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Case Study

Increasing kiwifruit leaf litter decomposition with the application of soil biostimulant Digester

Simon Budd, BioStart Limited, Tauranga.
D Jensen, Puketiro Orchard, Tauranga.

July 2011

Key words
 Leaf litter, Digester, Mycorrhizae, Nitrogen.


BioStart Digester is a microbial stimulant that aids in accelerating the decomposition of leaf litter and prunings. This trial aims to compare leaf decomposition rates of two rates of Digester against an application of Nitrogen and untreated control.

  • The trial was run in block 1 rows 9-10, bays 2-5, of mature Hayward.
  • Leaves were collected on 13 July 2011 and spread between wire mesh cages which were put back onto the orchard floor and pinned to the ground in the weed spray strip.
  • Treatments used were Control Nitrogen 30kg/ha Digester 4lt/ha Digester 6lt/ha Each treatment was replicated 4 times.
  • Treatments applied 13 July 2011. Weather at the time of application fine, clear and still. 
  • Treatments were applied using a calibrated knapsack.
  • Fresh weights for the leaves were recorded at day 0 and 98.
  • Photos were taken of the cages at day 0, 12, 45, 59, 73, 87, and 98 after application.
  • Soil type in the block is Katikati sandy loam, well drained.  No herbicide was used applied during the trial.



  • 98 days after treatment there were some clear differences. Digester at 4lt and 6lt/ha had clearly increased the rate of breakdown.

TreatmentRepFresh weight day 0 (g)Fresh weight day 98 (g)
N at 30kg/ha142.45.81
N at 30kg/ha242.16.55
N at 30kg/ha341.46.44
N at 30kg/ha441.610.62
Digester 4lt/ha142.35.56
Digester 4lt/ha241.12.06
Digester 4lt/ha341.76.48
Digester 4lt/ha442.54.94
Digester 6lt/ha141.94.08
Digester 6lt/ha241.22.18
Digester 6lt/ha342.30.75
Digester 6lt/ha441.31.95



TreatmentAverage fresh weight day 0 (g)Average fresh weight day 98 (g)% decomposed at day 98
N at 30kg/ha41.887.3682%
Digester 4lt/ha41.904.7689%
Digester 6lt/ha41.682.2495%


  • All treatments accelerated leaf litter decomposition over the control.
  • Digester at 6lt/ha resulted in the most complete decomposition.

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