In acid soils, when no-tillage
farmers intend to apply lime, the question arises as
to whether it should be incorporated into the soil or whether it can be left on the
soil surface. In this study, two types of limestone, calcitic (Lcal) and dolomitic
(Lmag), were tested in two olive groves of cv. Cobrançosa, with an initial pH of
4.9 (S. Pedro) and 5.5 (Raparigas). In S. Pedro, limestone was incorporated into
the soil (Lburied) and in Raparigas, it was left on the floor (Lfloor). The use of
limestone significantly increased soil pH in the 0–0.10
m layer in both experiments.
In the 0.10–0.20
m soil layer, only Lmag increased significantly the soil pH
in comparison with the control. Lmag was more effective than Lcal in increasing
cation exchange capacity (CEC) and reducing exchangeable acidity (EA) and aluminium
(Al3+) in the Lfloor experiment. Both limes increased leaf calcium (Ca)
concentration, and Lmag increased the leaf levels of magnesium (Mg). In Lfloor
experiment (higher soil pH), soil microbial carbon (C) decreased, and microbial
nitrogen (N) increased with liming, which may indicate an increase in bacteria in
the soil and a decrease in fungi. In Lburied experiment (initial pH of 4.9), liming
significantly increased accumulated (2018–2021)
olive yield (56 and more than
67 kg tree−1, respectively, in the control and liming treatments). In Lfloor experiment
(initial pH of 5.5), the accumulated olive yields did not differ significantly
between treatments (average values between 105 and 115 kg tree−1). The results
of this study provide evidence that liming may increase olive yield in very acid
soils and that dolomitic limestone should preferably be used by no-tillage
farmers,
due its higher solubility and faster effect on soil and trees.
This research was funded by the Operational Group
‘Novas práticas em olivais de sequeiro: estratégias de
mitigação e adaptação às alterações climáticas’, funded
by PT2020 and EAFRD (European Agricultural Fund
for Rural Development). The authors are grateful to the
Foundation for Science and Technology (FCT, Portugal)
and FEDER under Programme PT2020 for the financial
support to CIMO (UIDB/00690/2020) and CITAB
(UIDB/04033/2020).
