Boiling Water or Steam as Forms of Thermal Control – Brayden Connor
Introduction
The use of high temperatures to control weeds is common in both large farming operations as well as small gardens or plots. Flamers, infrared radiation, as well as hot water or steam all are efficient at destroying plants and preventing seeds from germinating. Pouring boiling water onto soil or plants will instantly kill any cells it touches by denaturing the proteins and bursting cell walls (Ascard et. al. 2007). When controlling or killing weeds or plants using high temperatures a risk of starting a fire is constantly present but using boiling water or steam solves this problem.
Fine Tuning
Control can be gained by using the boiling water as a foliar spray, onto the soil surface or injected into the soil followed by tillage to work it into the soil. Signs of plant damage such as leaf colour change appears within minutes of application (Ascard et. al. 2007). Multiple applications will have the greatest effect on the plants if one application does not have the desired effect.
Considerations
Although boiling water seems not very practical to use for large areas steam offers some advantages over water. Steam can be sprayed at much higher temperatures to reduce the contact time needed to kill the plant (Ascard et. al. 2007). Ascard et. al. also state in their article how perennial plants seemed to regenerate making multiple applications necessary (2007).
Costs
For small areas boiling water and steam have next to no cost at all other than the cost to purchase a teakettle or other boiling device. Using hand bottles as foliar spray will also allow much more selectivity than pouring into the soil. Boiling water as a means for controlling weeds in large fields can be extremely costly, and inconvenient, some drier areas may be completely unable to adopt this method.
Opinions
Boiling water is an inexpensive, easy, and environmentally friendly way to control weeds in small gardens. It allows selectivity and flexibility for what plants you want to kill and which plants you want to keep safe while using hand sprays or nozzles. Large-scale applications in fields or large plots will not allow selectivity forcing producers to use this technique only to burn off a field for a mass kill.