1. Bill Bowden, Chris Wilkins, WMG February 2017
Where has all the phosphorous gone? Long term effects of alternative phosphorus sources on soil fertility of a West Midlands gutless sand 2017 update
Bill Bowden, Chris Wilkins, WMG
February 2017

2. Location
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3. 2014 response to 1980 treatments left: 1188 kg P/ha (C500), nil, right 792 kg P/ha (C500)

5. Aerial (drone – thank you Stan from Murdoch University) view of trial site in October 2016.

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. 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
Biological activity

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10. I

11. Soil fertility measures
Note little difference in OC%, CEC and pH

12. Changes in fertility factors in top 10 cm
C:N 17

13. at a C:N ratio of 12 (the N build up was from clover ley pasture which would have been clover dominant for the 7 years of pasture), it says each year of pasture gives an OC% of about 0.05 – or 20 years to raise it 1%
At a C:N ratio of 12,
0.03 x 12 / 7 = 0.05% OC/year
OC% range = 0.35 to 0.80

15. Soil profile sampling in failed crop, October 2015

16. 2015 fractional recovery of P, cumulated to depth, of 1980 high P rate treatments

17. Sampling day sept 2016 looking south down high P plots (low P to left and right)

19. 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

20. questions