Soil Fertility and Plant Nutrition in High-Yield, High-Efficiency Crop Production Systems.

Crop yields per hectare must increase rapidly in the next 20-40 years due to increasing world population, increasing income to support improved diets, and decreasing arable land per capita.  Sustainably increasing yields requires enhanced soil fertility management to realize crop genetic yield potentials. The objectives of this paper are to discuss: (1) our current fertilizers and their production and properties; and (2) outline opportunities and challenges that confront our soil fertility science and industry communities. Selected crop yields have increased dramatically during the past 50-75 years due to improved genetic, agronomic and plant nutrition practices.  Current fertilizers have provided a means to supply crops with needed nutrients, but our current fertilizer molecules have been known for many years, and efficiency of nutrient use is less than desirable in many situations.  Future crop yield increases for specific locations must occur within roughly the current growing season length, and thus higher-yielding plants must have higher growth rates and associated higher uptake rates of nutrients and water. Our challenges are to determine needed nutrient concentrations and placements to produce diffusion and mass flow rates that will produce the needed nutrient supply rates.  Opportunities are associated with the potential to develop new fertilizer molecules that deliver nutrient ions to plants with reduced soil interaction and/or leaching loss potentials, new placement and timing techniques, and/or crop plants with root architectures that explore increased soil volumes and have higher nutrient uptake rates.  Failure to increase food supplies with sustainable production programs will lead to increased hunger and malnutrition as well as increased environmental degradation and political instability.  Our profession must embrace the opportunities and have innovative thinking and enhanced experimental techniques to meet the challenges