Fertilization with phosphorus increases soil nitrogen absorption in young plants of Eucalyptus grandis

Nitrogen (N) and phosphorus (P) are the nutrients that most commonly limit tree growth. Interactions between fertilization and soil type are well known, and in soils with moderate or low N availability, N-fertilization is frequently recommended to improve tree nutrition. The aim of this paper was to analyze how different doses of P and N applied in three different types of soils affect dry mass and nutrient accumulation and partitioning in Eucalyptus grandis young plants, and if fertilization with P may increase N uptake. Fertilization was applied as 1, 2 and 4 g of urea (46% of N) or 6, 12 and 24 g of triple superphosphate (20% of P) per plant. Dry mass and nutrient partitioning were analyzed 44, 72 and 84 days after transplanting (DAT). Interactions between soil type and fertilization were observed. Root:total mass ratio decreased with P-fertilization in all soils. Fertilization with P promoted growth and improved N and S absorption even more than N-fertilization, although some of the soils used have very low N-contents (0.03%). Our data suggest that fertilization with P increased N absorption through a mechanism that was not related to increased N demand by enhanced growth.