THE EFFECTS OF ORCHARD AND ENVIRONMENTAL FACTORS ON PHOSPHORUS AND NITROGEN CONCENTRATIONS IN APPLE AND PEAR FRUITS

Results of field trials show that annual variations in fruit phosphorus and nitrogen concentrations are often greater than those resulting from orchard treatments.
Apart from the direct and indirect (via crop load) effects of environment on nutrient uptake, the effects of treatments may alter from year to year.
Treatment effects may also change over a series of years and vary between sites.
In a trial at East Malling a soil phosphate application raised the phosphorus concentrations in fruit slightly, while they were increased by a grass sward (compared with cultivation) and decreased by soil nitrogen applications.
In a similar trial at Efford, phosphate had a greater effect, grass had little effect unless phosphate was also applied and nitrogen fertilizers had no consistent effects.

In another trial at East Malling sward treatments raised fruit phosphorus from the second year after sowing the grass, a situation only changed by two years of rotavation.
In contrast the sward reduced fruit nitrogen within a few months of sowing, and rotavation negated its effect within a year.
In the first trial the initial effect of sward on fruit nitrogen declined over five years with no consistent effects occurring thereafter.
Soil nitrogen applications usually raised fruit nitrogen levels.

In a current series of trials where the area of herbicide-treated soil is being varied, either on mature trees previously in a herbicide strip system or from planting, the beneficial effect of grass on fruit phosphorus (especially with irrigation) is again clear.
Adverse effects of overall herbicide on phosphorus concentrations were seen a few years after beginning the treatments.

Symposium on Mineral Nutrition and Fruit Quality of Temperate Zone Fruit Trees

M.A. PERRING

https://doi.org/10.17660/ActaHortic.1980.92.42