Biochar increases plant-available water in a sandy loam soil under an aerobic rice crop system
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2014
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The main objective of this study was to assess
the impact of biochar rate (0, 8, 16 and 32 Mg ha −1 ) on
the water retention capacity (WRC) of a sandy loam Dys-
tric Plinthosol. The applied biochar was a by-product of
slow pyrolysis (∼ 450 ◦ C) of eucalyptus wood, milled to pass
through a 2000 μm sieve that resulted in a material with
an intrinsic porosity ≤ 10 μm and a specific surface area
of ∼ 3.2 m 2 g −1 . The biochar was incorporated into the top
15 cm of the soil under an aerobic rice system. Our study
focused on both the effects on WRC and rice yields 2 and
3 years after its application. Undisturbed soil samples were
collected from 16 plots in two soil layers (5–10 and 15–
20 cm). Soil water retention curves were modelled using a
nonlinear mixed model which appropriately accounts for un-
certainties inherent of spatial variability and repeated mea-
surements taken within a specific soil sample. We found an
increase in plant-available water in the upper soil layer pro-
portional to the rate of biochar, with about 0.8 % for each
Mg ha −1 biochar amendment 2 and 3 years after its appli-
cation. The impact of biochar on soil WRC was most likely
related to an effect in overall porosity of the sandy loam soil,
which was evident from an increase in saturated soil mois-
ture and macro porosity with 0.5 and 1.6 % for each Mg ha −1
of biochar applied, respectively. The increment in soil WRC
did not translate into an increase in rice yield, essentially be-
cause in both seasons the amount of rainfall during the crit-
ical period for rice production exceeded 650 mm. The use
of biochar as a soil amendment can be a worthy strategy to
guarantee yield stability under short-term water-limited con-
ditions. Our findings raise the importance of assessing the
feasibility of very high application rates of biochar and the
inclusion of a detailed analysis of its physical and chemical
properties as part of future investigations.
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CARVALHO, M. T. de Melo; MAIA, A. de Holanda Nunes; MADARI, B. E.; BASTIAANS, L.; VAN OORT, P. A. J.; HEINEMANN, A. B.; SILVA, M. A. Soler da; PETTER, F. A.; MARIMON JR., B. H.; MEINKE, H. Biochar increases plant-available water in a sandy loam soil under an aerobic rice crop system. Solid Earth, Utrecht, v. 5, p. 939-952, 2014.