Organic vs. mineral

A comparative trial between living soil and mineral fertilisation.

 

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Table of Contents

A detailed description of the experiment follows immediately below, or you can simply click the link to jump straight to the relevant section of this blog:

  1. Experimental Setup
  2. Proper Watering
  3. Grow Diary
  4. The Results

Motivation

Whilst many growers provide nutrients to their plants using mineral fertilisers, the Living Soil community has grown significantly in recent years. Many myths and claims are shared and discussed across a wide range of media. However, research based on comparative studies is scarce or simply non-existent.

In addition to high-quality LED lights for plant cultivation, SANlight GmbH’s product portfolio is constantly expanding. Since 2025, SANlight GmbH has been distributing mineral fertilisers from the American manufacturer Hydroponic Research and is convinced that these products offer added value for the user. Before this range of mineral fertilisers was added to the SANlight product range, several empirical studies were carried out to demonstrate the product’s effectiveness and to ensure that customers receive the best possible support in future.

In numerous consultations, seminars and site visits, we are repeatedly faced with the same questions.

  • What is SANlight’s view on Living Soil and/or organic plant cultivation?
  • Can the same yields be achieved with Living Soil as with conventional mineral fertilisers?
  • What are the advantages and disadvantages of each cultivation method?

In answering the above questions, we were able to draw on our internal knowledge base to a limited extent. Our own data on this topic was scarce. Consequently, we could only share our own personal experiences and those of our customers. This prompted us to conduct our own trial in our grow chamber – the HOMEbox CLUB 18.

Definition

Living Soil or organic soil

Living Soil is not a scientifically defined term and can therefore be interpreted in various ways. Generally, it refers to the cultivation of plants in living soil.

The idea is to utilise plants, macro-organisms (worms, arthropods) and micro-organisms (bacteria, fungi, etc.) to make nutrients available to plants. In this process, nutrient availability arises primarily through the metabolism of these organisms, rather than through the addition of directly available nutrients. The Austrian company ‘Sonnenerde’ produces peat-free soils with a high proportion of various composts, which are referred to on their website as ‘Living Soil’. Various home-made composts are used in the production process, which bring the soil to life.

The customer receives a peat-free substrate that also contains activated biochar as a nutrient buffer. The biochar, which is also produced in-house, is enriched with nutrients during the composting process. The substrate is therefore already enriched with nutrients from the outset. Further nutrients are released through decomposition processes etc. during cultivation. In practice, raised beds are often used in indoor cultivation to maximise the substrate volume available to the plants as well as the micro- and macro-organisms.

 

The greater the volume of soil, the more nutrients can be made available to the plant. In principle, there is no need to use additional nutrients provided that there are sufficient numbers of micro- and macro-organisms present, and these can find enough nutrients in the substrate for their own metabolism. Living soil can therefore be used over long periods, provided that care is taken to ensure that the soil life does not die off.

Many growers criticise the fact that ready-made soils filled into small pots do not adhere to the living soil concept. According to research, soil is considered living soil if the following criteria are met.

  • At the microbial level, bacteria and fungi mineralise organic matter and make nutrients available to the plant.
  • No directly available nutrients are added from outside during the cultivation process.
  • Organic matter – humus, compost and plant residues – serves as an energy source for microbial life and as a nutrient store.
  • Plant–microbiome interaction: Plant roots selectively secrete exudates (sugars, amino acids, acids) to attract specific microorganisms – thereby actively controlling their rhizosphere community.

In our view, all the above points are met, meaning that the organic hemp soil, in combination with mulch, can be described as Living Soil.

The basic idea behind the experiment

The basic aim of the experiment is to generate data that allows for a comparison of the different cultivation methods. The questions are as follows.

  • Is it possible to grow plants in 18-litre pots filled with organic hemp soil (described by the manufacturer as ‘living soil’) until harvest without adding any additional nutrients?
  • How significant are the differences in yield when using this soil without additional fertiliser compared to conventional mineral-based cultivation?
  • Are there any differences in the quality of the end product between these two methods?

Fill the pot with soil – water – harvest

We see one of the major advantages of Living Soil in the simplicity of cultivation. In theory, and according to various manufacturers, it is possible to grow plants in a pot filled with Living Soil simply by watering them. In the organic hemp soil used, all nutrients are already present and/or will be made available by microorganisms in the medium term. This results in the advantage of a simple system, as the water supply can be easily automated using suitable watering systems. Furthermore, there is no risk of incorrect fertiliser dosing or similar issues. The use of beds with very large volumes is not considered in this experiment, as we regard this as impractical for a large number of potential users.

If it were possible to fill a pot with soil, water it and ultimately harvest a sufficient yield, this would probably be the simplest way to provide oneself with flowers.

Experimental Setup

The aim of the experiment is to compare, as realistically as possible, organic cultivation using water alone with conventional cultivation using mineral fertilisers. The experiment is being carried out in a closed system (HOMEbox CLUB 18) in which all growth-related parameters, such as temperature, humidity, light, etc., can be controlled. The room, with a net growing area of 14m², is divided into two sections, each with 7m² of table space.

Proper Watering and Full Water Holding Capacity

Filling – Planting – Watering

Different growing media require different preparation.

Depending on the manufacturer and product, each growing medium absorbs different amounts of water/nutrient solution and retains it to varying degrees. It is helpful for every grower to know the maximum amount of water/nutrient solution the substrate can absorb. From this, ideal watering quantities can be calculated based on the pot weight. This allows for effective control of watering and reliably prevents over- or under-watering.

For the CANNA Terra Professional Plus substrate, we have determined the values using an 11-litre pot.

Proper watering with CANNA Terra Professional Plus

A fully filled 11-litre pot that is completely saturated with water weighs 7.66 kg (including the 300 g weight of the pot).

 

  • For starting young plants in this substrate, we recommend a saturation level of 75%.
    – During the growing cycle, the saturation level should fluctuate between 50% and 75%.
    – Only once the 50% mark is reached should water be added to bring it back up to 75%.
  • Experts may go below or above these values to manage their plants accordingly.
  • The wilting point we have determined (depending on the VPD) is approximately
    – 39% during the vegetative phase
    – 45% during the generative phase

Correct watering for Sonnenerde organic hemp soil

Due to the peat-free nature of the organic hemp compost, this soil is very heavy and tends to become waterlogged. It is therefore particularly important to ensure that the substrate is not over-watered. We recommend watering the soil with 15% of the pot’s volume to start with. For an 18-litre pot, this equates to 2.7 litres of water or 2.7 kg. We have not yet been able to determine the exact wilting point. We recommend watering the soil again as soon as approximately 1 litre of water has transpired. See the specific example below.

 

  • A fully filled 18-litre pot with organic hemp soil weighs 11 kg, including the pot (empty pot = 0.48 kg).
  • If this is watered with 15%, i.e. 2.7 litres of water, the weight increases to 13.7 kg.
  • Only once the weight reaches 12.7 kg should the pot be watered again to bring it back up to 13.7 kg.

Group treated with mineral fertiliser

Pre-treatment of the substrate

To kill any spores, pests or pest eggs that may be present, the substrate is steamed for approx. 45 minutes at 80°C. In the next step, the soil is loosened.

Filling the pots

The pots were filled with 5 litres of substrate, which was then compacted using a tamper. A further 5 litres are then added and compacted. Only in the final step is the pot filled to the brim with soil. The soil is now watered in small amounts over several hours until it reaches a saturation level of 75%. Water with an adjusted pH is used for this. Finally, the young plants, including the rooting wedge, are potted into the soil.

Organic/Living Soil Group

Pre-treatment of the substrate

As organic hemp soil is a living substrate, it is not heated so as not to destroy the soil life.

Filling the pots

The pots are filled with soil to about 2 cm below the rim. The soil is lightly compacted by tapping the pot gently on the floor several times. Finally, the soil is covered with a 2 cm layer of organic fibre (mulched). The organic fibre on top helps to distribute the water more evenly and protects the top layers of soil from drying out. As the mulch decomposes naturally, the soil is continuously supplied with additional nutrients. Finally, the young plants, including the rooting wedge, are potted into the soil.

Grow Diary

In the drop-down menu below, you will find a detailed list containing all the relevant information about the entire grow. All VPD values given refer to a delta of -2°C in leaf temperature.

Week 1 - Germination

Week 1 - Germination

During the first 7 days after planting, the following target values were maintained. As the plants were extremely young, relatively low VPD values (high relative humidity) were maintained. Watering was not necessary in the first week for either experimental group.

Target values:

Day 1 2 3 4 5 6 7
Lighting duration [h] 18 18 18 18 18 18 18
Temperature Day [°C] 24 24 24 24 24 24 24
rH Day [%] 75 75 73 70 70 70 70
VPD Day [kPa] 0,41 0,41 0,47 0,56 0,56 0,56 0,56
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 70 70 68 65 65 65 65
Dimming [%] 30 30 30 30 30 30 30
PPFD at plant [µmol/m2/s] 250 250 250 250 250 250 250
Watering volume, mineral [l]
Watering volume, organic [l]
VBX [g/l]0
Shine [g/l]
EC/PH
Note Plants were not watered during the first week.
Week 2 - Potting

Week 2 - Potting

The plants were potted into their final pots exceptionally early for testing purposes. The aim was to determine whether seeds could potentially be germinated directly in organic hemp soil.

  • Five plants that were potted into organic hemp soil in their first few days failed during the first week.
  • One plant grown in CANNA Terra Professional Plus failed during the first week.

The young plants that failed were replaced by reserve plants that had been grown separately.

In general, we recommend germinating seeds in rooting plugs or seedling compost. Only once the first true (serrated) leaves have formed should the plants be transferred to their final pots.

As can be seen in the picture, the plants in Sonnenerde developed significantly more slowly.

 

Day 8 9 10 11 12 13 14
Lighting duration [h] 18 18 18 18 18 18 18
Temperature Day [°C] 24 24 24 24 24 24 24
rH Day [%] 70 70 70 70 70 70 70
VPD Day [kPa] 0,56 0,56 0,56 0,56 0,56 0,56 0,56
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 65 65 65 65 65 65 65
Dimming [%] 35 35 35 35 35 35 35
PPFD at plant [µmol/m2/s] 280 280 280 280 280 280 280
Watering volume, mineral [l] 0 0 0,5 0 0 0 0
Watering volume, organic [l]
VBX [g/l]0 0 0 0,8 0 0 0 0
Shine [g/l]
EC/PH
Note The plants were watered by hand just once on the mineral side.
Week 3 – Installing the watering system

Week 3 – Installing the watering system

The irrigation system was installed in the third week. Whilst the plants were only watered by hand once during weeks 1–2, from the third week onwards they required more water or nutrient solution and could be supplied via the irrigation system for the first time. The plants in the organic hemp soil were still lagging behind in their development. However, there were now sufficient roots present there too to allow the temperature to be raised slightly and the humidity lowered in order to stimulate transpiration. The light intensity was also increased to 360 µmol/m²/s during this week.

Target values:

 

Day 15 16 17 18 19 20 21
Lighting duration [h] 18 18 18 18 18 18 18
Temperature Day [°C] 24 24 24 24 24 25 25
rH Day [%] 70 70 70 70 70 65 65
VPD Day [kPa] 0,56 0,56 0,56 0,56 0,56 0,75 0,75
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 65 65 65 65 65 60 60
Dimming [%] 40 40 40 40 40 50 50
PPFD at plant [µmol/m2/s] 315 315 315 315 315 360 360
Watering volume, mineral [l] 0,5 1
Watering volume, organic [l] 1
VBX [g/l] 0,8 0,8
Shine [g/l]
EC/PH 0,8/6,2 0,8/6,2
Note manually controlled casting via the casting system
Week 4 – Vegetative Phase

Week 4 – Vegetative Phase

The plants developed without any problems on both sides. The plants fed with Hydroponic Research fertiliser were ready to flower this week. However, the plants in the Sonnenerde were not yet ready. It was therefore decided to extend the vegetative phase. The slower development of the plants in the organic hemp soil was also evident in their transpiration behaviour. Whilst the mineral-fertilised plants consumed 3.74 litres of nutrient solution this week, the plants in Living Soil transpired only 0.53 litres during the same period. However, both test groups were sufficiently developed to significantly increase the VPD value. Lighting was set to the maximum light intensity (66%) for the vegetative phase this week. We recommend never setting the lighting during the vegetative phase higher than 66% of the maximum intensity. This ensures that flowering induction and the associated reduction in day length do not have a diminishing effect on the DLI.

Target values:

 

Day 22 23 24 25 26 27 28
Lighting duration [h] 18 18 18 18 18 18 18
Temperature Day [°C] 26 26 26 26 26 26 26
rH Day [%] 60 60 60 60 55 55 55
VPD Day [kPa] 0,97 0,97 0,97 0,97 1,14 1,14 1,14
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 55 55 55 55 50 50 50
Dimmung [%] 50 50 50 50 66 66 66
PPFD at plant [µmol/m2/s] 360 360 360 360 500 500 500
Watering volume, mineral [l] 1,07 1,07 1,07 0,53
Watering volume, organic [l] 0,53
VBX [g/l] 1,25 1,25 1,25 1,25
Shine [g/l]
EC/PH  1/6,1  1/6,1 1/6,1 1/6,1
Note Manually controlled casting via the casting system
Week 5 – Initiation of the Flowering Phase

Week 5 – Initiation of the Flowering Phase

After 30 days in the vegetative phase, flowering was induced. When switching to a 12-hour light cycle, the light intensity was increased to 100% at the same time. As the distance between the light and the plants was still quite large, this does not correspond to the maximum achievable PPFD in this set-up. Due to the plants’ growth in height, the distance to the SANlight EVO 5-150 will decrease in the coming days, causing the PPFD to rise continuously. On the day of the light cycle change, the temperature was also raised and the relative humidity reduced to 50%.

The group of plants receiving mineral fertiliser was watered generously on days 30 and 32 to compensate for differences in transpiration rates between individual plants.

Target values:

 

Day 29 30 31 32 33 34 35
Lighting duration [h] 18 18 12 12 12 12 12
Temperature Day [°C] 26 26 28 28 28 28 28
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,3 1,3 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 66 66 100 100 100 100 100
PPFD at plant [µmol/m2/s] 510 520 520 710 720 720 720
Watering volume, mineral [l] 2,67 2,67 0,53 1,6 1,4
Watering volume, organic[l] 0,2 1,33 0,67 0,53
VBX [g/l] 1,25 1,25 1,6 1,6 1,6
Shine [g/l]
EC/PH 1,1/6,1 1,1/6,1 1,6/6,1 1,4/6,1 1,4/6,1
Note manually controlled casting via the casting system
Week 6 – Start of the Stretching Phase

Week 6 – Start of the Stretching Phase

As can be seen in the pictures below, the plants in the organic hemp soil have caught up significantly. Rapid vertical growth (stretch) has begun. On average, both test groups are the same height.

Target values:

 

Day 36 37 38 39 40 41 42
Lighting duration [h] 12 12 12 12 12 12 12
Temperature Day [°C] 28 28 28 28 28 28 28
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,47 1,47 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 100 100 100 100 100 100 100
PPFD at plant [µmol/m2/s] 720 720 740 740 760 760 770
Watering volume, mineral  [l] 1,6  1,6  4  1,67  1,67  1,67  2,13
Watering volume, organic [l] 0,53 1,07 1,07 1,07 1,07 1,20 1,40
VBX [g/l] 1,6 1,6 1,7 1,7 1,7 1,8 1,8
Shine [g/l] 0,35 0,35 0,35 0,35 0,35 0,35 0,35
EC/PH 1,6/6 1,6/6 1,7/5,8 1,7/5,9 1,7/5,9 1,8/5,6 1,8/5,6
Note
Week 7 – Stretching Phase

Week 7 – Stretching Phase

This week, the first flower buds became visible in both test groups at the same time. On day 49 (flowering day 19), some of the lower shoots and lower leaves were therefore removed from both groups. Vertical growth had slowed considerably over the past few days.

Target values:

 

Day 43 44 45 46 47 48 49
Lighting duration [h] 12 12 12 12 12 12 12
Temperature Day [°C] 28 28 28 28 28 28 28
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,47 1,47 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 100 100 100 100 100 100 100
PPFD at plant [µmol/m2/s] 820 820 840 840 840 880 880
Watering volume, mineral [l] 2  2,2  2,27  2,27  2,27  2,27  2,27
Watering volume, organic [l] 1,6 0 1,67 1,67 1,67 1,67 1,67
VBX [g/l] 1,8 1,8 1,8 1,8 1,8 1,8 1,8
Shine [g/l] 0,35 0,35 0,35 0,35 0,35 0,35 0,35
EC/PH 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8
Note

Transpiration patterns still varied, which can be attributed to the visibly lower biomass in the Bio Hanferde group. The figure below shows the transpiration patterns and the irrigation intervals over a 24-hour period.

Week 8 – Start of Flower Development

Week 8 – Start of Flower Development

Vertical growth had slowed considerably and was approaching zero. The plants were now beginning to build up flower mass. Both the VBX and Shine components of the Hydroponic Research fertiliser were used at the maximum recommended dosage. With our source water having an ØEC value of 0.35, this results in a total electrical conductivity (EC) of 1.8. Due to the high fertiliser content, the pH value only needed to be adjusted downwards slightly after mixing. The plants in the organic hemp soil are currently developing at the same rate and showed no signs of deficiency.

Target values:

 

Day 50 51 52 53 54 55 56
Lighting duration [h] 12 12 12 12 12 12 12
Temperature Day [°C] 28 28 28 28 28 28 28
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,47 1,47 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 100 100 100 100 100 100 100
PPFD at plant [µmol/m2/s] 880 880 880 880 880 880 880
Watering volume, mineral  [l] 2,27 2,33 2,33 2,33 2,33 2,33 2,33
Watering volume, organic [l] 1,67 1,73 1,73 1,73 1,73 1,73 1,73
VBX [g/l] 1,8 1,8 1,8 1,8 1,8 1,8 1,8
Shine [g/l] 0,35 0,35 0,35 0,35 0,35 0,35 0,35
EC/PH 1,6/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8
Note
Week 9 – Flowers Begin to Form

Week 9 – Flowers Begin to Form

Vertical growth had been fully completed. The flowers produced additional volume on a daily basis in both test groups. In the mineral-fertilised test group, the VBX concentration was reduced from 1.8 g/l to 1.6 g/l on the final day. As the plants now required less nitrogen, a lower dose of VBX was sufficient.

Target values:

 

Day 57 58 59 60 61 62 63
Lighting duration [h] 12 12 12 12 12 12 12
Temperature Day [°C] 28 28 28 28 28 28 28
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,47 1,47 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 100 100 100 100 100 100 100
PPFD at plant [µmol/m2/s] 880 880 880 880 880 880 880
Watering volume, mineral  [l] 2,33  2,33  2,33  2,33  2,33  2,33  2,33
Watering volume, organic [l] 1,73 1,73 1,73 1,73 1,73 1,73 1,73
VBX [g/l] 1,8 1,8 1,8 1,8 1,8 1,8 1,6
Shine [g/l] 0,35 0,35 0,35 0,35 0,35 0,35 0,35
EC/PH 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,8/5,8 1,6/5,9
Note
Week 10 – Generative Phase

Week 10 – Generative Phase

The flowers continued to produce a good yield. To ensure the plants did not become too waterlogged, the amount of water given to both groups was reduced.

Target values:

 

Day 64 65 66 67 68 69 70
Lighting duration [h] 12 12 12 12 12 12 12
Temperature Day [°C] 28 28 28 28 28 28 28
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,47 1,47 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 100 100 100 100 100 100 100
PPFD at plant [µmol/m2/s] 880 880 880 880 880 880 880
Watering volume, mineral  [l] 2,33  2,33  2,33  2,27  2,27  2,2  2,2
Watering volume, organic [l] 1,73 1,73 1,73 1,67 1,67 1,6 1,6
VBX [g/l] 1,6 1,6 1,6 1,6 1,6 1,6 1,6
Shine [g/l] 0,35 0,35 0,35 0,35 0,35 0,35 0,35
EC/PH 1,6/5,8 1,6/5,8 1,6/5,8 1,6/5,8 1,6/5,8 1,6/5,8 1,6/5,8
Note
Week 11 – First Signs of Discolouration

Week 11 – First Signs of Discolouration

The plants in both groups were now transpiring less and less. This is a sign that volume production is stabilising. That is why we tried to reduce the watering volume to the correct dose this week. We also reduced the EC value by using less VBX. This meant, in particular, that less nitrogen was supplied.

Whilst all the plants in the mineral group were a rich green, the first signs of discolouration appeared in the organic group, suggesting nutrient deficiencies. The symptoms occurred precisely in those plants that consumed the least water and were therefore growing in wetter conditions.

Target values:

 

Day 71 72 73 74 75 76 77
Lighting duration [h] 12 12 12 12 12 12 12
Temperature Day [°C] 28 28 28 28 28 28 28
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,47 1,47 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 100 100 100 100 100 100 100
PPFD at plant [µmol/m2/s] 880 880 880 880 880 880 880
Watering volume, mineral  [l] 1,6  1,6  1,6  1,73  1,8  1,8  1,8
Watering volume, organic [l] 1,13 1,13 1,13 1,27 1,33 1,33 1,33
VBX [g/l] 1,6 1,6 1,6 1,6 1,6 1,4 1,4
Shine [g/l] 0,35 0,35 0,35 0,35 0,35 0,35 0,35
EC/PH 1,6/5,8 1,6/5,8 1,6/5,8 1,6/5,8 1,6/5,8 1,4/5,8 1,4/5,8
Note
Week 12 – Autumn in the Breeding Chamber

Week 12 – Autumn in the Breeding Chamber

Autumn had set in. The plants in the organic hemp soil, in particular, showed significant discolouration, and the flowers were no longer developing any new mass. To stimulate chlorophyll reduction in the mineral-fertilised group, VBX was further reduced. Twelve days before the planned harvest, the plants were no longer given VBX. The flowers of the plants fertilised with Hydroponic Research were still growing larger and heavier. However, the first signs of deficiency were now appearing here too.

The ‘Meat Grinder’ strain from ‘The Grateful Seeds’ grown here is stated to have a flowering time of 63 days. All signs indicated that this schedule would be met.

Target values:

 

Day 78 79 80 81 82 83 84
Lighting duration [h] 12 12 12 12 12 12 12
Temperature Day [°C] 28 28 28 28 28 28 28
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,47 1,47 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 100 100 100 100 100 100 100
PPFD at plant [µmol/m2/s] 880 880 880 880 880 880 880
Watering volume, mineral  [l] 1,8  1,8  1,8  1,8  1,8  1,8  1,8
Watering volume, organic [l] 1,33 1,33 1,33 1,33 1,33 1,33 1,33
VBX [g/l] 1,4 1 1 1 0 0 0
Shine [g/l] 0,35 0,35 0,35 0,35 0,35 0,35 0,35
EC/PH 1,4/5,8 1,1/5,8 1,1/5,8 1,1/5,8 0,6/5,8 0,6/5,8 0,6/5,8
Note
Week 13 – The End is in Sight

Week 13 – The End is in Sight

This week, the Shine component of the Hydroponic Research fertiliser range was also reduced to 0. The plants were prepared for their upcoming harvest. Both test groups were watered with water only, without any pH adjustment. Furthermore, the temperature was gradually reduced to preserve as many aromatic compounds as possible. Towards the end of the week, watering was stopped completely. Just a few days left until harvest.

The autumnal colours of the organically grown plants are a feast for the eyes of enthusiasts. The mineral-fertilised plants are also developing strong and magnificent autumn colours.

The resin-coated flowers were heavy, and branches were bending, despite multiple supports.

Target values:

 

Day 85 86 87 88 89 90 91
Lighting duration [h] 12 12 12 12 12 12 12
Temperature Day [°C] 28 28 28 26 24 24 24
rH Day [%] 50 50 50 50 50 50 50
VPD Day [kPa] 1,47 1,47 1,47 1,47 1,47 1,47 1,47
Temperature Night [°C] 22 22 22 22 22 22 22
rH Night [%] 45 45 45 45 45 45 45
Dimming [%] 100 100 100 100 100 100 100
PPFD at plant [µmol/m2/s] 880 880 880 880 880 880 880
Watering volume, mineral  [l] 1,6  1,47  1,33  1,2  0,93  0,93  0
Watering volume, organic [l] 1,2 1,07 0,93 0,93 0,67 0,67 0
VBX [g/l] 0 0 0 0 0 0 0
Shine [g/l] 0,35 0 0 0 0 0 0
EC/PH 0,6/5,8 0,4/6,3 0,4/6,3 0,4/6,3 0,4/6,3 0,4/6,3 0,4/6,3
Note
Week 14 – The Harvest

Week 14 – The Harvest

After 63 days of flowering, the plants – which had been prepared through temperature reduction and water deprivation – were harvested. The harvest proved to be labour-intensive due to the dense growth combined with the heavy flowers. To document the results with photographs, each plant had to be removed individually and supported by a number of plant stakes. Once the plants had been removed from the box, they were photographed in groups. They were then cut and hung on the drying racks. The following images show some plants that were taken directly from the box. The three plants on the left are those that were watered only with water.

Target values:

 

Day 92 93
Lighting duration [h] 12 12
Temperature Day [°C] 24 24
rH Day [%] 50 50
VPD Day [kPa] 1,47 1,47
Temperature Night [°C] 22 22
rH Night [%] 45 45
Dimming [%] 100 100
PPFD at plant [µmol/m2/s] 880 880
Watering volume, mineral [l] 0  0
Watering volume, organic [l] 0 0
VBX [g/l] 0 0
Shine [g/l]0 0 0
EC/PH
Note

The Results

Yield, cannabinoids and terpenes

After drying at 18°C and 50% relative humidity, the flowers were separated from the plants and trimmed by machine. Three composite samples from each experimental group were analysed in the laboratory. All results refer to a residual moisture content of 12% of the dried flowers. The diagrams on the right show the total yield, the average yield per square metre and the average yield per plant.

Terpenes in detail

The detailed terpene analysis for the two test groups is shown opposite.

Cost comparison

We have compared the costs of all relevant consumables, such as soil, fertiliser, etc. The prices shown in the figure on the right are retail prices that would typically be paid in shops. We would like to add that, according to the manufacturer, the Sonnenerde could be revitalised at low cost using their soil activator. This would make the organic hemp soil suitable for further grows. Naturally, this would have a significant impact on the cost structure over the long term. However, this is not part of the experiment.

Cost breakdown: Hydroponic Research

Material Product Quantity Cost per unit Total cost
Soil Canna Terra Professional Plus 500 l 0,32 €/l 160 €
Fertiliser Component 1 HydroponicResearch VBX clean 4614 g 0,07 €/g 319,75 €
Fertiliser Component 2 HydroponicResearch Shine clean 872 g 0,12 €/g 102,46 €
Total cost 582,21 €

 

Cost breakdown: Sonnenerde

Material Product Quantity Cost per unit Total cost
Soil Sonnenerde Bio Hanferde 720 l 1,21 €/l 869,40 €
Mulch Sonnenerde Bio Faser 36 l 0,6 €/l 21,42 €
Total cost 890,82 €

To be continued...

Due to the increased interest from our customers and readers, we have decided to publish the blog post ahead of schedule. As a result, our detailed conclusions and the analysis of the soil and leaves are currently missing. We will, of course, provide these at a later date. We apologise for any inconvenience.

In the meantime, you can watch the videos of the experiment on our SANlight YouTube channel.

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