Question
Mike,
My Garden is located in Golden, CO and is in the sun filled south side of my property. In past years, I have had excellent tomatoe crops, with enough to share with friends and fill all of my canning jars. However this year, the plants are producing smaller fruit, about 1/2 the size of normal. I used the same type of seeds (Park's Early Girl & Sweet 100's)and the same 5-15-5 fertilizer as last year. The plants are now growing out the top of their 5' cages with less than an average amount of small green fruit and they continue to set flowers. I just hope it dosn't snow before they rippen up!

We have had several opions offered around the dinner table as to what happened this year and what to do about it:

1. I think the wet cool spring slowed the plant development and I didn't get enough phosphorus to the plants (simply put, too much nitrogen not enough phosphorus, too much water). The only thing to do about it is to try again next year and get the tarp out to cover the plants as the cold nights are nearing.

2. My wife thinks we should trim back the plants to promote fruit development. (I hate this idea, seems way wrong to cut back something you have worked on since late March!)

3. My girls said we sould have planted plum tomatoes! (I guess, they just like those, forgot to order those seed this year). Hmmmmmm.

So Mike, what's your thoughts, why the small fruit and is there any action to correct or salvage it this year?

Jim Fleming
Golden CO

Answer
Jim, this has been a common problem through many parts of the country this year.  Your first assessment is right on the mark.  When roots become water-logged, it inhibits their ability to draw in the necessary nutrients for proper growth.  

As you mention, the primary nutrient needed for larger fruit is phosphorus.  Both phosphorus and potassium are quickly depleted in poor draining soils.  You would have needed to supplement the soil much earlier in the season for it to have had any effect.  Unfortunately, there's not much that can be done at this stage in the season.

Next year, you can try building up the soil by supplementing it with organic amendments.  I personally have 12" raised beds filled with organic matter such as aged manure, peat moss, shredded leaves, and compost.  The raised soil improves drainage, reducing the likelihood of damaged roots.  The organic matter provides a constant source of balanced nutrients through the year.  I only fertilized once all year, and was fortunate enough to have large tomatoes despite the heavy rains.

By the way, I applaud your daughters' choice of paste tomatoes, but they too would have suffered due to the poor drainage and depleted soil.

I hope this answered your question.  Enjoy the rest of the season.

Regards,

Mike