Targeting phosphorus for yield and profitRoger Sylvester-Bradley, Head of Crop Performance

Best Practice Phosphorous Philosophy = RB209

• Maintain Soil P at Index 2 - or Index 3 if growing potatoes or veg

• At index 2, apply P to replace crop offtake- At < Index 2, build soil P up- At > Index 2 (or 3), run soil P down

• Check soil P Index of each field every 3-5 years- Take care with soil P sampling, etc.

… Keep everything the same each time

• NB there may be soil differences - esp. calcareous soils may need annual

P applications

i.e. “Feed the soil to feed the crop”.

= better than ‘best practice’

Best Practice … issues

• 80% of UK arable land now at P Index 2 (or more)

• Reducing soil P from Index 2 to Index 1 could …- Provide large £ savings in P inputs- Help achieve P targets set for UK water bodies

Current research questions:

(i) Can we reduce soil P … AND still enhance yields ?

(ii) Can fertiliser P efficiencies be increased ?& / or can Crop P Demands be reduced ?

(by breeding)

(iii) Can crop P sufficiency be monitored more reliably?

Managing soil-available P – results not always as expected

36 farms, following RB209 policy, data from SOYL 4 fields, normal arable rotations,

No P applied

P Index 0

P Index 1

P Index 2

Index2

Index2

See AHDB Project Report No. 570

Managing soil-available P – results not always as expected

36 farms, following RB209 policy, data from SOYL 4 fields, normal arable rotations,

No P applied

P Index 0

P Index 1

P Index 2

Biomass, kg ha-1

Crop P concentration, mg/kg

Do crops respond to fresh fertiliser P at soil P Index 1? (broadcast before sowing)

• Wheat, Barley, Oilseed Rape & Potatoes

• All sites at P Index 1

• P applied to seedbeds as TSP

• Nil to 275 kg/ha P2O5 applied .. 120 kg/ha P

• Crop Uptake <70 kg/ha P2O5 .. <30 kg/ha P

• Soil derived P provided ~80% of crop P requirements (range 42% … >100%)

• Average P recovery from broadcast TSP … only 4%.

Response to 120 kg/ha P

275 kg/ha P2O5

Crop biomass growth, kg/ha

Can we improve responses to fresh fertiliser P ? (at soil P Index 1)

• Economic responses to fresh broadcast TSP?- Potatoes: YES Barley: Maybe - Wheat & OSR: NO … (2 were –ve!)

• Placement - No effect on P recovery - Increased yield 4 times out of 10 … with barley & potatoes … with wheat & OSR, yields tended to decrease!

• AVAIL®-treated TSP - No consistent benefits

• Struvite … slow release, recycled P- Increased P recovery v TSP: … 8 / 10 times (4 sig.) … one small sig. decrease

- Only sig effects on yield with potatoes

VaderstadWhat about DAP ?Top-dressings ?

Can fresh seedbed P fertiliser fully correct P deficiencies ?

• 10 trials, 4 crops, 2011 to 2014

• Critical P contents from literature-Barraclough et al. & abroad esp. Australia

• Fresh P did not overcome ‘deficiencies’

• Site differences in crop P become more obvious by harvest, especially potatoes

• Good case for monitoring P at harvest.

Bollons, H.M. & Barraclough, P.B. (1997). Inorganic orthophosphate for diagnosing the phosphorus status of wheat plants. Journal of Plant Nutrition 20 (6), 641-655

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nil P +115 kg/ha P2O5

Monitoring for crop P sufficiency

Relationship between grain P content and yield

y = -100.59x2 + 80.173x - 4.6428R² = 0.8316

y = -70.16x2 + 56.223x - 1.1426R² = 0.8199

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0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55

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Grain P Content (%)

Peldon Cholsey

Critical grain P ?

Peldon 2016

Cholsey 2016

Normal grain P as in RB209

2,000 3,000 4,000 5,000Grain P, mg/kg

How common is low grain P ? … in YEN 2016 & 2017

24% less than ‘critical’

Only 17% more than ‘RB209’

RB209Critical ?

– Grain Nutrient Benchmarking – open to all farmsNovember 2017 … & harvest 2018

• Grain Phosphorus, P mg/kg

• Plus other key Nutrients:… Potassium, K (mg/kg)… Calcium, Ca (mg/kg)… Magnesium, Mg (mg/kg)… Sulphur, S (mg/kg) (N:S)… Manganese, Mn (mg/kg)… Copper, Cu (mg/kg)… Zinc, Zn (mg/kg)… Iron, Fe (mg/kg)… Boron, B (mg/kg)

• NOT Nitrogen

To apply for Grain NutrientBenchmarking• Any farm can apply …• Email: yen@adas.co.uk

Subject: ‘GNB’ stating the number of fields• Compare 2 fields (or more) for FREE • Labs will send labelled sample bags• 2017 samples: results in spring 2018• 2018 samples: results in autumn 2018

Conclusions – ‘Targeting P for yield & profit’

• Good P nutrition is vital for high yields

• We have large & valuable soil P reserves

• Crop offtakes often less than in RB209

• Soil P often runs down very slowly- Soil P Index 1 may be sufficient for most crops

• Inorganic fertiliser P is recovered poorly

• Need to improve P monitoring - More care in soil sampling etc.- Better interpretation of spatial effects - Crop analysis very useful … grain analysis probably

best

• Sign up for FREE grain P analysis - at the AHDB, ADAS or YARA stands, or on-line.

Monitor

Manage

Target

Thanks … especially to all our Collaborators, Partners & Funders