Phosphorus-use efficiency of Rytidosperma species: understanding the morphological and physiological mechanisms that confer efficiency

Heidi Ann Waddell

    Research output: ThesisDoctoral Thesis

    215 Downloads (Pure)


    [Truncated] Phosphorus (P) is an essential element for plant growth. However, rock phosphate, which is used to manufacture P fertilisers, is a non-renewable resource. Australian soils have low levels of plant-available P and plants native to these environments are reputed to be well adapted to low-P soils. This thesis examined growth rates, P-utilisation efficiency and root morphological adaptations of Rytidosperma species to P fertilisers. Rytidosperma comprises an ideal genus to examine the response of Australian grasses to P fertilisers as it forms the dominant component of many grasslands. Preliminary data suggested there are a range of growth rates and P-utilisation efficiencies amongst Rytidosperma species in response to P fertiliser.

    The growth response of nine Rytidosperma species relative to fast-growing Bromus hordeaceus and Lolium perenne was examined in Chapter 2. Growth response was measured as: maximum shoot yield, shoot yield in low-P soil, critical external P requirement (amount of P required for 90% of maximum growth) and agronomic P-use efficiency (shoot yield per unit P applied). There was a range of growth responses amongst the Rytidosperma species including slow and fast growth. Three Rytidosperma species, R. duttonianum, R. racemosum and R. richardsonii grew as fast as B. hordeaceus and L. perenne at high and low P supply. Species that were fast-growing at high P supply also had fast growth at low P supply, except for B. hordeaceus, which grew fast at high P supply, but had the lowest shoot yield at low P supply. Of the fast-growing Rytidosperma species, R. duttonianum and R. racemosum had a high critical external P requirement and lower agronomic P-use efficiency, whilst R. richardsonii had a low critical external P requirement and high agronomic P-use efficiency.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2015


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