How to Recognize Nitrogen, Phosphorous, and Potassium Deficiencies in Strawberries

Determining N, P, K deficiencies in strawberries through visual observations

Identifying nutrient deficiencies in strawberries can be a tricky business. First off, disease symptoms are often similar to those of nutrient deficiencies and it can be hard to tell the two apart. Secondly, multiple deficiencies can occur on the same plant, which makes it difficult to determine which nutrient is the culprit. And as if that were not enough, damage from environmental stressors, frost and pesticides can also confuse the issue. Since nitrogen (N), phosphorous (P), and potassium (K) are considered to be the building blocks of plants, this article will focus on identifying these three nutrient deficiencies in strawberries.

Nitrogen deficient strawberriesPhoto courtesy of University of California

Nitrogen deficient strawberries
Photo courtesy of University of California

Nitrogen

Strawberry leaves that turn light green and begin to yellow are often an indicator of nitrogen deficiencies. Purpling leaves are frequently associated with phosphorous deficiencies, but they can also signal a nitrogen problem. As the nitrogen deficiency exacerbates, leaf petioles shorten, turn red, and become brittle. The yellowing of the leaves becomes more uniform over the leaf surface. Mature leaves also begin to redden. On the flip side, an excess of nitrogen can diminish the quality of strawberry fruit and open the door for certain diseases. Nitrogen deficiencies show up in middle-aged to mature growth first, because the new growth monopolizes all of the available nitrogen. For this reason, do not take tissue samples off of the new growth, rather, take them from middle-aged growth.

Phosphorous

Phosphorous is an essential nutrient for fruit production, so fruits with P deficiencies tend to be small and soft. In general, strawberries do not have a very high demand for P and shortages of this macronutrient are rare. Visual symptoms of a P deficiency are difficult to discern, and by the time they appear the deficiency has already taken its toll on crop quality and yields. In severe cases, upper leaf surfaces take on a shiny appearance and turn dark green; the undersides take on a reddish-purple cast.

Potassium

Potassium is necessary for many plant functions such as enzyme activity, photosynthesis, and water movement. Deficiency symptoms first show up on mature leaves, particularly on the leaf margins. The damage works its way inward between the veins and eventually necrosis occurs. Short, brittle petioles and leaf scorch also indicate a K problem. Other noticeable differences include decreased runner production and deteriorating fruit.

Nitrogen, phosphorous and potassium are the nutrients that plants need in the largest quantities. They are so important to plant health that plants would fail to thrive without them and death would be a certainty. The visual signals that plants manifest when nutrient problems occur are good indicators of problems, but they are not definitive. Tissue sampling is the most reliable way of determining plants’ nutrient needs. The advantage of sampling is that problems can be addressed before the plants become stressed. For strawberries, it is particularly important to take foliar samples from mature, ternate leaves (petioles should be included). A good rule of thumb is to take samples three to five leaves away from the growing point.

KeyPlex is devoted to promoting overall plant health through good nutrition. The company offers a wide range of products for berry crops. For more KeyPlex strawberry solutions, visit http://www.keyplex.com/en/crop-keycards/strawberries.html

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