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With support from Defra we are exploring nitrogen metrics of the YEN dataset of crop performance, soils and inputs over 9 years. We've invited YEN sponsors to help guide how we analyse the data and what questions we ask.

Our first job is to define the Nitrogen Use Efficiency metrics to calculate and compare in the YEN dataset. Our suggestions are:

No.​

Name    

Calculation ​

Units      

1​

NUE (yield)

kg grain yield / kg N available (soil + fertiliser)  ​

kg/kg 

2​

NUE (yield/fert)

kg grain yield/kg N fertiliser applied (kg)

kg/kg

3​

Grain N offtake

DM yield x grain N% (= Grain N Yield)

kg N/ha

4​

Total Crop N Uptake

Grain N Yield (kg N ha) + straw N (DM straw x straw N%)    ​

kg N/ha

5​

N Harvest Index (NHI)

Grain N offtake / Total crop N uptake​

%

6​

N uptake efficiency (NUpE)

Total Crop N Uptake / N available (soil + fertiliser)​

%

7​

N Utilisation efficiency (NUtE)     

Crop yield (kg/ha) / Total crop N uptake​

kg DM/kg N 

8​

Grain N recovery

Grain N Yield / N available (soil + fertiliser)​

%

8a​

Crop N recovery

Total Crop N Uptake / N available (soil + fertiliser) 

%

9​

Apparent Fertiliser Recovery

(Total crop N uptake – soil N) / N fertiliser applied​

%

10​

Simple Fertiliser Recovery

Total Crop N uptake / N fertiliser applied​

%

11​

N balance (Grain)

N fertiliser applied – Grain N offtake

kg N/ha

11a​

N balance (Grain & Straw)

N fertiliser applied - Crop N offtake

kg N/ha

 

We can only assume soil N from RB209 field assessment using soil type, previous crop and over winter rainfall.

We do not have full information on manure N applications, so cannot estimate N from manures for most crops. However we can look at crops with no known manure use separately to those with regular manure history.

For wheat crops we also plan to look at protein content achieved compared to average protein achieved by the variety in the Recommended List, giving an indication of whether N supply was sub or super optimal.

If there are other metrics you think we should include, or we should define any of above differently, please let us know.

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Yield Enhancement Networks (YENs) were launched in 2012 to support and energise on-farm learning-by-sharing and thus to enhance farming progress.

Nitrogen Use Efficiency is a widely used term increasingly discussed across industry and with farmers. However it can mean different things to different people.

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YEN Nutrition brings together those wanting to achieve more precise crop nutrition.  High fertiliser prices now make this vital.  Assuming that 'crops know best' engagement in YEN Nutrition starts by benchmarking grain nutrients to show those that were limiting (or excessive) for each crop.