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Does NPK fertilizer ratio matter for determinate tomatoes?

Posted by ash1970 6b (My Page) on
Mon, Jul 21, 14 at 1:29


There are all sorts of (conflicting) advice out there about tomato fertilizer NPK ratios to maximize each stage from growth through set, fruiting and harvest - especially specific (and still conflicting) for containers or hydroponics.

I'm curious whether this matters for determinate tomatoes. In other words - just how "programmed" are determinates? Would the final results - amount of leaves, stems, flowers, fruits - be about the same no matter what NPK ratio, as long as the basic macros and micros are all there available for the plant to use?

Thanks for any comments.

-- your basic top-watering, inorganic-fertilizing, container-tomato first-timer

Follow-Up Postings:

RE: Does NPK fertilizer ratio matter for determinate tomatoes?

Hi A, I am not an expert on the subject of your question. However, I did want to encourage you to continue your quest for knowledge. I have grown maters in containers for awhile...and it is quite rewarding. There are important factors like pot size, growing medium, watering, ferts, support, and of course sunlight. I have an idea as to the answer to your question. However, I will let someone more learned weigh in. have fun!

RE: Does NPK fertilizer ratio matter for determinate tomatoes?

  • Posted by Drew51 5b/6a SE MI (My Page) on
    Mon, Jul 21, 14 at 12:50

Near harvest I myself like to stress the plant, make it think it's going to die. That way it puts everything in the fruit. Works well. I limit water, and nutrients. But hey that's me! Amazing cool with stone fruits, you can boost brix by 5 points or more. With indeterminate tomatoes I really do not do it. But it seems like a good idea with determinates. With indeterminates I usually lower nitrogen once fruit is formed. At times I may boost it like with cherry tomatoes that really run nutrients through. Often producing hundreds of tomatoes on one plant. It needs to be fed. Fruits usually do not form during very hot weather so it's a good time for nitrogen. When conditions are right for fruit formation, I do limit feedings.
Dry farming is a science, and these techniques are based on dry farming practices.

RE: Does NPK fertilizer ratio matter for determinate tomatoes?

I hope Al aka Tapla answers this question. You might want to post this on the tomato forum where many of us container grow and Dave aka digdirt is very knowledgable. Personally, I feed my I determinants and determinants the same fertilizer. I might change it during the course of the season but I don't think it matters whether it's indeterminate vs determinant. Tomatoes have nutritional requirements regardless.

RE: Does NPK fertilizer ratio matter for determinate tomatoes?

Thanks everyone for the comments.

After first looking through a few posts in the tomato forum, it just seemed that here might be a bit better for a chemistry-in-a-container oriented question. But I'll repost there as advised…

RE: Does NPK fertilizer ratio matter for determinate tomatoes?

  • Posted by Drew51 5b/6a SE MI (My Page) on
    Tue, Jul 22, 14 at 23:15

I agree tomatoes have requirements, but you don't care about that, you care about the fruit. the plant will eventually be discarded. Trying to improve fruit quality at times can hurt the plant. With trees, you just fix it after fruiting. I'm trying to increase yields too, and stressing the plant a little most certainly will increase yield. Too much and you get BER etc. it is a fine, advanced technique. You should be an experienced grower I guess to use such techniques.
Measuring brix is a great way to see how you are doing, and keeping track of yield weights. If you can get over 20 pounds per plant, you're not doing bad.

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