Editing Nutrient management (section)

====Prevention of the build-up of high soil nitrate concentrations====
Nitrate is the form of nitrogen that is most susceptible to loss from the soil, through [[denitrification]] and [[leaching (agriculture)|leaching]]. The amount of N lost via these processes can be limited by restricting soil nitrate concentrations, especially at times of high risk. This can be done in many ways, although these are not always cost-effective.

=====Nitrogen rates=====
Rates of N application should be high enough to maximize profits in the long term and minimize residual (unused) nitrate in the soil after harvest.
* The use of local research to determine recommended nitrogen application rates should result in appropriate N rates.
* Recommended N application rates often rely on an assessment of yield expectations – these should be realistic, and preferably based on accurate yield records.
* Fertilizer N rates should be corrected for N that is likely to be [[Mineralization (soil science)|mineralized]] from [[soil organic matter]] and crop residues (especially legume residues).
* Fertilizer N rates should allow for N applied in manure, in irrigation water, and from atmospheric deposition.
* Where feasible, appropriate [[soil test]]s can be used to determine residual soil N.

=====Soil testing for N=====
* Preplant soil tests provide information on the soil's N-supply power.
* Late spring or pre-side-dress N tests can determine if and how much additional N is needed.
* New soil test and sampling procedures, such as amino sugar tests, grid mapping, and real-time sensors can refine N requirements.
* Post-harvest soil tests determine if N management the previous season was appropriate.

=====Crop testing for N=====
* Plant tissue tests can identify N deficiencies.
* Sensing variations in plant chlorophyll content facilitates variable rate N applications in-season.
* Post-black-layer corn stalk nitrate tests help to determine if N rates were low, optimal, or excessive in the previous crop, so that management changes can be made in following crops.

=====[[Precision agriculture]]=====
* [[Variable rate application]], combined with intensive soil or crop sampling, allows more precise and responsive application rates.<ref name="Basso2016">{{cite journal|last1=Basso|first1=Bruno|last2=Dumont|first2=Benjamin|last3=Cammarano|first3=Davide|last4=Pezzuolo|first4=Andrea|last5=Marinello|first5=Francesco|last6=Sartori|first6=Luigi|title=Environmental and economic benefits of variable rate nitrogen fertilization in a nitrate vulnerable zone|journal=Science of the Total Environment|date=March 2016|volume=545-546|pages=227–235|doi=10.1016/j.scitotenv.2015.12.104|pmid=26747986|bibcode=2016ScTEn.545..227B|hdl=2268/190376|url=http://orbi.ulg.ac.be/handle/2268/190376|hdl-access=free}}</ref>

=====Timing of N applications=====
* Apply N close to the time when crops can utilize it.
* Make side-dress N applications close to the time of most rapid N uptake.
* Split applications, involving more than one application, allow efficient use of applied N and reduce the risk of N loss to the environment.

=====N Forms, including slow or controlled release fertilizers and inhibitors=====
* Slow or controlled release fertilizer delays the availability of nitrogen to the plant until a time that is more appropriate for plant uptake - the risk of N loss through denitrification and leaching is reduced by limiting nitrate concentrations in the soil.
* Nitrification inhibitors maintain applied N in the ammonium form for a longer period of time, thereby reducing leaching and denitrification losses.

=====N capture=====
* Particular crop varieties are able to more efficiently extract N from the soil and improve N use efficiency. Breeding of crops for efficient N uptake is in progress.
* Rotation with deep-rooted crops helps capture nitrates deeper in the soil profile.
* Cover crops capture residual nitrogen after crop harvest and recycle it as plant biomass.
* Elimination of restrictions to [[subsoil]] root development; subsoil [[soil compaction|compaction]] and subsoil acidity prevent root penetration in many subsoils worldwide, promoting build-up of subsoil nitrate concentrations which are susceptible to denitrification and leaching when conditions are suitable.
* Good agronomic practice, including appropriate plant populations and spacing and good weed and pest management, allows crops to produce large root systems to optimise N capture and crop yield.