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Gardening with Jack: Solarisation

By Jack Hardy

Hundreds of years ago in mediaeval times it was known that growing the same crop in the same area of land was unproductive. A rotation system was established so three areas grew distinctly different crops while the fourth lay fallow and was manured by cattle or other livestock. Each growing season the crop location changed so that diseases peculiar to one crop did not affect the next.

In modern times with modern fertilizers it is not necessary to have a fallow season but it is wise for gardeners to employ a rotation system so that once tomatoes have been grown in one area they are not sown again until three years have passed. A garden quartered into the growing of four different crops will remain healthy and productive for years. One suggestion for the crops could be 1 Tomato family, 2 Cucumber family, 3 Cabbage family, and 4 Lettuce and everything else.

OK, now let’s get back to Abaco and the real world. You would need a big garden to employ an efficient rotation system. Most of us do not have a big garden and we therefore plant tomatoes (or whatever) where we have grown them last year. Our growing season is long compared to northern climes and we need three or four different locations in which to raise our successive tomato crops. In plain terms, the rotation system is impossible to apply in small gardens with long growing seasons.

Mediaeval farmers knew nothing about nematodes but their crops were destroyed by them if the rotation system was not used. Nematodes are worm-like creatures that are by far the most abundant of all living things. Pin worms are nematodes, as are heart worms in animals. The ones that affect our soil are microscopic and cannot be seen. Their effects are obvious, however. If you have ever pulled a tomato plant that had ugly, swollen and twisted roots you were handling billions of tomato root-loving nematodes.

Nematodes that infest tomato roots cut off water and nutrients from the plant and it dies. These same nematodes do not attack other plants. Grow cucumbers, cabbages or onions in the tomato space and the new plants will not be affected – until next year when the nematodes that like their roots have massed in sufficient numbers.

Is there anything we can do about nematodes? Yes, but not by using a vermicide. The answer is to use the sun to heat up the soil and cause nematodes to die. This is achieved by laying down clear plastic sheeting. The process is called solarisation.

We all know that black surfaces grow hotter in the sun than white but for the purpose of solarisation we need clear plastic. The sun shines through and heats the earth far more efficiently than a layer of black plastic. Standard and Ace Hardware have the plastic sheeting you need. Get the thickest gauge you can afford and you will be able to use the already trimmed-to-size sheets for years.

The hardest job is to weed the area before laying sheeting, but once you have weeded and covered the ground you will not have to weed again until near Christmas. Cut the sheeting to cover your selected area, allowing an extra foot in all directions. Water the garden very well and then lay your sheeting.  Hold it in place with lengths of 2×4 lumber or rocks. Your garden will not look pretty but it will be improving.

Every week or so you can fold back the sheeting and water the ground deeply. If you know a rainy period is coming you can get nature to do the job for you. Water allows heat from the sun to penetrate deep into the soil.

Solarisation will not kill all nematodes but will keep the infested area under control. When October comes and you remove the sheeting you should still follow the rotation principle as far as possible.

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