Overtime, soilborne pathogens and weeds can become problematic in high tunnels and lead to a decline in crop yield and quality. From late spring through early fall, air temperatures inside Kentucky high tunnels can be very warm and even hot. For this reason, soil solarization can be integrated with other high tunnel management practices already in use.
Soil Solarization and its Advantages
Soil solarization is a sustainable, chemical-free method to help manage biotic soil issues, such as weeds or weed seeds, plant-parasitic nematodes, and soilborne pathogens. To solarize soil, clear plastic tarps are placed on irrigated soil to trap heat from the sun. When solar radiation is trapped under the plastic, it raises the soil temperature, especially in the top few inches. When soil temperatures reach or exceed 104°F, many organisms are weakened or killed.
How to solarize the soil
- Step 1: Prepare the soil. Soil must be smooth. Avoid clods and debris, which can slow soil heating, prevent the tarp from fitting tightly across the surface, and potentially create holes in the plastic tarp over time. Use a rototiller and/or disc to manage weeds beforehand and to create a smooth soil surface. It may be necessary to rake the soil smooth after tillage.
- Step 2: Irrigate the soil to 70% of field capacity. Soil moisture is crucial in order to transfer heat through the soil profile and reach the high temperatures needed for effective solarization. Ideally, a moisture sensor or tensiometer buried 6 inches deep should be used to confirm soil moisture. However, if those tools are not available, irrigate until the soil is very moist, nearly muddy to a depth of 6 inches. Closely spaced (one foot apart), drip irrigation tape will provide the most uniform soil moisture, but sprinklers may be used for a faster setup.
- Step 3: Lay a clear plastic tarp over the recently irrigated soil, with the edges pulled tight to maintain close contact and prevent air pockets from forming. It is recommended to use thin transparent polyethylene, 1 to 6 mil thick. Plastic should be clean, undamaged, and transparent to improve heat transfer and to reach the high temperatures necessary for effective solarization. It is important that there are no air pockets and that heat does not escape. One option to secure all sides of the tarp, is to dig a trench around the perimeter of the solarized area and bury the edges to ensure that the edges are completely sealed. Sod staples can help to secure the plastic tarp to the soil.
- Step 4: Finally, cover the edges of the tarp with soil to ensure that hot air does not escape through the sides and that the tarp is well-sealed. This traps heat, allowing soil temperatures to increase.
Source : uky.edu