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Case Study

Increased kumara yields with the application of biostimulant Mycorrcin

BioStart Limited.
Grower Ruawai, Northland.

March 2010

Key words
Kumara, Mycorrcin, increased yield.


 The treatment used was:

  • 7 October 2009 Terracin applied to the soil at 20lt/ha.
  • 2 November 2009 Mycorrcin added to the watering immediately post planting at 5lt/ha.
  • 1 December Mycorrcin added to watering at 5lt/ha.
  • Terracin used to reduce incidence of nematode damage when. Terracin is an alternative to normal sterilization products.
  • Just prior to the commercial harvest the block was divided into 3 areas, North, middle and South. The centre of each block was then transected by a line. Plants from every second row were lifted and the number of kumara were counted, weighed, graded and assessed for nematode damage.


Untreated (below):


Treated (below):



Untreated (below):


Treated (below):


Summary (below):

UntreatedTreated% increase
Total kg41.3752.56+27%
Total No.277458+65%
1st Grade No.156214+37%
2nd Grade No.81148+83%
Reject No.3996+146%
Avg kumara weight kg0.1490.115-23%
Avg total kumara weight/plant kg0.5520.701+27%
Avg No. kumara/plant3.6936.107+65%

Nematode damage:

No nematode damage was recorded.


The Mycorrcin treatment resulted in the following:

  • Total number and weight of kumaras were increased.
  • 1st Grade, 2nd Grade and reject numbers were all increased.
  • Average number of kumaras per plant increased.
  • Average kumara weight decreased
  • The dry growing conditions late season could have allowed the kumaras to be left in the ground for another couple of weeks to size up. This was not done as the risk of disease increases the longer the crop is left in the ground. 
  • No nematode damage was found. This may be a function of the dry growing conditions.

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