Acquisition and Allocation of Phosphorus in a Population of White Clover Plants in a Rotationally Grazed Pasture

This paper quantifies the processes of acquisition, allocation and retranslocation of phosphorus (P) within a white clover (Trifolium repens L.) population in a mixed grass-clover pasture during a regrowth period in early winter (13 May-8 July 1991). The work described is part of a broader study examining seasonal variation in these processes. The data allows an analysis of the changing P economy of plants and of whole populations. White clover plants were grouped by !heir hierarchy of branching. Within plants, stolons were grouped by order of branching, dissected into leaf, stolon and root, oven-dried, weighed and analysed for P content. The quantity of P lost from the plant population at grazing was estimated by measurement of the toss of leaf and stolon on tagged stolons. Grazing removed an estimated 29% of the total P in the population in May. Over the regrowth period, acquisition of P accounted for an estimated 25% of total P in the population by July. Net changes of 4.5% occurred in the allocation of P to plant organs, with stolon favoured in July. Net retranslocation of P among plant organs, plant orders and stolon orders was not quantitatively important.