Nutrient Declines Caused by High-Yield Crop Varieties and Intense Cultivation
Donald R. Davis, PhD
Format: Download Video of Slides & Audio
We will review growing evidence that ongoing increases in crop yields per acre have the unintended consequence of decreasing concentrations of nutrients, especially minerals. The nutrient declines are caused primarily by what is called the "dilution effect." It occurs whenever a plant can more easily add bulk than it can absorb additional minerals or make extra vitamins and other nutrients. The increased bulk dilutes nutrient concentrations, so we must eat more food and calories to obtain the same nutrients. Agricultural scientists discovered the diluting effect of fertilizers decades ago and frequently cite it, but it is surprisingly unknown to others. Recently, a new kind of dilution effect has been found, a "genetic dilution effect" in which increased yield comes from selective breeding or hybridization. So far it is proven in wheat, corn, and broccoli. High-yield, "green revolution" wheat varieties introduced in the 1960s show 25% to 50% declines in most minerals. Since 1950 broccoli head size and yield have increased, but mineral concentrations have broadly declined. Several studies of historical nutrient content data in vegetables and fruits show median declines of 5% to 40% over about 50 years, affecting about half of studied nutrients (minerals, protein, and vitamins). Further increases in crop yields are widely touted as a means to feed a burgeoning world population, despite nutrient declines and the fact that yield increases are not a genuine solution to excessive population.