CROP PREPARATION
12. Soil test and fertiliser
Test soil at least three months prior to planting (Autumn is best). If required,
a base dressing can be applied, to adjust pH to 5.5 ‐ 6.0 and nutrient levels (PK‐
Mg‐Ca) into balance.
Addition of calcium (Lime/Dolomite) prior to Winter is essential on most New
Zealand soils. Gypsum is used to increase calcium without increasing pH (1 ‐2
kg /100m2).
Add further fertilizer at planting e.g. controlled release prills: Triabon® (16 ‐3
‐10 +Mg+S) at 4kg/100m2 or AgroblenTM Brown (15‐3.9‐9.1 +Mg) at 4kg
/100m2.
When using bark based media, add 3 month Osmocote® (3.5kg/m3) and
Dolomite/Gypsum.
Weekly application of foliar feed is beneficial for stem and tuber growth.
Water soluble NPK fertilizers (Nitrosol®, Peters® Professional or Nutrifol®)
can be used.
High nitrogen formulas are suitable for the early stages of growth, with
adjustment to a high potassium mix as flower formation occurs. This is
important in a greenhouse situation as excess nitrogen will cause weak floppy
stems, decrease vase life as well as reducing the storage life of the dormant
tuber.
Do not over fertilize. Ensure that only a small, controlled amount of N is
available at tuberization (after flowering). Excess N can stimulate the
‘buttoning’ process ‐ refer #26. High salts can contribute to callousing ‐ #27.