Rootstock and scion effects on the leaf nutrient composition of citrus trees

Abstract

Four long-term citrus rootstock trials (navel orange, mandarin, Valencia orange, and lime soil trial) established at Irymple, in the Sunraysia district of Victoria, were tested for leaf nutrient composition in each of 2 years. Scion or rootstock significantly influenced leaf nutrient composition in orange and mandarin trees in all 4 trials. Poncirus trifoliata and citrange rootstocks and Ellendale tangor scion resulted in high to moderate leaf N, P, and K concentrations, while Symons sweet orange rootstock and Dancy mandarin gave low leaf nitrogen (N), phosphorus (P), and potassium (K) concentrations. Potassium concentrations of navel and Valencia oranges on rough lemon rootstock were lower than on most of the other rootstocks tested. For all rootstocks, however, leaf N, P, and K concentrations were in the high range in the navel orange and Valencia orange trials, while leaf K concentrations were in the high range in the mandarin trial. Citrange rootstocks and Ellendale scion also had higher concentrations of leaf magnesium (Mg), while Symons sweet orange, Cox sweet orange, and Rangpur lime had lower leaf Mg concentrations than other rootstocks and scions. In the Valencia rootstock trial, rough lemon and Rangpur lime induced the highest leaf sulfur concentrations, while citrange rootstocks gave the lowest. Soil depth in the lime soil trial influenced foliar P and K levels in Valencia orange trees but these differences were small. In all trials, rootstock, but not scion, strongly influenced chloride (Cl) concentrations of citrus leaves. Poncirus trifoliata rootstock accumulated high concentrations of Cl, and the citrange rootstocks moderate, while Cleopatra mandarin rootstock showed consistently low leaf C1 concentrations in all trials. Rough lemon rootstock was not consistently good at excluding C1, and Rangpur lime showed good C1 exclusion only in the Valencia rootstock trial. There was no evidence of a negative relationship between uptake of N and C1 by citrus rootstocks. Poncirus trifoliata had a lower uptake of sodium (Na) in the Valencia rootstock trial, while Cleopatra and Emperor mandarin rootstocks showed slightly higher leaf Na levels than most other rootstocks tested. The 2 citranges, mandarin, rough lemon, and Rangpur lime rootstocks induced higher boron (B) concentrations in leaves of navel orange compared with other rootstocks but they were still in the adequate range for citrus (Reuter and Robinson 1986), while sweet orange rootstocks had lower levels. Emperor mandarin scion on all rootstocks tested had the lowest B levels. Concentrations of iron and copper were rarely influenced by scion or rootstock. Rootstock significantly influenced leaf manganese (Mn) and zinc (Zn) levels in a number of trials, but scion effects were minor. In comparison with all other rootstocks, rough lemon induced higher Mn levels in some cases; sweet orange rootstocks gave higher leaf Zn levels in other cases; while Rangpur lime induced higher Mn and Zn levels in trees grown in the lime soil trial. In the first 3 trials, concentrations of Zn and Mn were low in many of the rootstocks and scions, indicating a need for a second micronutrient spray per growing season.