Mycorrhization, growth and nutrition of

• Although fertilization is commonly used in nurseries, the effects of high level of nitrogen on Pinus halepensis mycorrhization are still unknown. • The effect of fertilization at different N levels (low-LN: 35 mg/plant; medium-MN: 60 mg/plant; high-HN: 120 mg/plant), differing N sources (ammonium-(NH4)2SO4; nitrate-HNO3; ammonium+nitrate-NH4NO3) and inoculation with Pisolithus tinctorius and Lactarius deliciosus on the mycorrhization, growth and nutrient status of P. halepensis has been studied. • P. tinctorius 3SR showed higher mycorrhizal ability (100% of mycorrhizal seedlings) than L. deliciosus (nearer to 50%). The application of increasing doses of N resulted in a significant reduction of mycorrhizal seedlings but no differences were observed between NH4 and NO3 as N source at the 60 mg N/plant dose applied. The effects of fertilization on growth were mainly observed in uninoculated plants. The use of NH4 increased growth in non-mycorrhized plants. Nutrient status was similar in all cases except for K concentration, which was higher in plants mycorrhized with P. tinctorius. Interactions between inoculation and fertilization were found, mycorrhizal effects appearing only at LN fertilization. • It is advisable to avoid high doses of N fertilization in order to produce mycorrhizal P. halepensis seedlings