How Can You Control Plant Disease By Soil Management

Prevention is the best defense against soil borne diseases. Strict quarantine systems will restrict the transfer of soil borne pathogens from one area to another. Elimination of the host crop from the infested field will help in cases where no alternate hosts are available.

Crop rotation and tillage practices can be used to help control a disease by growing non susceptible plants for several years between susceptible crops, and by burying plant residues on which fungal spores might overwinter. By preventing the splashing of soil onto foliage during rainstorm, mulches can reduce the transmission of soil borne diseases.

Plant Disease - Soil Science - Soil management

Soil pH

Regulation of soil pH is effective in controlling some diseases. For example, keeping the pH low (<5.2) can control both the actinomycete caused potato scab and the fungal disease of turf grass known as spring dead spot. Raising soil pH to about 7 can control clubroot disease in the cabbage family, because the spores of the fungal pathogen germinate poorly, if at all, under alkaline conditions.

Air and Temperature

Wet, cold soils favor some seed rots and seedling diseases, known as damping-off. Good drainage and planting on ridges can help control these diseases. High levels of ammonium nitrogen tend to increase wilt diseases caused by Fusarium fungi. Steam or chemical sterilization is a practical method of treating greenhouse soils for for a number of pathogens. 

Plant Pathogens

Solarization, the heating of soil under clear plastic sheeting, is a practical way to partially sterilize the upper few cm of soil in some field situations. It should be remembered, however, that sterilization kills beneficial microorganisms, such as mycorrhizal fungi, as well as pathogens, and so may do more harm than good.

Disease - Suppressive Soil

Research on plant diseases ranging from take-all of wheat to Fusarium wilt of bananas documented the existence of disease-suppressive soils, in which a particular disease fails to develop even though both the virulent pathogen and a susceptible host are present. The reason that certain soils become disease suppressive is not entirely understood, but much evidence suggests that the pathogenic organisms are inhibited by antagonism from certain beneficial bacteria and fungi.

In some cases, diseases suppressiveness has developed through long-term crop mono culture in which the buildup of the pathogen during the first few years is eventually overshadowed by a subsequent buildup of specific organisms antagonistic to the pathogen. In other cases, the addition of large amounts and varied types of decomposable organic materialsm sometimes combined with lime, encourages a high level of microbial activity and diversity.

Plant disease - Soil Science and it's management

Scientists in California have discovered that rotating cauliflower with broccoli can provide a practical means of controlling verticillium with a serious disease of cauliflower, even in fields where the disease causing fungus is present. The leaf residues left after broccoli harvest break down in the soil to release glucosinolates and other volatile compounds specifically toxic to the Verticillium dahliae fungus, which cause the disease in cauliflower. The level of disease control was equal to that achieved using two conventional toxic fumigants.

Induced Systemic Resistance

The role of soil ecology in protecting plants from disease is not limited to below ground infections. Beneficial rhizobacteria have an intriguinf more of action called induced systemic resistance, which helps plants ward off infection by diseases or insect pests both above and below ground. The process begins when a plant root system is colonized by beneficial rhizobacteria that cause the accumulation of a signaling chemical. The chemical signal is translocated up to the shoot, where it induces leaf cells to mount a chemical defense against a specific pathogen, even before the pathogen has arrived the scene. The mechanism has been shown to effectively reduce damages by numerous fungal, bacterial and viral pathogens and several leaf-eating insect pests.