Developing Crop Varieties with Improved Nutrient-Use Efficiency

As one of the cheapest agricultural inputs ($200-400 per Ha) nutrient (NPK) fertilizers tend to be applied in excess of crop needs. Since all crops are heavily fertilized directly or from the rotational crop residue high nutrient use efficiency (NutUE) during high soil concentrations is the metric commonly targeted for improvement by breeders and biotechnologists in this field.  NutUE is often defined as the percentage of fertilizer nutrients recovered by a crop. NutUE  is the product of many components. On a coarse  scale NutUE is determined by  nutrient productivity (NutP) and the mean residence time of nutrients (MRT). In turn they are expressions of: 1. Nutrient uptake efficiency;  2. The fraction of the nutrients translocated to the seed;  3. The translocation index; 4. Soil supply efficiency; and 5. Developmental efficiency. Consequently on a fine genomic scale thousands of genes and hundreds of regulatory networks contribute to NutUE from seed germination to final harvest in the plant and hundreds more to the microbial activity in the soil. Improvement of cereal NutUE could enable practices directed toward reducing ground-water and coastal-water contamination by N, P and K. The decreased undesirable environmental effects and reduced dietary intakes could decrease several environmental, human and animal health problems. For brevity this presentation focuses on genes and regulatory networks with major effects on NutUE with an emphasis on patented technologies near commercialization and pending patents. Enhanced NutUE by plants should enable crops to be cultivated under low nitrogen availability, slow and  “intelligent” release fertilizers, water and biotic stress conditions or poor soil quality.