Editing Nutrient management (section)

===Reduction of greenhouse gas emissions===
* [[Climate Smart Agriculture]] includes the use of 4R Nutrient Stewardship principles to reduce field emissions of nitrous oxide (N2O) from the application of nitrogen fertilizer. Nitrogen fertilizer is an important driver of nitrous oxide emissions, but it is also the main driver of yield in modern high production systems. Through careful selection of nitrogen fertilizer source, rate, timing and placement practices, the nitrous oxide emissions per unit of crop produced can be substantially reduced, in some cases by up to half. The practices that reduce nitrous oxide emissions also tend to increase nitrogen use efficiency and the economic return on fertilizer dollars.

====Reduction of N loss in runoff water and eroded soil====
* [[No-till]], [[conservation tillage]] and other [[surface runoff|runoff]] control measures reduce N loss in surface runoff and [[Soil erosion|eroded soil material]].
* The use of daily estimates of [[Water content|soil moisture]] and crop needs to [[Irrigation scheduling|schedule irrigation]] reduces the risk of [[surface runoff]] and [[soil erosion]].

====Reduction of the [[Ammonia_volatilization_from_urea|volatilization]] of N as ammonia gas====
* Incorporation and/or injection of urea and ammonium-containing fertilizers decreases ammonia volatilization because good soil contact buffers pH and slows the generation of [[ammonia]] gas from [[ammonium]] ions.
* [[Urease inhibitor]]s temporarily block the function of the [[urease]] enzyme, maintaining urea-based fertilizers in the non-volatile urea form, reducing [[Ammonia volatilization from urea|volatilization]] losses when these fertilizers are surface applied; these losses can be meaningful in high-residue, conservation tillage systems.

====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.

====Water management====
=====Conservation tillage=====
* Conservation tillage optimizes soil moisture conditions that improve water use efficiency; in water-stressed conditions, this improves crop yield per unit N applied.
* Conservation tillage includes several cultivation practices such as no-till, in-row subsoiling, strip-till, or ridge-till processes, which aim to increase the soil surface with 30% or more of crop residue. Historically, crop residue, was regarded by farmers as trash and was discarded; however, research has shown that there are many benefits to retaining more than 50% of crop residue on soil surfaces for the promotion of enriched soil health, nutrient cycling, reduction in erosion, and increased microbial activity and diversity. The goal of conservation tillage is to enhance soil quality, improve nutrient cycling, reduce soil erosion, improve water conservation, and reduce run-off and the loss of vital nutrients such as nitrogen (Conservation Tillage Systems in the Southeast, 2023).<ref name=":0">{{Cite web |title=Conservation Tillage Systems in the Southeast |url=https://www.sare.org/resources/conservation-tillage-systems-in-the-southeast/ |access-date=2025-03-20 |website=SARE |language=en-US}}</ref> Conservation tillage positively impacts many aspects of farming practices, particularly nutrient and water management, which are closely interconnected and will promote environmental and agricultural sustainability. Reduced soil erosion leads to an increase in nitrogen retention and improves soil productivity. Improved soil health has been attributed to conservation tillage through increased biological activity and diversity in less tilled soil secondary to lower levels of destruction of organic matter, shift in higher concentrations of beneficial microorganisms, reduced diseased states, thriving root networks that retain more moisture and nutrients which is the foundation of a thriving ecosystem (Conservation Tillage Systems in the Southeast, 2023).<ref name=":0" /> In crops that have undergone conservation tillage, research has shown higher concentrations of organic matter, such as nitrogen and many other soil-beneficial elements is secondary to the amount of carbon that remains in the soil, increasing organic levels of carbon in soil is directly related to higher levels of crop residue, which in turn increases and stabilizes soil nutrient levels making nutrients readily available for plant uptake (Yu et al., 2025).<ref>{{Cite journal |last=Yu |first=Yalin |last2=Li |first2=Li |last3=Yang |first3=Jinkang |last4=Xu |first4=Yinan |last5=Virk |first5=Ahmad Latif |last6=Zhou |first6=Jie |last7=Li |first7=Feng-Min |last8=Yang |first8=Haishui |last9=Kan |first9=Zheng-Rong |date=2025-02-19 |title=Global synthesis on the responses of microbial- and plant-derived carbon to conservation tillage |url=https://link.springer.com/10.1007/s11104-025-07290-0 |journal=Plant and Soil |language=en |doi=10.1007/s11104-025-07290-0 |issn=0032-079X|url-access=subscription }}</ref>  Conservation tillage improves water conservation and reduces run-off by protecting soil from crusting, a seal that forms on the soil surface that has undergone intensive tillage practices. Increased crusting of soil prevents water from reaching lower levels of soil. Soil crusting causes increased water losses as it evaporates more quickly, stripping the soil of its naturally retained moisture from rainfall and irrigation. Researchers found a nearly 60 percent reduction in run-off losses in crops that underwent conservation tillage (Conservation Tillage Systems in the Southeast, 2023).<ref name=":0" /> Conservation tillage can also maximize the benefits of rainfall through the reduction of soil compaction by dispersing the energy of the raindrop over the soil residue, reducing the effects of soil compression and erosion, leading to an increase in soil water retention capacity, slowing water run-off and promoting infiltration, as water sits on the surface for more extended periods, and by increasing the capacity at which water traverses through soil due to the presence of larger channels that improve soil structure and promote infiltration instead of run-off (Conservation Tillage Systems in the Southeast, 2023).<ref name=":0" /> Decaying crop residue increases the available routes in the soil that allow water to be absorbed quickly and is beneficial with or without irrigation, leading to the reduced use of supplemental irrigation (Conservation Tillage Systems in the Southeast, 2023).<ref name=":0" />  Plant residues, which are increased in conservation tillage, could reduce the activity of nitrate reducers in soil up to 27-fold, leading to nitrogen retention (Cheneby et al., 2010).<ref>{{Cite journal |last=Chèneby |first=D. |last2=Bru |first2=D. |last3=Pascault |first3=N. |last4=Maron |first4=P. A. |last5=Ranjard |first5=L. |last6=Philippot |first6=L. |date=November 2010 |title=Role of Plant Residues in Determining Temporal Patterns of the Activity, Size, and Structure of Nitrate Reducer Communities in Soil |url=https://journals.asm.org/doi/10.1128/aem.01497-10 |journal=Applied and Environmental Microbiology |language=en |volume=76 |issue=21 |pages=7136–7143 |doi=10.1128/AEM.01497-10 |issn=0099-2240 |pmc=2976265 |pmid=20833788}}</ref> Agricultural practices, such as conservation tillage that promote nitrogen retention are important as nitrogen promotes the growth of plants and, when depleted, reduces agricultural productivity and sustainability. Conservation tillage is another way to naturally increase vital nutrients within the soil, such as nitrogen, resulting in reduced application requirements of nitrogen and many other nutrients required for productivity. It is also an effective way to conserve water and promote soil health.

=====N fertilizer application method and placement=====
* In ridged crops, placing N fertilizers in a band in ridges makes N less susceptible to leaching.
* Row fertilizer applicators, such as injectors, which form a compacted soil layer and surface ridge, can reduce N losses by diverting water flow.

=====Good irrigation management can improve N-use efficiency=====
* Scheduled [[irrigation]] based on soil moisture estimates and daily crop needs will improve both water-use and N-use efficiency.
* Sprinkler irrigation systems apply water more uniformly and in lower amounts than furrow or basin irrigation systems.
* Furrow irrigation efficiency can be improved by adjusting set time, stream size, furrow length, watering every other row, or the use of surge valves.
* Alternate row irrigation and fertilization minimizes water contact with nutrients.
* Application of N fertilizer through irrigation systems ([[fertigation]]) facilitates N supply when crop demand is greatest.
* [[Polyacrylamide]] (PAM) treatment during furrow irrigation reduces sediment and N losses.

=====Drainage systems=====
* Some [[subirrigation]] systems recycle nitrate leached from the soil profile and reduce nitrate lost in drainage water.
* Excessive drainage can lead to rapid through-flow of water and N [[leaching (agriculture)|leaching]], but restricted or insufficient drainage favors [[Hypoxia (environmental)|anaerobic]] conditions and [[denitrification]].

====Use of simulation models====
Short-term changes in the plant-available N status make accurate seasonal predictions of crop N requirement difficult in most situations. However, models (such as NLEAP<ref>{{cite web|title=Nutrient Management -- Nitrogen {{!}} NRCS|url=https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/technical/ecoscience/mnm/?cid=stelprdb1044740|website=www.nrcs.usda.gov|access-date=19 December 2017|language=en}}</ref> and [[Adapt-N]]<ref>{{cite journal|last1=Sela|first1=Shai|last2=van Es|first2=Harold M.|last3=Moebius-Clune|first3=Bianca N.|last4=Marjerison|first4=Rebecca|last5=Moebius-Clune|first5=Daniel|last6=Schindelbeck|first6=Robert|last7=Severson|first7=Keith|last8=Young|first8=Eric|title=Dynamic Model Improves Agronomic and Environmental Outcomes for Maize Nitrogen Management over Static Approach|journal= Journal of Environmental Quality|date=2017|volume=46|issue=2|pages=311–319|doi=10.2134/jeq2016.05.0182|pmid=28380574|doi-access=free}}</ref>) that use soil, weather, crop, and field management data can be updated with day-to-day changes and thereby improve predictions of the fate of applied N. They allows farmers to make adaptive management decisions that can improve N-use efficiency and minimize N losses and environmental impact while maximizing profitability.<ref>{{cite journal|last1=Saol|first1=T. J.|last2=Palosuo|first2=T.|last3=Kersebaum|first3=K. C.|last4=Nendel|first4=C.|last5=Angulo|first5=C.|last6=Ewert|first6=F.|last7=Bindi|first7=M.|last8=Calanca|first8=P.|last9=Klein|first9=T.|last10=Moriondo|first10=M.|last11=Ferrise|first11=R.|last12=Olesen|first12=J. E.|last13=Patil|first13=R. H.|last14=Ruget|first14=F.|last15=TAKÁČ|first15=J.|last16=Hlavinka|first16=P.|last17=Trnka|first17=M.|last18=RÖTTER|first18=R. P.|title=Comparing the performance of 11 crop simulation models in predicting yield response to nitrogen fertilization|journal=The Journal of Agricultural Science|date=22 December 2015|volume=154|issue=7|pages=1218–1240|doi=10.1017/S0021859615001124|s2cid=86879469|url=https://hal.archives-ouvertes.fr/hal-01413572/file/Salo_jas_2016_%7BDA6804FB-AC18-4BCF-9A62-48BA0EB4BD79%7D.pdf}}</ref><ref name="Basso2016"/><ref name="Cantero-Martínez2016">{{cite journal|last1=Cantero-Martínez|first1=Carlos|last2=Plaza-Bonilla|first2=Daniel|last3=Angás|first3=Pedro|last4=Álvaro-Fuentes|first4=Jorge|title=Best management practices of tillage and nitrogen fertilization in Mediterranean rainfed conditions: Combining field and modelling approaches|journal=European Journal of Agronomy|date=September 2016|volume=79|pages=119–130|doi=10.1016/j.eja.2016.06.010|hdl=10459.1/62534|hdl-access=free}}</ref>