Soil is the life support structure for crops as it habours components that are essential for growth, maturity and production. Its richness in these components defines its fertility which is revealed on the overall outlook of individual plants.
However much essential to the overall well being of crops these components are, some of these components are hazardous to them. The soil is the ultimate reservoir of all disease micro-organisms and pests that attack crops. It provides a habitat for harmful micro-organisms to thrive. These include bacteria, fungi, viruses and nematodes as well as mites, insects and weed-seeds.
Knowing the kind of harm these micro-organisms can cause to crops, eliminating them from the soil is definitely a priority to farmers. The horticulture industry has over the years achieved great strides in identifying and eliminating soil-related diseases. Their philosophy in addressing this challenge is tied to planting disease free crop into disease free soil and applying the practice of sanitation to prevent contamination.
It is however sad that during soil preparation farmers fail to sanitize their soil, thereby suffering the effects of pests and diseases in the process during growth and incurring losses in the end. Important to note is that by eliminating these harmful micro-organisms before planting is of much help than having to deal with them when crops are growing. Also it will give room for beneficial micro-organisms to thrive thereby increasing yields. As the old saying goes prevention is better than cure.
With the increasing emergence of resisistant pests and disease, farmers need to shift focus to prevention rather than to cure. They should purpose to eliminate them from the soil before planting.
Soil treatment is done either by use of chemicals or steam. While chemical treatment is more considered by farmers, use of steam is the recomendend practice. It was the first method to be used before discovery of chemicals and upto now it takes the winner’s slot in soil pasteurization. This is because its effectiveness and penetration can be measured by use of thermometer, there is no harzad on workers, it does not leave toxic residues on the soil and it virtually deals with all micro-organisms except those that can withstand high temperature.
As chemical treatment is most preffered, it is usually selective, some fumigants control all types of pests while others are specific for fungi or nematodes. That ‘s why soil analysis should be taken before applying. Their mode of action is that they form gases which are toxic to these pests.
Soil fumigation is applauded in dealing with diseases and pests that used to cause major economic loss threating food security. For example, verticillium wilt in potato which is caused by soilborne fungi, nematodes whose infestation leads to yield decline, viral diseases such as corky ringspot disease caused by rattle virus as well as weed-seeds.
In order to achieve good results, before carying out fumigation soil condition should be checked, the soil need to be moist but not wet, it need to be loose for gas penetration- any sod or lump need to be broken down and using compost, manure or any organic material should be avoided in order to prevent recontamination. After applying the chemical the soil should be sealed with a plastic paper.
Soil fumigation destroys a large population of microbes, the first organism to return after treatment grows without competition, hence care should be taken to prevent re-contamination. Any untreated soil, manures or mulches should not be added. Any planting material or tool should be sanitized before being introduced and farmers should ensure as much as possible to use certified, disease-free seeds or seedlings.