The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes

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The nitrogen legacy: emerging evidence of nitrogen accumulation in anthropogenic landscapes
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Watershed and global-scale nitrogen (N) budgets indicate that the majority of the N surplus in anthropogenic landscapes does not reach the coastal oceans. While there is general consensus that this 'missing' N either exits the landscape via denitrification or is retained within watersheds as nitrate or organic N, the relative magnitudes of these pools and fluxes are subject to considerable uncertainty. Our study, for the first time, provides direct, large-scale evidence of N accumulation in the root zones of agricultural soils that may account for much of the 'missing N' identified in mass balance studies. We analyzed long-term soil data (1957–2010) from 2069 sites throughout the Mississippi River Basin (MRB) to reveal N accumulation in cropland of 25–70 kg ha−1 yr−1, a total of 3.8 ± 1.8 Mt yr−1 at the watershed scale. We then developed a simple modeling framework to capture N depletion and accumulation dynamics under intensive agriculture. Using the model, we show that the observed accumulation of soil organic N (SON) in the MRB over a 30 year period (142 Tg N) would lead to a biogeochemical lag time of 35 years for 99% of legacy SON, even with complete cessation of fertilizer application. By demonstrating that agricultural soils can act as a net N sink, the present work makes a critical contribution towards the closing of watershed N budgets.

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water quality is increasingly being put at risk due to the widespread use of
commercial fertilizers massive dead
cells are developing in coastal areas due to widespread eutrification in some
rural areas nitrate levels are more than 10 times the drinking water standards
losses are being flies to hold form was accountable for nitrate pollution and the call so dealing with these problems continue to grow
it has been estimated that it would cost 2 comma decimal 7 billion dollars per year to meet water-quality targets for the Gulf of Mexico without commercial
fertilizers we wouldn't be able to feed the more than 7 billion people on the planet nitrogen fertilizer use has
led to dramatic increases in crop yields it's actually been said that some
more than half of the nitrogen in the human body started out in a fertilizer factory what should mass balance studies have shown that
human-dominated watersheds have a persistent nitrogen subplots in other words even after accounting for nitrogen outputs from watershed in crops and surface water a large portion of nitrogen inputs remain unaccounted for new
finding this nitrogen is actually accumulating in the room owns of agricultural soils just below the plow where in fact in our study we find
that this nitrogen accumulation in the woods so can account for a large portion of the missing antigen identified in mass balance studies in this study we
analyze long-term soil data from more than 2000 sites across the Mississippi river basin and we found accumulation on the order of 140 terror grams of nitrogen and in many areas this accumulation was not
present in the upper 25 centimeters the so-called plow layer in fact in these layers of how we actually found a depletion of nitrogen in the lower layers however we found significant accumulation accumulation on the order of 50 per cent of the nitrogen surplus what
this means is that more attention must be paid to the potential for nutrient legacies throughout the soil profile Our results suggest that the legacies of nitrogen in soil and groundwater can lead to long time lags between a former taking
action and the few scale and seeing measurable improvements in water quality of the water should scale since the 19 seventies a
range of stakeholders from farmers to policymakers to conservation authorities have been working to implement best management practices to reduce the leakage of fertilizer
from agricultural fields to ground water into nearby lakes and streams unfortunately nitrate concentrations have remained stubbornly high at a practical level there's a great deal of frustration about not seeing results after conservation measures are implemented modeling results suggest that the legacy nitrogen in the landscape could be leaching into the water weighs more than 3 decades after the start applying the nitrogen to the fields such legacies must be taken into account when attempting to understand long-term nitrogen dynamics and when setting policy calls regarding improvements in water quality to help set policy golds it is critical to quantify these legacies and time lags in human impacted landscapes across the world