CAN POTASSIUM APPLICATION AFFECT THE MINERAL AND ANTIOXIDANT CONTENT OF HORTICULTURAL CROPS?

Authors: Perkins Veazie, Penelope; ROBERTS, WARREN - OKLAHOMA STATE UNIV.

Submitted to: Proceedings of Symposium Fertilizing Crops for Functional Foods
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2003
Publication Date: 6/1/2004
Citation: Perkins Veazie, P.M., Roberts, W. 2004. Can potassium application affect the mineral and antioxidant content of horticultural crops? Proceedings of Symposium Fertilizing Crops for Functional Foods. (2)1-5. Available: http://www.ppi-ppic.org/ppiweb/FILELIB.NSF/0/FF0ADD280165677485256EB60061DA6B/$file/FCFF-Chapter2.pdf.

Interpretive Summary: Potassium has important functions in the human body and may also help lower blood pressure. Potassium was approved as a health claim by FDA in 2000. This means that foods meeting certain specifications and containing at least 350 mg potassium per serving can apply for the use of this health claim. Potassium has important functions in plants as well. Application of potassium fertilizer can enhance the potassium content of fruits and vegetables and the amount of vitamin C and carotenoids such as lycopene and b-carotene. Potassium (potassium chloride) was applied as to watermelon at 0 to 3 times recommended rates to watermelon plants and measurements of quality and yield were made. Yield and fruit diameter decreased and rind thickness increased in plots where 2 and 3 times the recommended rates were used. Lycopene content did not change at the high rates, and was highest in melons from plots where 0.5 the recommended rate was used. These results indicate that high rates of potassium fertilizer affect watermelon fruit quality and may decrease yields.

Technical Abstract: As consumers become increasingly aware of the importance of diet in avoidance of chronic diseases, the content of vitamins, minerals, and antioxidants in fruits and vegetables can greatly affect consumer demand. In humans, potassium is needed to regulate enzyme function, enable muscle contraction, and transmit nerve impulses. Increased potassium intake may lower hypertension. Good sources of potassium from fruits and vegetables are bananas, melons, tomatoes, potatoes, squash, citrus, and spinach. Potassium has multiple enzymatic and catalytic functions in plants. Increased potassium `fertility has been reported to decrease b-carotene and increase lycopene content in tomato, and enhance the levels of vitamin C and carotenoids in carrots, tomatoes, and citrus. Additionally, the U.S. Food and Drug Administration has approved the use of potassium as a health claim if the food contains at least 350 mg potassium, less than 140 mg sodium, no more than 20 mg cholesterol, no more than 3 g saturated fat, and no more than 15% of calories from saturated fat per serving. Several fruits and vegetables qualify for this health claim. The effects of potassium fertility on watermelon was studied to determine if modification of commonly accepted farm practices can enhance potassium content and lycopene of fruit without negative effects on quality.