Simulating the effects of different potassium and water supply regimes on soil water content and water table depth over a rotation of a tropical Eucalyptus grandis plantation

Made available in DSpace on 2018-11-26T17:51:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-06-01 Universidade de Sao Paulo Centre de cooperation Internationale en Recherche Agronomique pour le Developpement (CIRAD) Agence Nationale de la Recherche (MACACC) Agropolis Foundation Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Although large amounts of potassium (K) are applied in tropical crops and planted forests, little is known about the interaction between K nutrition and water supply regimes on water resources in tropical regions. This interaction is a major issue because climate change is expected to increase the length of drought periods in many tropical regions and soil water availability in deep soil layers is likely to have a major influence on tree growth during dry periods in tropical planted forests. A process-based model (MAESPA) was parameterized in a throughfall exclusion experiment in Brazil to gain insight into the combined effects of K deficiency and rainfall reduction (37% throughfall exclusion) on the water used by the trees, soil water storage and water table fluctuations over the first 4.5 years after planting Eucalyptus grandis trees. A comparison of canopy transpiration in each plot with the values predicted for the same soil with the water content maintained at field capacity, made it possible to calculate a soil-driven tree water stress index for each treatment. Compared to K-fertilized trees with undisturbed rainfall (+K+W), canopy transpiration was 40% lower for K deficiency (-K+W), 20% lower for W deficit (+K - W) and 36% lower for combined K deficiency and W deficit (- K - W) on average. Water was withdrawn in deeper soil layers for -W than for + W, particularly over dry seasons. Under contrasted K availability, water withdrawal was more superficial for -K than for +K. Mean soil water content down to 18 m below surface (mbs) was 24% higher for - K+ W than for +K+W from 2 years after planting (after canopy closure), while it was 24% lower for +K-W and 12% lower for -K W than for +K+W. The soil-driven tree water stress index was 166% higher over the first 4.5 years after planting for - W than for +W, 76% lower for -K than for +K, and 14% lower for -K -W than for +K+W. Over the study period, deep seepage was higher by 371 mm yr(-1) (+122%) for -K than for +K and lower by 200 mm yr(-1) (- 66%) for -W than for +W. Deep seepage was lower by 44% for -K- W than for +K+ W. At the end of the study period, the model predicted a higher water table for -K (10 mbs for -K+W and 16 mbs for -K-W) than for +K (16 mbs for +K+W and 18 mbs for +K-W). Our study suggests that flexible fertilization regimes could contribute to adjusting the local trade-off between wood production and demand for soil water resources in planted forests. CIRAD, UMR Eco&Sols, F-34398 Montpellier, France Univ Montpellier, Eco&Sols, CIRAD, INRA,IRD,Montpellier SupAgro, Montpellier, France CIRAD, UR AIDA 115, F-34398 Montpellier, France Univ Estadual Campinas, NIPE, BR-13083970 Campinas, SP, Brazil Univ Sao Paulo, Dept Ciencias Atmosfer, BR-05508900 Sao Paulo, SP, Brazil INRA, UMR 1391, ISPA, F-33140 Villenave Dornon, France Univ Sao Paulo, ESALQ, BR-13418900 Piracicaba, SP, Brazil Univ Sao Paulo, CENA, BR-13400970 Piracicaba, SP, Brazil Univ Estadual Paulista, Dept Solos & Recursos Ambientais, BR-18610300 Botucatu, SP, Brazil Univ Estadual Paulista, Dept Solos & Recursos Ambientais, BR-18610300 Botucatu, SP, Brazil Agence Nationale de la Recherche (MACACC): ANR-13-AGRO-0005 Agropolis Foundation: ANR-10-LabX-0001-01 CAPES: 017/2013