Anaerobically digested dairy as a renewable substitution for peat in media for nursery production

2014 Annual Report for GNE14-083

Project Type: Graduate Student
Funds awarded in 2014: $14,856.00
Projected End Date: 12/31/2015
Grant Recipient: University of Connecticut
Region: Northeast
State: Connecticut
Graduate Student:
Faculty Advisor:

Anaerobically digested dairy as a renewable substitution for peat in media for nursery production


Anaerobically digested dairy fiber (ADDF), a byproduct of methane production from dairy manure, shows promise as a locally sourced alternative to peat for growers in the Northeast.  ADDF has been shown to be a viable alternative to peat in a variety of greenhouse crop trials but there is currently no information published on using ADDF as a component of SPM for nursery crops.  Using ADDF in nursery media has the potential to benefit growers (by providing a locally sourced, inexpensive, sustainable alternative to peat), dairy farmers (by turning ADDF into a valuable horticultural product and providing a lucrative waste management solution) and the environment (by incentivizing dairy farmers to adopt anaerobic digesters and recycling nutrients in manure into horticultural crops)


Long and short term plant growth trials are being conducted to evaluate the performance of a variety of nursery crops in different stages of production grown in ADDF-containing media.  Aqueous extracts (Pour-thru) are used to regularly to monitor pH, EC and nutrient status of potting media in situ.  Plant size, stem caliper and number of shoots are measured regularly to evaluate plant growth over time.  Leaf tissue samples are to estimate nutrient uptake.    

This project began during the summer of 2014 and will conclude in June of 2015. This study is being conducted in the greenhouses, research fields and laboratories located at the University of

Objectives/Performance Targets


    1. To evaluate ADDF as a substitute peat in soilless potting media mixes.


    1. To evaluate nutrient availability in ADDF over time.


    1. To evaluate physical changes to ADDF over time.



Physical and chemical properties of two nursery mixes were evaluated.  The two mixes were composed of either bark-peat-sand (peat mix) or bark-ADDF-sand (ADDF mix) in a ratio of 4:2:1.  The peat mix was amended with 2.5g L-1 and the ADDF mix was amended with 4g L-1 gypsum.  There were no significant differences in physical properties and pH between mixes, however EC was slightly higher for the ADDF mix.


Liners of button bush (Cephalanthus occidentalis), silky dogwood (Cornus amomum) and divisions of blue moor grass (Sesleria caerulea) were planted in both ADDF and peat nursery mixes.  Button bush and silky dogwood were planted in #2 nursery pots (approximate volume 8.5L) and irrigated with drip emitters. The blue moor grass was planted in 2 quart nursery pots (approximate volume 2.8L) and irrigated by hand as needed.  Plants were moved from the greenhouse to the field on June 10.  A top dress application of Osmocote 15-9-12, 9 month release was applied at a rate of 45g to #2 pots and 4g to 2qt. pots.  PourThru samples were taken periodically to monitor media pH, EC and root zone nutrient status. Leaf tissue samples, plant size, caliper and stem number measurements were taken toward the end of the season but before dormancy was initiated.  Media shrinkage was measured twice throughout the growing season.


Preliminary data show no differences in size, stem caliper or number of stems between woody plants grown in the peat mix and ADDF mix. Analysis of PourThru samples  show elevated levels of orthophosphate in the ADDF mix for approximately 8 weeks after planting.


Cuttings were taken from ninebark and cranberry bush viburnum.  Cuttings were treated with rooting hormone and stuck in flats of sand.  Cuttings were rooted under intermittent mist until July 8.  Ninebark cuttings were transplanted into 2.5” pots and moved to a regular greenhouse.  Ninebark was trimmed to have 3 nodes for uniformity.  Rooted cuttings were moved to the field August 5.  Growth of rooted cuttings will be evaluated in the spring of 2015


Data entry, analysis and production of graphics have been ongoing as data is generated.

Impacts and Contributions/Outcomes

Research for this project is ongoing so there are few results to present through outreach activities or publications as of yet.  Results of previous ADDF trials with greenhouse crops will be presented at conferences including the 2015 Northeast regional meeting of The American Society of Horticultural Science.


Further ADDF plant growth trials will be conducted in the late winter through the spring of 2015 using herbaceous perennials.  Additionally, a greenhouse leaching trial will be conducted in the winter of 2015 to quantify nutrient runoff from cropped and uncropped ADDF nursery media.


Upon completion, this project will benefit nursery growers, dairy farmers and extension personnel who are interested in using ADDF as replacement for peat in potting media and adding value to ADDF. 


John Lamont
Graduate Student
University of Connecticut
1376 Storrs Road
Unit 4067
Storrs, CT 06269
Office Phone: 8603310723
Dr. George Elliott
Faculty Advisor
University of Connecticut
1376 Storrs Road
Unit 4067
Storrs, CT 06269
Office Phone: 8604861938