Nutrient Management Research Database

Potassium Requirements for Maximum Yield and Quality of Processing Tomato

Crop: Tomato

Soil Type:

State: California

Year: 1999

Hartz, T.K.

Uneven ripening is a common problem in California; the external symptom is called yellow shoulder. Uneven ripening can render the fruit unsuitable for use in diced or peeled tomato products. Potassium nutrition is linked to fruit quality and yield, and this work assessed the influence of potassium nutrition on tomato quality. Results indicate that high levels of potassium may be required to reduce fruit color disorders, especially if soils have high potassium fixation. To reduce field color disorders, potassium may need to be applied in excess of what is necessary to achieve maximum yields, making it potentially cost prohibitive to apply potassium to that degree. Potassium status does play a dominant role in contributing to uneven fruit ripening. Exchangeable soil potassium and soil cation balance were correlated with yellow shoulder and internal white tissue. Soil test suggest that fields with a potassium to magnesium ration of greater than 0.25 saw reduced levels of yellow shoulder and internal white tissue, meaning that the tomato industry can use these guidelines to test soils for the relative danger of uneven ripening and apply the appropriate soil amendments.

Field trials, tissue, and soil samples were conducted to determine the relationship between potassium status and yellow shoulder or uneven ripening. 140 tomato fields were surveyed in 1996 and 1997, as well as field trials in 1996

To reduce the risk of yellow shoulder and internal white tissue, growers may have to add potassium amendments in access of what is necessary to maximize yields. This may prove to be financially prohibitive, unless growers are getting a price premium for increased fruit quality.

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