Yellow Shoulder Disorder: An Issue For Tomato Growers In The Midwest

Yellow shoulder disorder was among the topics during the Ohio Produce Growers and Marketers Association annual convention on Monday. The convention was held this week in Sandusky, OH.

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Brad Bergefurd, who is with The Ohio State University Extension, discussed “Fresh Market Tomato Fertility” and mainly addressed the issues surrounding yellow shoulder disorder. Part of his message was that growers are not able to stop its spread once it sets in.

The fertility-based disorder appears to strike hybrid varieties for growers in the Midwest. Stress caused by high temperatures affects the plants, and the disorder can be triggered by insufficient exchangable potassium, excessive magnesium in relation to calcium, and soil pH above 6.7.

Bergefurd recommends doing tissue analysis of the tomato once the plant has its first flowers, specifically once a week in the mornings, with an iron meter. With the test results, growers can alter the nitrogen, calcium, potassium, and magniesum applied to reduce yellow shoulder disorder. He also recommends fertigating often, adjusting throughout the season, and at the end of the irrigation cycle, and irrigating often, as well.

Bergefurd also noted that yellow shoulder disorder is mainly seen in hybrid varieties, not heirloom.

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Avatar for Matt Matt says:

I can 100% back the fertigating with every watering. I am in south central Wisconsin and I still saw yellow shoulders on heirlooms that were not on drip tape with fertigation. I push potassium nitrate and calcium nitrate on an alternating basis and this has virtually eliminated yellow shoulders on ALL of my tomatoes. I don't apply ANY pre-plant fertilizer. I feel that the plants get better nutritional health when it is applied with the irrigation water. I am also able to reduce the amount of fertilizer I apply by 40-50%. I am not fertilizing the row middles and I can reduce the total usable applied nitrogen as well. If you follow tomatoes with Rye or alfalfa, any of the nitrogen pushed beyond the tomatos roots can be recaptured and brought back to the surface for use next season. We all need to work on using less fertilizer and prevent leeching. Drip irrigation is the best way of doing this. The fact that you get better plant health in an added bonus.

Avatar for Dr. Lux Dr. Lux says:

Since most of the quality characteristics of fruits such as firmness, color, taste, flavor, shelf life etc., are related to potassium nutrition, it might help to keep potassium levels in the soil prior to planting the crop above 300 ppm. Besides, it is crucial to keep a wide ratio of about 3:1 exchageable calcium to magnesium. Narrower ratio may tend to restrict availability to plants of potassium. To correct a narrow ratio, calcium may be added and incorporated in the soil prior to planting in the form of lime if soil is acidic or gypsum if the pH is above 7.2. These treatments will also reduce occurance of blossom-end rot in tomatoes.

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