A study of the potassium nutrition of the lemon tree (Citrus limon Linn) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science in Plant Science, Massey University, New Zealand

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Massey University
Villafranca lemon trees were grown for two years in con­tainers and provided with a standard nutrient feed. Potassium was supplied differentially, usually as foliar sprays of potassium chloride. The magnitude of the effect of varying numbers of sprays on leaf potassium was determined, the main response being the short-term nature of this effect. Similarly the considerable ben­efits of a limited number of manganese or zinc sprays on the leaf concentration of these elements was demonstrated. Determinations of the levels of the main minerals in the leaves showed the seasonal variations of each one, and led to a recommendation on sampling time for the determination of each ele­ment. It was also possible to demonstrate possible mineral element interactions, the most interesting being the lack of a potassium - magnesium anatgonism. It was shown calcium levels fell with in­creased leaf-potassium to maintain the cation balance. But in another situation the range in plant nutrient status was such as not to maintain an equivalence in the cation/anion ratio or the total leaf cation content. In this latter instance this did not result in a predicted effect on leaf organic acid content. The possible dangers of excessive chloride accumulation were considered; and the problem of leaf chlorosis where potassium is in low supply. A recommendation was made on the use of nutrient solution feeds for young citrus trees, especially with respect to trace element supply. Various effects of potassium supply on fruit quality were also demonstrated.
Potassium fertilizers, Lemon, Lemon Physiology