|Plant Production and Soil Science Research under Research Program for Organic Food and Farming in Finland
Arja Nykänen (1), Kaija Hakala (2), Arja Halinen (3), Asko Hannukkala (2), Marjo Keskitalo (2), Anna-Maija Kirkkari (4), Ansa Palojärvi (5), Kaisa Tolonen (6) and Tiina Tontti (2)
MTT Agrifood Research Finland, Ecological production, Huttulantie 1, 51900 Juva, Finland, tel. +358 15 321 230, e-mail: arja.nykanen[a]mtt.fi, Internet: www.mtt.fi
MTT Agrifood Research Finland, Plant Production Research, 31600 Jokioinen, Finland, tel. +358 3 41811, e-mails: kaija.hakala[a]mtt.fi asko.hannukkala[a]mtt.fi marjo.keskitalo[a]mtt.fi, Internet: www.mtt.fi
MTT Agrifood Research Finland, Ecological Production, Karilantie 2A, 50600 Mikkeli, Finland, tel. +358 15 321 220, emails: arja.halinen[a]mtt.fi tiina.tontti[a]mtt.fi Internet: www.mtt.fi
Work Efficiency Institute, P.O.Box 28, 00210 Helsinki, Finland, tel. +358 9 2904 1200, anna-maija.kirkkari[a]tts.fi Internet: www.tts.fi
MTT Agrifood Research Finland, Environmental Research, Soils and Environment, 31600 Jokioinen, Finland, tel. +358 3 41811, e-mail: ansa.palojarvi[a]mtt.fi , Internet: www.mtt.fi
ProAgria, Urheilutie 6, 01300 Vantaa, Finland, tel. +358 20 7472 400, kaisa.tolonen[a]proagria.fi Internet www.proagria.fi
Key words: potato late blight, Phytophthora infestans, caraway oil, red clover, Trifolium repens, meat-bone meal, waste composts, soil fertility, test kit
In a three-year Research program of Organic Food and Farming in Finland there are six projects under theme plant production and soil science. The projects focus on potato and red clover cultivation, waste composts and meat-bone meal as organic fertilizer and on-farm soil quality testing. Preliminary results are now available.
The Finnish Ministry of Agriculture and Forestry started a three-year Research Program on Organic Food and Farming in 2003. The program consists of 15 projects under different themes over the whole food chain. The annual budget for this programme is about 2.2 MEUR.
Under plant production and soil science theme, there are six projects: ‘Control of potato late blight by caraway oil in organic farming’, ‘Disease management in organic seed potato production’, ‘Red clover efficiently into organically produced milk’, ‘Development of meat-bone meal as organic fertilizer’, ‘Waste composts in organic crop production – future risks and possibilities’ and ‘On-farm soil quality assessment’.
Potato late blight caused by an oomycete Phytophthora infestans (P.i) is the main factor determining the length of the growing season of organic potato by killing the canopy (Zwankhuizen and Zadoks, 2002). Management of the new sexually reproducing P.i. population characterised by early oospore-derived epidemics is a challenge for conventional production and can be crucial for the economy of organic potato producers (Fry et al. 1993, Lehtinen and Hannukkala, 2004). In Finland there are currently no compounds available for direct blight control in organic production. Caraway (Carum carvi) seeds contain biologically active essential oils, which have shown potential in controlling potato late blight.
Red clover (Trifolium pratense) is the most common fodder legume in Finnish organic grasslands. The persistence of clover is often poor and patchy after the second production year. The focus in the project is to give tools for farmers to choose the best red clover varieties for their fields, based on yield production, resistance to pathogens and over-wintering. Further, spatial connection between red clover growth and soil properties is studied.
Re-cycling of nutrients from municipalities back to the fields is one aim of organic farming. Organic waste such as meat-bone meal and waste composts from municipalities are often considered as unwanted material because of possible heavy metals and microbiological risks. In Finland it is not permitted to use them in organic production at the moment, but their fertilization effect and risks of use are studied in two projects.
At present, soil fertility testing is based on soil chemical analysis. However, organic farming is dependent on biologically mediated processes and functions of the whole soil system. Therefore soil quality should be seen as soil's ability to function, depending on the usage of soil. This quality is based on chemical, physical, and biological soil properties.
Caraway essential oil as a bio-control for late potato blight is developed through caraway oil extractions, formulation and efficiency experiments. Also the effect of caraway oil on potato plant, potato leaf RNA-levels and potato late blight spore production and growth are investigated. The aim of the study on Phytophthora infestans in organic production is to define factors of success and failure in disease management and test efficacy of cultural crop management practises including row spacing and mechanical defoliation to suppress the progress of potato late blight epidemics. The project is conducted using two major approaches: surveys and interviews on farms and field experiments carried out by research institutes.
Plant physiological, molecular biological (RAPD-PCR, UP-PCR) and statistical methods (bi-additive model) are used to find out the most persistent red clover varieties for organic grassland production over different growing conditions. In addition, spatial variation of soil characteristics, N-fixation (with 15N-dilution technique and N-difference technique) and yield of red clover-grass leys are studied on a two-hectare field under organic farming.
Municipal waste composts are tested as a fertilizer for potato, grassland and cereals in one field experiment. The microbiological quality (Salmonella, Coliforms, Colifags, Clostrides) of the composts is analysed, as well as the nutrients and heavy metals and their effects on soil biological fertility. The yield, its hygienic quality and nutrient and heavy metal content of the harvested crops are also analysed. Meat-bone meal is studied as a fertilizer for cereals on farms and the instructions for the use are developed.
A practical soil quality test for on-farm use is developed by modifying a soil quality test kit to be suitable for Finnish conditions, based on existing test kits and expertise. On-farm testing is carried out together with advisors.
Results and brief discussion
Caraway essential oil has delayed the onset of late blight for about 10-14 days in field conditions (Hannukkala et al. 2001; Keskitalo 2002). The control activity of oil is based on the prevention of late blight spore production and growth already at a low oil concentration. In contrast to previous studies, caraway oil seemed to have some systemic effect on potato plant. Formulation decreased volatilization of the caraway oil and changed its adhesiveness to spores, but effect against late blight was not improved in greenhouse tests.
All organic potato growers interviewed were very concerned about leaf blight, as it has become common that blight stops the growing season by the middle of the August as happened in 2003. The season 2004 was even more severe. The weather in most potato growing regions was extremely conductive for potato late blight and many organic fields were totally defoliated by blight at the end of July when no marketable tuber yield had developed. In both years the epidemics started earlier and were more severe on fields where potato was grown for two consecutive years compared to good crop rotation. From the statistics in 2003 it was shown that potato was the most common pre-crop for potato in organic production.
It was also obvious that many farmers using green manure did not actually realise the nitrogen requirements of potato. According to the statistics and interviews green manure was very often provided for the potato crop resulting considerable uncontrolled overdose of nitrogen. The onset of tuber formation was delayed due to excessive release of nitrogen from green manure. In addition very thick and tall stand was extremely favourable for devastating blight epidemic before onset of tuber formation.
Widening of the row space in field experiments did not delay the blight epidemic, but in some sites slightly slowed defoliation in both years. Glass et al. (2001) have obtained similar results. Very preliminary data from 2004 indicate that mechanical defoliation after appearance of blight in crop considerably decreases yield but has very little effect on the prevalence of tuber blight.
The over-wintering of a red clover variety seems to be essential for persistence of a red clover sward. A variety, which might not be the most productive in the beginning of growth, but accumulates nitrogen and carbon into its roots seems to be the most persistent and most productive in the long run. For example clover variety Betty (a Swedish tetraploid), which has shown to be the most winter hardy clover variety in Finnish conditions, invested relatively more biomass into the roots than a local variety Jokioinen or an Estonian high-yielding tetraploid variety, which is less winter-hardy than Betty (Figure 1). Of the pathogens found in a selection of organic clover fields in Finland only one of 14 collected Fusarium strains could infect red clover, while all Sclerotinia strains infected all the tested red clover varieties. The pathogenic Fusarium strain was the only one, which could enter the clover cells, which probably explains the pathogenity.
igure 1. Soil bound biomass / harvested biomass of different clover varieties ‘Jokioinen’, ‘Betty’ and ‘Ilte’.
The variation of yield and clover content of red clover-grass can be surprisingly high inside a field. The dry matter yield of first cut varied from 2 800 to 7 270 kg ha-1 and second cut from 2 570 to 6 770 kg ha-1 in dry matter in 2004. The clover content varied 4-75 % and 1-73 % in dry matter respectively. Very preliminary results show slight correlation between sward yield and some soil characteristics, as pH, potassium, manganese, cobalt, copper, molybdenum and iron
Farmers, who used meat-bone meal as a fertilizer for cereals, were quite satisfied with it, but spreading of greasy and fine meat-bone meal was problematic on many farms. Farmers were wishing for pelleted or pilled form of meat-bone meal, which could be used as traditional chemical fertilizer. Framers would be interested in using it in the future, if permission is possible to get. The fertilization effect was clearly visible on their fields.
The nutrient, heavy metal and bacteriological composition of waste composts varied according to the origin of the compost. The current limits of bacteria and heavy metals were not exceeded in any of the composts. None of the composts had any long-term negative effects on soil biological fertility. The amount of soluble nutrients, especially nitrogen and phosphorus, was very low in all the composts compared to their total nutrient contents. The composts were applied according to the valid legislation, which governs the use of composts by their total nitrogen and phosphorus contents. The amount of the plant-available nutrients given via the composts was therefore not sufficient to create measurable fertiliser effects. The amounts of the composts used had no negative effects to the soil.
The preliminary test kit for soil quality is in the testing phase on farms at the moment and experiences are collected.
It is possible to delay the onset of late blight for 14 days by using caraway oil. The aims of the ongoing studies are to find ways for further delay, which also improves the economical feasibility to control late blight with caraway oil. Also, the combination of caraway oil with other plant-based extracts is studied. As a preliminary conclusion there are limited possibilities for effective enough blight management in organic potato production, when disease pressure is very high as in 2004. Changing towards more diverse crop rotations and better control of nitrogen release can delay the onset of blight epidemics considerably. Increasing row spacing and mechanical defoliation have very limited value in blight control.
According to the microbiological and chemical analyses all the tested composts were suitable for use as plant fertilisers. However, the amount of compost used should be greater in order to fulfil the nutritional demands of plants and thereby accomplish larger yields.
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Glass, J. R., Johnson, K. B.& Powelson, M. L., 2001. Assessment of barriers to prevent the development of potato tuber blight caused by Phytophthora infestans. Plant Disease 85:521-528.
Hannukkala, A., Keskitalo, M., Laamanen, J & Rastas, M. 2002. Control of potato late blight with Caraway and Dill extracts. In: H.T.A.M. Schepers and C.E. Westerdijk, editors. Proceedings of the sixth workshop of an European network for development of an integrated control strategy of potato late blight. Edingburgh, Scotland, 26-30 September 2001. PPO-special report 8: 279-280.
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