Soil Chemistry, Food Security and Human Health: Manipulating Soil Nutrient Chemistry.

In agriculture we have been manipulating soil nutrient chemistry for millenia, with the initial goal of increasing food production from soil, and more recently to also improve the nutrient density of food or improve processing before human consumption. While total additions of nutrients to soil in developed countries has plateaued or declined over the last 40 years, developing agricultural economies are still increasing use of nutrients on soil to improve crop production. It has been estimated that the global yield gaps for maize, rice and wheat could be closed in almost 75% of the area of agricultural land globally solely by increasing nutrient inputs, particularly in South America and Africa. Inefficiencies in the use of nutrients for crop production cannot be closed solely through plant breeding, but through development of new fertilizer formulations, new nutrient delivery systems, better timing of application and better placement of those new products at the right rate. In addition we must consider how to ameliorate soil constraints to root growth such as acidic soils, saline soils, sodic soils, element toxicities (e.g. boron) and develop management strategies for these issues based on sound soil chemistry. Key constraints to crop growth in many regions are now not only manifest in topsoils that are relatively more easily corrected, but in subsoils that pose challenges to effective amelioration. Subsoil nutrient decline is a less well recognised phenomenon that could pose serious limitations to crop production in future unless we develop management strategies soon. Soil chemists plays a key role in improving nutrient use efficiency and alleviating soil constraints by developing more accurate and spatially dense diagnostic tests of deficiency or toxicity, by understanding fertilizer reactions and behaviour in soil to inform development of new formulations and by providing early warning of soil degradation that could impinge on the quantity or quality of food produced.