1. Where has all the phosphorous gone? Long term effects of alternative phosphorus sources on soil fertility Bill Bowden, WMG Craig Scanlan, DAFWA, Northam February 2015

2. Background to the talk Rediscovering the site What the old trial was all about: – Sources – Peak P – P budgets and residual value What current measurements can we show: – Chemical fertility: P, OC%, CEC, N – Physical: Wetting, compaction, bio-ploughs, water use – Biology: disease, weeds

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7. What the old trial was about? – Alternative sources of P to orthophosphates (Super, DAP etc) Water soluble phosphates – The commercial fertilisers Less soluble phosphates – The raw minerals – A, B and C grade rock Ps – Calcined rock P – Reactive rock P – Lime super and partially acidulated super – Peak P – how real is it? Christmas Island story Duchess, Mt Weld etc – P budgets and residual value Where does the P go Changes in P availability Changes in soil fertility

8. 80Ba6 – Sources of P on pale grey sand History of site – Pre trial – not well documented Semi-cleared 1973 and super and sub-clover spread into regenerating scrub Occasional grazing by sheep Site cleared (200 metres by 100 metres) in 1980 – Trial (Bolland et al, 1987, AJEA, 27:647-56) P treatments top-dressed in May 1980 and incorporated with tines 1980-1986 crop sequence:- Illyarrie lupin, Seaton Park sub-clover, Pitman serradella, Illyarrie lupin, volunteer pasture, volunteer pasture, cross plot Jacup wheat, Mortlock oats, Forrest barley Basal muriate of potash and gypsum applied at 100 kg/ha in sowing years (1980-83 and 1986) and 30 kg/ha MnSO4 in lupin years.

10. Residual effects of fertilisers Change soil fertility: –Carry forward of nutrient –Build up of soil organic matter –Build up of soil nitrogen pools –Induced deficiencies –Non-wetting soils –Weeds and diseases

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18. 2014 response to 1980 treatments left: 1188 kg P/ha (C500), nil, right 792 kg P/ha (C500)

19. 2014 response to 1980 treatments extreme left: 420 kg P/ha (super), centre 1388 kg P/ha (Core), extreme right 792 kg P/ha (C500)

23. 2015 - Watch this space Take soil profile samples to complete the P budget Bioassay with a wheat crop –Responses to N, P, NP and deep cultivation –Test strip diagnostics –Risks with management of residues, weeds and non-wetting Investigate soil compaction and bio-plough effects Use soil bank and current samples to follow changes in soil fertility

24. Three key messages Poorly soluble P sources can have long term residual effects Poor, long term volunteer pasture lets soil OC levels build up Watch this space for interesting long term soil fertility effects

27. Acknowledgements Thanks go to the 1980 instigators of the trial: Mike Baker and Mike Bolland. To the landowners, David Frankland, Geoff Pearson. To the funders, NACC, and to the sponsors, the West Midlands Group and DAFWA

28. Questions?