**Abstract**

Cultivation of cucumber in greenhouses is predominantly carried out in soilless cultivation systems mainly in substrate culture. The use of organic and completely compostable substrates is of rising interest in such systems, unclean sheep wool was formed as substrate slabs, peat slabs and coconut fiber slabs were compared with mineral substrates rockwool and perlite. In general can be stated, intensively in greenhouses cultivated crops such as cucumbers, suffer often from inadequate abiotic or biotic growth conditions in particular in the rhizosphere. Many studies were done to find growth promoters or biostimulators to stabilize the growing condition in the rhizosphere, in case of stress situation as fluctuating salt concentration EC and pH value, but also in case of temperature stress. K-Humate, Lactate and *Bacillus subtilis* were investigated as biostimulators in such situations. Different concentration and combination of these biostimulators were investigated but also the methods of application on leaves and roots respectively. Very successful was used for the stabilization of the EC value for cucumber plants growing in substrate the application of K-Humate and *B. subtilis* (FZB24®) as single component and combined. Following the results, it can be assumed, the application of the combined biostimulators with all substances if applied over the roots was a stimulating effect visible, whereas if applied over the leaves an inhibiting effect for cucumber plant growth. Application of the biostimulators solution with all three components BS-FZB24® (0.2%), K-Humate (0.01%), and LACTOFOL "O" (0.1%) were tested regarding their effects in case of strong but short time pH and temperature stress the growth of cucumber plants. There are a strong correlation between green biomass of treated cucumber plants and their root mass. It can be assumed that one of the effects of stress prevention through the biostimulators is primarily based on increasing root growth.

**Keywords:** soilless cultivation, organic and mineral substrates, humates, lactates, *Bacillus subtilis*, abiotic stress influence

#### **1. Introduction**

Cucumbers (*Cucumis sativus* L.) is a vegetable originated from the rain forest of northeastern India. Therefore, they are growing in particular in temperate areas in

glass-greenhouses, in order to secure the appropriate temperature and humidity whereas in sub-tropical regions mostly in plastic greenhouses to secure the suitable humidity or to safe the cucumbers from heavy rainfalls. In all cases very important are the growing conditions in the rhizosphere. In the rainforest, the cucumbers are growing in a soil with a high amount of organic matter. Therefore, substrates suitable for cucumber cultivation in greenhouse should have specific physical properties, as pore volume, air and water capacity and density of the substrates [1]. In general, substrates from three groups can be used, mineral or inert, artificial and organic (**Table 1**).

In general can be stated, intensively in greenhouses cultivated crops such as cucumbers, suffer often from inadequate abiotic or biotic growth conditions in particular in the rhizosphere. Many studies were done to find growth promoters or biostimulators to stabilize the production process or to enhance plant growth of cucumbers under these conditions. Following such reports and own research the wide range of effects produced by Humates based on humic acids, have beneficial effects on the growing conditions in the rhizosphere. Many experiments were showing positive effects of different Humates as 'Bioregulator' in substrate culture of cucumbers. Other organic substances with a similar effect were tested as Lactates (salts of lactic acid) because these substances have proven biostimulatory effects and as an approach to improve the nutrient balance and plant vitality. Investigations have shown that Lactates have more stable bonds with several metal ions than other chelates. This effect can be very important to improve the nutrient supply of

*Growth Promoting and Stabilizing of Cucumber Plants Cultivated in Soilless Cultivation…*

Furthermore, as mentioned the biological conditions in these intensive cultivation systems are completely changed, in particular in the inert and artificial substrates. Many microorganisms from the rhizosphere can influence plant growth and plant health positively, and are therefore often referred to as "plant growth promoting rhizobacteria" [2]. Different microorganisms are tested regarding these effects best result could be induced by *Bacillus subtilis* (syn. *B. amyloliquefaciens ssp. plantarum*) regarding these growth and plant health promoting mechanisms as well

In several studies, cucumber growth in different substrates was investigated using mineral nutrient solution and with organic nutrients. Furthermore, plant growth-promoting agencies as the mentioned Humates, Lactates and Bacillus subtilis were investigated single or in combination regarding their effect as Bioregulator in the rhizosphere as well on the epigean part of the plants.

Following these investigations, different effects in relation to plant growth factors or conditions could find out in particular under stress conditions for plant

*Effect of biostimulators humate, lactate and* Bacillus subtilis *on stressors during growth of cucumbers under*

the cucumbers in soilless cultivation systems.

*DOI: http://dx.doi.org/10.5772/intechopen.96536*

as the interactions between them.

growth (**Figure 1**):

**Figure 1.**

**67**

*protected cultivation.*

Which of the substrates is suitable, depends also from availability in the region of the basic material, the economically preparation and environmental tasks as possibilities of reuse or environmentally friendly waste disposal. All substrates have some limitations in comparison to the natural growing conditions of cucumbers:


A proper regulation of the growing condition in the rhizosphere of cucumbers in greenhouses, is also from high importance because the wide relation of shoot and leave to the roots - 100:1, that means a comparable little root system have to secure water and nutrients for a big biomass.

Nowadays, mainly mineral or Rockwool is used as substrate in greenhouses for fruity vegetable production as tomatoes and cucumbers. Therefore, most of the studies with different substrates for cucumber cultivations are including as 'control' the Rockwool as slabs or as granules in containers.


*\* PU foam mixed with recycled PU-granules.*

#### **Table 1.**

*Classification of substrates for hydroponically cultivation of vegetables as cucumbers and others.*

#### *Growth Promoting and Stabilizing of Cucumber Plants Cultivated in Soilless Cultivation… DOI: http://dx.doi.org/10.5772/intechopen.96536*

In general can be stated, intensively in greenhouses cultivated crops such as cucumbers, suffer often from inadequate abiotic or biotic growth conditions in particular in the rhizosphere. Many studies were done to find growth promoters or biostimulators to stabilize the production process or to enhance plant growth of cucumbers under these conditions. Following such reports and own research the wide range of effects produced by Humates based on humic acids, have beneficial effects on the growing conditions in the rhizosphere. Many experiments were showing positive effects of different Humates as 'Bioregulator' in substrate culture of cucumbers. Other organic substances with a similar effect were tested as Lactates (salts of lactic acid) because these substances have proven biostimulatory effects and as an approach to improve the nutrient balance and plant vitality. Investigations have shown that Lactates have more stable bonds with several metal ions than other chelates. This effect can be very important to improve the nutrient supply of the cucumbers in soilless cultivation systems.

Furthermore, as mentioned the biological conditions in these intensive cultivation systems are completely changed, in particular in the inert and artificial substrates. Many microorganisms from the rhizosphere can influence plant growth and plant health positively, and are therefore often referred to as "plant growth promoting rhizobacteria" [2]. Different microorganisms are tested regarding these effects best result could be induced by *Bacillus subtilis* (syn. *B. amyloliquefaciens ssp. plantarum*) regarding these growth and plant health promoting mechanisms as well as the interactions between them.

In several studies, cucumber growth in different substrates was investigated using mineral nutrient solution and with organic nutrients. Furthermore, plant growth-promoting agencies as the mentioned Humates, Lactates and Bacillus subtilis were investigated single or in combination regarding their effect as Bioregulator in the rhizosphere as well on the epigean part of the plants.

Following these investigations, different effects in relation to plant growth factors or conditions could find out in particular under stress conditions for plant growth (**Figure 1**):

#### **Figure 1.**

*Effect of biostimulators humate, lactate and* Bacillus subtilis *on stressors during growth of cucumbers under protected cultivation.*

glass-greenhouses, in order to secure the appropriate temperature and humidity whereas in sub-tropical regions mostly in plastic greenhouses to secure the suitable humidity or to safe the cucumbers from heavy rainfalls. In all cases very important are the growing conditions in the rhizosphere. In the rainforest, the cucumbers are growing in a soil with a high amount of organic matter. Therefore, substrates suitable for cucumber cultivation in greenhouse should have specific physical properties, as pore volume, air and water capacity and density of the substrates [1]. In general, substrates from three groups can be used, mineral or inert, artificial and

Which of the substrates is suitable, depends also from availability in the region of the basic material, the economically preparation and environmental tasks as possibilities of reuse or environmentally friendly waste disposal. All substrates have some limitations in comparison to the natural growing conditions of cucumbers:

• Different physical, chemical and biological conditions in the substrates

• Missing of a buffer for stress situation as fluctuation of the pH and salt concentration (EC) or limitations of macro- or micro nutrients

• Microorganisms in the rhizosphere can have different functions as

**Mineral - inert Organic Artificial** Expanded Clay Coconut fiber Aggrofoam\* Gravel Wood fiber PU-foam Perlite Peat Polystyren-foam Pumice Mix substrate Polyphenol-foam Rockwool Compost UMF-foam

> Sheepwool Pine bark

*Classification of substrates for hydroponically cultivation of vegetables as cucumbers and others.*

• Under natural soil or organic growing media conditions, humates are available

mineralization of organic material, stress reduction and as growth regulator.

A proper regulation of the growing condition in the rhizosphere of cucumbers in greenhouses, is also from high importance because the wide relation of shoot and leave to the roots - 100:1, that means a comparable little root system have to secure

Nowadays, mainly mineral or Rockwool is used as substrate in greenhouses for fruity vegetable production as tomatoes and cucumbers. Therefore, most of the studies with different substrates for cucumber cultivations are including as 'control'

• Strong reduction of the volume for root growth

*Cucumber Economic Values and Its Cultivation and Breeding*

as a buffer for fluctuation of salt concentration

water and nutrients for a big biomass.

Sand Moss peat Zeolite Straw

*PU = Polyurethan; UMF = Urea-Methanal foam.*

*PU foam mixed with recycled PU-granules.*

*\**

**66**

**Table 1.**

the Rockwool as slabs or as granules in containers.

organic (**Table 1**).
