Introduction to integrated methods in the vegetable garden
. You have difficulties to improve the fertility of the soil in your vegetable garden!
. Your vegetable plants are stunted, eaten up by pests or affected by diseases!
. The organic treatments you use are ineffective!
In the pages of this website, effective solutions are proposed to answer these frequent problems encountered in the vegetable garden.
The author : Serge BAESEN
. Former computer scientist, network administrator.
. Secretary AFIS Marseille & Provence.
. More than 40 years of experience in market gardening and fruit growing in Hendecourt-lès-Cagnicourt in the Pas de Calais (more than 5000 m² of cultivable land in the Manor belonging to the Good Shepherd community in the 1970s), and in Estoublon in the Alpes de Haute-Provence (1600 m² property + rental).
This website is aimed at beginners and experienced gardeners who wish to learn about to integrated methods in the vegetable garden, as well as at all other people who are interested in these new cultivation techniques.
Introductory notes :
The site is organised into chapters and articles which can be accessed by clicking on one of the titles in the menu at the top of each page. At the top of each page, articles belonging to the same chapter are listed in a box on the right.
- At the bottom of each page, a search engine makes it possible to find the location of a word located in one or more other pages.
- A word written in bold with a green colour refers to another page where its definition is specified.
- The arrow ⇛ returns to the original page where the reader was.
- For fertilizer doses, the reference area of one hectare often used in agronomic studies, is reduced to 1 are (100 m²) which is more meaningful for an amateur gardener. A simple rule of three enables the doses to be recalculated in relation to the surface area of the vegetable garden.
Smartphone : for a correct vision of the tables, a horizontal position of the screen is preferable.
Integrated methods in agriculture, still referred to as "integrated agriculture », consist of the coherent implementation of all cultivation techniques that allow, on the one hand, to obtain healthy and economically profitable crops and, on the other hand, to meet the requirements of environmental protection and human health. These techniques are evaluated according to scientific methods. Practices that are not based on scientific evidence are therefore discarded. In summary, the integrated methods in agriculture are as follows:
The preservation of the soil's biodiversity and humus capital is ensured by periodic inputs of organic matter, in particular by composts obtained using proven techniques passing through a thermophilic phase, as well as by intercropping plant cover.
Organic and industrial fertiliser inputs are precisely adjusted to the soil's nutrient reserves and to the actual needs of the plants, which vary throughout the crop cycle. For example, in vegetable crops, carrots need more nitrogen in the first two months to form their leaves, and more potassium in the following months to form their roots. Nutrient reserves are determined by periodic laboratory analysis. Thus, integrated methods in agriculture incorporate precision farming techniques that aim to limit the use of inputs in agricultural plots.
To reduce the nuisance of bio-aggressors, alternative methods to pesticides are favoured as long as they prove to be effective. These methods, summarised under the name of Integrated Biological Crop Protection (I.B.C.P.), consist of implementing a combination of treatments such as varietal choices, crop rotations and the use of biocontrol processes that counteract the development of bio-aggressors.
Forecasting models are set up using alternative treatments to pesticides approved for conventional or organic agriculture against bioaggressors. For example, in sheltered cultivation, pest predators are imported in the spring as soon as the first aphids appear, which can become very prolific on certain vegetable crops (turnips, red beets, carrots, etc.).
The destruction of pests with plant protection products is not considered until the pests present a real danger. Phytosanitary treatments are only applied if the aggressiveness of the pests exceeds a certain threshold posing a serious problem for the environment and when the harvest is seriously compromised. In integrated metods, it is accepted that part of the crop is lost if the final harvest is still economically viable.
The decision to treat with plant protection products is made on a case-by-case basis after determining the benefits/risks. In the first instance, plant protection products that have a limited impact on the environment and proven efficacy are used.
Regarding weed control, mechanical weeding is favored over chemical weeding when possible (a).
All these measures can be applied to the vegetable garden after adaptation. Their description and implementation with specific examples are described in various articles on this website. All these measures have been verified by the author on open-air and sheltered crops.
a) Manual or mechanical weeding is ineffective against certain weeds such as horsetail or bindweed because of their rhizomes that go deep into the soil. A weedkiller is then necessary to destroy these weeds.
As you read through this website, you may get the impression that there is little difference between organic and Integrated methods in agriculture. Some of the farming techniques used are indeed common. Other techniques are forbidden in organic farming, such as mineral fertilisers. Organic farming is defined in terms of an obligation of means, whereas integrated agriculture consist is defined in terms of an obligation of result. This results in differences in cultivation techniques, yields and environmental consequences, the most well-known of which are the following:
Like organic farming, Integrated methods in agriculture aims to respect the health of the consumer and the environment. However, the Integrated methods in agriculture are strictly based on scientific data that have been widely demonstrated and validated by numerous controls carried out in the laboratory and in the field, which is not always the case with organic agriculture, which sometimes uses remedies whose effectiveness has never been proven (such as nettle purin).
Organic farming refuses synthetic inputs (fertilisers and plant protection products) for ideological reasons. It is often said that anything synthetic is dangerous, hence the exclusive use of so-called natural substances in organic farming, even though these substances can be as toxic (or even more toxic) than synthetic products. For example, the pyrethrins used in organic agriculture against pests are also toxic against ladybirds, lacewings and hoverflies, whereas this is not the case with spirotetramat (movento), which also respects predatory bugs, parasitoids and arachnids (a).
Organic farming is closed to certain scientific and technical innovations in the fields of genetics, agricultural chemistry and phytopharmacy in particular, which is not the case for integrated methods in agriculture. Bans in organic farming complicate the management of authorised inputs in this sector, with negative consequences for soil biodiversity. For example, in the case of a deficiency of a predominant element, in integrated agriculture only the missing element can be supplied with an industrial fertiliser. This is not the case with an organic input, which is the only fertiliser authorised in organic farming, although this type of input always includes several nutrients in varying doses depending on their origin, which can lead to a deficiency caused by the import of other elements in excess.
The ban on synthetic pesticides in organic farming has resulted in an increase in the dose of active ingredients approved for use in this sector and in the number of phytosanitary treatments due to their reduced effectiveness. Copper-based compounds against fungal and bacterial infections are often used in organic farming, although copper is not biodegradable, accumulates in the soil and is toxic for the environment. In integrated agriculture, synthetic and organic plant protection products are often used alternately by professional farmers, which increases the effectiveness of these treatments and reduces the active doses. Synthetic plant protection products are also more targeted, which reduces their impact on the environment (b).
Reasoned protection and biological protection; figures that speak for themselves:
Comparison of the quantity of fungicides applied in 1998 in the two sectors:
Integrated protection: 6 kg/ha
Organic protection: 86.4 kg/ha
Comparison of the total number of phytosanitary treatments in 1998
Integrated protection: 12
Biological protection: 23
Source: CIREA study from 1994 to 1998
The excessive use of copper in organic farming to control fungal infections also has the effect of disrupting plant nutrition. Excessive copper use creates a chlorotic phenomenon even in soils that are not very sensitive to this phenomenon, direct phytotoxicity on the leaves and a reduction in rootlets, sometimes leading to plant mortality (1).
Organic farming yields are not only lower than those of Integrated crop protection (c), but also more uncertain due to the difficulties of managing pests, diseases and weeds. Organic farming itineraries are much less secure than integrated agriculture, sometimes leading to untenable situations for organic farmers, as demonstrated for example in french during the bad weather in the summer of 2016 in apple growing (d).
a) This synthetic insecticide is used by professional farmers to control pests of pome and stone fruit trees, lettuce, witloof chicory, cabbage, onions and shallots, spinach and strawberries.
b) Most of the synthetic plant protection products used today and their metabolites are degraded by the microflora more or less rapidly depending on factors such as organic matter content, soil pH, temperature.
c) In 2018 for soft wheat, the yields are 35 and 40 qx for organic and 90 to 100 qx for conventional; more details by clicking : here.
d) Due to damage caused in 2016 by excess moisture in orchards, organic farmers used synthetic fungicides leading to withdrawal of Organic Agriculture (AB) certification for the farms concerned and for a minimum of 3 years. More details: here.
This website is a technical and practical knowledge base for amateur gardeners. Many useful tips are given on how to maintain the cultivation soil, how to undertake balanced and healthy composting, and how to help vegetable plants better resist bio-aggressors. Fundamental notions of agronomy and pedology are explained in order to understand the integrated methods in agriculture.
A first version of this website was mainly aimed at gardeners living in the Provence-Alpes-Côte d'Azur region, taking into account local particularities. As the success of the site has gone far beyond this regional limit, the texts have been improved for other regions of France and countries with a temperate climate.
By reading the pages of this website, and for small areas of cultivation, you will learn how in market gardening one can significantly limit the use of synthetic or organic pesticides to fight against many bio-aggressors and this by implementing environmentally friendly cultivation techniques such as biocontrols, crop rotation, varietal choice. Productivity losses are very low, if not zero. But to achieve such a result, you must respect all the recommendations that form a whole. If, for example, you neglect soil maintenance, your plants will be poorly nourished and more prone to disease. You will also have to spend money on insect protection, importing useful helpers and, above all, not being stingy with elbow grease.
Some of the advice given on this website is difficult to consider for field crops because of the size of the cultivated areas, the technical means that would have to be put in place, their financial costs and because they are less effective (for example: sulphur and copper for cereal diseases). What is possible on a small scale is not necessarily possible on a large scale. For example, it is difficult to ask a farmer who grows hectares of wheat to protect his crops with insect nets or to plough his fields with a fork spade so as not to harm earthworms.
In integrated agriculture, labels are beginning to emerge that guarantee production certified by laboratory analyses, providing more guarantees to consumers than organic agriculture for a more attractive price. For example, the "zero pesticide residue" label (a). This is also the objective of the "New Fields" collective created by French market gardeners and arboriculturists, or of the "tomorrow the earth" group of producers, of the "Nature and Flavour Tomatoes" alliance grouping three French producers: Savéol, Prince de Bretagne and Solarenn (b). I recommend these producers to all those who do not have the possibility to maintain a vegetable garden and/or fruit trees.
Some organic enthusiasts claim that these labels are fake organic. Those who practice integrated methods do not claim that their fruit and vegetables are grown according to organic farming methods, which do not tell the whole story about the traces of pesticides approved in this sector (c).
a) The absence of residue is determined, for each Active Substance analysed, by a result below the Limit of Quantification (LQ). Limit of quantification expresses the lowest concentration of analyte that can be quantified precisely and accurately. At present, the performance of measuring instruments leads for the majority of residues to a limit of quantification of 0.00001 g/kg.
b) The tomatoes are guaranteed to be free of synthetic pesticides and no copper is permitted in organic farming.
c) See the article "Some remarks on pesticides registered in organic farming - copper and sulphur based compounds", in particular the paragraph on organic wines, by clicking here
In many cases, Integrated methods in agriculture are more environmentally friendly than organic farming. Here are some examples:
Ammonia volatilization from nervous organic fertilizers (slurry, dried blood...) used in organic farming is unavoidable, whereas fast-acting synthetic fertilizers such as potassium nitrate used in integrated production are not affected by this nitrogen loss. For example, losses through volatilization account for 70% of the ammonia fraction in slurry (2).
The use of synthetic fertilisers in integrated agriculture to meet the varied needs of plants throughout their crop cycle is more precise than in organic farming, which uses only organic fertilisers (a). The evolution of an organic fertilizer is not controlled and depends on environmental factors that are not controllable (such as climatic hazards). The use of ammonitrates (b) has become the most common form of nitrogen application in integrated agriculture , and is less associated with ammonia volatilization.
Organic farming is less profitable per hectare than integrated agriculture. To compensate for this lower profitability, the area under organic crops has to be increased, with the consequence that areas of natural biodiversity are reduced.
Further arguments in favour of Integrated methods in agriculture are given on the following pages of this website, supported by numerous scientific references.
b) For different types of organic fertilisers, the rate of nitrogen mineralisation varies greatly. Factors such as climatic conditions and the physical and biological characteristics of the soil are involved. 30-80% of the organic nitrogen in poultry manure is mineralised within a few weeks to a few months. For cattle manures, 20-40% of the organic nitrogen is gradually mineralised during the crop year following application. In contrast, cattle manure and green waste composts that have undergone a long maturation phase of about 12 months mineralise very slowly - only 10-15% of their organic nitrogen is mineralised in the year following application.
b) ammonitrates : mineral fertiliser based on ammonium nitrate.
Brief presentation of the chapters.
All the chapters described below can be accessed by clicking on one of the options in the general menu at the top of each page. Each chapter is divided into articles that can be accessed from the menu or from a box at the top right of each page. The title of the page displayed is indicated by an arrow.
Before the first crops are grown, a laboratory analysis of a soil sample is essential to determine its physical and biological characteristics and its fertility potential. Important concepts in agronomy and pedology are covered, including the properties of humus and how it is formed. Absorbent complexes and cation exchange capacity are also studied.
Plant roots are not limited to the extraction of nutrients. These plant organs are involved in nutrient exchange with microorganisms concentrated in a specific area of the soil called the rhizosphere, which must therefore be protected. A diversion is undertaken to analyse the characteristics of resistant soils (also called suppressive soils) where vegetable plants are less affected by telluric pests.
Soils that are too rich in limestone, clay or sand can be corrected by soil amendments to obtain a garden soil that is compatible with the cultivation of many vegetable plants. For the amateur gardener, composting is the easiest way to improve the fertility potential of the vegetable garden. But this should not be done in any way. The choice of organic materials and the way in which composting should be carried out are described in order to obtain a sanitized compost with the qualities of forest mull.
Some agro-ecological theorists are convinced that Wrong grass (commonly known as " crazy grass") should no longer be fought. However, adventitious flora compete for food with vegetable crops. Wrong grass play a role in preserving biodiversity, but they are also vectors of disease and provide a refuge for pests. While their presence is useful in biodiversity corridors, Wrong grass must usually be eliminated from a crop plot to avoid unmanageable complications, such as polyphagous pests that can survive in Wrong grass and carry incurable diseases. Wrong grass are also incompatible with certain biocontrol methods such as insect netting, which considerably reduce the use of pesticides (synthetic or approved for use in organic farming).
For thousands of years, the spade and plough have been the tools of choice for improving the physical properties of a crop's soil. There are now other tillage methods that aim to rebuild soil biodiversity. In some techniques where ploughing is not used, tillage is reduced to a minimum or even abandoned. Each method has its disadvantages and advantages. An article describes why ploughing and pseudo-ploughing, alternating with other shallow tillage techniques, are simple methods that are effective and sufficient to maintain a home garden, provided that a certain amount of compost is added every year to compensate for natural humus losses.
Vegetable plants have intense and instantaneous nutrient requirements during certain periods of their crop cycle. Mineral reserves in the soil may be insufficient. Because of uncontrollable factors, organic fertilizers alone cannot accurately meet the requirements of vegetable plants during the most critical periods. The reasoning behind fertilising a vegetable garden is to use mineral fertilisers, especially to control nitrogen requirements more precisely, which also has the advantage of considerably reducing losses of soluble elements (especially nitrates) to the water table.
Like humans, plants become susceptible to disease when they are poorly nourished. A well-composted soil, complemented by accurate nutrient inputs throughout the crop cycle, increases the plants' natural defences against pests, yields and taste quality.
Regarding the use of mineral fertilisers, an article describes how easy it is to cheat in organic farming.
Agroecology is a catch-all term that can be used by any apostle of pseudo-science and mysticism. However, it is possible to define a scientific agroecology based on well-established scientific data, particularly with regard to ecosystem services, without forgetting to specify their limits.
Plant predators, known as bio-aggressor, are present everywhere in nature. As soon as a variety of vegetables is grown, bio-aggressor are given the opportunity to thrive. But these bio-aggressor are also prey for their own predators, which take advantage of the opportunity to multiply. In the end, a new balance is created that reduces the impact of bio-aggressor on crops. Some bio-aggressor, like their predators, are polyphagous, and both can accommodate other hosts and prey when they cannot find their preferred food. It is interesting to know the interactions between bio-aggressors, hosts and predators of bio-aggressor in order to promote natural regulation for the benefit of crops.
Creating biodiversity corridors in order to achieve natural bio-aggressor control is not always an easy objective to achieve. Many often uncontrollable factors act in a favourable or unfavourable way to crops. In addition, some bio-aggressors have no known predators in France and pose a threat to the environment. Examples are described showing how ecosystem services can be optimised for the benefit of vegetable crops. It is then discovered that the choice of certain host plants planted in an ornamental garden next to a vegetable garden plays an important role in the regulation of bio-aggressors. On the other hand, other associations produce contradictory effects and even favour the establishment of bio-aggressors.
An article is reserved for an in-depth critical study of one of the best-known disciplines of agroecology built on mystical and pseudo-scientific foundations: permaculture.
When ecosystem services fail to regulate the population of a bio-aggressor, it is necessary to try to protect crops by other physical or biological means before using plant protection products. In vegetable growing, active biocontrol methods to control certain bio-aggressors have become essential because they are often effective. sails against insects are a good way to protect vegetable plants against the bio-aggressors when these plants do not need to be pollinated (especially root vegetables and salads). When this is not enough, it is possible to reduce a pest population by importing their own predators if the latter are absent or insufficiently present. This type of treatment aims to control the development of the insect pests. For microbial bio-aggressors (bacteria, fungi and viruses), crop rotation and varietal choice are often the only more or less effective means of reducing their proliferation.
In recent years, biocontrol plant protection products have appeared, such as cultures of bacteria or viruses that are supposed to parasitise bio-aggressors, pheromone traps designed to capture breeding insects, or biodegradable herbicides derived from the living world to reduce weed development. Most of the biocontrol methods and plant protection products registered for non-professional use are discussed in detail on a page of this website with details of their advantages and weaknesses. The most common insect pests are described as well as the biocontrol methods that should be adopted to control them.
Can we really do without all pesticides? Plants are living beings that can be sick and need to be cared for like domestic animals. In integrated agriculture, the use of synthetic and/or organic pesticides is decided when all other plant protection methods have failed, and especially when a bio-aggressor presents a danger to the environment.
50% of French organic farmers are convinced that pesticides are not used in organic farming. However, slurry bordelaise, pyrethrins, nem oil and others are phytosanitary products approved for use in organic farming that are far from harmless. Several articles describe their properties and the toxic risks for humans and the environment.
The ban on synthetic pesticides in France from January 2019 for private individuals has caused many problems, as these pesticides are particularly essential for reducing "regulated insect pests", which must be controlled to protect the environment. Synthetic pesticides are also essential to combat fungal and bacterial diseases that are often uncontrollable with biocontrol methods. A critical analysis of nettle manure, which is widely presented as an alternative to synthetic pesticides, is full of surprises.
Find out more.
List of some websites related to integrated agriculture, biocontrols and the invasion of pseudo-sciences in agriculture.
In response to a growing demand for information from home gardeners, there is no shortage of books, press articles and websites suggesting a host of trendy tips: The weed-conserving culture, the dung horns and 'light sprays' of biodynamic agriculture that are said to have the supernatural power to improve plant growth, the cosmotelluric and magnetic beeswax antennae of electroculture, genodics or protein music that would help plants fight their predators, or the return to the old beliefs and recipes of our grandparents such as the lunar calendar, astral forces, nettle purins that could fool crop predators.
Nettle manure is one of the "Natural Preparations of Low Concern" (NPP) which would have no phytopharmaceutical activity, but would still be useful for crop protection. A list of PNPPs is available by clicking here. While some substances are known not to be dangerous for humans (such as sucrose, celery, lemongrass, etc.), others classified as PNPPs are not harmless. For example, decoctions of aloe vera leaves used as a bio-stimulant are on the list of probable carcinogens. This effect has been established by experiments on rats (4) and curiously, nobody is calling for a ban on this substance. Glyphosate, recently classified by the IARC (a) as a probable carcinogen, has become the bête noire of environmental NGOs, but not aloe vera.
Most natural remedies used in agriculture for hundreds of years, or even millennia, have never been tested for their benefits/risks. Their supposed properties are based on mostly empirical observations propagated from generation to generation. However, it would be very useful if all the checks were carried out to find out whether these substances are really effective and whether they do not present hidden risks for human health and/or the environment, as was the case with rotenone, which was used for many years in organic farming before it was banned when researchers discovered that it promotes Parkinson's disease.
I understand that some people are attracted by cultivation practices that are more respectful of the environment, just as it is normal to be concerned about preserving one's health. I have even noticed that experienced gardeners have been tempted by the promises of the various forms of organic agriculture (natural agriculture, permaculture, biodynamic agriculture, etc.), which have been lumped together under the heading of agroecology, whose very broad scope, which goes beyond a scientific position, allows anyone to claim to be a part of it. If we were to gather together all the nonsense written here and there claiming to be agroecology, we could write an encyclopaedia.
How did we get here?
There is a way of thinking in our society that deals with fundamental issues related to health, new technologies, agriculture and the environment, most often according to the methods of pseudo-sciences (b). This way of thinking, known as ecologism (or environmentalism), which is made up of multiple ideological and philosophical currents, claims to derive from a science; ecology.
The environmental problems caused by human activities and in particular intensive agriculture are real and there is no question of denying them. But it is unreasonable to believe that solutions to these problems can be found by spreading fear of new technologies, returning to the archaic farming methods of our ancestors and trusting in the magic powders of the witch doctors.
Everyone agrees on the principle of significantly reducing the use of pesticides, restoring soil biodiversity, converting to a more environmentally friendly form of agriculture... However, the solutions proposed must be realistic and validated by rigorous scientific studies. However, because they are not based on a credible scientific approach, the solutions proposed by the various schools of ecology are most often retrograde, misleading and illusory when they are not contrary to the desired goals.
From the utopian and appealing principles promoted by the ideologists of ecologism to their concrete application in the field, how many market gardeners and amateur gardeners have found themselves with disappointments and unenthusiastic results that they could have avoided if they had been better informed!
a) IARC: International Agency for Research on Cancer.
b) Pseudo-science: knowledge that appears to be scientific but does not meet the criteria of the scientific method.
The founders of biodynamic agriculture (also known as biodynamics) are convinced that cosmic forces are at work in heifer horns filled with dung that are buried on Michaelmas Day and dug up on Midsummer's Day, the contents of which are then used to spray the soil and plants. When the cows graze on the grass, their horns, directed towards the sky, are said to act as antennae to capture and store cosmic forces. One should laugh at such simplistic talk. And yet, biodynamics has no shortage of followers who are sensitive to mysticism and so-called natural methods in agriculture, which is not unusual these days, even in the land of Diderot.
Biodynamics has developed mainly in viticulture, bringing together around 500 winegrowers in France. The followers of biodynamics claim to be part of an organic approach and to belong to the agroecology movement.
Biodynamics was invented in 1920 by the philosopher Rudolf Steiner, founder of the spiritual doctrine of anthroposophy. Biodynamics contains the classic ingredients of mysticism and pseudo-sciences that have been used in agriculture for a long time, such as the influence of lunar cycles, the use of plant macerations or purins (camomile, horsetail, nettle, etc.) and more recently essential oils... In France, there is no official label protecting the name biodynamics. Only two associations (Demeter, Byidivin) offer private specifications to which farmers who claim to use this farming method must subscribe.
There is no serious scientific work that has demonstrated the existence of the cosmic forces described in biodynamics that influence crops. This practice in agriculture is defended on websites where adepts explain that it works. There will always be people who believe in the invisible energies of vitalism that can be manipulated, even if the results evoked by their followers are devoid of scientific proof.
The articles on this website are inspired in particular by the following works:
- Guide Pratique de la Fertilisation - 7ème édition - André Gros - La Maison Rustique.
- Le sol vivant - Base de pédologie, biologie des sols – J.M. Gobat, M. Aragno, W. Matthey – presses polytechniques et universitaire Romandes.
- Ecologie – approche scientifique et pratique – 6e édition - Claude Faurie, Christiane Ferra, Paul Medori, Jean Devaux, Jean-Louis Hemptinne – Lavoisier.
- Idées reçues et agriculture ; Parole à la science – Académie d’agriculture de France.
- Eléments de décision pour une fertilisation raisonnée en azote sur les cultures fruitières et légumières ; Ctifl, 31-7-2012.
- Gestion durable de la flore adventice des cultures ; Bruno Chauvel, Henri Darmency, Nicolas Munier-Jolain et Alain Rodriguez, coord. Éditions Quæ
© Serge BAESEN 2018
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1) Auréa AgroSciences ; Conséquences des excès de cuivre dans les sols et les végétaux https://www.aurea.eu/wp-content/uploads/2017/11/Consequences-des-exces-de-cuivre-dans-les-sols-et-les-vegetaux.pdf
2) COMIFER – Calcul de la fertilisation azotée ; guide méthodologique pour l’établissement des prescriptions locales -Edition 2013.
3) RACINE ET SYSTEME RACINAIRE DES ARBRES : STRUCTURE ET DEVELOPPEMENT – Plante & Cité – ingénieurie de la nature en ville - http://www.plante-et-cite.fr/data/fichiers_ressources/pdf_fiches/synthese/RACINE%20ET%20SYSTEME%20RACINAIRE%20DES%20ARBRES%20_%20STRUCTURE%20ET%20DEVELOPPEMENT.pdf
4) Cancer environnement > Monographies du CIRC > Vol.108 : Cancérogénicité de certains médicaments, plantes médicinales