Due to the high value of the fruit, the European chestnut (Castanea sativa Mill.), usually
grown in agroforestry systems, has been planted as a single species in orchards managed with
increasingly intensive cropping practices, such as the regular use of fertilisers. This justifies research
into establishing fertilisation programmes oriented towards ecological intensification. In this study,
the results of fruit production, plant nutritional status and soil properties are reported from a field
trial in which three NPK fertilisers (20:7:10, 13:11:21 and 7:14:14) and a control treatment were used.
Chestnut yields did not vary significantly between treatments, although the mean values of the
control showed a clear downward trend. N supplied by the fertilisers seems to have been the
most important factor in the difference between the fertilised and control treatments, since leaf N
concentrations were lower in the control and often below the lower limit of the sufficiency range.
Soil inorganic N levels in the autumn, and tissue N concentrations of the herbaceous vegetation
developing beneath the trees, indicated risks of N loss to the environment and highlighted the
importance of this vegetation remaining during the winter. The chestnuts’ poor response to fertiliser
applications was attributed to the buffering effect of the large perennial structure of the trees on
the distribution of nutrients to the growing plant parts. In large trees, it seems appropriate to base
the annual fertilisation plan on leaf nutrient concentration. Thus, farmers probably should avoid
spending money on fertilizer applications as long as leaf nutrient concentrations do not approach the
lower limits of sufficiency ranges.
This work was funded by the Operational Group “EGIS–Estratégias de Gestão Integrada do
Solo e da Água em Espécies Produtoras de Frutos Secos”, funded by PT2020 and EAFRD (European
Agricultural Fund for Rural Development). The authors are also grateful to the Foundation for
Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES
(PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020), SusTEC (LA/P/0007/2021) and
CITAB (UIDB/04033/2020)
