Variation of soil organic matter over time in silvopastoral systems under Pinus radiata D. Don Mosquera-Losada MR1, Rodríguez-Rigueiro FJ1, Rigueiro-Rodríguez A1, Ferreiro-Domínguez N1,2 1Department 2Forest
of Crop Production and Engineering Projects. Escuela Politécnica Superior. Universidad de Santiago de Compostela, 27002 Lugo, Spain
Research Centre, School of Agriculture, University of Lisbon, Tapada da Ajuda, 1349-017 Lisboa, Portugal
E-mail:
[email protected]
INTRODUCTION In the silvopastoral systems established in Galicia (NW Spain), the availability of nutrients to the pasture and trees may be limited by the high soil acidity. The use of sewage sludge as organic fertiliser could increase the tree and pasture growth as well as modify the soil organic matter (SOM) content, being the SOM the most important pool of carbon storage in terrestrial ecosystems
OBJECTIVE To evaluate during twelve years the evolution of SOM in a silvopastoral system established with Pinus radiata D. Don in Galicia (NW Spain) which was fertilised with three doses of sewage sludge (160, 320 and 480 kg total N ha−1) combined with lime (2.5 t CaCO3 ha–1) or without lime
MATERIALS AND METHODS LOCALIZATION (Galicia, NW Spain)
TREATMENTS 1. No fertilisation (NF) 2. 160 kg N ha-1 of sewage sludge (S1) 3. 320 kg N ha-1 of sewage sludge (S2)
2.5 t CaCO3 ha–1
4. 480 kg N ha-1 of sewage sludge (S3) 5. No fertilisation (NF) 6. 160 kg N ha-1 of sewage sludge (S1) 7. 320 kg N ha-1 of sewage sludge (S2) 8. 480 kg N ha-1 of sewage sludge (S3) 9. 500 kg ha-1 of 8% N – 24% P2O5 – 16% K2O (MIN)
EXPERIMENTAL DESIGN
FIELD SAMPLING
Randomized block design (9 treatments and 3 replicates)
A composite soil sample per plot was collected at a depth of 25 cm in December from 1998 to 2011
27 experimental units (96 m2) with 25 Pinus radiata D. Don (3 X 2 m) Sowing with Dactylis glomerata L., Lolium perenne L. and Trifolium repens L.
LABORATORY ANALYSES The SOM was determined by using the Saverlandt method
STATISTICAL ANALYSIS:
ANOVA and LSD
RESULTS The SOM levels were high in all years (11.26-15.0%) compared with exclusively agricultural systems Second year SOM : effect of the fertilisation, the liming and the tilling process From the second year from pasture and trees
SOM: incorporation of litter into the soil
Last years of the experiment SOM: the trees allowed the passage of light to the undergrowth due to the fall of the needles which could have increased the soil temperature and therefore the mineralisation rate Figure 1. Evolution of soil organic matter (%) over time. Different letters indicate differences between years.
CONCLUSION:the SOM was modified by the management practices such as the fertilisation, the liming and the tilling process as well as by the
establishment of the pasture and the trees. In any case, the SOM was high in all year compared with exclusively agricultural systems. This result demonstrates the great potential of the SS to enhance C sequestration in the soil compared with common agricultural systems, and therefore its implementation should be considered as a land use option in Europe
ACKNOWLEDGEMENTS We acknowledge support of the Xunta de Galicia (Consolidation funds and Consellería de Cultura, Educación e Ordenación Universitaria (Programa de axudas á etapa posdoutoral DOG nº122, 29/06/2016 p.27443, exp: ED481B 2016/071-0))
