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Composting for hemp

Composting is the science of building a dense soil, with a microbial life, that supports intense and healthy plant growth through biochemical reactions and other life processes. This complex and symbiotic relationship between plants and microbes is highlighted in the article of our first issue, “Living Soils”.


In essence, composting refers to the decomposition of organic matter and minerals from beneficial microorganisms to humic acid and bio-available nutrients. Nutrients feed into plant growth processes, while humic acid acts as an electromagnetic buffer maintaining optimum pH and electrical conductivity (EC). For more details on this regulatory process, see the article in the second issue “EC and pH in soil and hydroponics”. The activities of bacteria, fungi, nematodes and larger organisms such as insects and worms, also create a soil structure with excellent aeration and water retention properties, necessary for productive root systems.


On the contrary, the extensive use of synthetic fertilizers and pesticides causes the complete erosion and removal of the humic acid-rich mineral soil of an ecosystem, leaving dead and compact soils without available nutrients. This leads to important economic and environmental issues. With all rich soils having disappeared, growth can only be triggered by the addition of more chemical fertilizers, thus requiring a perpetual and growing financial investment. The continuous disposal of waste, both from fertilizer packaging and from water runoff, as well as from the substrate consumed in the greenhouse crop, is expensive and increases pollution by plastics and chemicals, harmful to humans, wildlife and animals. In addition, with the resistance of plants to diseases dependent on pesticides, these poisonous chemicals are released into the atmosphere, increasing toxic reactions and the extinction of species. Organisms that distinguish atmospheric CO2 and NO2 produced by humans have been destroyed in commercially cultivated soils, which cover large parts of the earth. This makes a significant contribution to climate change.


As the cannabis industry and pharmaceutical production expand across Europe, large-scale businesses will have to face the same challenges. The use of organic fertilizer (compost) targets these problems on many levels. It can eliminate harmful runoff, pesticide use and waste from packaging and significantly reduce the need to purchase substrate. These functions translate into huge cost savings, while at the same time implementing a sustainable and environmentally efficient approach to cultivation.


Creating Bio-Fertilizer for Hemp


Organic fertilizer can have many different recipes that can be considered as “bio-software” programs designed to meet the specific needs of a crop. Based on the combination of the materials and organisms used, virtually any production target can be achieved. Depending on the variety and method of cultivation, the cycle of industrial hemp and medicinal cannabis is between 2 and 7 months from the seed/clone to the harvest. This places hemp in the category of plants that prefer to absorb nitrogen as nitrate or NO3-, produced primarily through bacterial metabolism. However, due to the duration of the growth cycle and phosphorus needs for flower growth, cannabis also benefits from the creation of a diverse fungal network within the substrate. Beneficial bacteria, fungi and nematodes also consume dead plant matter that would otherwise attract pathogens. The best recipes for hemp are, therefore, bio-fertilizer divided into 50-50 or 60-40 % bacterial and fungal populations.


A basic recipe for creating such a fertilizer, described by Dr. Elaine Ingham, well-known microbiologist and founder of Soil Foodweb Inc., is as follows: 50% woody materials, 40% green plant materials and 10% high-nitrogen materials. Woody materials are carbon-rich dead materials such as wood shavings and hay, green plant materials are fresh greens, leaves and plants such as syphyte and other herbs, while high-nitrogen materials include feces of bats, chicken, cow or horse and other types of manure. You also need to add “starter” fertilizer or a “composting tea”, which contains the microorganisms you want to multiply. These microbes will decompose the pile of your ingredients into a homogeneous, nutrient-rich compost. Start-up fertilizer can be a natural mineral from a thriving forest or a high-quality organic fertilizer decomposed with or without the help of earthworms. Fertilizer from earthworms, which depend on microbes to digest their food, has been shown to contain some of the most effective nitrogenous cycles and disease prevention organisms and is able to enhance the size and taste of fruits in a variety of crops.


The pile must be protected from rain and must be well ventilated. Materials should be pre-soaked in chlorine-free water for three days before building the pile. Place the materials in layers: start with coarse wood at the bottom to leave air pockets that will ensure proper airflow, then add hay, then add the green vegetable layer, and finally a thin layer of high-nitrogen material and “start fertilizer”. Repeat this finishing process until the pile is about 1.5 meters high. Piles can be made separately, with a diameter of about 1.5 m each, or for large-scale production, piles are made in rows of 100 m long with a width of 1.5 m and a height of 1.5 m, called “bales”. A long thermometer and ideally a humidity meter should be inserted into the center of the pile. The humidity level of the pile should be maintained around 50%, water may need to be added periodically to maintain this level. As soon as the central temperature of the pile ranges between 55-65C for three days, ensuring that the bacteria multiply and are not deprived of water or oxygen, it is time to “turn” the pile by turning the upper part of 60% of the pile, usually with a fork. You need to repeat this procedure every three to ten days, under constant monitoring in order to maintain the temperature range at 55-65 ° C. After 70 days, the pile should be ready: it will be reduced to half of the original height and will become dark brown, brown, and tufted in appearance, indicating the presence of abundant life and humic acid.


This recipe can further target the needs of growers, by inoculation of the composting pile with liquid preparations of special strains of bacteria and fungi. For example, bacteria from the genus Azospirillum stabilize and recycle nitrogen, while pseudomonas species create soluble phosphorus for use in plants. Actinomyces bacteria and the fungus Trichoderma consume dead plant materials, excluding pathogens harmful to the roots of plants. There are thousands of different species of bacteria and fungi that perform a wide variety of specialized chemical reactions benefiting the life of the plants around them.


The application of fertilizer to industrial hemp fields should be done before planting each crop. If the soil contains contaminants, fertilizers created by the cultivation of specific types of bacteria and fungi, will absorb heavy metals and excessive amounts of elements such as magnesium, calcium and sulfur, which may have been created through commercial cultivation practices, and store them safely away from the plant. Bacteria and fungi can even clean up soils with poisons such as arsenic and hydrogen cyanide. Collectively, these methods are known as Biological Restoration.


For medicinal cannabis grown in a greenhouse, bio-fertilizer can be mixed with coconut, pumice, perlite or other substrates, and can also be applied weekly as a coating during both vegetative and flowering cycles. The used substrate from the greenhouse can be added to the existing composting piles and regenerated with fresh nutrients and humic acid. This recycling process can effectively eliminate the need to introduce a new substrate, greatly reducing the costs and environmental impacts of operation.


By Sama’a Djomehri

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