Which of the following is not an effective method of sealing a fumigant into the soil?

• A. Use of plastic mulch
• B. Cultipacking
• C. Flood irrigation
• D. Light irrigation

Answer: (C)

Sealing a fumigant into the soil means creating a tight, low-permeability layer so the gas stays in the target zone long enough to work and to minimize its escape to the atmosphere. A barrier like plastic mulch forms an impermeable surface that prevents vapor from drifting upward. Cultipacking compacts the surface soil, reducing pore spaces and pathways that fumigant gas could use to move upward or laterally. A light irrigation adds just enough moisture to fill some pores and help tighten the seal without creating deep, open channels for gas to escape.

Flood irrigation, on the other hand, introduces a large amount of water that can overwhelm the seal. It can create surface runoff and soil channels, mobilize air and water flows through the soil, and carry fumigant away from the treated zone. This disrupts the barrier and increases the likelihood of fumigant loss, so it’s not an effective sealing method.