16. RESUMEN EJECUTIVO
16.6 Conclusiones Financieras y Evaluación de Viabilidad
Ines Fritz1, Sonja Haindl, Markus Pruckner, Rudolf Braun
Key words: vermicompost, compost tea, plant growth, DGGE, microbial community
Abstract
Vermicompost was used to produce elutriates (aerated compost teas) containing micro-organisms together with all soluble nutrients from the compost. Micro-organisms growth was actively influenced during the extraction process by substrate addition. Teas of different production procedures have been analysed by chemical, microbiological and molecular biological (DGGE) methods accompanied by plant growth tests in laboratory scale. A slight change in micro-organism population in soil and an increased plant growth were determined as effect. The optimised tea was applied to cereals (wheat and barley) and vegetables (radish, rucola and peas) in field studies as well as to tomatoes under greenhouse conditions. The soil was investigated during the experiments to detect microbial or chemical changes. Plants were monitored during vegetation to compare plant growth and health, finally, crop yields were determined. The results for all field experiments showed only marginal differences, more often in plant quality than in quantity.
Introduction
Generally, compost elutriate (compost tea) is produced by putting a defined quantity of compost into water and mixing it for a definite time (Scheuerell, 2004). Actively aerated compost teas with additives are recommended to be produced (Ingham, 2006) expected to enhance the growth of beneficial and suppress pathogenic micro-organisms.
During the brewing process, micro-organisms and also all soluble nutrients of the used compost are extracted into the tea which could be applied directly on soil or by spraying on the plant foliage. Applied to the soil, the tea will go towards the roots, thus nutrients can be used by the plant and the micro-organism population of the rhizosphere could be (positively) affected (Bess, 2000). It is probably an interaction of several factors (mineral nutrients, micro-organisms, plant growth regulators) which result in an improved plant growth after the application of vermicompost teas (Edwards et al., 2006). There are only a few scientific papers about this topic which are also controversial. That is the reason why we investigated compost tea production and the effect on plants in detail.
Materials and methods
Compost teas were produced in an extraction vessel in the scale of 850 litres from 10 litres compost. Several physical and chemical parameters were determined after the tea production and during the elution process every 6 hours. Microbial (total and fungi-CFU), respiration rate and molecular biological analyses (DGGE) were analysed from final teas, were further processed by calculation of the Shannon-Weaver diversity index (Brodie, 2003) and evaluated by cluster analysis.
Plant growth test with cress and tomatoes were performed in an air-conditioned room. Applied tests included radish, rucola and peas in small field areas at the institutes own site (applied as foliar spray) and tomatoes under greenhouse conditions in a partner institute (applied to soil). Yield quantity was determined by weight, quality either as visual appearance of the plants or by taste of the harvest.
Results and Discussion
Production conditions did influence the chemical and microbiological composition of the final tea (Table 1). Since no other quality criteria had been defined before, those teas with the highest count of micro-organisms and the highest diversity in the microbial population were selected for the following plant tests. A tea produced by sequential extraction of vermicompost followed by an addition of green leaf compost and sunflower press cake was identified to support plant growth in laboratory experiments better than other recipes and was used for all further experiments.
1 University of Natural Resources and Applied Life Sciences, Vienna, Department IFA-Tulln, Konrad Lorenz Straße 20, 3430 Tulln, Austria, E-Mail: [email protected], Internet: www.ifa-tulln.ac.at
Table 1: Selected results of vermicompost-teas produced under different conditions. Production additive E485nm (colour) NO3 [mg/l] K [mg/l] P [mg/l] Fungi (CFU/ml) Bacteria (CFU/ml) Shannon- index b.
polenta, flour, silica, tap water 0.072 5.9 70 13 4.0 * 105 1.0 * 108 2.85
polenta, flour, silica, deionised water
0.201 51 305 23 6.7 * 105 7.5 * 107 2.96
polenta, oat bran 0.905 57 405 13 2.2 * 105 5.0 * 108 2.95
wheat flour, oat bran,
sunflower press cake 0.652 40 324 11 4.0 * 10
5 2.4 * 108 2.98
compost leachate, wheat flour,
oat bran 0.149 5.2 95 4.6 1.9 * 10
6 3.1 * 108 2.87
citric acid 0.130 97 94 19 2.0 * 105 6.1 * 107 2.73
citric acid, 96 h extraction 0.050 3.4 95 11 2.1 * 106 2.8 * 107 3.08
green leaf compost, oat bran 0.103 26 82 1.6 2.2 * 105 7.3 * 107 3.09
green leaf compost, oat bran, 96 h extraction
0.060 3.6 82 1.9 7.1 * 105 8.8 * 107 3.39
compost leachate, oat bran 0.503 88 288 4.2 4.6 * 104 2.7 * 106 3.36
green leaf compost, sunflower
press cake 0.116 6.2 97 5.4 8.9 * 10
5 2.5 * 108 3.10
Neither support of plant growth nor microbiological parameters did change significantly during a storage time up to 72 hours at 10°C. At higher temperatures the tea was not stable longer than 24 hours which has to be considered for routine production and application, especially during hot summer time.
Micro-organisms detected by molecular biological methods in the compost could not be found again in soil after tea application. Nevertheless some slight changes in the soil composition were detected, proving that the observed small quality improvement in vegetables was related to the tea application. Significant differences in crop yield (harvest weight) were not observed.
Conclusions
Vermicompost-tea was found to be beneficial for plant growth and biomass production in laboratory experiments, correlating with microbiological parameters. All parameters were influenced by brewing and storage conditions in multiple ways. Nevertheless, compost tea quality was reproducible under certain conditions. Field experiments showed a more often beneficial effect of vermicompost-tea to crop quality but never to harvest quantity. If compost tea was applied to the field in the recommended amounts it is obvious that it does not act as fertiliser, more likely as a form of plant support.
It is strongly advised to follow up by investigating microbial population dynamics on plant surfaces due to tea application monitoring plant health and infection probability because of displacement effects.
Acknowledgments
The data summarized in this paper were generated in two research projects. The first was co-financed by the European Fond for Regional Development (EFRE) and by the government of Lower Austria (WST3, Technopol). The second was financed by the government of Lower Austria (Bodenbündnis).
References
Brodie, E., Edwards, S., Clipson, N. (2003): Soil fungal community structure in a temperate upland grassland soil. FEMS Microbiology Ecology. 45/2:105-114.
Edwards, C. A., Arancon, N. Q., Greytak S. (2006): Effects of Vermicompost Teas on Plant Growth and Disease. BioCycle. 47/5:28
Ingham, E. R., Rollins, C. A. (2006): Adding Biology - For Soil and Hydroponic Systems. Nature Technologies, LLC, Sonoma. 68
Scheuerell, S. J., Mahaffee, W. F. (2004): Compost Tea as a Container Medium Drench for Suppressing Seedling Damping-Off Caused by Pythium ultimum. Biological Control. 94/11:1156-1163