Response of Mature Phosphorus-Deficient Apple Trees to Phosphorus Fertilization and Liming.

The aim of the study was to examine response of mature phosphorus (P) deficient apple (Malus domestica Borkh.) trees to phosphorus fertilization and liming. The experiment was carried out during 2003-2005 in a commercial orchard in Central Poland on 'Jonagold' apple trees/M.26 planted in 1996 on a coarse-textured soil with low both pH (4.6) and organic matter (1.2%). Calcium-lactate soluble phosphorus concentration in the soil was within an optimal range despite appearance of leaf phosphorus deficiency symptoms. Soil and foliar applications of phosphorus, and soil liming were applied. Soil phosphorus fertilization was made in the first year of the experimental at a rate of 100 kg P per ha as triple superphosphate. Foliar sprays of a soluble compound containing organic phosphorus were performed 5 times per season at 2-week intervals, starting 4 weeks after full bloom. Soil liming was applied in the fall 2002 at a rate of 1100 kg Ca ha-1 as hydrated lime. Additional combination as soil phosphorus fertilization plus liming was also applied. Plots unsupplied with phosphorus and lime served as a control. The results showed that liming and liming plus soil P application increased soil pH, and phosphatase activity in the soil, and improved phosphorus nutrition, tree vigor, yield, fruit color, and firmness after storage; effect of these treatments was not found only in the first year of the study. In all years foliar phosphorus sprays improved phosphorus nutrition of apple trees, and fruit color and firmness after storage. In 2 out of 3 years foliar phosphorus application increased yield. The vegetative and reproductive responses of 'Jonagold' apple trees did not depend on soil phosphorus fertilization. It was concluded that maintaining an optimal pH of soils for apple trees limits the incidence of orchard phosphorus deficiency and that foliar phosphorus sprays should be applied in phosphorus-deficient apple orchards to improve yield, and fruit appearance and storability. [ABSTRACT FROM AUTHOR]