High Tunnel Soil Salinity - Tips to Protect Crop Yields

By Blake Jackson

Research at Penn State’s High Tunnel Research and Education Facility has shown that soluble salt levels in high tunnel soils can rise over time, regardless of whether growers use inorganic fertilizers or organic nutrient sources. In spring 2008, measured levels ranged from 0.37 to 9.38 mmhos/cm, highlighting the potential for accumulation under protected structures.

High tunnels create unique growing conditions that limit natural leaching from rain and snow, while drip irrigation further reduces the movement of salts out of the soil. This buildup can negatively affect plant growth, with some crops more sensitive to elevated soluble salt levels than others.

A two-year nutrient management study examined the effects of inorganic fertilizers and compost. Inorganic fertilizer applied through drip lines supplied 75 lbs nitrogen, 150 lbs phosphate, and 75 lbs potash per acre annually.

Compost incorporated at 1 or 2 inches supplied much higher nutrient levels, with 2 inches adding nearly double the nutrients of 1 inch. While inorganic fertilizer had minimal impact on salt levels, compost applications increased soluble salts significantly, with 2 inches of compost raising levels up to 1.9 mmhos/cm over two years. Higher salt levels were linked to reduced pepper yields.

To manage soluble salts, growers should regularly monitor soil levels, avoid over-application of nutrients, and use fertilizers with low salt indexes. Site selection with good drainage can promote natural leaching, while sprinkler irrigation during seedling establishment helps reduce salt stress.

Crop rotation based on salinity tolerance and targeted leaching with irrigation six inches of water removes roughly 50% of salts, 12 inches about 80% are effective strategies.

Proper management of irrigation timing and volume, considering soil texture, along with careful nutrient applications, helps maintain optimal growing conditions in high tunnels while preventing salt-related crop losses.

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