Potassium management in intensive horticulture

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Potassium management in intensive horticulture

• Wim Voogt Jop Kipp
• Applied Plant research
• Glasshousecrops division
• Naaldwijk The Netherlands

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Content

• K supply
• Yield
• Quality
• Crop uptake
• K fertilisation in practice

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Way of expression

• K as K, not K2O

• Quantity
• kg K ha-1
• (mol K ha-1)
• Example
• 500 kg K ha-1
• (603 kg K2O)

• Concentration
• mmol K l-1
• mg K l-1
• Example
• 6 mmol l-1
• 235 mg l-1

• Ratio
• N K K Ca
• mol mol
• kg kg
• Example
• N 20 mmol/l, K 7 mmol/l
• mole ratio N K 2.86
• weight ratio N K 1.0

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Quantity of available K in greenhouse crops
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K fertilisation

• Crop requirements
• Uptake
• Yield
• Quality aspects

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K and yield
Relation between the content of water-soluble K
(mg K 100g dry soil-1) at planting and the
relative yield
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K in experiments and trials

• The dilemma of changings in nutrient solutions

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K in experiments and trials

• The dilemma of nutrient solutions
• either
• increase EC / osmotic pressure
• shift in cation ratios

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Cut - flowers

• Carnation
• Rose
• Gerbera

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Rose

• No yield effects
• No effects on vase life
• effect on stem elongation (Mg K effect)

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Carnation

• No effect on
• vase life
• stem and bud breakage

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K uptake
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Total K demand vegetable crops
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K demand determined by

• Available quantity
• concentration
• EC, other nutrients
• Season
• Cultivar
• Climatical conditions

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Effect of climatical condition
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Uptake concentrations
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Distribution of d.m., K, Ca and Mg of total
uptake
(Voogt (1993), Roorda van Eysinga and Van Haeff
(1964) and Voogt (unpublished data))
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K fertilisation in practice
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Crop

• Standard nutrient solution
• Crop specific
• adjustments for
• substrate saturation
• start of the crop
• heavy fruit-load/vegetative development
• termination of crop

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• Nutrient solutions for soilless crops
• fertiliser formulations
• crop, water source specific
• concentrated solutions (100 times)
• A B tank or separate fertiliser injection
• Trickle irrigation

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Important

• Sampling method
• Right information
• water quality
• fertilisers (mixture, brand)
• crop stage
• pH control
• Make adjustments on time
• Adjustements/corrections adequate period

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Relation between concentration supplied and in
the root environment for tomato in hydroponic
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Example nutrient solution
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Adjustments to crop development
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Judgement of analytical data
2. Other parameters
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Rules for adjustment

• 1. Determine deviation analysis from standard
• 2. Adjustments for growing stage
• 3. Corrections for EC ajustments
• 4. Corrections for water quality
• Closed systems, corrections for draiange water
• 5. Equal settlement of cations/anions for
  equilibrium of the total ion-sum