Getting Rid of Tomato Diseases in Containers

Q. I grow tomatoes in boxes I have built. I know one is supposed to plant tomatoes in a different place every year and I don't want to just throw away the dirt in these boxes. I don't have many places to put this dirt so my question is, “Can I put this dirt in my compost bins?”  
I have two cement block bins. What, if anything can I do to that dirt in order to use it in the same boxes next year at planting time? It's expensive to buy all new dirt and I am poor.

A. Being poor is a good reason to grow your own food. I wish more poor people did it. If you want to grow tomatoes in the same soil year after year, it is probable you will have increased problems down the road if you don't do something about it. In our climate, problems are mostly due to accumulation of soil diseases over time.

            Growing different crops in this same soil helps reduce this problem and is called crop rotation, an important practice in organic vegetable production. By growing different crops from different families in the same soil, we help in interfering with this buildup of disease problems.

Tomato foliage disease, probably early blight.

            In the off season when you're tomatoes are not in production you could put some cold weather vegetables in that soil until you are ready to plant tomatoes again. This can be radishes, beans, beets, broccoli, lettuce, spinach, endive and the like. This will help to reduce the disease cycle but, unfortunately, soils need a bit longer rest from the same crop than just one season of production.

            You can solarize this soil by using the sun and this will help to reduce some of the disease potential. If these are small boxes, moisten and put the soil in a clear plastic bag for a few days in full sun and let it bake. If you can get the temperature of the soil in the plastic bag over 165°F for at least 30 minutes you will substantially reduce disease problems.

Nice pic and discussion on solarization from Ventura County Extension

            While you're at it and the soil is removed, you should surface sterilize the sides of boxes as well. You can sanitize them using a bleach solution or other sanitizer.

            If the boxes are too large to do this, after you're tomatoes are finished for the season, spade the soil deeply with a spading fork and turn it over. Make sure it is well aerated and as ‘fluffy’ as possible.

            Do not turn the remaining tomato plants over in the soil and decompose them that way. Remove and compost them, solarize them or discard them if you can't compost them.

            Moisten the soil lightly and cover it with clear plastic making sure the edges of the plastic are buried and the plastic is sealed around the edges. Let it bake in the sun for several days.

            Regardless of whether you took the soil out of the box or not, amend it with more compost and a starter fertilizer and replant. And by the way, if the containers are emptied, wash down the inside and sterilize it with a 10% bleach solution and let it air dry before you fill it again.