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bower · August 31, 2017

Here's an interesting link about "yellow shoulders":
http://agdev.anr.udel.edu/weeklycrop...omato-ripening

".. We measured fruit (pulp) temperatures of between 86o and 105oF morning through evening hours in July. When temperatures are greater than 85-88oF lycopene is not produced. Temperatures need to drop below 85oF before it is consistently produced. Inside the plant we see a reduction in potassium (K) just before yellow shoulders is seen. This year in our tissue testing we saw drops in K of 3-4% in a matter of weeks going from 4-6% (which is good) to 2-3% (which is poor). Usually within a week or two of this drop we see yellow shoulders start up. There are also drops in calcium (Ca), nitrogen and at times magnesium (Mg)..."

"We see the same problems in high tunnels; only we see them a month earlier than in the field. For now, best recommendations are to add more potassium and calcium to plants and make sure plants are well watered. You can add either nutrient through the drip or as foliar sprays. Foliar sprays will help, but it is difficult to raise the potassium levels 2-4% points as would be needed. I have found that boron also plays a role in helping with the uptake of K, Ca, sulfur and Mg, but all the data are not in at this time to make a recommendation..."

I would like to know what you did with ferts, AKMark, to solve the problem!
I managed to find some soluble high K ferts but it was obviously too late for fruit that had already grown to full size in a deficient condition.

This article also says:
" One unusual way of avoiding the problem all together is to harvest tomatoes when pink color is first seen and let the fruit ripen at room temperature in the dark. Because the lycopene is produced as the fruit ripens it is often possible to avoid yellow shoulders by removing the fruit from the high temperatures and other stresses. "
But I'm not sure that would work, where the potassium deficit (from any cause) has already affected the fruit during setting and growth.

It might help if the cause (heat) has just kicked in when they're ready to ripen.

August 31, 2017	#18
bower Tomatovillian™ Join Date: Feb 2012 Location: Newfoundland, Canada Posts: 6,793	Here's an interesting link about "yellow shoulders": http://agdev.anr.udel.edu/weeklycrop...omato-ripening ".. We measured fruit (pulp) temperatures of between 86o and 105oF morning through evening hours in July. When temperatures are greater than 85-88oF lycopene is not produced. Temperatures need to drop below 85oF before it is consistently produced. Inside the plant we see a reduction in potassium (K) just before yellow shoulders is seen. This year in our tissue testing we saw drops in K of 3-4% in a matter of weeks going from 4-6% (which is good) to 2-3% (which is poor). Usually within a week or two of this drop we see yellow shoulders start up. There are also drops in calcium (Ca), nitrogen and at times magnesium (Mg)..." "We see the same problems in high tunnels; only we see them a month earlier than in the field. For now, best recommendations are to add more potassium and calcium to plants and make sure plants are well watered. You can add either nutrient through the drip or as foliar sprays. Foliar sprays will help, but it is difficult to raise the potassium levels 2-4% points as would be needed. I have found that boron also plays a role in helping with the uptake of K, Ca, sulfur and Mg, but all the data are not in at this time to make a recommendation..." I would like to know what you did with ferts, AKMark, to solve the problem! I managed to find some soluble high K ferts but it was obviously too late for fruit that had already grown to full size in a deficient condition. This article also says: " One unusual way of avoiding the problem all together is to harvest tomatoes when pink color is first seen and let the fruit ripen at room temperature in the dark. Because the lycopene is produced as the fruit ripens it is often possible to avoid yellow shoulders by removing the fruit from the high temperatures and other stresses. " But I'm not sure that would work, where the potassium deficit (from any cause) has already affected the fruit during setting and growth. It might help if the cause (heat) has just kicked in when they're ready to ripen.