The recovery efficiency (RE) of crop nutrients is defined as the increase in nutrients in aboveground crop biomass per unit applied, after applying the nutrient in the form of fertilizer, manure, or another source. It is among the most critical indicators of fertilizer use efficiency because any applied nutrient not taken up by crops is prone to losses, with economic as well as environmental consequences (see our Issue Brief on Nutrient Use Efficiency).
Previously, it was thought that, on a global scale, only about 30–40% of the fertilizer nitrogen (N) applied is recovered by crops in the first year. In this new analysis, the authors compiled 2,436 pairs of observations from 407 field studies worldwide to revisit that claim.
The analysis found that the global mean fertilizer-N recovery efficiency in this dataset was 48%, i.e., higher than previous estimates. Using a data-driven modeling approach, the authors demonstrate that it could be increased to 78% mainly through optimal, site-specific combinations of nutrient (4R), crop, and soil management.
Such high levels of recovery efficiency are not utopia – many well-managed farms, for example in North America and Europe, are already achieving them. The data used in the study mainly came from Asia, North America, and Europe and included three major crops: maize, wheat, and rice. Hence, more research needs to be done to fill regional as well as crop-specific data gaps. Overall, this analysis demonstrates the global potential for achieving high productivity levels while keeping losses of N to water and air at acceptable levels.
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How about a foliar nitrogen? 90% efficient, zero ammonia volatilisation, use when crops achieve LAI 2 to2.1, eliminates losses to groundwater… can even be used to apply 30kg+ M/ha in each application. Some tank mixes with fungicides, PGRs and even SU herbicides are possible.
If the nitrogen isn’t going into the soil, then NOx gas production is also reduced. Yield increases become possible on poor soil types, and in nitrogen sensitive areas and nitrogen vulnerable zones heels can increase….