the same number. UKY Table 3 ECe (saturated paste) thresholds without yield loss include tomato 2.5 mmhos/cm moderately sensitive and lettuce 1.3 moderately sensitive. ECe is not 1:2.

Uncover for rain, or leach with a measured sprinkler

Plastic-off winters and replacement years sit with film work on high-tunnel plastic replacement. A second inflated layer is a different job on double-poly inflation. Drip hours for an inch of water stay on drip irrigation.

If a grower discovers that the EC or soluble salt levels are elevated, they can mitigate the injury risk by removing the polyethylene cover from the high tunnel structure over the winter to allow natural precipitation to leach the salts from the soil, leach prescriptively with clear water, or relocate the high tunnel to another location.

Source: Penn State Extension — Thomas Ford, Did Common High Tunnel Production Issues Impact Your Yields? (updated 23 April 2024).

In the fall of 2007, the soluble salt level was on average 0.40 mmho/cm. That November, the tops of the tunnels ripped off due to high-speed winds and because the plastic was getting old. We decided to leave the tops off until the spring. In April of 2008 we put new tops on and had the soluble salt level of the soils analyzed. On average, the soluble salt level decreased to 0.09 mmho/cm or about 77%. Between November of 2007 and April of 2008 we got about 11.5 inches of rain.

Source: Penn State Extension — Elsa Sánchez, Dealing with High Soluble Salt Levels in High Tunnels (updated 16 December 2025). The soil-test-report sibling prints the same drop as about 78%.

Remove the plastic every few years during the winter to help flush excess salts out of the soil and potentially reduce soil pH. Some growers use farm equipment to push snow into tunnels during the winter for a similar effect.

Source: University of Minnesota Extension — Soil health and nutrient management in high tunnels. Replacement-year wording: Leave the plastic off your high tunnel for the winter in years when you are replacing it. This allows rain water or snow, which is very low in alkalinity, to infiltrate the soil.

As a general guideline for leaching out soluble salts from the top foot of soil, apply 6 inches of water to leach about 50% of the salts, apply 12 inches to leach about 80% of the salts and 24 inches of water to leach about 90% of the salt from the soil.

Source: Penn State Extension — Thomas Ford, Did Common High Tunnel Production Issues Impact Your Yields? (updated 23 April 2024), citing California Fertilizer Association / Western Fertilizer Handbook (1985) as a starting point. PSU dealing-with page has a typo (“24%”); the yields and soil-test-report pages print 24 inches.

The conclusion of the study was that 6 in of water did not leach a statistically significant amount of potassium or magnesium from the soil. However, applying 12 in of water leached approximately 60 lb of K/acre and 95 lb of Mg/acre, though this was much less than the formerly estimated 80%.

Source: Rudolph, Lark, and Jacobsen — Soil Salinity in High Tunnel Production (University of Kentucky Center for Crop Diversification CCD-FS-24, March 2022). Do not treat the 6 / 12 / 24-inch handbook line as a Kentucky silt-loam guarantee.

Most growers find that if they use oscillating sprinklers in the high tunnel that they can lay out a network of small catch basins on the high tunnel floor. The sprinklers are turned on and when the targeted amount of water is caught in the basins the leaching process is completed.

Source: Penn State Extension — Thomas Ford, Did Common High Tunnel Production Issues Impact Your Yields? (updated 23 April 2024). Clear-water leach: When confronted with these options most growers opt to conduct a prescriptive leach with clear water (EC < 0.6 mmhos/cm) to lower soil soluble salt levels.

While flooding high tunnels is commonly cited as a way to mitigate salts, this practice can result in nitrate leaching, which is an environmental concern. Practice other methods to mitigate salts before resorting to flooding.

Source: University of Minnesota Extension — How to correct problems caused by using too much compost and manure (Hoidal / Rosen / Pagliari; reviewed 2021).

To avoid soluble salt buildup in high tunnels, incorporate high tunnel soils thoroughly and flush with irrigation water after removing summer crops. If tunnels will remain unplanted over the winter, growers are advised to consider planting a cover crop or removing the plastic to allow rainfall to leach soluble salts.

Source: UMass Extension Greenhouse Crops and Floriculture — Soluble Salts and Electrical Conductivity (EC) for Greenhouse Crops (last updated 27 October 2016).

When it is time to replace the plastic layers on a high tunnel (typically every four or five years), it may be useful to leave the high tunnel uncovered for several months (usually during the winter) to allow precipitation to naturally leach the salts through the soil and out of the root zone. Between the months of November and February, most regions in Kentucky have historically received approximately 15 inches of rain, which would be enough water volume to leach the majority of the salts past the root zone of vegetable crops.

Source: Rudolph, Lark, and Jacobsen — Soil Salinity in High Tunnel Production (University of Kentucky Center for Crop Diversification CCD-FS-24, March 2022). Kentucky November–February rain is that factsheet’s historic figure, not a national inch count.

Sourced Amazon test and leach parts

Titles and featured one-time prices were copied from live amazon.com product pages 17 October 2026, about 03:30 UTC. Kit frames stay on manufacturer product pages. These meters and strips are not a lab 1:2 report. Skipped tonight: B09YTHWYBS Melnor oscillating sprinkler (no featured offer); B00I9UQXQS Melnor GB350Y unavailable; B0B557Z9RS soil EC clone HTTP 404; B0GD23WYST soil probe HTTP 403.

EQIP pays for the structure, not the meter

Soil tests, EC/pH meters, water strips, probes, sprinklers, and soil amendments sit outside the High Tunnel System Initiative payment unless your county office writes them in. Confirm with your NRCS district conservationist. Tunnel Spec does not invent a dollar. FAQ: high tunnels can be used for crops in the natural soil profile or in raised beds — that is a production sentence, not a salinity payment.

Under the High Tunnel System Initiative, financial assistance is provided only for the structure itself. Electricity, venting systems, lighting, etc. can be installed providing the additions meets manufacturer’s designs and specifications. However, the grower is responsible for those costs.

Source: USDA NRCS High Tunnel System Initiative FAQ (Updated November 2024; Oregon-branded).

Producers can install heating, ventilation, or electrical systems at their own expense.

Source: USDA NRCS Pennsylvania — Seasonal High Tunnel System for Crops. One state office page, not a national meter payment.

The practice does not include greenhouses or low tunnel systems.

Source: NRCS Conservation Practice Standard 325 High Tunnel System.

High tunnels can be used for crops that are grown in the natural soil profile or in raised beds.

Source: USDA NRCS High Tunnel System Initiative FAQ (Updated November 2024; Oregon-branded).

Rules vary; call your county NRCS office.

FAQ

Why do soluble salts build up in a high tunnel?

Penn State: high tunnels exclude rain and snow that would leach salts, and drip irrigation also limits leaching. UMN Hoidal: there is no natural rainfall to flush salts, and evaporation can bring dissolved nutrient salts to the surface. Sources named on those pages include fertilizer, manure-based compost, fertigation, and irrigation water with high alkalinity or dissolved salts. This page does not invent a salt-year count.

How should I test high-tunnel soil for salts?

UMN: test high-tunnel soils every year and include soluble salts / EC; test irrigation water at least once for pH and alkalinity. Ask your state extension soil lab for a soluble-salts add-on — Penn State Agricultural Analytical Services Laboratory uses a 1:2 soil:water dilution (optional test currently $5 on that page). UMass: a 1:2 slurry is suitable for on-site pH and EC pens; always match the interpretation table to the method (1:2, 1:1, saturated paste / SME, or pour-through). Pour-through is for containers. UVM: 10–15 subsamples per tunnel, 5–8 inches; salts often sit near the surface. Handheld meters are a screen, not a substitute for the lab method your table came from.

What EC number is “too high”?

Only as the cited lab states, and only for that method. Penn State 1:2: <0.40 mmhos/cm negligible; some yield loss on salt-sensitive crops above 0.40; 0.40–0.80 mmhos/cm very slightly saline with 25–50% yield decrease named for carrots, onions, peppers, lettuce. UMN’s 2023 farm study (method not named as 1:2 on that page) printed 2–4 mmhos/cm as slightly saline for carrots, onions, strawberries, raspberries and 4–8 mmhos/cm as moderately saline for cabbage, celery, lettuce, peppers, sweet potatoes — do not equate those figures with PSU 1:2. UKY Table 1 is a different EC1:2 vegetable guide (0–0.40 “very low / nutrient levels too low”). PSU: 0.40 dS/m equals 0.40 mmhos/cm. Do not mix SME, 1:1, 1:2, and ECe numbers.

How do I leach salts — and when do I take the plastic off?

Penn State and UKY both reprint the California Fertilizer Association / Western Fertilizer Handbook guideline: about 6 inches of water to leach about 50% of salts from the top foot, 12 inches about 80%, 24 inches about 90%. UKY’s Lexington Maury silt-loam pilot (Lark and Jacobsen 2021): 6 inches did not leach a statistically significant amount of potassium or magnesium; 12 inches leached about 60 lb K/acre and 95 lb Mg/acre — much less than the formerly estimated 80%. PSU: oscillating sprinklers plus catch basins; leach with clear water EC < 0.6 mmhos/cm; re-test. Winter uncover: PSU left tops off Nov 2007–April 2008, 11.5 inches of rain, average 0.40 to 0.09 mmho/cm (~77%). UMN: leave plastic off in replacement years; flooding can leach nitrate — try other methods first. Film-replacement timing sits on the plastic-replacement page.

Does EQIP pay for soil tests, EC meters, or leaching water?

Tunnel Spec does not invent eligibility or dollars. The High Tunnel System Initiative FAQ says financial assistance is provided only for the structure itself; the grower is responsible for electricity, venting, lighting, and similar additions. The Pennsylvania seasonal high tunnel page says producers can install heating, ventilation, or electrical systems at their own expense. Meters, test kits, lab fees, soil amendments, and extra irrigation for leaching sit with those grower costs unless your county office writes them in. Confirm with your NRCS district conservationist. See what EQIP will not pay for.

Rules vary; call your county NRCS office. Tunnel Spec does not determine eligibility, payment rates, or inspection outcomes. Confirm soil tests and leaching with your NRCS district conservationist. As an Amazon Associate, we earn from qualifying purchases.