FAIR-CT98-9574 Cultivation and processing systems for the cost efficient recovery of fibres from flax for use as a staple textile

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Crops for Textiles/Fabrics/Cordage : FAIR Area 1.2 - Green Chemicals and Polymers Chain : Fibre : Textiles/Fabrics/Geomembranes

	Contract No:	FAIR-CT98-9574
	Date Prepared:	April 2000
	Source:	Progress Report

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Progress Report Executive Summary

Introduction

This project is carrying out replicated trials on small plots in order to establish the principles for maximising yields of flax straw and fibre through selection of varieties, seed rate and harvesting strategy. It also aims to determine the optimum combinations of desiccant type, application timing and retting time (for the standing, desiccated crop) in order to facilitate decortication and maximise fibre yield. It also aims to provide samples of well-retted straw for decortication and determining the percentage of recoverable fibre, tow and shive, in relation to the crop agronomy.

Activities

In the first year replicated small plot trials were carried out at three sites around the UK:

• South West England, by University of Plymouth, at Seale-Hayne Faculty of Agriculture, Newton Abbot, Devon.
• East Midlands of England, by Independent Agricultural Services, at Huit Farm, Earl Shilton, Leicesters.
• North East Scotland, by The Scottish Agricultural College (SAC), Craibstone Estate, Bucksbum, Aberdeen.

A winter crop was drilled at the beginning of October, at a trial site at the University of Tras-os-montes & Alto Douro (UTAD), Vila Real, in Portugal. It is intended that a traditional spring-sown crop trial will also be carried out on the same site.

Well retted samples of straw were selected for decortication on a small-scale, laboratory-based, "linen processing system" by The Agricultural Research Institute of Northern Ireland (APJNI).

Results

Task 1: Small plot flax-growing trials. To evaluate the effects of seed rate, desiccant type and variety on. straw yield and the retting behaviour of the standing crop, in different climates and soil types. trials on all three sites were drilled in the first half of May. This was later than originally intended due to adverse weather conditions In fact the most Northern site (Aberdeen) was drilled first (1 May), with others on 7 and 15 may. At two of the sites, there were no differences between the varieties tested in terms of crop emergence or crop vigour, but at the Leicester site, Laura appeared to be a more vigorous variety.

With a thousand seed weight (TSW) of around 6g and a germination level of around 94% - 97%, seed rates of 45, 60, and 75 kg/ha were drilled, aiming to establish populations of approximately 566, 800 and 1000 plants per square metre respectively. The varieties used were Laura and Escalina. These populations are considerably lower than those used for traditional linen-flax crops. Actual populations achieved were similar at the Devon and Leicester sites, but a little higher at the Aberdeen site. The average populations (plants per square metre) were as indicated below.

Seed Rate (kg/ha)	Laura	Escalina
45	575	563
60	850	861
75	987	1019

The two varieties tested grew to similar heights at the Devon and Aberdeen sites, but at the Leicester site Laura was significantly taller than Escalina by about 30%. The actual crop heights were similar at the Devon and Aberdeen sites (around one metre), but significantly shorter at the Leicester site (60 to 80 cm). Increasing the seed rate had no effect on crop height. Results suggests that latitude and day length may influence crop development and that maximum stem height and stem diameter are reached by the end of flowering. The time from drilling to flowering appeared to increase further Northwards, whilst duration of flowering appeared to decrease further Northwards.

The application of desiccants was made according to the manufacturers recommendations. Glyphosate (fully translocated) was applied at the MPF + 2 weeks timing. This tended to coincide with the end of flowering. Results suggests that at this time the stems may have reached their maximum height and diameter. This would tend to suggest that the maximum level of fibre content may also have been reached. However, seed formation was in its very early stages and subsequently virtually no seed was produced from the plots sprayed at this time. Diquat and glufosinate ammonium (both contact only) were applied during the ripening of the seed capsules. This allowed the development of valuable harvestable seed, but delayed desication and harvest of the crop significantly. This proved to have some negative implications for the quality of the straw and fibre produced.

At all three sites, glyphosate was applied at the intended application stage. This coincided with the end of flowering and was around one month before the application of diquat. . Diquat and glufosinate ammonium were applied at their intended timings at the Devon site, but at the other sites application was slightly delayed due to adverse weather conditions. At these two sites diquat and glufosinate ammonium were applied on the same day. The earlier application date for Glyphosate ensured that the weather conditions were more reliable, especially at the more Northern sites.

Increasing seed rate and the higher plant populations that arose had no consistent effect on the efficacy of the desiccant treatment. There was no difference in desiccation between the two varieties tested. At two of the sites there was no difference between varieties in terms of their-response- to-the desiccant-treaments, but at the Leicester site the Escalina crop more quickly than Laura following treatment with diquat. However, at this site, the Escalina was already senescing by the time the diquat was applied and this would have accelerated the desiccation process.

Glyphosate and diquat both successfully desiccated the crop, but- glufosinate ammonium failed to do so at all three sites. Glyphosate desiccated the crop within '21 to 28 days. Desiccation was complete and uniform over the whole stem. (At the Devon site, desiccation was initially rather uneven but this soon became uniform. This initial unevenness could have been due to a three week period of very dry weather following application). Diquat treatment desiccated the crop relatively quickly, within 14--days, but desiccation tended to be uneven, especially on the lower parts of the stems. Glufosinate ammonium only desiccated the very upper parts of the stems, which naturally senesced anyway and tended to be no better than untreated control plots. Generally, the glyphosate treated plots were well desiccated by the time the diquat treatments were applied.

Desiccated standing-crops successfully retted in the field, prior to harvest.(Glyphosate treated stems retted uniformly and reached a stage acceptable for processing after 40 to 45 days, this was typically 14 to 21 days after complete desiccation Diquat-treated stems retted rather unevenly due to the uneven desiccation, but on average reached a stage acceptable for processing after around 30 to 35 days. Again this was typically 14 to 21 days after complete desication.

Harvest date was difficult to determine due to uneven desiccation and retting progress, and tended to be a compromise between under retted lower stems and over retted upper stems. There were no significant differences between varieties in terms of the retting process and increasing seed rate had no effect on retting at the seed rates tested. Results from the Leicester site suggested that the diquat-treated stems readily began to over-ret and lose their strength. This could have implications for both harvesting and processing. However, the glyphosate-treated stems appeared not to over-ret as easily, and they retained their strength for up to around 90 days after treatment.

Average yields of straw were similar from the sites at Leicester and Aberdeen, but significantly greater at the Devon site. This probably reflects climatic conditions and soil fertility, since the Devon site produced the tallest crop. Yields from the Leicester site were lower than expected, when compared to the farm's typical yields. There were considerable harvesting difficulties associated with wet weather. These were worse for the later applied diquat treatment.

There was no consistent difference between the varieties tested. At the Devon site the two varieties grew to similar heights. At the Aberdeen site, Escalina grew slightly taller than Laura and tended to produce a slightly higher yield. Increasing seed rate did not produce a consistent increase in straw yield, only at the Leicester site there was a tendency for more seeds to increase yield.

There was no consistent difference between diquat and glyphosate. Glufosinate treatment was not included in the yield results since it failed to desiccate the crop. At the Devon site, diquat tended to produce a higher yield than glyphosate, possibly due to the earlier desiccation timing used with glyphosate. At the Leicester site there was no significant difference between diquat and glyphosate. At the Aberdeen site glyphosate tended to produce the higher yield. Results from all three sites indicates that glyphosate-treated stems have a tendency to "lean" or lodge, but this did not cause any problems at harvest.

There was a tendency for percent total fibre content to decrease Northwards. At the Devon site Escalina tended to have a high percentage fibre content. There was no difference between the glyphosate and diquat desiccated stems. Increasing seed rate had no effect on fibre content. Data is incomplete since many of the diquat-treated plots could not be processed due to over-retting after a delayed harvest. At the Leicester site, Escalina had a significantly higher percent fibre content. Glyphosate-treated stems had a significantly higher percent fibre content than diquat-treated stems Increasing seed rate tended to increase percent fibre content. At the Aberdeen site (diquat data only), there was no significant difference between Escalina and Laura, but increasing seed rate tended to increase % fibre content.

The standing, desiccated crops retted to a stage acceptable for processing, prior to harvest, at all three sites. This process took-around 14 - 21 days after the complete desiccation of the stem,. Regardless of the desiccant used or stem maturity at desiccation. Undesiccated stems (in untreated control plots) and poorly desiccated stems, (in the glufosinate ammonium-treated plots) did not ret adequately. This may indicate that colonisation by the fungi responsible for retting only progresses after complete desiccation of the stem tissue. Furthermore, it was observed that stems which desiccated unevenly tended to produce similarly uneven retting, making decisions on harvest date complicated and quality of the product for processing variable. It is likely that there are several species of fungi involved in the retting process and these vary according to site location, weather and time of year.

The retting process was similar for the two varieties tested with no observable differences at any site. Increasing seed rate had no effect on the retting process, at the seed rates tested. However, it was observed that the glyphosate-treated stems tended to retain their strength, and thus their potential for successful processing, for a longer period than the diquat-treated stems. The diquat treated-stems tended to over-ret much more readily, this may make them less suitable for processing. The different fungicidal properties of the desiccants tested and/or the different weather conditions following treatment at the different timings, may explain this effect.

Samples of well-retted stems were selected and for decortication on a small scale laboratory "linen" processing system. This system was designed to decorticate straight, aligned stems for the recovery of "long" fibre. The percent recoverable fibre obtained using this processing system was very variable, but generally it tended to decrease further Northwards. The proportion of fibre which was classed as "long" fibre varied from 30% to 55% of the total fibre. Generally, Laura and Escalina produced similar percent fibre contents, with Escalina only slightly higher. Generally, increasing seed rate had no significant effect on fibre content at the seed rates tested, although there was a tendency for it to increase.

The different desiccants were applied at very different timings and any differences between them may be more due to the timing (eg weather conditions) than the treatments themselves. At the Devon site there was no significant difference at all between the desiccant treatments, while at the Leicester site diquat provided a very significantly lower percent fibre content.

Discussion

On the basis of the results from the first year of small plot trials it was concluded that it was possible to grow flax crops successfully in the wide range of climates found throughout the UK. The crop adapts its growth habit to suit climate, latitude and day length, although cooler temperatures and longer days may delay and shorten flowering.

Laura and Escalina produce crops with similar stem heights, but actual height varies depending on site-specific conditions. Both varieties responded in similar ways to the desiccants used, ret in the same way and produce similar straw and fibre yields. Any variation seen may be due to site specific conditions. Of the varieties tested, Laura appears to be the best "all-rounder", having performed more reliably over a wide range of conditions in this season.

At the seed rates tested, increasing the seed rate increases the plant population, but did not affect desiccation, the retting process, straw yield or fibre content.

Glyphosate provides uniform and complete desiccation of the whole stem and is a suitable desiccant for use on flax. Diquat may provide uneven desiccation, the upper parts of the stem may be well desiccated, while the lower parts remain green. It is therefore less suitable as a desiccant for use on flax. Glufosinate ammonium did not desiccate the stems at all and is therefore not an acceptable desiccant for use on flax.

Desiccation at the end of flowering did not significantly reduce straw yield. Additionally, it virtually eliminates seed production and may reduce the risk of adverse weather affecting the application of desiccants and/or the harvesting of the straw.

Desiccated standing crops retted successfully, and were suitable for processing without the need for a period of dew retting on the ground. Retting to a condition suitable for processing, tends to take 14 to 21 days approximately after complete desiccation of the stems, regardless of the desiccant used. Crops desiccated with glyphosate were suitable for harvesting and processing earlier in the season than crops desiccated with diquat. Crops desiccated with glyphosate remained "processable" and retained their fibre strength, for longer than crops that were desiccated with diquat. (ie the harvest window was much wider).

Straw yields, that tended to be related to crop height, were lower at the Northern sites. There were no consistent differences in yield between the varieties tested. Increasing seed rate did not increase straw yield at the seed rates tested. Desiccant type had no consistent effect on straw yields.

As far as percent fibre is concerned, results were incomplete and inconclusive, but Escalina may potentially have a higher fibre content than Laura.

Conclusions

On the basis of results so far the following recommendations are made;

The optimum seed rate is 45 kg/ha

The most reliable variety is Laura.

The most appropriate desiccant is glyphosate

The MPF +2 weeks is an appropriate application timing (this could be simplified by defining as end of flowering)

The desiccation of the crop should be completed after approximately 28 days.

The crop should be allowed to ret while standing, prior to harvest.

Retting should progress sufficiently to allow processing of the crop after a further 21 days.

The crop should then be cut and baled immediately, with no period of dew- retting required.