Soil Chemistry and Agronomic Biofortification for Improved Human Health.

Declines in soil quality and the concept of peak soil have been proposed as mechanisms for a possible decline in the nutritional value of foods over time. A variety of factors including simple depletion of plant nutrients to excessive use of fertilizers and even genetically modified crops are listed as possible contributing factors. Nutritional value is determined by the concentrations of minerals, vitamins, protein, amino acids, anti-oxidants, and many other constituents, in the edible portions of plants. Credible surveys do suggest that concentrations of Ca, P, Fe, Mg, Cu, Na, K, protein, riboflavin, and ascorbic acid may have declined in fruits, vegetables, and grain over time. However, the extent to which soil quality or nutrient depletion played a role is difficult to determine given that cultivars, changes in use of fertilizers, changes in agricultural practices, increased use of irrigation, and even increasing atmospheric CO₂ concentrations can all influence plant composition. Crop yields have increased dramatically in the past 50 years and simple mass balance would suggest soil depletion for any element not replaced through fertilization. Clearly in some developing countries significant human health effects from vitamin, Fe, I, and other mineral deficiencies exist and can be related to diet and/or soil characteristics. In many areas of the world, the fortification of food with vitamins and minerals and consumption of dietary supplements would offset declines in the nutritional quality food. Further, changes in dietary preferences and food availability make it difficult to elucidate the influence of soil quality on per capita nutrient intake. The entire nutrition value chain, from nutrients in the soil to human consumption, has multiple entry points for enhancing the nutritional quality of food including soil and foliar fertilization, biofortification, fortification, and human vitamin and mineral supplementation. Sustainable intensification can play an integral role in addressing nutrition issues.