An Unintended Consequence of Increasing Crop Yields.

Increasing agricultural productivity has long been the central goal of crop scientists. Their successful doubling or tripling the yields of major food crops is considered a great triumph. However, there is growing evidence that increased yields tend to decrease concentrations of many nutrients. Early experiments with fertilizers and irrigation found “dilution effects” caused by yields increasing more than the uptake or synthesis of nutrients, thus diluting nutrient concentrations. Recent studies are beginning to show the extent of dilution effects under production conditions. They also reveal a new kind of dilution effect, a genetic dilution effect caused by yield increases from selective breeding instead of from environmental methods. Several studies of historical nutrient content data in vegetables and fruits show apparent median declines of 5% to 38% over about 50 years, affecting about half of the studied nutrients (minerals, protein, and vitamins). A study of 160 years of archived wheat samples from one farm shows broad mineral declines of 23% to 49% during 35 years following the introduction of high-yield, “Green Revolution” varieties. Side-by-side plantings of low- and high-yield varieties show genetic dilution effects in wheat, corn, and broccoli ranging from 1.6% to 3.7% per decade. It is often said that we must further increase yields to solve the problem of feeding a growing population. However, one may ask, do increasing yields genuinely solve this problem, and should agricultural scientists, policy makers, and the public become more aware of the trade-offs between yield and nutrient concentrations?