Determination of the fertiliser requirements of pear trees from tree performance, leaf analysis and fruit quality data.
Wooldridge, J.;
Deciduous Fruit Grower Year: 1994 Vol: 44 Issue: 1 Pages: 28-31 Ref: 5 ref.
1994
บทคัดย่อ
ABSTRACT :
The responses to lime, K (as KCl) and N (as limestone [calcium] ammonium nitrate) at various rates were investigated over 8 years in a field trial with pear cv. Williams' Bon Chretien seedling rootstock on a fine silt-clay soil with a pH of 4.4. All plots received a pre-planting (1984) application of superphosphate. Calcareous limestone was applied at 0, 14 or 30 t/ha 90 days before planting to give pH levels of 4.4, 5.5 or 6.0; these were maintained thereafter by annual topdressings of dolomitic limestone [magnesian limestone] and calcareous limestone. Potassium was applied in 1985 in Sep. and Nov. at rates equivalent to a total annual application of 264, 1090 or 1910 kg/ha. No further K was applied until 1989 when the respective plots received 60, 120 or 180 kg/ha; in 1990 they received 70, 140 or 210 kg/ha and in 1991 they received 90, 180 or 270 kg/ha. Between Sep. 1984 and Sep. 1989 N was applied at the standard Infruitec-recommendation rate, at 28-day intervals between bud beak and leaf se
nescence. Thereafter the trees received 50, 100 or 150% of the N rates recommended for bearing orchards. Leaf analyses were carried out in Jan. between 1987 and 1992 and fruit yields and analytical data were recorded following harvest in early Feb. in 1990, 1991 and 1992. Trunk circumferences, 150 mm above the graft union were measured each winter. The results showed that there were no significant interactions between treatments. The main effects are discussed. Growth was best at a soil pH of approx equal to 5.5. However, liming exacerbated Zn, Mn and B deficiencies and also impaired K utilization. In the young trees, the trunk circumference increased progressively over the range 50-150 mg of Bray 2 extractable K/kg soil. It was thus possible that the development of young trees could be improved by increasing the soil level of K above the currently recommended 100 mg/kg. In bearing trees, spring and postharvest applications of 60-180 kg KCl/ha progressively increased trunk circumference and yields; however,
the highest rates may have contributed to a delay in fruit maturation. The highest N application rate appeared to be surplus to requirements.