Agriculture Reference
In-Depth Information
Gravity-fed applicators
use the size of the nozzle orifice and the pres-
sure created by gravity to regulate the output of fumigant. Constant speed is
necessary to maintain a uniform delivery rate. In most applicators, a constant
head gravity flow device keeps the pressure at the orifice(s) constant as the
tank or container of fumigant empties. Needle valves, orifice plates or discs,
and capillary tubes are used to adjust the flow rate.
Low-pressure fumigators usually use the soil itself or water to keep the
fumigant from vaporizing and moving off target too quickly. Some of the
methods used are:
•
soil injection
•
soil incorporation
•
drenching or flooding.
1. Soil Injection
Soil injectors use a variety of mechanisms to insert the fumigant into the
soil (usually to a depth 6 inches or more) and then cover the area with soil
again to seal in the fumigant.
Figure 8.19
shows an operator using a soil
injection chisel.
2. Soil Incorporation
Soil incorporators are used when applying low-volatility fumigants. The
fumigant usually is sprayed onto the soil surface. The area is immediately
cultivated, usually to a depth of 5 inches or less, and then compacted with a
drag, float, or cultipacker. Power-driven rotary cultivators are also used.
3. Drenching or Flooding
This method uses water as a sealant. The fumigant may be applied in the
water as a drench.
Equipment used depends on the size and timing of the application. It may
be applied with a sprinkling can, sprinkler system, or irrigation equipment,
or the fumigant may be applied by spraying the soil surface and immediately
flooding the area. The depth of the water seal (usually 1 to 4 inches of wetted
soil) depends on the volatility of the fumigant.
The principal mechanisms include:
•
chisel cultivators, blades, or shovels
•
sweep cultivator shovels
