Rhizosphäre, Rhizo sphère, Rhizos P here: how to cope with phosphorus scarcity?
Phytoseminar IBG-2
Speaker: Dr. Philip Hinsinger (
Montpellier SupAgro-CIRAD-INRA-IRD)Summary:
A major challenge in the coming decades is to achieve the necessary ecological intensification of agroecosystems in order to cover global food demand while decreasing agricultural inputs such as fertilizers. Past intensification has dramatically altered the cycles of nitrogen (N) and phosphorus (P), leading to a massive eutrophication of aquatic ecosystems, alongside the steady decrease of N and P efficiency.
For P, at the current rate of consumption of P fertilisers, the fast exhaustion of high grade phosphate ores worldwide clearly challenges the sustainability of current P fertiliser use in developed countries in the coming decades. A better understanding of the processes governing P bioavailability to crops is thus needed. This talk will stress the importance of rhizosphere biogeochemistry, which is currently ignored in most models of plant nutrition. Indeed, their central hypothesis is that the driving force of nutrient acquisition it the absorption process which results in a decrease in nutrient concentration at the surface of the root, leading to a diffusion gradient in the rhizosphere. While P depletion in the rhizosphere is largely documented, we have repeatedly shown that depletion of P may be an exception rather than the rule in low P input conditions. Such findings invalidate classical models of nutrient acquisition.
Such
models most often underpredict P uptake by crops in low P soils. This suggests that processes that are not accounted for in such models play a key role in determining P bioavailability. Among these, root-induced pH changes as well as changes of ionic (e.g. carboxylates, calcium) concentrations have been shown to be major drivers of changes of inorganic P availability in the rhizosphere. In addition, the fate of organic and microbial P may also be altered by rhizosphere processes, implying complex interactions with communities of soil organisms. Better understanding the impact of such processes on P bioavailability shall help designing more P efficient crops and
agroecosystems.