how to correct an apparent nutrient deficiency causing yellow shoulder in my tomatoes
I am new to hydroponics, when I went to the Hydo store I explained that I wanted to grow tomatoes in 20L buckets using DWC method with bubblers to each bucket. The plants (Improved Apollo)are growing in a shadehouse with polycarbonate roof. I was recommended to use Dutch Master Gold One Flower nutrient at the standard dosage. I have done this and the plants are almost at ceiling height with 5 or more trusses on each plant x (10) the fruits are looking very appealing but this is not the reality. The fruits have a very hard core under the calyx and a hard white icy looking band of flesh under the skin there is not much taste. I have done some googling and it appears that the problem is yellow shoulder caused through a potassium deficiency. Does this sound a likely cause and can I do anything to rectify it? I do hope you can help me I am finding it difficult to find an experienced person to give me a bit of guidance. By the way I am female 76yrs of age, living in Australia in a temperate zone.
Outside United States hydroponics
I certainly do not know the nutrients contained in ‘Dutch Master Gold One Flower nutrient at the standard dosage’ but can give some suggestions. The Yellow shoulders disorder can be eliminated through a close nutritional program monitoring. Have you done any plant tissue tests on your tomatoes? Some cultivars are more susceptible than others. Be sure that yours is not one of those cultivars. What is the pH of your nutrient solution? Make sure it is not above 6.8. Does the nurtrient solution contain excess magnesium in relation to calcium? Are the growth temperatures adequate? Temperatures >90F are a predisposing factor to Yellow shoulders.
You have rightly pointed it out, insufficient exchangeable K+ triggers this disorder. Increase K+ to over 3%by dry matter depending on your tissue test results and do not wait until late to adjust K+ status of nutrient solution and pH. You could apply Potassium, Calcium or magnesium salts (Potassium Nitrate, Sulfate of Potash, Potassium Carbonate, Calcium Nitrate, Calcium Chelate, and Magnesium Oxide).