The Ca/Al ratio is determinant for root deepening in the soil subsurface layer. Liming this layer can improve root growth and nutrient absorption. Thus, a greenhouse trial was carried out using soil columns. Two varieties of coffee plants (Catuaí and Icatú), one Al-sensitive and the other Al-tolerant, respectively, were evaluated in limed and surface-fertilized soil, whereas 0.0; 0.49; 1.7; 2.9; 4.1; 6.6 and 9.3 t ha-1 of limestone were applied to the subsurface soil. Plants were cultivated for 6.5 months in soil accommodated in PVC columns, subdivided in three rings. In the two lower rings Al saturation varied from 0 to 93 %. Limestone application in the subsurface raised the Ca and Mg contents in the shoot and roots, and P concentration in the upper leaves of both varieties. Following subsurface limestone application, Ca utilization efficiency decreased for both varieties, by the shoot as well as by roots. The P utilization efficiency by the shoot decreased only in the Icatú variety. Subsurface limestone application reduced the Al content in the aerial part of Icatú and in Catuaí roots. The leaf concentration of P, Ca and Mg remained at adequate levels in both varieties, indicating that fertilization and acidity correction of the surface soil layers were efficient at maintaining the plant nutrient levels, independent of Al levels in the soil subsurface.
subsurface liming; coffee tree nutrition; Al tolerance; Al toxicity
