A question that I am often asked is about the need to sterilise soil in areas where a crop is grown each year, such as tomatoes or potatoes.
The reason that a number of gardeners wish to sterilise the soil in a given area is because they believe that the process will clean up pathogens (diseases) that have occurred while growing the previous season’s crop.
Some gardeners go to great lengths to remove all the top soil from a plot or glasshouse and replace it with fresh top soil.(that is a lot of work and expense). There are also other gardeners that have reported to me that they have grown their tomato plants in the same area, year after year (one said 30 odd years) with no problems.
Some gardeners will remove their tomato plants before they start to go off, at the end of the season and send all the material to a landfill to be safe. Others let the plants die in place and even dig the decaying material into the soil where they are going to grow again next season. These gardeners feel that the dead material contains the elements that the next crop needs and the recycling of the material is of benefit. In most cases they have healthy plants year after year.
Another set of gardeners doing this, will find that they have diseases attacking the new establishing crop and will have many failures. Some gardeners do not want to take any risks and practice high hygiene standards.
If we take a situation of a tomato plant growing in the wild from a seed dropped in a bit of bird poo, that plant matures and produces fruit. The fruit rots on the ground and when conditions are right a bunch of seedlings will appear all in competition with each other.
Many of the plants will grow to maturity and repeat the cycle, year after year.
Maybe some years a disease will strike and wipe out the plants, but likely new seedlings will appear the following season and do well.
The question must be asked, how can some gardeners grow in the same area every year without problems where others must adhere to rotation cropping over a three year cycle to avoid losses?
I believe that two aspects come into play one of which is very interesting and is likely not to be considered a possibility by many. It is the power of the mind and influence your thoughts have over plants. If we have a gardener that is worried about planting his tomatoes in the same spot as last seasons crop he somehow conveys these thoughts to the new crop and maybe creates them to fail.
Another gardener may only think of the positive aspects and sees in his mind’s eye the seedlings growing strong and true and the delicious tomatoes that he will enjoy in days to come.
- Do the plants pick up these thoughts at some level we do not understand and grow to fore fill them?
- Is this the same power that we acknowledge when we say ‘that gardener has green thumbs’?
- Do these green thumb gardeners have a very positive attitude about their gardening thoughts and have formed a link with their plants to the benefit of both?
I feel that there is some truth in this and the closer one feels to nature the better the results.
On the more practical side of things, that can be measured scientifically, we can see two types of gardeners in their different methods.
One gardener will use chemical herbicides, fertilisers (without thought) and chemical sprays. The damage done by these chemicals to the soil life is great and pathogens run rife having no beneficial soil life to balance them out or control them.
Common weed killers such as glyphosate linger in the soil for months and plants growing in those treated areas will not be as good as plants of the same type grown in non treated areas.
A fact of nature is if the soil life is diminished in an area then any ensuing crops are more likely to have more health problems.
Now take the gardener who avoids the use of chemicals and may only use very small amounts of man made fertilisers as a boost for a crop at the right time. The same gardener will be building up their populations of beneficials in the soil by applying natural products of animal manures, calcium, composts and other minerals. His soil teems with life, including good worm populations and the plants growing there will be strong and more able to overcome any diseases that may be floating around.
Many gardeners over the years have used a product called Jeyes Fluid or in more recent times the same but called Natures Mate. 80 mils of this product would be added to 10 litres of water to saturate the soil in one square metre. Many gardeners swear by this but a problem has arisen that the product is no longer available to my knowledge.
Yates has a chemical sterilizing agent called Basamid which you need to be very careful in its use and it is not cheap either. One of its advantages is that it does kill most weed seeds as well as the good and bad things in the soil. After its use, plants seem to thrive in the first season from reports I have heard.
Many years ago a gardener from Invercargill gave me a solution to control the root disease of brassicas (Club Root) It is a simple recipe where you take a quarter teaspoon of potassium permanganate (Condy’s Crystals) and 3 desert spoons of table salt into one litre of warm water to dissolve, then added to a further 9 litres of water. One litre of this solution is placed in each planting hole to reduce the damage of club root. It works well for this problem.
Potassium permanganate is a strong oxidizing agent of which the sodium chloride (table salt) complements its action in soil.
Taking the aspect of how well it controls club root disease (which most other chemicals do not) then it is a logical assumption that it can clean up other diseases or reduce their number in the soil.
I have suggested in the past to gardeners that wish to clean up areas in their glasshouse or soil where a crop of tomatoes is to be grown, to use the above recipe at double the rate (half teaspoon of potassium permanganate with 6 desert spoons of salt to drench 5-10 square metres of area. Leave for a couple of weeks then flood the area with water. Once the soil has dried to moist then apply Simalith, Dolomite & Ocean Solids (for the minerals and calcium) Cover with a layer of animal manure based compost. Use Mycorrcin and Magic Botanic Liquid as a soil drench to feed and promote the beneficial soil life, after which you can plant up. Potassium permanganate from a chemist (if they have it) is expensive, selling a 25 grams amount for about $7.00 Where a number of garden centres have 150 grams for about the same price.
If you feel the need and peace of mind to sterilize a garden area and are unable to obtain Jeyes Fluid then this would be a good alternative.
On the other hand if you have the right frame of mind, looking after your soil and the soil food web then nature will work for you controlling the diseases giving you healthy plants with crops of nutritional density.