Polyculture Trial - Apple Polyculture vs Monoculture - How Do they Compare in Terms of Costs, Soil Health, Biodiversity, Production and Time?

We are shifting our focus to perennial polyculture experiments and forest garden yields and have been working on a new perennial polyculture trial that we're aiming to start in April 2024. It's a long-term comparative study looking at the input and outputs of growing an Apple tree in polyculture vs monoculture.

Apple Polycutlure vs Apple Monoculture Study 

During this post, I'll present the trial garden and trial design, cover what we will record, and take a look at some of the shortcomings of the study.

So, let's start with a look at the garden where we'll be growing the trials.

Trial Garden Overview 

Location: Shipka, Bulgaria, Southeast Europe

Köppen Climate Classification - Dfc borderline Cfb

USDA Hardiness Zone: 5b (conservative) - 7a (risky)

Latitude: 42° 

Elevation: 565 m

Average Annual Rainfall: 610 mm 

Prevailing Wind: NW & NE

Garden Area - 352m2

Garden Location on our Project Map - See here

We'll be growing four trials on the plot as seen in the below image. We chose this plot as each trial will more or less experience equal environmental conditions. There is a very mild slope on the site from N - S and no slope W-E.

Perennial Polyculture Research Garden - Orexis

The plant we chose to feature in the trial is Apple - Malus pumila ‘Red Cap’

Here's some info on this cultivar

• Origin: A mutation of a spur Red Delicious with a sweet taste and a crisp texture.
• Growth: Strong growth, develops more shoots in comparison with other spur mutants of Red  Delicious.
• Fruit Colour: Ripens with a full deep dark red colour.
• Fruit Size: Big, elongated fruits.
• Fruit Storage: Good, similar to other clones of Red Delicious.
• Taste: The fruit is sweet, with crunchy and firm flesh, which becomes softer during long storage. 
• Flowering: Early to midseason bloom.  It blooms relatively early, but for a long period. Good pollinator cultivars include Evereste, Idared and Golden Delicious.
• Production: Early and regular, at the end of September and beginning of October.

We've selected feathered whips (generally bigger than a whip with well-developed side branches) 2nd year on the graft with Rootstock - MM106. The selected plants will be of equal shoot and root mass.

The Four Trials 

We'll be growing 4 trials with each trial planted in a 56m2 area. The trials will include 2 polycultures and 2 monocultures as shown below.




Polyculture 1  - Suitable for broadscale application- Apple planted with two Nitrogen fixing shrubs (Elaeagnus umbellata) and bulbs at the base of the tree. The spacing of the shrubs and bulbs is such that a compact utility tractor can operate within the orchard, leaving two strips of wildflowers between tree and shrub rows.

You can find an example of how this polyculture would look within an orchard setting in the below image.



Polyculture 2 - Intensive polyculture. only really practical for gardens or small market gardens, schools, parks or small scale landscaping in general. It will be high maintenance.



Monoculture Organic - Apple cultivation with the full works of organic synthesized proprietary products applied  (all recommended fertilizers, herbicides, pesticides and fungicides).

Monoculture Conventional - Apple cultivation with the full works of non-organic synthesized proprietary products applied (all recommended fertilizers, herbicides, pesticides and fungicides).

Species List for Each Trial
Qty	Botanical	Common	Family	Function
Orexis- Polyculture 2
CANOPY LAYER
1	Malus pumila 'Red Cap'	Apple	Rosacea	Productive - Food
SHRUB LAYER
1	Ribes rubrum	Redcurrant	Grossulariaceae	Productive - Food
1	Ribes nigrum	Blackcurrant	Grossulariaceae	Productive - Food
2	Elaeagnus umbellata	Autumn Olive	Elaeagnaceae	Support - Nitrogen Fixation - Productive
HERB LAYER
6	Symphytum x uplandicum	Comfrey - 'Bocking 14'	Boraginaceae	Support Mulch/Polleniser
2	Foeniculum vulgare	Fennel	Apiaceae Umbelliferae	Productive - Support
2	Origanum vulgare	Oregano	Lamiaceae	Productive - Support
10	Allium tuberosum	Chinese Chives	Alliaceae	Productive - Support
GROUND LAYER
48	Allium ursinum	Wild Garlic	Caryophyllaceae	Support Polleniser
Native Ground Cover - See Existing Flora Sheet
BULBS - Tree Pits
4	Galanthius sp.	Snow Drops	Amaryllidaceae	Support Polleniser/Mineral Repositor
4	Corydalis bulbosa	Crested Lark	Papaveraceae	Support Polleniser/Mineral Repositor
4	Crocus nudiflorus	Autumn Crocus	Iridaceae	Support Polleniser/Mineral Repositor
Orexis- Polyculture 1
CANOPY LAYER
1	Malus pumila 'Red Cap'	Apple	Rosacea	Productive - Food
SHRUB LAYER
2	Elaeagnus umbellata	Autumn Olive	Elaeagnaceae	Support - Nitrogen Fixation - Productive
GROUND LAYER
Native Ground Cover - See Existing Flora Sheet
BULBS - Tree Pits
4	Galanthius sp.	Snow Drops	Amaryllidaceae	Support Polleniser/Mineral Repositor
4	Corydalis bulbosa	Crested Lark	Papaveraceae	Support Polleniser/Mineral Repositor
4	Crocus nudiflorus	Autumn Crocus	Iridaceae	Support Polleniser/Mineral Repositor
Orexis-Organic
CANOPY LAYER
1	Malus pumila 'Red Cap'	Apple	Rosacea	Productive - Food
GROUND LAYER
Native Ground Cover - See Existing Flora Sheet
Orexis- Conventional
CANOPY LAYER
1	Malus pumila 'Red Cap'	Apple	Rosacea	Productive - Food
GROUND LAYER
Native Ground Cover - See Existing Flora Sheet

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What we will Record

What we will record - Soil Physical Analysis - Three Soil physical tests will be taken every 3 years in the locations seen in the below image, and should be rotated so that they are taken in a different quarter of the area every 3 years.

What we will record - Annual soil mineral analysis - Each year soil samples within each plot will be collected and sent off to the lab to test for  N-P-K-Mg-Ca and soil organic matter.


Our project mission is to develop and promote practices that can produce food and other resources for humans while enhancing biodiversity, so it's important to us to record biodiversity within the trials. We'll attempt to do this via simple botanical and invertebrate surveys.

What we will record - Botany - On the first week of each month during April - September, we’ll photograph all flowering vegetation within each trial plot, identify species and record on sheets.

What we will record - Invertebrates  - In the 2nd week of May - July, and September we will carry out  2 surveys (Thur & Fri) . The surveys will consist of';

• Sweep netting - 10 mins - Ground/grass layer 
• Vegetation Beating - 10 mins - Tree/shrub and herb layer
• 4 Pitfall traps set on Thursday and emptied on Friday.

The number of unique species identified will be recorded for each plot.

What we will record - Biomass - All arisings from mowing will be weighed and recorded for each trial. For the two polyculture trials, we'll also record the biomass trimmed from the E.umbellata shrubs that will be cut annually and kept trimmed to 1 m width and 1.5 m height. All trimmings will be weighed fresh and recorded on site.

The below image indicates (in greenish grey) the area of each plot that will be mown.

What we will Record - Growth and Development - The development during the year will be recorded using the BBCH Scale I.

Growth will be recorded by the girth of stem at the base and new growth at end of the season, the no. of flowers in the spring, and the weight of  the fruits in the autumn.

What we will Record - Management - Polyculture 1 and 2 - Time and Cost to Manage each Trial

Fertility - Apply 20 L of compost to the surface of the planting area every spring for 4 years. 

Mulching - Apply a thick mulch (10 - 20 cm deep) when the ground is thoroughly soaked and before the dry season begins for 4 - 5 years. 

Irrigation - Applying approx 20 L of water every 20 days without rain (or when the soil is dry below the surface). 

Weed/Mow - Mow area every 4th week of the month April - September.

Pruning - Formative prune when young i.e pruning to form the desired shape of the mature tree. Standard prune every year, i.e remove deadwood and crossover branches.

What we will Record - Management - Organic and Conventional - Time and Cost to Manage each Trial

Fertility - Application of recommended fertility additives.
Spraying - Application of recommended organic pesticide, fungicide, and herbicide additives.

Irrigation - Applying approx 20 L of water every 20 days without rain (or when the soil is dry below the surface). 

Weed/Mow - Mow area every 4th week of the month April - September. 

Pruning - Formative prune when young i.e pruning to form the desired shape of the mature tree. Standard  Prune every year i.e remove deadwood and crossover branches.

What we will Record - Time and Cost to Establish each Plot

Plant, Materials and Labour costs will be recorded for each trial.

You can find a slideshow of this trial design here.

Thank you Simon Leupi for your feedback and suggestions on the study design, and to Chris Mallorie for discussing the trial with me, and working on the organic fertility and pesticide protocol.

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