As the name suggests, a soil drench is chemical in a liquid form that is used to drench or wet the soil under a sick plant or tree. The chemical is directly absorbed by the roots of the affected plant and is translocated throughout the plant. A number of chemicals are sold in the form of soil drenches. There are general guidelines on how to use the soil drench process for disease control in plants.
Benefits of Soil Drenching
The greatest benefit of soil drenches is to the environment and other healthy plants close to the plants or trees that require treatment. By applying fungicides, insecticides or herbicides in the form of drench, there is minimal chance of chemical drift to other plants. Though plant injections or implantations are also relatively safer for the environment, there are even fewer disadvantages related to soil drenching as compared to implantation or injection, suggests Mary Louise Flint in "Lawn and Residential Landscape Pest Control."
All soil drench chemicals have to be diluted with the recommended amount of water prior to application. Also make sure that the plant being treated is well watered, as drought stress results in slower translocation of chemical through the plants. An adequate level of moisture in soil is also critical in helping the roots absorb the chemical.
The rates of applications are listed on the product label and usually advise application by inch height of plant or by inch of trunk diameter. Make sure you know whether the trunk applications are based on the diameter or the circumference of the tree. The circumference is the distance around the trunk, while the diameter is the straight distance across trunk. To calculate diameter, multiply circumference by 0.32.
Measure and set aside the required amount of water in a bucket. In another bucket, add half of this water then mix in the measured amount of chemical. Fill bucket with remaining measured water. Mix well. Pour this mixture into the soil around the plant base or around the tree trunk. Pesticides or herbicides applied to plants in the form of soil drenches are slow to take effect, as it takes time for the chemical to move through the plant.