Introduction to integrated methods in the vegetable garden
chapter crop sol
Composting with thermophilic phase
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Analysis of the physico-chemical properties of cultivated soils ♦
. Texture and structure of cultivated soils ♦
. Clay-humus complexes and cation exchange capacity ♦
. Other interesting data that may be included in a laboratory analysis ♦
Influence of pH on the fertility potential of cultivated soils ♦
Humus; formation and evolution ♦
Soil fertility: is the apocalypse coming tomorrow? ♦
The microbial world and soil fertility ♦
Rhizosphere, mychorizae and suppressive soils ♦
Correction of soils that are very clayey, too calcareous or too sandy ♦
Stimation of humus losses in cultivated soil ♦
Compost production for a vegetable garden ♦
⇒ Composting with thermophilic phase
Weed management in the vegetable garden ♦
To plow or not to plow? ♦
The rotary tiller, the spade fork, and the broadfork ♦
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Compost storage phase.
This phase consists of gradually gathering organic matter without attempting to accelerate fermentation. No materials that accelerate fermentation or water are added. Often, low-temperature fermentation cannot be avoided, and its activity will vary depending on the moisture content of the bio-waste. This storage period corresponds to the mesophilic phase described in books and websites on composting. Without the addition of nitrogen (urea or ammonium nitrate) but with the addition of water, this first stage of composting is considered to be the initial phase of composting, characterised by a gradual rise in temperature to 30-40°C°.
During this low-temperature phase, and if there is sufficient moisture, the organic matter is invaded by mesophilic microorganisms. Bacteria and fungi begin to break down and digest tough debris. These microorganisms absorb simple molecules (sugars, alcohol, amino acids, etc.) and begin to break down more complex molecules (cellulose, proteins, starch, etc.), producing significant amounts of CO₂. If this mesophilic phase lasts several months, the compost is colonised by macro-organisms that participate in the decomposition process by feeding on organic matter rich in proteins, sugars and fats.
The mesophilic phase is not necessary to proceed to the next phase described below. This is particularly true given that it is important to avoid wasting materials with high energy value, which will be very useful in the thermophilic phase.
Thermophilic phase of compost sanitation
This is an active fermentation phase where the temperature at the centre of the pile must reach at least 55°/65°C. In some industrial composters where air is introduced by a blower, the temperature can easily reach 70°C. An 800-litre household compost bin containing a lot of grass clippings can reach this temperature. If there are not enough grass clippings or if the gardener cannot obtain dried blood, guano or other nitrogen-rich organic matter, mineral nitrogen (urea or ammonium nitrate) must be added to reach 55°C. For those who can compost in large piles (several cubic metres), the temperature can reach 75 to 80°C when the substrate is rich in highly putrescible materials such as sugar and starch. However, it is best not to exceed 70°C so as not to hinder the composting process.
Before starting the thermophilic phase, as far as possible, earthworms that do not like temperatures above 35°C (mainly very colourful epigeic worms that reproduce very quickly in compost) and rose chafer larvae should be removed from the compost and placed in a container filled with potting soil.
Compost is frequented by other useful organisms such as woodlice, lules (julida), polydesmes (useful millipedes), forficules (earwigs), and hermitia larvae (black soldier flies), which will normally leave the compost to seek shelter elsewhere as soon as the temperature rises above 35°C. It should be noted that woodlice, although sometimes maligned, play an important role in the early stages of organic matter decomposition, provided that the environment is sufficiently moist
Deposit of thermophilic microorganisms in the centre of compost whose temperature has exceeded 65°C
If the substrate contains sufficient highly putrescible organic matter, adding pelletised urea or ammonium nitrate, seeded with mature compost residue, causes the temperature to rise very quickly, within one or two days. This process saves time by avoiding the mesophilic phase.
Initially, organic matter is broken down by an army of actinomycetes (a) and then thermophilic bacteria, mainly archaebacteria, which become predominant, but also fungi (Rhizomucor pusillus, Rhizopus microsporus, Aspergillus fumigarus).
Mesophilic microorganisms, on the other hand, disappear. During this phase, composting consumes a lot of oxygen and water and produces gases (CO₂, methane, etc.).
The compost must therefore be well aerated, which requires the gardener to turn it frequently. It is also necessary to water it from time to time, especially in summer, in order to maintain constant humidity without saturating the compost with water.
Cooling phase of compost
When the temperature of the compost drops below 35°C, a new mesophilic phase takes over until the temperature of the compost matches the outside temperature. The beneficial organisms previously placed in a holding bin are returned to the compost. The mesophilic flora finishes breaking down the last polymers that remained intact after the thermophilic phase. Part of the humus is produced during this phase by incorporating the remaining nitrogen into complex molecules. Moisture control remains important throughout the process. Unlike in the previous phase, the addition of nitrogen fertiliser does not cause the temperature to rise, which shows that the thermophilic phase is well and truly over. The added nitrogen is not lost, as it is incorporated into the humus formation process. All plant debris that is low in lignocellulosic material must disappear (except for the toughest pieces, which must be sorted out).
It is common during this cooling phase for macro-organisms to be slow to colonise the compost if the amateur gardener has not previously built up a reserve of these macro-organisms. This is not a problem, as it is mainly the mesophilic microbial flora that quickly takes over. This can easily be seen by examining a sample under a microscope.
The actual cooling phase lasts for a period of varying length, corresponding to the humification work carried out by beneficial organisms specialised in the decomposition of tough cellulosic materials. These include epigeic woodlice and, above all, rose chafer larvae. In general, it does not take long for these beneficial organisms to colonise compost, and the colonies grow stronger every year as long as the gardener maintains at least one compost heap in the cooling phase. A colony of several hundred rose chafer larvae is particularly effective at reducing organic residues that would have resisted the thermophilic phase to their simplest form. Simply collect these larvae and shelter them in winter in a container filled with compost (or leave them in a composter throughout the winter); the adults will not leave in the spring and will lay their eggs in the compost. After two to three years, you will end up with an abundant colony of rose chafer larvae that can be easily maintained by periodically adding compost that has completed the thermophilic phase from another composter.
For small compost bins, it is best to start composting at the beginning of summer to take advantage of the ambient heat. In Provence and during the summer season, watering should be done every 1 to 2 days. One cubic metre of compost in the thermophilic phase consumes at least 10 to 15 litres of water every day
For individuals, urea is ideal for increasing the nitrogen dose. Urea is dissolved in a watering can containing about ten litres of water. This solution is poured onto the surface of the compost. Pelleted urea can be purchased from agricultural cooperatives. However, this urea is only available in 50 kg bags. You will then have a supply of mineral nitrogen for at least 10 years, bearing in mind that this mineral fertiliser will also be used to meet the high nitrogen requirements of your vegetables at a certain point in their development cycle.
The temperature rise to 55/65° can be measured using a laboratory thermometer. This measurement must be taken 20/25 cm from the edge of the compost.
The destruction of all pathogenic germs is only possible if all elements of the compost are subjected to a temperature of 55/65° for at least 15 days. This requires frequent turning to ensure uniform treatment (1). It is essential that certain plant waste undergo this heat treatment, such as melon stems and leaves, which may contain Fusarium spores, or tomato remains, which may contain Alternaria or Didymella lycopersici (blackleg) spores.
During composting in piles, the more resistant debris is placed in the centre and then covered with finer debris, followed by watering. The thermophilic phase must last at least one month, but it will be more effective if it lasts longer with successive additions of highly fermentable materials and nitrogen. To this end, and in the event of a shortage of highly fermentable organic materials, a bag of low-quality flour can be used for every cubic metre of compost, which is not very expensive for an individual.
Tip
Grass clippings are also a valuable source of nitrogen. The challenge is to have a sufficient supply of grass when deciding to launch a thermophilic phase for more than 1 m³ of organic matter. It is strongly advised not to store freshly cut grass in bags, as it contains a lot of water and will start to ferment, producing toxic substances and unpleasant odours. The grass should be bagged after drying in the sun for several days. The final dry product should resemble hay.
a) Actinomycetes are not fungi, but bacteria with diverse morphologies; they can be spherical or grouped into rudimentary or highly branched filaments. Throughout their life cycle, actinomycetes can combine these different forms. The filaments emerge from the germ that gave rise to them to create a radiating structure resembling fungal hyphae. Actinomycetes multiply less rapidly than other bacteria.
Compost maturation phase
Affinage à l’aide d’un tamis
This phase consists of removing foreign elements (stones, pieces of metal or plastic, etc.) and insufficiently decomposed elements such as pieces of wood from hedge trimmings using a sieve. Earthworms and other useful organisms must be recovered and placed in another compost in the mesophilic phase.
Tough debris is transferred to a younger compost heap or spread over the surface of the cultivated land to form a layer that will evolve according to the principles of BRF (ramial chipped wood (a)). This debris will therefore continue to decompose on site, sometimes for several years, which helps to neutralise humus losses and feed beneficial organisms
The product of the refining phase can be spread on the soil if the next crops accept it (especially to be avoided for liliaceae …), or stored to enter the next phase of maturation.The product of the refining phase can be spread on the soil if the next crops accept it (especially to be avoided for liliaceae …), or stored to enter the next phase of maturation.
It is best to use a sieve with 3 mm mesh. Using a hand protected by a gardening glove, force the slightly damp organic matter through the mesh, which will also break down the last large pieces of organic debris (compacted decomposed grass, pieces of straw or decomposed branches, etc.) into fine particles. Clogging of the mesh is the result of compost that is too wet or not fully decomposed
a) Cultivation technique invented in Canada. Shredded branches, mainly from deciduous trees, are spread on the soil surface in an attempt to recreate the forest litter layer. Fungi play an important role in the decomposition of organic matter due to the presence of atmospheric oxygen.
Compost maturation phase
The final product is stored in a well-ventilated area for at least three months and will continue to evolve. Some of the elements such as nitrogen, phosphorus and potassium consumed by the microflora for its own development return to the compost in a form that can be assimilated by plants or contribute to the formation of more complex compounds. During this phase, organic matter is reorganised into more stable compounds to form humus. At the end of this maturation phase, the compost must not contain any organic matter that is easily degradable by microorganisms. After spreading, this compost continues to evolve to form agricultural humus and then C.A.H. with clay.
At the beginning of the maturation phase, the pH of household compost can range from 8 to 9. Do not attempt to acidify it, as this could cause odour problems and nitrogen loss. Compost rich in woody waste requires a maturation phase of 4 to 6 months.
Some useful creatures found in compost heaps
Iules (Julida)
Larve de Cétoine dorée
Cloporte
Mouche soldat noir
Chrysalide de cétoine dorée entourée d’un cocon constitué de débris végétaux, recueillie dans un compost
Deux espèces de cétoines recueillies dans un compost
Woodlice in the Mediterranean region.
The Mediterranean region is known for its diverse range of woodlice, which can be found in forests, meadows and anywhere where organic matter accumulates. Woodlice are crustaceans that develop symbiotic relationships with bacteria that produce cellulases in their intestines, enabling them to break down tough woody materials. It is therefore beneficial to preserve these small crustaceans, even though they have a reputation for attacking certain crops such as strawberries.
Larva of Hermitia illucens (also known as black soldier fly).
Very common in mesophilic compost as soon as vegetable and fruit scraps are added. These maggots develop very quickly and their digestate contributes to the transformation of organic matter.
The larva of the rose chafer beetle.
This larva is frequently found in composts. It is often confused with the cockchafer larva, which is never found in composts. The females lay eggs in summer and the larvae develop for more than a year in a compost. Several generations of larvae can therefore be found. The adults feed on nectar and pollen from flowers. These larvae and chrysalises must be removed from a compost before the thermophilic phase, as they cannot withstand the rise in temperature and the gases produced during this composting phase. Larvae will attempt to rise to the surface and may be found dead on top of the compost.
Like the larvae of Hermitia illucens, rose chafer larvae feed on decomposing organic matter. In summer, after the thermophilic phase, females arrive and lay eggs in the compost, which hatch fairly quickly to produce larvae. Their development can be very rapid, and it is not uncommon for compost to contain hundreds of larvae, which then significantly accelerate the final decomposition of organic matter. Tough particles are attacked by these larvae. Their excrement is fairly easy to identify in the form of small, elongated droppings measuring 1 to 2 mm. The larvae begin by attacking the surface layers of compost, leaving behind their excrement, which accumulates where the larvae have taken up residence. This excrement is collected for use in the compost maturation phase.
Pathogens resistant to the composting process
Certains agents pathogènes sont difficilement neutralisés lors d’un compostage à chaud de résidus végétaux contaminés. Leur élimination est possible si la température est constante dans toute la masse du compost sur plusieurs jours. Mais cette situation est rarement atteinte la température n’étant pas homogène dans le compost surtout sur les bords où il existe une perte calorique. Les agents pathogènes les plus connus sont :
Fusarium wilt.
Plant vessels are invaded by a very common soil fungus (Fusarium oxysporum), causing the plant to wilt and die quickly. All vegetables can be affected, particularly tomatoes, melons, cucumbers, courgettes, onions, potatoes and celery. This type of fungus is subdivided into several varieties. For example, according to the ESIAB website, “in tomatoes, a distinction is made between Fusarium oxysporum f. sp. radicis lycopersici, which attacks the root system, and Fusarium oxysporum f. sp. lycopersici, which attacks the aerial parts of the plant”.
According to some researchers (Mercedes Castejón-Muñoz G. J. Bollen), Fusarium oxysporum would be destroyed if a temperature of 55°C were maintained throughout the compost for 30 minutes (2), with a survival rate of only 0.001% of propagules (a). Any widespread wilting observed on tomatoes during hot weather is probably the result of a Fusarium wilt attack.
As it is not always easy to diagnose fusarium wilt, some professional gardeners take the precaution of avoiding cold composting wilted stems and leaves. When burned, this waste poses no danger and can be added to compost, allowing mineral salts such as potash and phosphates to be recovered (incineration in residential areas; see local regulations).
Cruciferous Hernia.
This fungal disease caused by Plasmodiophora brassicae mainly affects cabbage crops. Cauliflower and broccoli are particularly susceptible. The disease manifests itself through the appearance of growths on the roots and crown, causing the plant to die. According to some authors, the fungus can be destroyed by heating the entire compost to a temperature of around 55°C for at least 96 hours
Blackleg of cabbage.
This disease is caused by the fungus Olpidium brassicae, which can also affect tomato roots and lettuce. This fungus is also a vector for a phytovirus. Olpidium brassicae is not destroyed after thermophilic composting at a temperature of 50 to 70°C for 2 to 3 weeks, followed by a 5-month maturation phase (2).
Tomato cork roots.
This disease is caused by the soil-borne fungus Pyrenochaeta lycopersici, which thrives in so-called “tired” soils that have been used for successive tomato crops. There are several strains corresponding to different soil temperatures. The fungus can be destroyed at temperatures of around 73°C (3).
Rhizoctonia.
In principle, rhizoctonia should not pose a problem if composting is carried out correctly and, above all, if all the elements undergo a thermophilic phase. The addition of nitrogen as a degradation activator on potato and beet residues is known to promote the disappearance of brown rhizoctonia (4). However, even a few potato, tomato, celery, cabbage or carrot peelings that have not undergone a thermophilic phase are enough for this cryptogamic infection to spread to new crops. If in doubt, it is best to burn crop residues.
a) propagules: structures for dispersal and reproduction, such as spores
Notes :
– The Fusarium genus belongs to a group of fungi known as soil-borne plant pathogenic fungi (SPPF), which also includes Verticillium, responsible for severe and relatively frequent attacks on certain vegetable crops such as celery, tomatoes, aubergines, potatoes, etc. SPPFs produce survival structures such as chlamydospores with thick walls or highly resistant sclerotia that can survive for several years in the soil. SPPFs are grouped into two functional categories: soil dwellers and soil invaders. The first category generally includes non-specialised fungi that infect seedlings and young roots, while the second category includes pathogens that are specific to their host. High humidity combined with low temperatures is often responsible for fungal infection. However, some fungi tolerate lower water levels and prefer warmer soils (25 to 35°C).
– Calcium cyanamide destroys all microorganisms, both good and bad, and should therefore be used sparingly if it is decided to use it to compost plant waste infected with resistant pathogenic microorganisms.- Calcium cyanamide destroys all microorganisms, both good and bad, and should therefore be used sparingly if it is decided to use it to compost plant waste infected with resistant pathogenic microorganisms.
For soils that are too rich in limestone or sand, here is a recipe for a clay-humus amendment. At the beginning of the maturation phase, the compost is enriched with clay in the following manner :
The principle is to mix compost with clay or marl (containing approximately 50% clay) in order to facilitate the formation of clay-humic complexes. Finely ground clay or marl must be used after passing through a sieve (mesh diameter approximately 2 mm) in order to remove unnecessary grains of sand. Marl contains enough limestone for CAHs to form.
Preparation of a clay-humus amendment
Amendement argilo-humifère
The preparation of clay-humus amendments requires the presence of limestone to stabilise the clay-humus complexes. For commercially purchased clay, it is necessary to check whether it contains limestone using a vinegar test. To do this, pour a few drops of vinegar onto a sample of a few cm³ of clay, which should produce foam if the clay contains limestone.
The proportions of the mixture depend on the clay content of the marl. The proportions are approximately one volume of marl to 5 to 10 volumes of compost for marl containing 50% clay. For very calcareous soil, this amendment may contain up to 1/3 clay. This mixture is kept slightly moist throughout the maturation phase.
Incorporating compost into the growing medium
Many vegetable plants cannot tolerate recent compost additions, let alone the incorporation of manure that has not fully decomposed. The presence of organic matter increases the risk of fungal diseases.
This is particularly true for garlic, cucurbits and tomatoes. It is therefore preferable for beds that will receive these crops to incorporate compost into the garden soil in the autumn by pseudo-tilling. For plants that can tolerate recent compost application, the compost is incorporated into the garden soil in early spring.
For garlic and tomatoes, you will have even fewer problems if the compost was incorporated a year ago. In this case, you should only use mineral fertiliser to top up the soil in spring.
1) Guide du traitement des déchets ; réglementation et choix des procédés – Alain Damien
2) Induction of heat resistance in Fusarium oxysporum and Verticillium dahliae caused by exposure to sublethal heat treatments ♦
3) I G. J. Bollen et all. 1989 inactivation of soil-borne plant pathogens during small-scale composting of crop residues ♦
4) G.J. Bollen, 1984. The fate of plant pathogens during composting of crop residues – Composting of agricultural and other wastes / Gasser, J.K.R., – p. 282 – 290. ♦
5) La technique betteravière – bien gérer le rhizoctone brun N°1007 16-9-2014