Using natural and biological products in cultivation for increased sustainability.

It is no news that we, humans are trying to set the world to our advantage. Darwin’s “Survival of the Fittest” makes that a natural occurrence. But not to the extent of exhausting all resources or damaging our production- and living- environment beyond repair.

The ecological foot print of horticulture / floriculture cultivation (including consumption safety) can be brought down by using products that support, activate and make changes in line with the natural processes, instead of products that disrupt the natural processes and impose a replacement of nature.
That should be a principle of all agri activities, including landscape and forestry:
‘increasingly understanding nature; not to impose, but to join in with our activities’

It is an understatement that comprehending the intricacies of nature is a challenge and difficult to accomplish, if at all. Note that even using natural and biological products is interfering in nature’s processes and dynamics, direct or indirect.
“Understanding the complexity of the interactions is instrumental in the exploitation of beneficial Pseudomonas spp. in controlling plant diseases” Anthony van Leeuwenhoek et al 2007. This also counts for all other products.

This essay is based on a good number of reports, texts and own trials. Many references towards functions of the products are non-specific; description of results are open-ended. Like:
-acts in relation with the roots, endophytic or exophytic-
-colonizes the roots-
-produce hormones and other compounds-
-increases resistance to biotic and abiotic stress-
-suppresses diseases-
-promotes growth-
-supports physiological processes-
Then moreover, all this does not happen simultaneously and consistently, if at all and it does not happen in a measurable way.
In a comment by researcher and extensionist M. B. Dicklow, University of Massachusetts: “If one word could be used to describe research trials with these materials, that word would be inconsistent”
Many issues regarding these products have to be considered. The natural material itself and its source, the often very complex, partly unknown way they function, product safety, possible side effects, trade and shelflife and so on. There is no mention of negative ecological side effects, although there are indications from some trials that biomass formation is affected negatively.
The outcome depends on application method, soil type, crop and conditions and other, often unknown, environmental and other factors. The substances often have to settle in on specific soils and hence may need time. The positive effect on poorer soils seems to be more pronounced than richer soils.

Notwithstanding the apparent limited knowledge and variable outcomes, there are many records and indications, supported by research, that these products, specific or general, stimulate and increase a more conducive rhizosphere environment, protect the plants against biotic and abiotic stress and stimulate resilience and growth.
Since often results are not as per expectation and dissimilar; applications shall be monitored and registered. Trials shall be conducted and replicated. In this way a personal and crop specific knowledge base is built up for the future. It is also recommended to follow the intensive research worldwide that keeps on throwing light on the opportunities and possibilities to implement fungi, bacteria, hormones and other bio substances.

The soil is an crucial factor in growing plants; conditions in regard to composition, structure and texture is a first step. Soil health is based on a dynamic balance between bio organisms, organic- and inorganic- compounds and environmental factors. Organic matter is a must for a vibrant biologic activity.
Over the years many favorable bio organisms and compounds have been discovered and isolated for induction or inoculation into the soil. These organisms and materials can contribute to a more balanced, healthier soil. They do more than just soil activity; they enter often in a relation with the plants (roots), as such contributing to many physiological processes and providing hormones, vitamins, organic and inorganic compounds to the plant.

The canopy of the plants, apart from balanced uptake, require certain climatic conditions and protection against pests and diseases. Often the climate is not optimum and plants’ physiological processes do not function properly, which may lead to forms of stress. There are many natural growth stimulating products, sometimes for specific circumstances, that help the plant to function better and resist adverse conditions.
A healthy and strong growing plant, with a hard cuticle and maybe a good wax layer, is able to protect itself to a certain point against predators, fungi and bacteria. These aggressors and invaders of the crop also have natural enemies. Sometimes not enough; then they can be distributed in the crop. Selected predating or parasitic creatures and organisms are commercially available.
Other options are found in pheromone- and other traps, repellents from natural sources or intercropping with repellent plants. Fungi and bacteria are suppressed by selected organisms or compounds that are synthesized from organisms.

The use of natural- and biological products is also defined by the many systems of cultivation nowadays, from fully enclosed environment to open field cultivation. In cultivation in fully closed environment (no natural light) and based on data, some biologicals may offer an option, but it may interfere with the precise cultivation programs and recipes. That is also the case with all forms of substrate growing, when strict, especially nutrient, schemes are employed. Certain products may be useful at specific points of time, but trials are recommended.
Less facilities, resulting in less crop control, in natural ventilated green house, net and shade house and open field, offer more options for the use of natural products, growth stimulants and plant protection substances. Especially the factor soil in cultivation opens a many window. Open field cultivation in soil could be using all options of natural compounds and biologicals.
Another aspect of cultivation is the use of adverse and chemical pesticides and in addition chemical nutrients. Many of these products affect the natural substances and biological, including especially the natural enemies and disease controlling organisms. Obviously ‘kill it all’ disinfectants are the worst.

Soil Conditioners

There are several specific mineral and organic products that can help to improve the conditions of the soil. However, in the first place a good soil management is essential. Structure of the soil and organic material are two important features. Only with a conducive environment the soil conditioners can do their work by releasing nutrients, trace elements and other compounds, the same for the function of fungal and bacterial organisms that control pathogens and induce symbiosis between plant roots and soil.
Organic material, as manures and plant wastes, will break down in the soil, create bio activity and releases nutrients in a gradual way. Organic matter content improves the structure of the soils, water and nutrient holding capacity.
Vermicompost is the organic material broken down by earthworms, the end product being vermicast. Rich in nutrients in, for the plants easily assimilating form. Induces to a bio dynamic soil.
Substances as humic acids, fluvic acids and humin are found in natural bio dynamic soils, in the organic matter. These substances (also humate, the closest stage of degradation to coal) are found in concentrated form in Leornadite and oxidized lignite layers. From studies and analysis it is known that they have a function in stabilizing the soil and influencing positively the root environment (rhizosphere), directly and indirectly, as catalysts and bio stimulants, by absorbing and solubilizing elements (humic acid has many more times nutrient holding capacity than clay) and offering nutrients, vitamins and trace elements to plants in interaction with the roots, stimulating the uptake even under stressful conditions. In general they increase plant’s resistance and recovery in biotic and abiotic stresses. Fluvic acids are able to reduce toxins and heavy metals in the soil and residues of spray chemicals. They support and increase several physiological functions, e.g. flower bud formation. Can be applied to soil or sprayed on plants.
Humin and Biochar (charcoal is a form of biochar) are a source of amino acids and interact with the soil environment. Nutrient release. The products can be inoculated with organisms.
Sea weed and algae, containing Alginic acid and amino acids, available from different species (Ecklonia spp, Ascophyllum spp, others), in extracted form or raw. Applied to the soil they release cytokinine and other phytohormones, act as bio stimulant. They produce microbicides against plant pathogens. The material is a soil conditioner, improving structure and composition (nutrient balance).

Organisms

For suppression of hazardous plant pathogens, induction or inoculation of parasitic, antagonistic or otherwise interacting bio agents may be helpful. These organisms may reduce the pathogens by competing them on space and food (mainly carbon from plants), directly attacking them through myco-parasitism, supporting plant’s defense systems, release of toxic substances and other forms. Most are strong organisms and out-grow quickly competitors, as such colonizing the root zone (rhizosphere) for 10% or more. Root surface colonization is often an important aspect (biofilm). This may be penetrating in the roots (endophytic) or external action (exophytic). Successful colonization depends on many abiotic and biotic factors. In this symbiotic system, the roots deliver tremendous amounts of carbon to the rhizosphere.
The increase or decrease of the beneficial and pathogenic organisms is not a stable condition in the dynamics of bio activity in the soil. Inoculation of organisms is meant to stabilize towards a more healthy balance in fungi and bacteria, but the soil is resilient, may level the increased number of a certain organism and will return to its natural condition.
Trichoderma spp. and strains (T. koningii, T. viride, T. atroviride, T. harzianum, others), a fungus that may reduce incidence of plant disease fungi like Phytophtora, Rhyzoctonia, Fusarium spp, Pythium, Sclerotinia and others.
Indirectly they support the root activity of the plant, increasing growth potential and creating resistance to biotic and abiotic stresses. They have the ability to penetrate in the root cells.
Each spp. will have specific actions and functions.
Pseudomonas fluorescens is a strong aerobic bacteria that survives in many adverse conditions, like temp. up to 40 degr.C and high salt levels, resistant to chemicals, not to mancozeb! and not to pH below 4.5. Bacteria live in the rhizosphere, is opportunistic and enters in roots and stems of plants. It is found that there is an intensive symbiosis between root and bacteria, with activities and secretion of substances. It is one of the most occurring bacteria in the root microbiome and if sufficiently colonized, Pseudomonas strains can control a number of pathogens, like Pythium and Fusarium spp. and other Oomycetes. Interestingly Fusarium fight back with secretion of fusaric acid, a poison for Pseudomonas. Pseudomonas bacteria produce antifungal substances, like antibiotics and even the poison hydrogen cyanide. They induce plant resistance against pathogenic bacteria. Mutation is a possible occurrence in this bacteria. P. clororaphis has insecticidal properties. Is part of the N fixing in the soil.
Bacillus subtilis (also B. amiloliquefaciens and others) protect plants by pre-emptive colonization. They inhabit the root system of the plant competing with bio organisms, also disease causing organisms. Produce and secrete antibiotics. Favourable temperature is 25-35 degr. C.
B. subtilis (strains QST713, GB 01, others) is used as a fungicide/bactericide, because of its ability to produce antibiotics, but also as an insecticide, secreting insecticidal toxins. As fungicide/bactericide it has a suppressing effect on Sclerotinia sclerotiorum, bacterial wilt (Ralstonia), Pyhtium, Fusarium, Rhizoctonia, bacterial leaf spot. Is more effective in combination with Pseudomonas.
Spores in dormant stage will survive for centuries and longer.
Bacillus thurigiensis (other spp. of this microbe are kurstaki and israelensis) The commercialized compounds are effective against larval stages of Lepidoptera, Diptera, Hymenoptera and Coleoptera.

Coniothurium Minitans. Effective against Sclerotiana

ASPERGILLUS. Some spp are able to produce hormones, auxines and other substances for growth promotion, using an endophytic type of symbiosis with the plants. In one case it promoted growth under high temperature. It solubilizes minerals e.g. phosphorus and releases ABA and JA. A. niger spp. is effective against nematodes, often together with oxalic acid. Aspergillus has a limited ability to release fixed iron in the soil.

AZOSPIRILLUM. Bacteria lives in root zone and in exophytic symbiosis with plants. Able to fix N, produces auxines and growth promoting compounds. As such induces increased uptake (root development: lateral roots and root hairs), helping the plant to overcome stress. It also suppresses certain diseases.

AZOTOBACTER and RHIZOBIUM especially, but also other bacteria are Nitrogen fixing bacteria.

MYCORRHIZAE lives in a complex symbiotic relation with the plant roots, mutualistic or parasitic. Further, Mycorrhizae play an important role in soil biology and chemistry. The fungus colonizes the host plant's root intracellular (arbuscular mycorrhiza) or extracellular (extomycorrhiza). Most plants (90%) have an association with M., exchanging carbon (sugar) for minerals and water. M. in many spp, will be the fungus with the largest network of hyphal cover, across the soil, in different plant species. The network could cover roots of more plants and spp, simultaneously. Mycorrhizae play a role in solubilizing Phosphorus.

STREPTOMYCES lydicus Acts as a broad spectrum biocide and fungicide

RHIZOBACTERIA is a group of micro organisms living in the rootzone, being active in the biological dynamics of the soil and in relation with plants, often with production of phytohormones.

GLIOCLADIUM virens Control Pythium

Bacteria solubilizing minerals

Most of these organisms deploy more activity in the soil than only solubilising and mobilizing minerals. Activities are much integrated in the soil bio dynamics and also in interaction with the plant roots.
Phosphate solubilizing microbes (PSMs) are a group of bio organisms able to hydrolyse organic and inorganic insoluble phosphorus compounds in to soluble P form, easily assimilated by plants.
Potassium solubilizing bacteria (KSBs) are a number of bacteria producing organic and inorganic acids and other compounds to release potassium from various geological compounds. They also function as plant growth promoters.
Some bacillus spp. are able to solubilize zinc and silicate.

A large number of organic- and inorganic compounds were discovered over the years, that have a positive interaction with soil and plants
Sicilic acid, a metalloid element, acts as a bio-stimulant for the growth of the plant and helps the plant to resist and overcome infections and stress factors like heat, drought and salinity. It is an important nutrient element, but also has a function in the physiological processes and acts with phytohormones. As such it gives the plant a more vigorous growth.
Triacontanol (TRIA) is a bio substance improves growth, through enhanced photosynthesis, protein synthesis, uptake of water and nutrients, enzymes activities and free amino acids content. Act on Nitrogen fixation.
Salicylic acid (SA) Has a multifunction in growth and development, photosynthesis, transpiration, ion uptake and transport. Salicylic acid supports plant defense against pathogens.

Hormones

AUXINS, consisting of IAA and others. The synthetic auxines include root hormones and herbicides. They have an important role in cell division and differentiation, initiating lateral and adventitious root formation. Control certain processes of vegetative growth and acts at responses to light, gravity and florescence. Supports resistance to stressful conditions through biosynthesis of various metabolites.
GIBBERELLIC acid. Stimulates plant elongation and seed germination.
ABSCISIC acid (ABA) reacts to environmental stress, regulates dormancy and plays a role in movement of stomata
CYTOKININS (CK) increases growth of shoots, flowers and fruits
ETHYLENE (ET) helps to mature fruits. It is more related to growth inhibition than growth stimulation.
JASMONATES, another bio compound react to damages from biotic and abiotic stress and other factors by producing defence molecules and repair. It reacts with many other phytohormones and as such is important in many physiological processes.

Biological Biocides, Fungicides

Strobilurins are a group of fungicidal products from the same source, the mushroom Strobilurus tenacellus and some others. Many of them are active against a broad spectrum of pathogenetic fungi like downy mildew, rust, powdery mildew and many leaf spots (Alternaria, Cercospora, Anthracnose and Sphaceloma). Some also provide good control of soil-borne diseases such as Fusarium, Cylindrocladium and Rhizoctonia stem and root rots, but not black root rot (Thielaviopsis). It is synthesized to make it more stable for use in agriculture.
Streptomycines Streptomyces is used as a bactericide in cultivation of crops. Concern is environmental antibiotic resistance in the larger environment.

Biological Pest Control Organisms and Extracts

BEAUVARIA BASSIANA is a fungus living in the soil. It acts against thrips, aphids, white fly, caterpillars, beetles.
PAECILOMYCUS LILACENUS A fungus active against nematodes. Recommended to add Trichoderma.
P. VARIOTII has insecticidal activity against white fly.
VERTICILLIUM LECANI. Affects a broad spectrum of insects.

Soaps and oils may be derived from plants or from animals.

Oils are extracted from pepper (chili), garlic, cinnamon, pongamia, azadarachta (neem) and many others. Neem oil is also taken from the Azadarachta seed kernels (NSKE).
These oils when sprayed on plants have insecticidal effect, more protective than curative.
Neem applied to soil can have systemic effect. It may be slow in results and may degrade within days
Fish oil is from fish fats
Pyrethrum + canola oil is effective on insects and mites
Streptomyces avermitilis in fermented form it is the basis for avermectine/abemectine
Saccharo polyspora spinosa is fermented to spinosyns, an insecticide against caterpillars and other predators.
Diatomaceous earth is good for soil application against soil insects. It is phytotoxic on many plants. Effective insecticide, but killing bees.

Repellents

There is a long list of plants that have repellent effect on predators and pathogens. Sometimes plants themselves demonstrate this impact; also the effective ingredient is sometimes extracted and used in concentrated form. Some examples: (local names from India)
Marigold (Tagetes erecta), kaner (Dalium sp), lat jeera (Achyranthus aspera), Aak (Calotropis procera), jarayan (Lantana camera), citronella (Cymbopogon nardus), keweda (Pandanus oderatissima), lemon grass (Cymbopogos flexuasis), tulsi (Ocimum sanctum), laxmana (Solanum indicum), mahendi (Lawsonia inermis), mulatti (Glycyrrhiza glabra), union (Allium cepa), garlic (Allium sativum), tumeric (Curcuma domestica) neem (Azadarachte indica), babool (Acacia nilotica), vilayati babool (Prosopis juliaflora).
Well known are of course Pyrethrum (original source for pyrethrin), Nicotiana (original source for nicotine) and several plants containing the insecticidal rotenone. The last two products are generally banned because of high toxicity and environmental hazard.
The several repellent plants can be intercropped in 5 to 10% of cultivated space.

Traps

Pheromone traps. The pheromone is placed above water, attracts the insects that fall into the water. Together with a light point attraction is increased, but may extend far beyond the one’s own cultivated area.
Light traps make mostly use of UV light in the spectrum range 330 – 370 nm. Sticky material or electrocuting kills the insect.
Yellow, blue and white sticky cards or sheets. The colors attract insects that get trapped in the covering glue material. It may be used to identify pests (10 cards/acre) in the crop and the incidence, if a good number of cards (50/acre) or strips are placed, it helps to reduce the population. Blue attracts specially thrips, white and yellow more general insects.
Bait. A mix of a sugary substance in a bulk material (rice husk) and added an ingestion insecticide. The sugar attracts the insecticide kills. 10kg ricehusk+1kg jaggery (6-8hrs) 500gr methomyl, distribute small balls
Many other inventions, although often for home gardens.

Natural Enemies

In a healthy environment natural enemies of many pests are present. However, by using (wrong) chemicals many of these natural enemies are killed. If the pest enemies are introduced, care has to be taken to use compatible spray products to spare these bugs. The enemies may be parasitic or predating. In the open and semi open green houses induction of natural enemies is often a difficult option, unless sufficiently isolated with insect nets in top and sides and double doors. There are also some pathogenic organisms, as mentioned earlier.
As such, working with natural enemies is a program or system (e.g. IPM). Some examples.
Steinernema carpocarpsae beneficial nematodes against insects
Heterorhabditis bacteriaphora
Nosema slow acting organism against grasshoppers
Trichogramma ostriniae against corn borer
Encarsia Formosa against white fly
Phytoseiulus persimilis, Neoseilus californicus and Ambleisius cucumeris against spider mite
Coccinella septempunctata (Lady beetle) aphids
Crysoperia carnea (Predatory Lacewing) caterpillars
Orius osidiosus against thrips