What are the two basic fumigant metering methods?

What are the two basic fumigant metering methods?

• A. Constant pressure plus orifice and ground-wheel-driven metering pumps
• B. Gravity feed and manual hand pump
• C. Pneumatic siphon and electronic metering
• D. Vapor balance and timer-based injectors

Answer: (A)

Fumigant metering must deliver a precise, steady amount of fumigant to the soil for effective control and to minimize off-target exposure. The two basic methods to achieve this are constant pressure with a fixed metering orifice and ground-wheel-driven metering pumps. With constant pressure plus an orifice, the system holds a steady pressure in the metering line and forces fumigant through a fixed opening. The flow rate through that orifice is predictable when pressure is stable, so the applicator gets a consistent discharge along the treatment path. This is ideal for uniform soil treatment because fluctuations in pressure don’t change how much fumigant is released per unit time. Ground-wheel-driven metering pumps rely on mechanical drive from the equipment’s wheels to move a precise volume of fumigant with each revolution or stroke. This creates a repeatable, travel-speed–dependent dosage, helping maintain consistent application even if other conditions vary. The other options don’t represent the two fundamental approaches: gravity feed and manual hand pumps don’t provide reliable, controlled flow; pneumatic siphons, electronic metering, and vapor balance/timer-based injectors involve different control concepts or timing mechanisms rather than the basic two methods described above.

Fumigant metering must deliver a precise, steady amount of fumigant to the soil for effective control and to minimize off-target exposure. The two basic methods to achieve this are constant pressure with a fixed metering orifice and ground-wheel-driven metering pumps.

With constant pressure plus an orifice, the system holds a steady pressure in the metering line and forces fumigant through a fixed opening. The flow rate through that orifice is predictable when pressure is stable, so the applicator gets a consistent discharge along the treatment path. This is ideal for uniform soil treatment because fluctuations in pressure don’t change how much fumigant is released per unit time.

Ground-wheel-driven metering pumps rely on mechanical drive from the equipment’s wheels to move a precise volume of fumigant with each revolution or stroke. This creates a repeatable, travel-speed–dependent dosage, helping maintain consistent application even if other conditions vary.

The other options don’t represent the two fundamental approaches: gravity feed and manual hand pumps don’t provide reliable, controlled flow; pneumatic siphons, electronic metering, and vapor balance/timer-based injectors involve different control concepts or timing mechanisms rather than the basic two methods described above.