Nutrient use efficiency

Abstract

Much of the recent gains in global crop production have been underpinned by greater use of fertilizer, especially nitrogen and phosphorus, and continued improvements in plant nutrition will be needed to meet the increasing demands for food and fiber from a growing world population. Climate change presents many challenges to improvements in nutrient use efficiency by its direct effects on the growth and yield of plants, and hence on nutrient demand, and by its influence on soil nutrient cycling, nutrient availability, and uptake. However, the consequences of climate change on plant nutrition are difficult to predict because of the complexity of the soil–plant–atmosphere system. Empirical data suggests that enhanced as well as reduced nutrient availability and uptake may occur as a result of climate change, depending on the nutrient in question and the component of the climate that changes. Notwithstanding the uncertainty of the effects of climate change on soil nutrient availability and plant nutrient uptake, improvements in nutrient use efficiency will be required to sustain productivity into the future.Over significant areas of the world’s arable land, high inputs of nutrients have increased soil nutrient reserves and fertilizer use efficiency is low, while in other regions, impoverished soils and low rates of fertilizer use have limited the capacity of farmers to provide adequate amounts of nutritious food. Developing varieties with enhanced nutrient use efficiency provides a way of improving productivity in both situations, although the traits that are targeted may differ. The two pathways by which nutrient use efficiency can be improved are by better uptake efficiency or by enhanced utilization efficiency. The relative importance of these strategies will reflect the amount and availability of nutrients in the soil. Genetic variation in nutrient use efficiency in plants is well documented, but improvements in nutrient use efficiency in the major food crops so far have been modest. Reasons why progress has been limited include inconsistent and sometimes confusing definitions of nutrient use efficiency, incomplete understanding of the genetic and physiological bases of differences in nutrient use efficiency, lack of field validation of assays, and little consideration of genotype × environment interactions in the expression of nutrient use efficiency. However, currently a powerful array of molecular and genomic techniques promises considerable advances in understanding nutrient use efficiency and developing varieties that are more nutrient efficient. Combined with traditional disciplines of plant breeding, crop physiology, and agronomy, new opportunities are developing to study genetic differences in nutrient use efficiency and to allow agriculture to meet the challenges of increased production of quality grain in a variable environment.