During this season CSBP trialed different granular phosphorus (P) fertiliser products and rates on very P deficient sites in Dandaragan and Trayning to answer which kind of fertiliser returns the best profit and why. The symptoms of P deficiency are well known, such as P plays a vital role in photosynthesis and therefore shows up as leaf chlorosis/necrosis, reduced root (and shoot) growth and vigour, less tillers, delayed plant maturity, smaller heads and lower yields. It is also known that P is therefore required especially during the early growth stages, that plant roots take up P via diffusion along a concentration gradient from soil to root and thus P needs to be in soil solution close to the young roots. While inadequate P supply can rarely be rectified with P applications during the season, as P is immobile in most of our soils and needed early to meet plant demand, fertiliser P at seeding has to be placed effectively and in a high enough concentration. So, given that WA is sowing earlier and experiencing more frequent drier starts to the season, which P fertiliser is up to the task?
Our results suggest that at current fertiliser costs Agras (9.1 P) financially outperformed the higher concentrated MAP (22.8 P) product in Trayning and Dandaragan at the same P rates. Furthermore Agras was giving a return that was either better, or statistically not worst than double the MAP rates or even higher MAP rates.
Treatments and harvest results:
Trayning: 10P as Agras on left vs. 0P on right
Dandaragan: 0P on left vs. 10P as Agras on right