High phosphorus fertilization reduces mycorrhizal colonization and plant biomass of three cultivars of pineapple
A strategy to increase the productivity of pineapple agricultural systems is the excessive application of chemical fertilizers. In the state of Veracruz, Mexico, pineapple fields are being fertilized with P (180 to 240 kg ha-1) to maximize yields so that fertilizer applications keep increasing. We assessed the interaction between chemical phosphorus fertilizers, the establishment of mycorrhizal associations and biomass production of Cayenne, Champaka, and MD2 cultivars of pineapple in a greenhouse experiment. Plants were inoculated with a mycorrhizal consortium and grown with 0, 80, 200, 300, 500, and 600 mg phosphorus kg-1 soil additions in 8 kg pots for 8 months. Phosphorus reduced mycorrhizal colonization already at the lowest phosphorus fertilization dose in two of the three cultivars and became minimal for all cultivars from 200 mg P kg-1 soil. At the two highest phosphorus fertilization levels, shoot dry biomass and the dry weight of leaf D was reduced in all cultivars. The results show that the farmer´s practice of adding excessive fertilizer as an insurance principle is reaching the levels where fertilization is becoming detrimental for production and mycorrhizal benefits for the crop and the soil are being eliminated.