Why are soil fumigants typically applied before planting?

Soil fumigants are applied before planting primarily because they can be toxic to plants. The purpose of these fumigants is to eliminate pests, pathogens, and weeds in the soil that could hinder the growth of crops. By applying these chemicals prior to planting, farmers ensure that the soil is free from harmful organisms that could affect the young plants as they germinate and establish themselves.

Applying fumigants before planting helps to create a conducive environment for the crop, reducing the risk of disease and competition from weeds. Given their toxic nature, applying them after planting would pose a significant risk to the crops, potentially causing harm or even death to the plants as they would already be in the soil environment interacting with the fumigants.

Other options, while they might address some benefits of soil fumigants, do not capture the critical reason for their timing in application in the context of plant safety and pest management. Cost-effectiveness, enhancing soil fertility, or improving crop yield might occur as indirect benefits, but the primary consideration for the application timing is the toxicity of soil fumigants to plants.