|Tıbbi ve Aromatik Bitkilerin Organik Tarım ve Hayvancılıkta Kullanımları ve Toprak Islahındaki Rolleri
Reyhan BAHTİYARCA BAĞDAT Mücahit PEHLUVAN
Tarla Bitkileri Merkez Araştırma Enstitüsü Doğu Anadolu Tarımsal Araştırma Enstitüsü
PK: 226 06042 Ulus/Ankara Dadaşkent/Erzurum
Bitkisel ve hayvansal üretim faaliyetlerinin ana unsuru olan toprak; içme ve sulama sularının da önemli bir kaynağı ve koruyucusudur. Son yıllarda çeşitli kirlilik etmenleri ve yanlış uygulamalarla ciddi tehditler altında kalan tarım topraklarımızın ıslahında geç kalınması, gelecekte ekolojik dengenin bozulması başta olmak üzere daha pek çok önemli problemleri beraberinde getirebilecektir. Organik tarım bu ıslah sürecindeki alternatiflerden biri ve en etkili olanı olarak görülmekte, tıbbi ve aromatik bitkilerin bu tamir sürecinde aktif rol oynamaları beklenmektedir. Bu bitkilerin organik tarımda alternatif ekim nöbeti sistemleri içersinde yer alarak verimi artıracağı, allelopatik etkileri sayesinde ekolojik yabancı ot kontrolünde etkili olacağı, çeşitli bitkisel sanayi atıklarının organik gübre olarak değerlendirilebileceği ve toprağın bitki besin maddelerince zenginleştirileceği kaydedilmektedir. Bu bitkilerden izole edilen ekstraktların çeşitli yabancı ot ve zararlılara karşı toksik etki gösterdiği ve mücadelede olumlu sonuçlar alındığı bildirilmektedir. Yine organik hayvancılıkta tıbbi ve aromatik bitki ve ekstraktlarının doğal anti-biyotik, -mikrobiyal ve -bakteriyel olarak yem rasyonlarında kullanılmaları tamamen doğal organik gübre atıklarının oluşmasını da sağlayacaktır. Tamamen doğal ve zararsız bu insektisit, pestisit ve organik gübrelerin kullanımları toprağın ıslah sürecinde etkili mekanizma oynamalarının yanı sıra, zaten sınırlı ve tehdit altındaki yer altı sularımızında muhafazasında etkili olabileceklerdir.
Anahtar kelimeler: Tıbbi ve aromatik bitkiler, Organik tarım ve hayvancılık, ekim nöbeti , allelopatik etki, yabancı ot kontrolü, organik gübreler.
Use of Medicinal and Aromatic Plants in Organic Farming and Livestock and Their Roles to İmprove Soil
Soil, the main source of plant and livestock production, is also basis to form and protect the drinking and underground water. The pollution effects and unproper aplications may cause serious treatments on our farming lands, at the end. Being late in improving the farming lands may also destroy ecological balance and can cause further tragic problems in the future. Organic farming seems to be an alternative and effective process which improves and repairs the structure of the soil. It is expected, in this process, medicinal and aromatic plants can play an active role. These plants can take part in alternative rotation systems and increase the yield. Because of their allelopathic influences they can be effective in controlling weeds. It is reported that the industrial waste of the medicinal and aromatic plants can be used as organic manures to improve the soil. The extracts isolated from these plants present a toxic effect and fight succesfully with weeds and several larvaes of insects. In addition, medicinal and aromatic plants and their extractions can be used as natural anti-biotic, -microbial and -bacterial as feeding material in organic livestock. These then indirectly provide natural organic manure for farming. The certain medicinal and aromatic plants can function as insecticide, pesticide and organic manure to improve the soil and protect the underground water, which they are already ruined.
Keywords: Medicinal and aromatic plants, Organic farming and livestock, rotation, allelopathic effect, weed control, organik manures.
Soil, water and air, the main sources of living are in a tight and balanced relationship with each other. Any kind of disturbance would affect each others. Unfortunately, willingly or not, human being disturbed the balance. At present they have been managing to repair its tragic effects after seeing it. The first 40 years of the 20th century saw simultaneous advances in biochemistry and engineering that rapidly and profoundly changed farming. The introduction of the gasoline powered internal combustion engine ushered in the era of the tractor, and made possible hundreds of mechanized farm implements. Fields grew bigger and cropping more specialized to make more efficient use of machinery. At the same time, increasingly powerful and sophisticated farm machinery allowed a single farmer to work ever larger areas of land. Foundation the international campaigns encouraged the development of hybrid plants, chemical controls, large-scale irrigation, and heavy mechanization in agriculture around the world. During the 1950s, sustainable agriculture was a topic of scientific interest, but research tended to concentrate on developing the new chemical approaches. After seing the chronic effects of DDT (1972) and other pesticides on the environment cause to ban some of them. Intensive agriculture has increased crop yields but also posed severe environmental problems (Anonymus, 2005).
Sustainable agriculture would ideally produce good crop yields with minimal impact on ecological factors such as soil fertility. A fertile soil provides essential nutrients for crop plant growth, supports a diverse and active biotic community, exhibits a typical soil structure, and allows for an undisturbed decomposition. Organic farming systems are alternative to conventional agriculture which is known, that rely on ecosystem management and attempts to reduce or eliminate external agricultural inputs, especially synthetic ones. It is a holistic production management system that promotes and enhances agro-ecosystem health, including biodiversity, biological cycles, and soil biological activity (Benvenuti and Macchia, 2003). Organic farming relies heavily on the natural breakdown of organic matter, using techniques like green manure and composting, to replace nutrients taken from the soil by previous crops. This biological process, driven by microorganisms, allows the natural production of nutrients in the soil throughout the growing season, and has been referred to as feeding the soil to feed the plant. In chemical farming, individual nutrients, like nitrogen, are synthesized in a more or less pure form that plants can use immediately, and applied on a man-made schedule. Each nutrient is defined and addressed separately. Problems that may arise from one action (e.g. too much nitrogen left in the soil) are usually addressed with additional, corrective products and procedures (e.g. using water to wash excess nitrogen out of the soil). Organic farming uses a variety of methods to improve soil fertility, including crop rotation, cover cropping, application of compost, and mulching. A 22-year farm trial study by Cornell University published on July 13, 2005 concluded that Organic farming produces the same corn and soybean yields as conventional farms, but consumes less energy and contains no pesticide residues (IFOAM, 2005). Organic farmers also use processed natural fertilizers such as bone meal, blood meal, and various mineral powders such as rock phosphate and greensand, a naturally occuring form of potash. Medicinal and aromatic plants the masters of the wild life are the important chain of this cycle. They are also important for organic livestock. The current researches revealed that medicinal and aromatic plants could be taken a successefully part in alternative rotation systems, as organic fertilizers enrich of the soil microactivity and nutricient, and also in weed and insecticide control. According to ancient Indian handwritings, plant extracts have been used nearly 4 thousands years as insectiside. It was also recorded that 700 plant species has so far been used for fighting artropods (Thacker, 1999).
Organic production in agriculture was started in Turkey in the mid 1980s, and since then gained popularity. Over the last decade, it has grown dramatically in size and scope due to the progressive interest in Europe. The largest demand is for dried products and nuts, followed by field crops, fresh and processed fruits, vegetables, berries, medicinal and aromatic plants, industrial crops, and other row/processed products. Currently, 111 324 ha are organically managed by 15 795 producers, representing only 0.10% of all growers (Gubbuk and Pekmezci, 2004). Recently there has been an increased interest in the development of integrated plant protection programmes, especially those including alternative soil and plant protection methods, such as: resistant varieties of different crops, special crop rotations, intercropping of some plants, soil solarization, biological control, plant extracts of certain medical and ornamental plants, different kind of organic manure (poultry, cattle, pigeon and sheep) and tillage (Mateeva, 2000). The newest general tendency showed by industry and consumers towards the utilization of natural products has opened the way to the use of medicinal plants even on markets ruled by the use of synthetic products. Under such conditions, some new questions rise concerning the necessity for the above plants to respect the three conditions "quality-safety-effectiveness" and the opportunity to fit their utilization inside well planned and scientifically oriented programmes. In many cases, the cultivation of some medicinal plants with an interesting profitability could represent an important tool for a rational and sustainable exploitation of many marginal environments. In those environments, considered to be "fragile" ecosystems, the use of the commonly adopted cropping techniques is generally not advisable. It is particularly important, therefore, to study and point out new cropping systems, which must be managed applying the most conservative and environmentally friendly methods. The organic cropping techniques give important opportunities in such sense, and the cultivation of some selected medicinal plants (Carrubba and Torre, 2003).
Researcher currently carries out the following results on soil fertilization and organic farming. It’s recorded in the study conducted by Saha et al. in Kharapur (İndia) in 2005 that the affect of organic and inorganic fertilizers on Aloa Vera was found in favour of organic fertilizers. The treatments were: control (no fertilizer); farmyard manure (FYM) at 10.8 t/ha to supply N at 40 kg/ha; vermicompost at 3.175 t/ha + liquid vermiwash at 307 m3/ha to supply N at 80 kg/ha; NPK at 120-60-120 kg/ha; NPK at 80-40-80 kg/ha; and NPK at 40-20-40 kg/ha. Significant increases in biological and gel yield, plant height, number of leaves per plant and chlorophyll content were observed due to fertilizer treatments. Organic fertilizer in the form of vermicompost and vermiwash was effective and comparable to the inorganic fertilizers in increasing gel moisture, gel ash and aloin content. The organic A. Vera thus produced is expected to be a better marketable product.
Kandemir and Engin (2002) searched Iris histrioides F.’s effect, a Euxinion and endemic plant, on soil fertility. They took some samples from the above and below ground parts of the plant, in the vegetative and generative growth periods, and analysed them. The analysis results showed that, N%, P% and K% contents were determined higher in above-ground parts of the plant during the vegetative growth phase.
In another soil fertilization study conducted by Balak and Misra (2004) searched the soil ESP and pH value on cultıvatıon of German chamomile at all level of sodicity. Increasing the amount of the fertilizers significantly reduced the ESP of the soil. It is concluded that chamomile can be successfully employed for soil reclamation.
Weeds are often one of the biggest problems encountered by farmers and backyard farmers, especially during the transition period from conventional to organic farming. These problems can be overcome with well designed crop rotation, a soil improvement program and other ecological and preventative practices (Andres and Zettel, 1988). Crop rotation is a very traditional practice, which was given less importance for decades but is now regaining its importance in agricultural practice as a means of controlling weed seed banks and soilborne diseases and pests (Fomsgaard, 2006). Alternative rotatıon systems should be carefully designed in organic farming. They may help not only improving the soil but also fighting and controlling the weed population. Medicinal and aromatic plants can be succesfully take part in this system because of their allelopathic effects. Allelopaty is an interaction between rotation plants during any plant production, it can be defined as a direct or indirect harmful effect a chemical compounds released into the environment. Phytotoxic substances prevent germination in arid conditions and cause to some difficulties after producing any other crops and also some weed species. Aytotoxity and heterotoxity are spesific types of allelopathy which occurs in the same way (Temel and Tan, 2004). There are arranged following researches conducted to determine the allelopathic effects of some plants in our and other countries.
The allolaopathic effect of Lavandula angustifolia was studied in a nursery garden in Russia. During the cultivation, the microorganism numbers, their group composition and the N-fixing activity of the soil were studied. Allelopatically active substances in the rhizosphere of three-year-old plants were shown to promote the active growth of microorganisms assimilating organic and mineral N-containing compounds. The growth of soil microorganisms was less depressed than in one-year-old plants, but potential N-fixing soil activity was much lower. Microorganism numbers were found greater in the inter-row spaces than in the rhizosphere (Sidorenko et al., 1995).
Dudai et al. (1999) evaluated 32 aromatic plants essential oil for allelopathic properties. Extracts from Origanum syriacum, Micromeria fruticosa, and Cymbopogon citratus were selected for further study and it is recorded that the germination of several species, including wheat, was strongly inhibited by essential oils when applied at 20-80 ppm. C. citratus oil inhibited wheat radicle growth by 50% at 16 nl/ml and inhibited seed germination by 50% at 32 nl/ml. Essential oils mixed with the top 0.5 cm of soil inhibited germination of wheat and Amaranthus sp. seeds. This effect depended on soil type and the most active essential oil was the aldehyde from C. citratus. The main components of the essential oils of O. syriacum, M. fruticosa and C. citratus were carvacrol, pulegone and geranial plus neral, respectively.
In a field experiment carried on Tekelioğlu village in Manisa (1997), was aimed to research the effect of some plants species on density of weed in the cotton field grown ecological agriculture conditions. It was also investigated the effect of these plants in case using as a green fertilizers on yield and quality of cotton. As cultivar, Nazilli 84 was used and studied with seven variants as green fertilizer. According to the results, green fertilizers and preceeding crops (onion, radish, rye, barley, oil seed rape, common vetch) did not inhibit the emergence of Xanthium strumarium however, it was observed that radish inhibited the emergence of Sorghum halepense (99.72 %). The highest cotton yield was obtained from onion variant (200.947 kg/da) and the lowest was in common vetch (165.713 kg/da) (Kayandan et al., 2002). In another cotton research, the efficacy of neem product (phytopesticide FWB) was compared with perfekthion against sucking pests of cotton (jassids, thrips and whiteflies). Perfekthion proved to be more toxic but its effect lasted for 4 days only while neem product (FWB) was less toxic despite its effect lasted for 6 days. Moreover, neem product is defined much safer and non-polluting (Aslam and Naqvi, 2000).
The research project carried out from Başpınar et al. (2003), which hasn’t published yet, recorded Tagetes sp. inhibitory effects (59.5 %) on root nematods compered with controls. And it was also searched the effect of wheat and rye remains’ on cultivars and weeds agitated to soil in different proportions. Although the applications didn’t affect the cultivars, they affected germination of Portulaca oleracea L. and Amaranthus retroflexus L. seeds. In addition these plants Qasem and Hassan (2003) found Alhagi maurorum, Capparis spinosa, Citrullus colocynthis, Lavandula officinalis [L. angustifolia], Origanum syriacum, Rhus coriaria, Ricinus communis, Rosmarinus officinalis and Teucrium polium highly effective on Malva sylvestris and Portulaca oleracea weed species. Foliage leachates or volatile materials of many of these species significantly inhibited germination and growth of the two weeds. Addition of 2 g kg-1 dried shoot materials of L. officinalis or R. officinalis to the potted soil mixture was highly toxic and greatly reduced weed germination and growth. In a different allelopathic study performed in Canada, in ginseng production aera, recorded that pine bark mulches improved control of weeds and diseases compared to oat straw mulch (Reeleder et al., 2004).
In a similar study intent to determine the allelopathic effect of several aromatic plants was conducted on seedlings of wheat, cucumber and radish in Gansu Province. The results showed the aqueous extract of the stems and leaves of Artemisia annua, Solanum nigrum and Datura stramonium had the strongest allelopathy on test receptor plants, and their synthetic inhibitory effect (SE) was 47.66%, 32.89% and 26.63%, respectively. The SE of Xanthium sibiricum, Portulaca oleracea, Cephalanoplos segetum, and Chenopodium album was 21.71%, 20.93%, 20.83% and 20.2%, respectively, while Vicia amoena (SE 3.5%), Setaria viridis (SE 2.2%), and Cymamchum chinense (SE 1.97%) had a weaker allelopathy. Chenopodium ambrosioides (SE - 1.03%), Polygonum caespitosum (SE - 1.63%) and Avena fatua (SE 5.33%) had no evident allelopathy, but Artemisia annua affected the seedling height and fresh weight of radish, cucumber, wheat and maize, with the SE being 54.07%, 38.46%, 33.35% and 20.88%, respectively. Artemisia annua had a 44.70% of SE on wheat growth, and thus, had a certain value to develop and use. Nerium oleander was selected one of the species exhibited strong allelopathic activity for paddy weed control (Shen et al., 2005; Tran-Dang-Khanh et al., 2005).
Raising livestock and poultry, for meat, dairy and eggs, is another traditional, farming activity that complements growing. Organic farms attempt to provide animals with "natural" living conditions and feed. Feed is also organically grown, and drugs, including antibiotics, are not ordinarily used (and are prohibited under organic regulatory regimes). Drugs and synthetic food supplements are key components. Animals are often given preventive treatment of antibiotics in their daily feed, and supplements are added to increase the nutritional value of a variety of substances used as feed. Hormones may be used to optimize certain characteristics (e.g. produce more meat or more milk). Living conditions are often set as the minimum necessary for survival and growth. While today, small growing operations often do not include livestock, domesticated animals are desirable parts of the organic farming equation, especially for true sustainability, the ability of a farm to function as a self-renewing unit. Nowadays, numerous medicinal and aromatic plant drogs, extracts or essential oils used as anti-biotics, anthelmintic in organic livestock and as larvicidal, adulticidal, ovicidal, oviposition-deterrent, insecticide and acaricide in organic fighting and also recovering some plant deaseases.
Urticum is a formulation of essential and aromatic oil extracts from a mixture of medicinal and spice plants. Using urticum to control powdery (Uncinula necator) and downy (Plasmopara viticola) mildews on grape was tested with the cultivar Italian Riesling in the vineyard region of Fruska Gora [Yugoslavia] during 1994-99. Urticum at 1% was compared with a conventional treatment (0.015% propiconazole + 0.25% metalaxyl with mancozeb + 0.025% hexaconazole + 0.2% propineb) and an untreated control. Urticum provided better control of downy mildew (90.8 to 97.1%) than of powdery mildew (85.4 to 94.8%). Good protection was achieved compared to the conventional treatment (Robotic et al., 2000).
Altuğ and Kaptan (2002) searched several medicinal plants considered as possible alternatives to anthelmintic drugs for parasite control on organic farms in Turkey. These are briefly described with recommendations for use and include: garlic (Allium sativum, effective against Ascaris and Enterobius), wormwood (Artemisia vulgaris, effective against Protostrongylus, Dictyocaulus and Bunostomum), goosefoot (Chenopodium ambrosioides and C. anthelminthicum), juniper (Juniperus communis for the treatment of ascariasis), cucurbits (Cucurbita pepo and C. maxima for control of Haemonchus contortus), male fern (Dryopteris filix-mas for Dicrocoelium control), fleabane (Chrysanthemum cinerariifolium [Tanacetum cinerariifolium], a general anthelmintic, effective against Ascaris), tansy (Tanacetum vulgare for nematode control), hazel (Corylus avellana for Ascaris control) and lupin (Lupinus albus for control of Trichuris, Strongyloides and Ascaris). Some brassicas (Raphanus sativus, R. raphanistrum and Brassica rapa [B. campestris]) and tobacco (Nicotiana sp.) are also listed briefly. Petiveria alliacea (Phytolaccacea) is a herbaceous plant of great importance in traditional medicine and also has been reported to be effective as an insecticide and acaricide (Perez et al., 2005).
In a recent study, several medicinal plants essential oils were evaluated for larvicidal, adulticidal, ovicidal, oviposition-deterrent and repellent activities towards three mosquito species; Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. The essential oils of Juniperus macropoda and Pimpinella anisum found highly effective as both larvicidal and ovicidal. The essential oil of P. anisum showed toxicity against 4th instar larvae of A. stephensi and A. aegypti with equivalent LD95 values of 115.7 micro g/ml, whereas it was 149.7 micro g/ml against C. quinquefasciatus larvae. Essential oils of Zingiber officinale and Rosmarinus officinalis were found to be ovicidal and repellent, respectively towards the three mosquito species. The essential oil of Cinnamomum zeylanicum resulted into highest repellent (RD95) values of 49.6, 53.9 and 44.2 mg/mat against certain mosquito species (Veena-Prajapati et al., 2005).
Three studies with regard to the influence of herbs and essential oils on growth and carcass traits were carried out with male broilers over periods of 35 days (trials 1 and 2), respectively. The effects of oregano and its essential oil, savoury, Nigella sativa and cacao husks as feed supplements were investigated. Graded supplement of oregano (0, 2, 4, 10 and 20 g/kg) and its essential oil (0, 0.1, 0.2, 0.5 and 1.0 g/kg) reduced daily feed intake of broilers compared to control animals. Enrichment with essential oil significantly improved feed efficiency. Savoury, N. sativa and cacao husks increased daily feed intake of broilers in trial 2. In comparison to control animals liveweight at the end of the feeding period was significantly higher in all experimental groups of trial 2 (10 g cacao husks, 10 g cacao husks+5 g Nigella sativa, 10 g N. sativa and 50 g N. sativa) (Halle et al., 2004).
The use of medicinal and aromatic plants has never been out of focus throughout history. Our time, on the other hand, is witnessing a different approach to their utilization. For the first time in history, they have become industrial products for world-wide use. New concepts, such as nutraceuticals, cosmeceuticals, phytotherapy, aromatherapy, etc. are widening their use and new applications in functional foods, animal husbandry and agricultural pest management are taking place. New clinical evidence is also emerging on the effectiveness of medicinal plant products (Başer, 2003). In this arrangement it has been managed to focus on the above aspects from a global point of view. Various uses of these plants in organic farming systems are investigated and ordered. According the results, medicinal and aromatic plants can be used in alternative rotation systems succesfully enhancing the soil microactivity and floral and faunal diversity (Mäder et al., 2002). Their extracts and essential oils can be used in organic fighting as insecticid, acaricide and also larvicidal. Owing to allelopathic effects of certain species, they can also take part in alternative rotation systems and ecological weed controls. Currently, we met them as anti-microbial, -biotic and bacterial in organic livestock as food suppliers.
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Organic Crop IFOAM (2005Production Overview Accessed Nov. 29, 2005.
^ ) Principles of Organic Agriculture (pdf) Accessed 2005-12-12
^ Maeder, P. et al (2002) "Soil Fertility and Biodiversity in Organic Farming", Science, 31 May 2002 296: 1694-1697 Accessed 2005-12-12
^ InfoBull10.qxd. URL accessed on 2005-12-18.
In preference to the use of off-farm inputs, organic farming emphasizes management practices, taking into account that regional conditions require locally adapted systems. Utilizing both traditional and scientific knowledge, organic agricultural systems rely on agronomic, biological, and mechanical methods (these may require external inputs of nonrenewable resources, like tractor fuel), as opposed to using synthetic materials, to fulfill any specific function within the system. Organic farming usually subscribes to the Principles of Organic Agriculture.
However, a prominent 21-year Swiss study found an average 20% lower organic yields over conventional methods, along with 50% lower expenditure on fertilizer and energy, and used 97% less pesticides. A major US survey published in 2001, analyzed of some 150 growing seasons of data on various crops and concluded that organic yields were 95-100% of conventional yields. Comparative yield studies are still scarce, and overall results remain "inconclusive".
Organic Crop Production Overview Accessed Nov. 29, 2005.
^ IFOAM (2005) Principles of Organic Agriculture (pdf) Accessed 2005-12-12
^ Maeder, P. et al (2002) "Soil Fertility and Biodiversity in Organic Farming", Science, 31 May 2002 296: 1694-1697 Accessed 2005-12-12
^ InfoBull10.qxd. URL accessed on 2005-12-18
Science v.296, n.5573, 31may02
Paul Mäder,1* Andreas Fliebach,,1 David Dubois,2 Lucie Gunst,2 Padruot Fried,2 Urs Niggli1
An understanding of agroecosystems is key to determining effective farming systems. Here we report results from a 21-year study of agronomic and ecological performance of biodynamic, bioorganic, and conventional farming systems in Central Europe. We found crop yields to be 20% lower in the organic systems, although input of fertilizer and energy was reduced by 34 to 53% and pesticide input by 97%. Enhanced soil fertility and higher biodiversity found in organic plots may render these systems less dependent on external inputs.
Intensive agriculture has increased crop yields but also posed severe environmental problems (1). Sustainable agriculture would ideally produce good crop yields with minimal impact on ecological factors such as soil fertility (2, 3). A fertile soil provides essential nutrients for crop plant growth, supports a diverse and active biotic community, exhibits a typical soil structure, and allows for an undisturbed decomposition. Organic farming systems are one alternative to conventional agriculture. In some European countries up to 8% of the agricultural area is managed organically according to European Union Regulation (EEC) No. 2092/91 (4). But how sustainable is this production method really? The limited number of long-term trials show some benefits for the environment (5, 6). Here, we present results from the 21-year "DOK" system comparison trial (bio-Dynamic, bio-Organic, and "Konventionell"), which is based on a ley rotation. The field experiment was set up in 1978 on a loess soil at Therwil, Switzerland [(7) and supporting online material). Two organic farming systems (biodynamic, BIODYN; bioorganic, BIOORG) and two conventional systems (using mineral fertilizer plus farmyard manure: CONFYM; using mineral fertilizer exclusively: CONMIN) are emulated in a replicated field plot experiment (table S1 and fig. S1). Both conventional systems were modified to integrated farming in 1985. Crop rotation, varieties, and tillage were identical in all systems (table S2).
We found nutrient input (N, P, K) in the organic systems to be 34 to 51% lower than in the conventional systems, whereas mean crop yield was only 20% lower over a period of 21 years (Fig. 1, Table 1), indicating an efficient production. In the organic systems, the energy to produce a crop dry matter unit was 20 to 56% lower than in conventional and correspondingly 36 to 53% lower per unit of land area (tables S4 and S5).
Soil aggregate stability as assessed by the percolation method (11) and the wet sieving method (12) was 10 to 60% higher in the organic plots than in the conventional plots (Fig. 2A). These differences reflect the situation as observed in the field (Fig. 3, A and B), where organic plots had a greater soil stability. We found a positive correlation between aggregate stability and microbial biomass (r = 0.68, P < 0.05), and between aggregate stability and earthworm biomass (r = 0.45, P < 0.05).
Soil pH was slightly higher in the organic systems (Fig. 2B). Soluble fractions of phosphorus and potassium were lower in the organic soils than in the conventional soils, whereas calcium and magnesium were higher. However, the flux of phosphorus between the matrix and the soil solution was highest in the BIODYN system (13). Soil microorganisms govern the numerous nutrient cycling reactions in soils. Soil microbial biomass increased in the order CONMIN < CONFYM < BIOORG < BIODYN (Fig. 2C). In soils of the organic systems, dehydrogenase, protease, and phosphatase activities were higher than in the conventional systems, indicating a higher overall microbial activity and a higher capacity to cleave protein and organic phosphorus (12). Phosphorus flux through the microbial biomass was faster in organic soils, and more phosphorus was bound in the microbial biomass (14, 15). Evidently, nutrients in the organic systems are less dissolved in the soil solution, and microbial transformation processes may contribute to the plants' phosphorus supply.
Mycorrhizae as members of the soil community ameliorate plant mineral nutrition and contribute to soil aggregate formation (16). Root length colonized by mycorrhizae in organic farming systems was 40% higher than in conventional systems (7) (Fig. 2C).
Biomass and abundance of earthworms were higher by a factor of 1.3 to 3.2 in the organic plots as compared with conventional (17) (Fig. 2D). We also investigated epigaeic arthropods that live above ground, because they are important predators and considered sensitive indicators of soil fertility. Average activity density of carabids, staphylinids, and spiders in the organic plots was almost twice that of the conventional plots (18) (Fig. 2D).
Healthy ecosystems are characterized by high species diversity. The DOK trial shows that organic farming allows the development of a relatively diverse weed flora. Nine to 11 weed species were found in organically managed wheat plots and one species in conventional plots. Between 28 and 34 carabid species were found in the BIODYN system, 26 to 29 species in the BIOORG system, and 22 to 26 species in the CONFYM system (18). Some specialized and endangered species were present only in the two organic systems. Apart from the presence and diversity of weeds, direct effects of pesticides and the density of the wheat crop stand are most likely influencing arthropod activity and diversity.
Under controlled conditions, the diverse microbial community of the BIODYN soil decomposed more 14C-labeled plant material than the ones of the conventional soils (22). In the field, light fraction particulate organic matter, indicating undecomposed plant material, decayed more completely in organic systems (23). Hence, microbial communities with an increased diversity in organic soils transform carbon from organic debris into biomass at lower energy costs, building up a higher microbial biomass. Accordingly, the functional role of diverse plant communities in soil nitrate utilization has been quoted (24), as well as the significance of mycorrhizal diversity for phosphorus uptake and plant productivity (25). The consistent results of these two studies (24, 25) and our own within the soil-plant system support the hypothesis that a more diverse community is more efficient in resource utilization. The improvement of biological activity and biodiversity below and above ground in initial stages of food webs in the DOK trial is likely to provide a positive contribution toward the development of higher food web levels including birds and larger animals.
The organic systems show efficient resource utilization and enhanced floral and faunal diversity, features typical of mature systems. There is a significant correlation (r = 0.52, P < 0.05) between above-ground (unit energy per unit crop yield) and below-ground (CO2 evolution per unit soil microbial biomass) system efficiency in the DOK trial. We conclude that organically manured, legume-based crop rotations utilizing organic fertilizers from the farm itself are a realistic alternative to conventional farming systems.
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26. We sincerely thank all co-workers in the DOK trial, especially W. Stauffer and R. Frei and the farmer groups. We also thank T. Boller and A. Wiemken and two unknown referees for their helpful comments. This work was supported by the Swiss Federal Office for Agriculture and the Swiss National Science Foundation.
Fig. Sl. DOK field trial design: treatments under study.