AGRI-BRIEFS   AGRONOMIC NEWS ITEMS

From Agronomists of the Potash & Phosphate Institute 655 Engineering Drive, Suite 110 Norcross, Georgia 30092-2837 Phone (770) 447-0335

Fall 2002, No. 1

Consumers today are seeking benefits from functional foods…foods that contain naturally occurring phytochemicals with medicinal value. Tomatoes and soybeans are examples. They contain nutraceutical compounds like lycopene and isoflavones. The health effects of many of these compounds are not yet fully understood, but science is changing that quickly.

Soybean isoflavones potentially help prevent chronic diseases including cancer, heart disease, osteoporosis, and menopausal symptoms. Isoflavones in soybean seeds function as antioxidants and antiestrogens.

Potassium influences plant composition. By governing the water flow in plant cells and by catalyzing more than 80 plant enzymes, it reduces the quality damage caused by insects and diseases and increases vitamin C in many fruits and vegetables. Long before lycopene became recognized as a functional food ingredient, science demonstrated that potassium boosts its concentration in tomatoes by as much as 70 percent.

A report in a recent issue of the peer-reviewed Journal of Agricultural and Food Chemistry confirmed a positive link between potassium fertilization of soybeans and their isoflavone content. The work showed that, particularly in low fertility soils, potassium fertilizer increased the major isoflavones – genistein, daidzein, and glycitein – by up to 16 percent. Residual fertilizer from corn grown the previous year produced about the same effect.

Managing soybeans for optimum isoflavone content demands attention to other factors including temperature, choice of cultivar, irrigation, and yield. High temperatures during the seed-filling period dramatically reduce isoflavones. Many cultivar differences occur primarily because of differences in the timing of seed-filling relative to seasonal temperatures. It’s possible that potassium boosts isoflavones by providing some degree of tolerance to such heat stress. Irrigation can enhance isoflavones, and their concentration generally increases with higher yields.

Worldwide, fertilizer use has increased the amount of calories available per capita, but micronutrient deficiencies remain widespread. In fact, it is estimated that 2 billion people are still malnourished in micronutrients and vitamins. There is a need to do a better job of supplying a nourishing diet. Agronomists can help by:

• paying attention to the growing conditions that impact crop nutritional content

• pointing out micronutrient-dense and nutraceutical-rich species and varieties of crops

• promoting balanced fertilization with nitrogen, phosphorus, potassium, secondary nutrients, and micronutrients such as zinc or manganese

• increasing production of vegetables, fruits, and legumes