Organic agriculture and biodiversity
We are pleased to highlight below preliminary results from research comparing biodiversity in an organic farm in the Western Ghats of Karnataka, India, to levels in conventional farms. The research was supported by Third World Network, and two papers presenting part of the results were presented at the Organic World Conference 2011.
The results demonstrate that biodiversity levels are higher in the organic farm compared to conventional, as exemplified by insect biodiversity. The difference is evident even on farms using low amounts of pesticides. Pest control in the organic farm is achieved via biodiversity. Having genetic diversity amongst the cropping system enables the selection and maintenance of resistant clones. The rich biodiversity present in the organic farm also provides ample plant pest repellents while beneficial insects play significant roles in controlling pest populations. Growing crops organically also enables the plants to develop and express their resistance pathways, inducing natural plant defences, such that over the years crop losses due to diseases have become negligible and the plants eventually require no botanical repellents.
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of Biodiversity through Sustainable Agriculture
Biological diversity and agriculture are intrinsically linked. Since agriculture is a dominant human activity and occupies about 38 percent of available land space globally (even more in India), the decisions that farmers make can dramatically affect biodiversity at all levels. The introduction of modern farming practices (mechanization, mono-cropping, elite varieties and hybrids and GM crops combined with the heavy use of agrochemicals (fertilizers, pesticides and herbicides)) has greatly reduced the biological diversity on farms and surrounding ecosystems. Yet a good organic farmer understands the importance of biodiversity and tries to mimic nature and design his farm so it resembles a complex ecosystem. Like nature, s/he provides niches for diverse plants, animals, insects, bacteria and fungi competing with each other and living in harmony. As we learn more about the complex and subtle interactions between plants, pathogens, pests and predators we can began to appreciate the tremendous value of biodiversity and the ‘ecosystem services’ (such as pollination, pest control, water conservation, nitrogen and carbon sequestration etc.) that it provides.
The Mojo plantation spice farm is a living example of how biodiversity can be conserved and even thrive through sustainable agriculture. It also serves as a window to the amazing range of biodiversity found in the Western Ghats (which we stand to lose if present practices continue. Located at 1100m altitude in the rainforest tracts of Kodagu district of the Western Ghats of Karnataka, we receive up to 5000 mm (200 inches) of rain annually, most of it between June and September. The plantation is densely forested with native trees and the primary crops are cardamom, coffee and pepper and vanilla and some areas are left uncultivated. While this environment places limitations and challenges on the types and quantities of crops we can grow, it fosters a tremendous amount of biodiversity which we are documenting. The surrounding area of Galibeedu and Kaloor is best described as a ‘Shola -grassland’ eco-system which is unique to the W. Ghats.
There is mass extinction of amphibians taking place globally as a result of habitat destruction, overuse of toxic pesticides and a recently identified fungal infection. Amphibians are considered ‘indicator species’ as they are highly sensitive to environmental changes and they have been mutated and wiped out in most of North and Central America and Europe. The Western Ghats are known for their remarkable amphibian diversity. Conservation of these rare species of frogs is crucial and requires identification and documentation of their reproductive habits etc. On our organic farm, we have documented many species of frogs, toads, caecilians and tree frogs including the very rare Rhacophorus lateralis which was re-discovered here in Kodagu district after 100 yrs. This species mates on leaves of a branch overhanging a pond/tank and the female rolls the leaf into a nest for protection. One of the most complex genus of frogs is Philatus – the bush frogs. New species are still being discovered and some of them have a very limited range. We have identified at least 6 species of Philatus including 3 recently discovered species that were previously not known from this area. Frogs predominately feed on insects and therefore help keep pest populations under control.
We also have a rich diversity of birds (over 100 listed), spiders, and predatory insects such as robber-flies, dragonflies, wasps, mantids, ants that keep populations of herbivore pests in check. Of the more than 1 million of species of insects, a mere 150-200 are considered agricultural pests, yet spraying of toxic chemicals indiscriminately wipes out biodiversity leading to serious imbalances on farms and in nature. It is this very diversity that enables a fine-tuned balance between the agricultural ‘pests’ and their predators that nature has evolved for millennia.
Scientific study to compare biodiversity levels on organic versus conventional farms
Have focused on insect diversity as they are essential for agriculture.
representation of Shannon’s biodiversity index for different crops and
treatments (G = Organic; N= NPK; P= Pesticide +NPK)
Loss of habitat is a major threat to loss of species diversity worldwide. Organic farms and fallow lands can provide primary habitats for encouraging species of local small wildlife and therefore contribute significantly towards conservation of biological diversity. They can also serve as corridors to connect large tracts of wilderness.
Enhancing Plant Defense through Ecological Farming Practices
Sujata and Maya Goel
Mojo Plantation, Galibeedu Post, PO Box 101, Madikeri 571 201, Karnataka, India.
Key Words: Ecological farming, biodiversity, plant defense, spice cultivation
Our Organic Spice Farm at Mojo Plantation is located in a high rainfall zone in Kodagu district, in the Western Ghats of Southern India. Our main crops are cardamom, coffee, vanilla, black pepper, turmeric, some spice trees, and fruits like banana, orange, pineapples. At an altitude of 4000 meters, we receive an annual rainfall of about 5 meters between the months of June to September. The unique agroclimatic nature of this region has allowed the cultivation of crops under the canopies of the rainforests. As a result, most plantations harbour a rich diversity of plants, small mammals, insects, birds, and reptiles. However, heavy use of fertilizers and pesticides have posed a serious threat to this fragile ecosystem and therefore it is important to adopt sustainable agricultural practices. Organic farming enables a balance between land use and conservation of biological diversity. The Western Ghats harbour a small pocket of unique and rich species diversity and it falls upon the farmers and residents of this region to protect this wealth. Therefore, we cultivate crops like cardamom and pepper that can be grown in the shade of the rainforest trees, employing practices which are in tune with the forest ecosystem. We have been completely organic for the past 15 years and have encouraged others to do the same.
Methods and Results
Farming Practices and Crop Protection at Mojo: Emulating natural ecosystems and adapting them into our farming systems has been done over the years by traditional farmers all over the world. The major underlying principle of farming at Mojo has been to recycle all forms of organic matter through composting cycles, generation of biogas, animal husbandry, towards enhancing crop productivity. During the early years, our cardamom fields were infested with the cardamom stem borer (Conogethes punctiferalis). The larva of this moth bores into the succulent ‘stem’ of the cardamom plant, feeds into the centre, cocoons, and the new moth emerges to lay eggs in the canopy of the trees above or in the leaf litter below. One mother gives rise to about 200 larvae, and heavy infestations can devastate a cardamom crop. In order to circumvent the damage, we developed bioassays to screen local plants for their efficacy as pest repellents, and finally used the most common ones found in this region. These were Pongamia pinnata (karanj, Indian beech), Annona reticulate (custard apple), Ocimum tenuiflora (wild tulsi), Vitex negundo (chaste tree, neergundi), Lantana camara (lantana), and Nicotiana plumbaginifolia (wild tobacco).
Other plants like Adathoda vasica (adulsa), Alpina galanga (galanga), Acorus calamus (vacha), Crotolaria retusa (rattlepods), Calotropis procera (ak, milkweed), Azadirachta indica (neem), Cassia fistula (amaltas) are used for traditional crop protection. The leaves can be added to the soil to control soil pests or infusions can be used as foliar sprays. In fields where plants of the mustard family (Brassicacea) can be incorporated into the cropping systems, several fungal diseases can be controlled. After harvest, if mustard plants are mulched into the soil, microbial activity releases isothiocyanates which act as mild fumigants and suppress fungal growth (Angus et al, 1994). This provides an excellent protection to crops against infestations like Rhizoctonia, Pythium, and Sclerotinia. Phytopathogenic fungi like Trichoderma are effective in controlling Phytophthora which causes root rots of several host plants, whereas Bauveria bassiana and Verticilium leccani have been used effectively against larvae of beetles and mealy bugs.
Cow urine and whey from cheese can be used as protective foliar sprays against a range of bacterial and fungal infestations, and wood ash is excellent for discouraging populations of aphids in vegetables.
Encouraging Biodiversity in Crop Fields: On organic farms such as ours which have no trace of chemicals around, parasitic insects colonize native plant species and play significant roles in controlling pest populations. Beneficial microorganisms contribute to a rise in detritus activity of the soil, increased nitrogen fixation, and increase in nutrient cycles. Areas where grasslands are encouraged become sponges for harnessing rain water to replenish water tables and aquifers. The integration of fallow lands into cultivated areas also enables pest-predator balances, and promotes an even distribution of predators which offer effective pest control in the field (Crowder et al, 2010), and attracts pollinators.
Through our years of growing crops in a fragile ecosystem, we find that screening and selecting genetically resilient strains is a sound practice in disease management. Use of chemicals and pesticides have degraded lands and water bodies all over the world. If we now find it essential for species survival to revert back to holistic farming practices, it is imperative to understand what is happening within the plant system when it is subject to disease and other stress factors.
Induction of Plant Defense: Plants have developed a wide range of defense mechanisms to survive different stress factors including diseases (Bruinsma et al, 2009). Resistance genes confer genetic protection. However, what is now coming to be understood is that plants have evolved highly sophisticated mechanisms to defend themselves against a wide range of herbivorous insects and pathogenic microbes, fungi and viruses. When a plant comes under attack, a primary set of defenses get triggered which allow them to cope with multiple aggressors. When the attack gets more severe, the production of plant hormones like jasmonic acid, salicylic acid and ethylene gets induced (Arimura et al, 2005). These hormones in turn induce a cascade of enzymatic reactions that finally result in synthesis of compounds (terpenes, tannins, phenolics) which directly act to repel the insect, inhibit its digestive enzymes, affect their reproductive cycles, and in some cases, release volatiles which attract the predators of the insects feeding on the plant! In others where a fungal or bacterial microbe invades the cell, the cell itself necroses and dies, immediately arresting the further invasive growth of the pathogen.
Many of these pathways act together, or sometimes antagonistically, enabling what is best described as a “cross talk” between metabolic pathways. It is this cross talk which provides a powerful regulatory mechanism and helps the plant to prioritize and “decide” which defense strategy to follow, depending upon the attacker. In some cases, the simultaneous activation of multiple defense pathways result in enhanced levels of induced resistance to diseases.
Insects feeding on a plant trigger release of volatiles which can prime neighbouring plants for enhancing their defense against those insects. This priming results in improved direct defense (reduction in insects feeding on the host plant), or indirect defense (attraction of parasitoids or predatory insects like wasps). Even roots release a number of metabolites in response to elicitation by jasmonates, salicylates and chitosan which show antimicrobial activity. Rhizosphere of some trees have been shown to suppress pathogenic fungal communities.
In nature, plant defense traits are polygenic and thus this variation becomes a fantastic reservoir of natural adaptive mechanisms in response to changes in biotic stress. We have found that over the years crop losses due to diseases have become negligible, the plants require no sprays (we have not used the botanical repellents for the past 8 years) and exhibit an overall vigour that is gratifying for any farmer to see.
With more information coming forth on induced defense mechanisms of plants, it is logical to create conditions where plants can fend for themselves. Growing crops organically enables the plants to develop and express their resistance pathway. Creating conditions within the agri-ecosystem to encourage biological diversity enables crops to be surrounded with balanced populations of predators (spiders, dragon flies, wasps, mantids, frogs, birds, shrews, etc.), which help in disease management far more effectively than any spray.
Finally, we have come to realize that it is only when farming is based upon “natural principles” can it be truly sustainable. Ecological farming is based on nurturing and nourishing the soils. Having healthy predatory populations within the agri-ecosystem naturally reduces the pest damage caused to crops. Having genetic diversity amongst the cropping system also enables us to select and maintain resistant clones. The heavy rainfall zones in the Western Ghats have a fragile ecology and are extremely prone to soil erosion. It is important to try and adopt agricultural practices which emphasize soil conservation and build up of organic and conservation of biodiversity.