nitrogen and irrigation management of potatoes

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nitrogen and irrigation managementof potatoes

• Sarah Sinton, Bruce Searle

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N and water are the main drivers

• Both N and water in the right amounts are needed
  to grow a great potato crop.
• Optimise tuber yield and quality.
• Accurate irrigation enhances N uptake.
• Minimise wastage, leaching.
• Crop needs change every year.

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How crops are managed

• Focus has been on maximising yields.
• Putting plenty of N on to cover all bases.
• Potato roots can reach 70 cm.

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Yields, N applied, N left
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How crops are managed

• Focus has been on maximising yields.
• Putting plenty of N on covered all bases.
• How much N is already in the soil?
• How much will be mineralised?
• The Potato Calculator.

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Canopy development
Full Canopy
Full Senescence
Emergence
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Partitioning of resources
100 partitioned to tops
25 tops 75 tubers
100 tubers
Biomass
tuber biomass
tuber initiation
tops biomass
Thermal time
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The soil model
Saturated
Field capacity
Wilting point
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Early deficit 2003-04, Canterbury
Yield reduction between 4.5 and 14.6 t/ha
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Later deficit 2004-05, Canterbury
Yield reduction between 0.5 and 6.3 t/ha

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How crops are managed

• Focus has been on maximising yields.
• Putting plenty of N on covered all bases.
• How much N is already in the soil?
• How much will be mineralised?
• Experience with Canterbury crops.
• Emphasis on N when in fact water was limiting.

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Lysimeter installation
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Rainfall and drainage
N treatments applied
N at planting
210 mm drainage
90 mm drainage
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N Leached at 80cm
Leaching from N treatments
Leaching from N already in the soil
N treatments applied
Leaching from N at planting
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Final points

• You need to understand the interaction between
  the crop, soil and weather to best optimise N and
  water use.
• You need to know
• - What the soil can supply
• - How much is needed (if theres a shortfall)
• - When to apply them
• The Potato Calculator can help you do this.

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Acknowledgements

• Sustainable Farming Fund
• HortNZ
• Ballance Agri-Nutrients
• McCain Foods Ltd
• Environment Waikato
• Horizons
• Hawkes Bay Regional Council
• HortResearch
• CFR
• Eurogrow
• Many potato growers
• gt A decade of Public Good money for earlier
  research