March 2026 ESRFnews
14
remaining in the soil can still leak away unless we can
capture it first
Agronomists have long known that calcium bound
phosphorus tends to remain more accessible to crops
whereas phosphorus bound to iron and aluminium
minerals is usually fixed more tightly and is harder for
roots to extract . In a long - running field experiment
on tropical soils in Brazil – where weathering leads to
especially strong fixation – researchers compared what
happens when fertiliser is stopped under different
tillage systems , and then used ID21 XANES to identify
which phosphorus species remained . Published this
year , the results show that no - till management preserves
more accessible calcium - bound phosphorus , while
conventional tillage drives more of the legacy phosphorus
into iron - and aluminium - bound forms that plants
struggle to use ( Soil Tillage Res . 256 1 ) .
“ Historically , soil phosphorus dynamics have been
investigated mainly using wet chemical extraction
methods , which define phosphorus pools operationally
but cannot distinguish the molecular forms , ” says
study author Lenir Fátima Gotz at the University of
São Paulo in Brazil . “ In contrast , the ESRF beamlines
allow us to resolve subtle differences among different
inorganic phosphorus species in a non - destructive way .
This capability is critical for understanding how legacy
phosphorus is stored and transformed under different
management systems when fertilisation is suppressed
Management is not the only lever that can shift
how phosphorus is held in soils Fertiliser design
can do it too In 2023 Aline do Amaral Leite at the
Federal University of Lavras in Brazil and colleagues
examined the production of biochar a charcoal like
soil amendment made by heating plant waste or manure
in low oxygen They found that in biochar derived
from poultry manure the phosphorus mostly ends
up in calcium phosphate minerals because calcium
dominates the feedstock But when magnesium
PHOSPHORUS FERTILISER
THE OTHER FERTILISER PROBLEM
While phosphorus is mainly responsible for algal blooms , nitrogen fertiliser
carries a dif ferent environmental cost . Producing ammonia – the basis of
most nitrogen fertilisers – accounts for more than 2 % of global greenhouse -
gas emissions ( Sci . Rep . 12 14490 ) . The footprint has prompted a search for
cleaner production routes and more ef f icient crops .
One promising direction is to rethink how ammonia is made . In 2024 ,
researchers used operando grazing - incidence wide - angle X - ray scattering
at the ESRF ’ s ID31 beamline to watch , in real time , how reactive interfacial
layers form during lithium - mediated nitrogen reduction – an emerging
alternative to conventional Haber – Bosch chemistry . By tracking structural
changes as the reaction proceeds , the team could identify which interphase
structures favour ammonia formation and which lead to degradation , helping
to guide the development of lower - carbon nitrogen production ( Energy
Environ . Sci . 17 3482 ) .
Another route is to rely more on plants that can f ix their own nitrogen . In 2024 ,
Jieshun Lin at Aarhus University in Denmark and colleagues identif ied a genetic
regulator that switches of f nitrogen f ixation when soil nitrate is abundant . Using
X ray f luorescence microscopy at the ESRF s ID21 beamline they mapped
zinc distributions inside root nodules and showed that shifts in zinc levels help
activate this switch Nature 631 164 Removing the regulator could therefore
create a condition in which nitrogen f ixation is no longer shut down by the plant
says co author Kasper Andersen at Aarhus
FIGURE 1 : MICRON - SCALE PHOSPHORUS CHEMISTRY IN IRON - TREATED SEDIMENTS
E N V I R O N . S C I . : P R O C E S S E S I M P A C T S 2 7 5 6 3 / C C B Y 3 . 0
X - ray f luorescence maps from ID21 show organic - rich particles from the sediment to which spherical pyrite ( FeS
2
) particles are attached .
Phosphorus ( P ) occurs together with iron ( Fe ) and calcium ( Ca ) f inely dispersed over the organic matrix and not in distinct Fe - particles . The results
explain why Fe addition has not prevented P release from these organic - rich sediments over the long term .
200 µ m
100 µ m
A B B