Sustainable Cultivation of Plant-derived Indigo for Diversification and On-farm Value-added Dye Pigment Production

Sustainable Cultivation of Plant-derived Indigo for Diversification and On-farm Value-added Dye Pigment Production

Summary

A comparison of indigo yielding plants showed that varieties of Indigofera tinctoria, Indigofera suffruticosa and Persicaria tinctoria can all be grown in Middle Tennessee. The first year showed that P.tinctoria was much more hardy to stress conditions and able to grow in a range of weather conditions. The I.tinctoria and I.suff were both difficult to germinate in greenhouse starts and difficult to direct seed, resulting in fewer established plants. Initial indigo extraction data for P.tinctoria indicates a range of variables impacts final pigment color, including growing and processing conditions. Preliminary dried indigo quality results are pending.

Objectives/Performance Targets

Our main objectives were determining if the three indigo varieties could be cultivated at our Middle Tennessee farm and what the best conditions were for growing the different varieties. We measured green harvest weight per row foot and then isolate the pigment from the indigo harvest. Our goal is to determine which indican-containing plants are most likely to be profitable and successfully grown in our region. The plants in the study are dyer’s knotweed (P. tinctoria), and two types of indigo (Indigofera suffruticosa and Indigofera tinctoria). We will assess variables in the processing technique to determine the way this project can be scaled onto other farms.

The research trial involves growing and processing 100 row-feet of each of the three variables of the three indigo varieties utilizing organic practices. Where applicable, we used varying inoculation, mulch and fertilizer variables. The trial will determine the most suitable methods for cultivating the selected crop(s), based not only on green vegetative yield but also isolated pigment yield after extraction of the indigo pigment. By investigating different nutrient regimes I can determine maximum profitability based on the volume and purity of final product (pigment) yield after taking into account input costs.

For the leguminous crops, both I.suffruticosa and I. tinctoria, the 4 row trail will be as follows:1) No Input/No Innoculant, 2) No Input/Innoculant, 3) Compost/Innoculant, 4)Compost/No Innoculant

For the P. tinctoria, the 4 row trial is as follows:1)No inputs, 2) Composted manure, 3)worm castings, 4)Fish emulsion.

Indigo will be harvested in batches based on variety and processed along side each other so date of harvest and conditions are the same. Our method of processing uses non-specialized equipment. After the harvest and processing, our partner ASK Apparel will do comparison testing of the quality of the natural indigo pigment from the different production methods and plants by making dye vats and testing the strength and clarity of the pigment and compare to imported natural indigo.

Accomplishments/Milestones

In addition to getting preliminary growing data on growing and processing Indigo varieties in Tennessee, in 2010 we did several outreach events to share our experience growing indigo. We hosted a 2 day workshop during our indigo harvest period in October 2010 in which 20 people came to the farm to learn more about growing and harvesting indigo. We also had a booth at the Southern Sustainable Agriculture Working Group (SSAWG) conference in January 2011, allowing us to interact with more growers and extension personnel and do more outreach on the growing of natural dyes in general and indigo in particular. While we were not able to share final research project results at this conference, we collected names and contact information for those interested in learning the final results of the project and potentially raising indigo at their farms. We also taped the footage for our Indigo growing instructional video and are finalizing the content.

In 2011, we are running a I. tinctoria germination trial to determine the best strategy for starting Indigofera species from seed. The trial has heat, scarification, and soaking variables for the seeds so we can find out the best way for starting these seeds. We are also planting 100 row feet of P.tinctoria under a fish emulsion and compost trial under drip irrigation. We will also plant 2 – 50 foot rows of I. tinctoria under drip irrigation and compost. Focusing on these successful inputs and under irrigation we hope to get a more accurate idea of the potential harvest per row foot can be for these crops if nutrient input was maximize.

Impacts and Contributions/Outcomes

Due to different germination rates, variable irrigation, and severe weather conditions (i.e. a 500 year flood in Middle Tennessee leading to us moving farms) the varieties did not established at the same rate. P.tinctoria was our most successful variety. There was a lag time in planting, as a second and third round of starts for Indigofera varieties were necessary. After establishment, both the I. suff and eventually the P.tinctoria were more susceptible than I. tinctoria to deer and cattle browse when the electric fence broke down. Due to problems with the fencing, we learned young I. suff was most desirable to both deer and cow grazing, creating 100% loss of this crop. At full growth (approx 3-4 feet) I. tinctoria was resistant to cow grazing. P. tinctoria was top or heavily browsed by cows that escaped into our fields later in the season (at full growth). Our estimates put livestock damage on P. tinctoria at about 70%, concentrated on the P3 and P4 variables of our test plots. We plan to move to a new smaller field for 2011 away from any livestock and under irrigation to overcome 2010 growing hurdles.

We processed the P. tinctoria over a 1 week period, harvesting and processing 2 different variables in tanks on 2 different days over a 2-3 day time frame. We attempted to standardize the temperature of the soaking liquid using heaters had a difficult time keep consistent temperature between the trials during the variable fall weather. In 2011 for our smaller test, we will only have two varieties so we can process them all over the same days and harvest a little earlier in the season. We harvested the I.tinctoria and dried it for composting rather than doing the wet precipitation processing. This was because we felt the volume of leaf matter was too low to run a large enough precipitation vat and we would be better off trying the composting method on these dried leaves.

Running this research project has greatly improved our knowledge of indigo crops and we look forward to continuing our study this growing season to finalize some of our research and make it into a form that other producers can utilize. We have found a lot of individual and press interest in the project, leading us to believe this can be a valuable niche / value added product for Southeastern farms.

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