Uptake zones for phosphorus in spring by pasture on different strata within a hill paddock

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Abstract
Approximately 85,92, and 90% of P uptake, as 32P, in spring by mixed pasture on campsites, 25° slopes, and 45° slopes respectively was from within the surface 7 cm of soil; most uptake was from the 0–3 cm soil zone. Significant P uptake from depths greater than 30 cm was unlikely. Approximately 90% of P uptake by pasture on all strata was from within 13 cm upslope and downslope of the P source. The extent of P uptake by pasture from the upper 3 cm of soil was similar both upslope and downslope from a P source, but uptake from greater depths was affected by slope. The angle of predominant root activity was between the vertical and a line normal to the soil surface, an angle which departed more from the vertical as surface slope increased. 32P placed at 11 cm depth on the outside edge of stock tracks was available to plants further downslope than when placed at shallower depths.