If our soils and crops have challenges with nematodes, it is because we have managed them in a way that is conducive to developing nematode populations. Soils with balanced and healthy microbial populations can completely shut down pathogenic nematodes and prevent them from becoming a problem.
The long term solution is to rebuild soil levels of microbial active carbon (not total organic matter). Rebuilding microbially active carbon can occur quickly if we manage soils to achieve that objective.
A short term solution can be to apply high application rates of humic substances, high application rates of molybdenum, and high application rates of ocean minerals. This application can shift the soil microbial population, and enhance the species that antagonize pathogenic nematodes. It is not possible to describe what a high application rate is in a one size fits all recommendation. It all depends on your context. Rates can vary significantly based on the existing soil environment.