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FAIR-CT97-3751
Optimised production and harvesting technique of the alternative crop Stevia rebaudiana Bertoni |
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Proposal No: | FAIR-CT97-3751 |
| Date Prepared: | February 2001, January 1999 | |
| Source: | Third Annual Progress Report
First Annual Progress Report |
Objectives
The project aims to significantly improve cultivation techniques for this crop by closely integrating agronomists, process technologists and agricultural machinery engineers. One of the main objectives of the work will be to reduce production costs. The implementation of the results should allow, within some years, the cultivation of 5,000 to 10,000 hectares of Stevia on poor soils in southern Europe. the specific objectives of the project are to look at:
The lack of knowledge concerning mechanisation represents an important gap in cultivation of this crop. To meet the requirements for an economically feasible cultivation in the EU it is necessary to bridge this gap with research covering the development of:
The project also includes an economic cost/benefit analysis of the production costs in the EU.
Activities
Task 1: Development of an optimised cultivation technique through mechanisation
Sub-task 1.1. Screening for usable herbicides in greenhouse tests. The expected phases 3 and 4 were finished in March 2000. As a general result, more herbicides have to be tested for their application in Stevia. No herbicide was found to act against perennial weeds without damaging Stevia. It was found that the herbicide Sethoxydim does act as a tillering enhancer with the small plantlets develop tillers at the highest tested dose. This behaviour is not normal for Stevia, which normally only develops tillers after the first cut. This compound might be used to increase the leaf production in the first year of cultivation.
Sub-task 1.2. Field testing of selected herbicides As it was shown in test phase 2 and 3 that the obtained results for Linuron differed from the results previously obtained. Hence, it was decided to start directly with the field trials and hence for the herbicides Metobromuron, Propizamide and Propaquilzafob test phase No.4 was cancelled due to climatic problems and these were tried directly in the field tests. Now all herbicides have been tested in the field. The best results in terms of herbicide control were found with Metobromuron. All other herbicides were deficient in effects. It was surprising but, at the recommended dose levels the control of some herbicides differed significantly from the expected effects. The main problems are associated with perennial grasses. As a consequence, the tests for weed control with herbicides have to be extended. One recently released herbicide, oxifluorfen, has already been tested. Oxifluorfen acts as a pre-emergent herbicide. The suitability for application in Stevia production is still under investigation. As a consequence, the tests for weed control with herbicides have to be extended and this Task will be completed next year.
Sub-task 1.3 Evaluation of Weed Tolerance of Stevia This work in on-going and the first results have been obtained. The Task will be completed next year.
Sub-task 1.4 In Row Weed Control by mechanical methods This work in on-going with the following results obtained during the reporting period The devices Bow-Row and Finger-Hoe have been tested. The Bow-Hoe seems useful to control weeds between the rows. The Finger- Hoe was not suitable as it lifted the young plants. This test has to be repeated in the second vegetation year. The main problems are the perennial weeds such as Cyperus rotundus or Cynodon dactylon. All the mechanical devices tested exert a tillering effect on such weeds. Further work is required and this will be continued next year, including the introduction of several devices for mechanical weed control that are under construction and in the workshop of the Institute of Agricultural Engineering of the University of Hohenheim.
Sub-task 1.5 Only in final year of project
Sub-task 1.6 Direct seeding technique This work is on-going. During the reporting period results obtained showed that the germination of cleaned seeds reached around 94% in laboratory test. Field tests to show the germination level under field conditions can now start. A first test of seeding with the pre-emergent herbicides Metobromuron, Linuron and Oxifluorfen was made, but no germination was obtained. A big problem is micro-erosion that occurs with direct seeding. As Stevia is a light germinator a conventional seeding in 2-3 cm depths is not applicable. The seeds have to be placed on the surface, but due to micro-erosion the seeds are buried and so do not germinate. A natural agent was investigated for fluid seeding. But there was no germination. In addition there were probably problems with protection against fungi and soil insects. A special direct seeding device is under construction and will be used to make field tests.
Task 2: Stevia-Harvester
Sub-task 2. 1: Development of Harvester the modified harvester has been used in field tests, showing excellent adaptation to Stevia plants, although some improvements in some construction details have to be made, so the task will be completed during next year.
Sub-task 2.2: Prototype of Pick-up System This has also gone through field tests and been shown to be successful and finished, unless anything new is observed in further field tests of during the next reporting period.
Sub-task 2.3: Prototype Engineering and Testing Field test showed the prototype was working well. Some small modifications have to be made . All technical problems can be solved. The Task is now on time and will be completed next year.
Task 3 Separation Process for Leaves and Stalks
Sub-task 3.1: Development of the separation process of stalks and leaves A process has been tested and shown to work and the Task completed next year.
Sub-task 3.2: Development of the surface dressing technology A device was installed and assembled in Cartaya and tests carried out, over three periods, with generally good results. It is expected that all technical problems can be solved and will enable this task to be completed successfully next year.
Task 4 Economic Evaluation of the feasibility of Stevia crop
Data is being monitored on an on-going basis and should lead to a final result next year.
Task 5 Agronomic characteristics of Stevia rebaudiana
Sub-task 5.1: Determination of Nutritional Requirements Field tests have been carried out and some results obtained from leaf samples and trial harvests. The work is continuing.
Sub-task 5.2: Determination of Water Requirements On-going measurements have shown differences between the two experimental sites. Trial for Cartaya will be adapted to the results already obtained and the final results produced during the last project year
Sub-task 5.3: Development of Biomass From the on-going work, the most interesting results were observed in Cartaya, where under the tested conditions, a very low water requirement for a sufficient yield was established.
Achievements
Summary
Introduction The overall objectives are an investigation of biomass development during the vegetative cycle as well as development of an optimised cultivation system through mechanisation. This is to be achieved through the following actions:
Activities During the reporting period most of the work concerned plant development and weed control. The following has been achieved:
Progress The activity started later than was hoped, resulting in loss of a cultivation campaign, to which poor climatic conditions in winter/spring 1997/1998 contributed. A main focus of the project is the organisation of the field trials. In the event, the original selected test farm was not longer available, hence a new partner was required. A draft contract is under negotiation.
The following results have been achieved so far:
Discussion Manual weed control in Stevia crop would consume around 550 working hours per hectare. This is not feasible for European farms. Hence, methods for effective weed control have to be developed using chemical and mechanical control, that might including hand-labour. The most important results from the screening for usable herbicides in the greenhouse are as follows. The herbicides Linuron and Sethoxydim did not affect the germination rate of Stevia seeds, if used at the recommended dose level. The herbicide Propaquizafob did not affect the germination of Stevia seeds at any of the tested levels. Hence, useful herbicides have been identified.
The treatment of established Stevia plants in pots with Linuron, Quizalofob-ethyl and Sethoxidim did not show any damages in the plants. The test is still ongoing as not all herbicides have been tested. As Stevia is a perennial plant, it is necessary to know if a continuing treatment with the tested herbicides will lead to a damage in the long-term. Therefore this test phase will be maintained throughout the 36 months of the project.
The seed germination in soil is good (about 50%) under laboratory conditions. The most important results of studies on direct seeding techniques have shown that cleaning of the seeds can double the germination rate, but the desired level (90%) has not been reached. The final germination rate will be measured with pilled seeds. Through the pilling procedure a further cleaning can be expected, while the conventional cleaning process can be improved.
Future activities In the next project period (to the start of year 2000) the greenhouse herbicide screening tests should be finished and results of the mechanical weed control system should be available. The germination tests and the cleaning and pilling should be improved for further field test of the pilled seeds. A first pre-prototype of the Stevia harvester and separator will be available for first field tests in order to improve the construction already achieved. The first results concerning the impact of fertilisers and water will become available and the first approach towards constructing a biomass-model will be made.
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by CPL Press:
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