Rhizobium Grants the Reduction of Phosphate Fertilization during the Production of Coffee Seedlings

The use of bacterial inoculants is an attractive alternative that could reduce the consumption of chemical fertilizers in crops. In the production system of quality coffee seedlings, it is essential to achieve an adequate balance of nutrients that allows for healthy plants that are resistant to subsequent handling. The objective of this work was to evaluate the effect of Rhizobium sp. inoculation on the growth, nutrition and quality of coffee seedlings cultivated with different doses of phosphoric fertilization. Inoculation tests were carried out under nursery conditions using Coffea arabica L. cv. “Isla 5–15” and Coffea canephora Pierre ex Froehner cv. “Robusta” seeds inoculated with the Rhizobium sp. Rpr2 strain. Sixty days after sowing, the hypocotyldonal graft was performed, and the resulting plants were also treated with the bacterial inoculant. Plants were then planted in substrate with different doses of phosphorus (P): 25, 50, 75 and 100%. At seven months of cultivation, variables of growth (plant height, stem diameter, number of leaf pairs, main root length, root volume, dry mass of the aerial part, root and total), phosphoric nutrition (leaf and root P contents) and posture quality index were evaluated. The inoculation stimulated the aerial part (37%), root growth (34%), the quality index of the grafted postures (30%), and phosphorus absorption (42%) and allowed a decrease from 25 to 75% of the mineral fertilizer. For the first time in Cuba, the benefits of rhizobial inoculation on the nutrition and quality of coffee seedlings were demonstrated. The inoculation of grafted coffee seedlings with Rhizobium sp. Rpr2 through the inoculation method proposed in this study can be recommended as a new easy, cost-effective and efficient inoculation approach to obtain additional benefits for coffee growth, improving the absorption of nutritive elements and the quality characteristics of the coffee seedlings.