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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:

  1. Control: 4lt/ha Digester added to Glyphosate at spray out. Standard fertiliser program. 4lt/ha Mycorrcin added to water immediately post planting.
  2. Treated: 4lt/ha Digester added to Glyphosate at spray out. Standard fertiliser program. 4ltlt/ha Mycorrcin added to water immediately post planting. 4lt/ha Mycorrcin added to Paraquat herbicide spray. 

Just prior to the commercial harvest the block was divided into 3 areas, East, middle and West. The centre of each block was then transected by a line. Sample plots of 10m long and 8 rows wide were then hand harvested. The kumara numbers were counted, weighed and graded.

  • Small >100 grams.
  • Premium 100 – 600 grams.
  • Jumbo < 600 grams.

Right: Block layout.


Control (below):


Treated (below):


Control (below):


Treated (below):


Mycorrhizal responses:

Sub plots (below):

ControlTreated% increase
No. plants332348+5%
No. premium9111211+33%
No. Jumbo139134-4%
No. Small159183+15%
Total No.12091528 +26%
Weight Premium (kg)260.43346.26+33%
Weight Jumbo (kg)113.65116.77+3%
Weight Small (kg)10.7211.38+10%
Total weight (kg)384.80474.41+23%

Per plant (below):

ControlTreated% increase
No. premium2.743.48+27%
No. Jumbo0.420.38-10%
No. Small0.480.52+8%
Total No.3.644.39+21%
Total weight Premium (kg)0.781.00+28%
Total weight Jumbo (kg)0.340.34+0%
Total weight Small (kg)0.030.03+0%
Total weight (kg)1.161.36+17%
Average weight premium (kg)0.2850.2850%
Average Jumbo weight (kg)0.8170.871+7%
Average Small weight (kg)0.0670.062-7%

Return on investment (below):

  • Return on investment has been extrapolated to a per hectare basis.
Premium grade $/ha$36,170$48,091
Jumbo $/ha$11,049 $11,352
Small $/ha$744$790
Gross return/ha$47,964$60,234
Cost of BioStart/ha$138$207
Net return/ha$47,826$60,027


The Mycorrcin treatment resulted in the following:

  • A +5% increase is plant survival rates.
  • A +33% increase in the number and weight of Premium grade kumara.
  • A +26% increase in the total number and +23% increase in total weight of kumara.
  • Based on the sample plot field gradings the treatment increased net return by $12,201 per hectare.

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