There are a number of reasons for tomato blossom end rot: –
- Too much nitrogen
- Limey or sandy soil conditions
- Variable moisture content accentuated by extremely dry or wet weather conditions
The video below includes a little information on blossom end rot with pictures of what it looks like in case you are not sure. There are other subjects covered in the video for other gardening problems but the tomato blossom end rot is one of the first covered.
All the conditions are fairly easily taken care of, nitrogen comes from the feed, compost or perhaps a mulch you have used so clearly if you are having problems with your tomatoes and suspect this to be the cause you need to moderate any supplementary feeding reducing the amount that you do or reducing the strength of the solution. If a mulch is the problem then change the type to one that does not provide nitrogen, plastic or newspaper are good options.
If your soil has a lot of lime or sand in it then you could consider using containers or growbags, alternatively you could just take more care over the soil preparation and get a lot more well rotted compost into the soil to combat its natural condition.
Watering needs to be done consistently and regularly, I would suggest 2 or 3 times a day unless of course the weather has been extremely wet in which case you probably need to stop watering completely until things get a little dryer. If you tend to experience this type of weather you should pay special attention to your soil preparation to make sure you have a situation where the soil drains easily. The objective when watering is to make sure the soil is always moist but not completely saturated as this prevents air gaining access to the plant roots.Little but often is a good rule to follow.
You may also want to consider a watering system to make sure you can meter the amount of water your plants get. The system on the left is about the best you can get in the States and although the reviews on it have highlighted a couple of minor irritations it does the job and makes sure that your plants are watered consistently.
The system available in the UK has had mostly 5 star reviews but did get one very bad review, I suppose this could have been a Friday afternoon production, but mostly the people who bought it were more than happy.
I have to be honest I use the old fashioned watering can for my plants and they are fine, but if you have a busy lifestyle and do not always have the time to water your plants then a watering system for you is a must have.