Articles
THE USE OF LEAF ANALYSIS IN ADVISORY WORK IN THE UK
The development of standard ranges of leaf nutrient concentrations for optimum growth has provided a method of measuring the nutritional status of the trees in individual orchards.
A standard method of leaf sampling is followed to reduce errors associated with variation in nutrient concentrations with time and position of the leaf on the tree.
Standard nutrient concentrations for satisfactory growth have been determined from experimental response data and orchard survey data.
A number of ‘marker trees’ are sampled each year to provide a method of adjusting the standard nutrient concentrations according to seasonal influences.
Leaf analysis is accepted as being a more accurate guide than soil analysis to the adequacy of the orchard fertilizer programme.
Soil analysis is used as a complementary tool and where leaf nutrient concentrations are below the optimum, it can be used to assess whether the cause is low soil nutrient levels or poor nutrient uptake from the soil due to other limiting factors.
In practice leaf analysis results are often used to reduce rather than increase the amount of fertilizer used.
A 1978 survey of 217 commercial Cox orchards showed that 40 per cent of the leaf nitrogen levels, 40 per cent of the leaf phosphorus levels and 70 per cent of the leaf potassium levels were above the optimum for satisfactory growth, indicating a general need to reduce applications of these nutrients.
In contrast leaf calcium and magnesium levels tended to be at or below optimum.
Survey information indicates a considerable difference in mean leaf nutrient concentrations in commercial orchards of the two varieties Cox’s Orange Pippin and Bramley Seedling.
In most years there is a general relationship between leaf nutrient concentrations and fruit storage quality.
However fruit analysis at or shortly before harvest is recommended for this purpose because this is more accurate than leaf analysis for predicting the occurrence of storage disorders.