Plant available silicon in bare fallow soils after 90 years of annual supplies of manure, lime and fertilizers
- 1Université Catholique de Louvain (UCLouvain), Earth and life Institute, Soil Science, Louvain-La-Neuve, Belgium (zimin.li@uclouvain.be)
- 2CNRS, IRD, Coll France, CEREGE, Aix Marseille Université, 13545 Aix-en-Provence Cedex 04, France
- 3INRA/AgroParisTech, UMR 1402 ECOSYS, Équipe Ecotoxicologie, RD-10, F-78026 Versailles Cedex, France
Silicon (Si), non-essential but beneficial to plants, plays a crucial role in maintaining plant functions by alleviating a number of biotic and abiotic stresses. Applying manure, lime and chemical fertilizers to soils may impact the pool of plant available Si, but their impact over decades to century is unknown.
Here, we determined the evolution of the content of plant available Si in a silty soil derived from Quaternary loess (Haplic Luvisol), submitted to a long-term bare fallow experiment initiated in 1928 in Versailles (INRA, France). On this bare fallow soil, different treatments were applied annually since 1929, among which, manure, lime (CaCO3), NaNO3 and (NH4)2SO4) and compared to control soil. Archived soil samples were already characterized for their basic properties (pH, CEC, OC, N, oxalate-extractable Al, Fe and Si, DCB extractable Fe, particle size distribution, elemental analysis). Here, we computed the total reserve in bases (TRB), and we determined the content of plant available Si (CaCl2-Si) through a kinetical extraction using 0.01 M CaCl2.
TRB was 110 cmol (+) kg-1 in 1929. During the 90 years period, TRB (cmol (+) kg-1) remained constant in manured plots, decreased to 96 in control/NaNO3 plots and to 84 in the (NH4)2SO4 plot whereas it increased to 160 in the CaCO3 plot. The initial CaCl2-Si content did not differ between the treatments, as it ranged between 25 and 30 mg kg-1 in 1929. Annual manure supply resulted in the progressive increase of CaCl2-Si up to 60 mg kg-1. In this treatment, CaCl2-Si (30 to 60 mg kg-1) and OC (18 to 40 g kg-1) contents were strongly and positively correlated, suggesting the continuous silicon through manure supply (probably phytoliths), and their dissolution at pH 6.6-7.6. In the four other treatments, OC content regularly decreased from 18 to 5 g kg-1 from 1929 to 2019, but CaCl2-Si largely differed between them. Our data suggest a strong impact of pH on CaCl2-Si as well as the occurrence of two sources of bioavailable Si: phytoliths in limed plots (pH 6.6 to 8.8) and clay minerals in acidified plots submitted to annual (NH4)2SO4 application (pH from 6 to 3.5).
Our preliminary results show that, in a given soil type, the pool of bioavailable silicon is strongly affected by soil properties, especially soil pH, OC content and weathering stage.
How to cite: Li, Z., Meunier, J.-D., Van-Oort, F., Keller, C., and Delvaux, B.: Plant available silicon in bare fallow soils after 90 years of annual supplies of manure, lime and fertilizers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20657, https://doi.org/10.5194/egusphere-egu2020-20657, 2020
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NIce work. Why does manure appear to uniquely enhance the Si bioavailability. Is it the higher OM content of those plots?
many thanks for your comments, Aaron Thompson.
Q1, manure increase Si mobility due to its induced pH-increase to dissolve some clay silica..
Q2. manure application gloablly increase the OC content due to OC input.
Yes, manure is in fact dead biomass from plant debris. So, applying manure, in this case, would also supply phytoliths.
Best regards, Bruno
OK. That maybe explains why the plots with high pH from lime addition (I think that was the amendment) do not have as high a Si bioavailability as the manure ammended plots.
Yes. Possibly, phytoliths supplied with manure could dissolve in favourable pH conditions since manure had also an impact on pH. We do not master yet the composition of manure but we Know that it varied with time.
Cheers, Bruno
Dear Ziming Li and co-authors
Thanks for sharing this beautifull data from exceptional samples.
Did you try to compare your Bioavailable Si vs. pH relationship with solubility diagram of opal (i.e. phytoliths) and clays (what clays do you have in your soil?).
I was also wondering i() what is the reason that manure increases pH and (ii) how would you explain the different phases of BioSi variations you have with time for CaCO3 and manure?
Thanks,
Damien
Dear Damien,
thanks for your comments,
following the reply of Mr. Delvaux, soil clay minerals are charactiried by smectite, kaolinite.
regards,
Zimin
Very nice question, dear Damie
Bioavailable Si vs. pH relationship with solubility diagram of opal (i.e. phytoliths) and clays (what clays do you have in your soil?): Yes we will do that when we get the analytical data after 128 days (CaCl2-kinetic extraction) as we did it in Zimin et al., Supp. Data (Plant and Soil 2019, Geoderma 2020).
What is the reason that manure increases pH: we do not master the sources of plant debris used in manure supplies, but we now that manure composition varied in time.
Would you explain the different phases of BioSi variations you have with time for CaCO3 and manure? Manure consists of plant debris. So, manure application had supplied phytoliths. CaCO3 did not.
Cheers, Bruno
Thanks Bruno and Zimin Li for your replies. Further questions regarding the temporal trends:
- how can you explain for lime that you start to decrease BioSi, then increase, then again decrease? pH is not changing much in these cases.
- For the temporal trend with manure I understand from your reply that you can explain part of it depending on the type of manure that varied with time. This could e.g. change the slope of increase since it supplies some bioSi but how could it decrease bioSi from 1960 to 1980?
Very interesting anyways!
Damien
how can you explain for lime that you start to decrease BioSi, then increase, then again decrease? pH is not changing much in these cases. We need to analyze the data at different time steps (from 6 hours to 128 days...) when we get the data, after lockdown...
For the temporal trend with manure I understand from your reply that you can explain part of it depending on the type of manure that varied with time. This could e.g. change the slope of increase since it supplies some bioSi but how could it decrease bioSi from 1960 to 1980? Possibly yes. But we cannot reply now. (1) We need to get the above mentioned analytical data. (2) We also need to get informations on manure composition (different sources were used...)
Very interesting anyways! Many thanks
hello everybody,
There is also another point, which has to be taken into account, although it is difficult at this stage to estimate its impact. The different amendments induce changes in Da and soil thickness. In fact, we should work in stock to be sure of what is going on....We will have to do that !;-))
Catherine
Yes, of course
Yes, Catherine.
Excellent summary,we shoud go deeper later, tracing what we could see.
Regards,
Zimin
many thanks, Damien,
Very interesting questions. We do not exzactly master this issule rightnow due to lockdown, data is stoppted. I will further analyze more details to trace it.
regards,
Zimin
Thx everyone for your replies. Hope lockdown will end soon to continue this research!
Damien