ROOTSTOCK AND SCION EFFECTS ON THE LEAF NUTRIENT COMPOSITION OF CITRUS TREES

Four long-term citrus rootstock trials (navel orange, mandarin, Valenc ia orange, and lime soil trial) established at Irymple, in the Sunrays ia district of Victoria, were tested for leaf nutrient composition in each of 2 years. Scion or rootstock significantly influenced leaf nutr ient composition in orange and mandarin trees in all 4 trials. Ponciru s trifoliata and citrange rootstocks and Ellendale tangor scion result ed in high to moderate leaf N, P, and K concentrations, while Symons s weet orange rootstock and Dancy mandarin gave low leaf nitrogen (N), p hosphorus (P), and potassium (K) concentrations. Potassium concentrati ons of navel and Valencia oranges on rough lemon rootstock were lower than on most of the other rootstocks tested. For all rootstocks, howev er, leaf N, P, and K concentrations were in the high range in the nave l orange and Valencia orange trials, while leaf K concentrations were in the high range in the mandarin trial. Citrange rootstocks and Ellen dale scion also had higher concentrations of leaf magnesium (Mg), whil e Symons sweet orange, Cox sweet orange, and Rangpur lime had lower le af Mg concentrations than other rootstocks and scions. In the Valencia rootstock trial, rough lemon and Rangpur lime induced the highest lea f sulfur concentrations, while citrange rootstocks gave the lowest. So il depth in the lime soil trial influenced foliar P and K levels in Va lencia orange trees but these differences were small. In all trials, r ootstock, but not scion, strongly influenced chloride (Cl) concentrati ons of citrus leaves. Poncirus trifoliata rootstock accumulated high c oncentrations of Cl, and the citrange rootstocks moderate, while Cleop atra mandarin rootstock showed consistently low leaf Cl concentrations in all trials. Rough lemon rootstock was not consistently good at exc luding Cl, and Rangpur lime showed good Cl exclusion only in the Valen cia rootstock trial. There was no evidence of a negative relationship between uptake of N and Cl by citrus rootstocks. Poncirus trifoliata h ad a lower uptake of sodium (Na) in the Valencia rootstock trial, whil e Cleopatra and Emperor mandarin rootstocks showed slightly higher lea f Na levels than most other rootstocks tested. The 2 citranges, mandar in, rough lemon, and Rangpur lime rootstocks induced higher boron (B) concentrations in leaves of navel orange compared with other rootstock s but they were still in the adequate range for citrus (Reuter and Rob inson 1986), while sweet orange rootstocks had lower levels. Emperor m andarin scion on all rootstocks tested had the lowest B levels. Concen trations of iron and copper were rarely influenced by scion or rootsto ck. Rootstock significantly influenced leaf manganese (Mn) and zinc (Z n) levels in a number of trials, but scion effects were minor. In comp arison 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 tre es 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, indicatin g a need for a second micronutrient spray per growing season.