Progress 07/15/20 to 03/14/21

Outputs
Target Audience: Nothing Reported Changes/Problems:Due to the increased interest based on the commercial promise of this work, we have completed more than the initially planned four experiments. As was initially suggested in our proposed Task 2, we have identified the factors limiting continual flat re-use. However, these factors seem to come up unacceptably early in the current commercial farm. We are shifting our focus into how it can be better implemented in future farms. This means that the engineering efforts are currently more focused on the physical characteristics of the growth system than was previously expected. What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Identify the growth medium that allows germination equally well as our current commercial medium but which does not present microbial issues. Verify the benefit of improved uniformity in growth provided by new nozzle design. Test and improve upon a harvester that is more uniform, including at the edges. Discover the optimal harvesting blade height which allows regrowth but does not result in unacceptable amounts of leaves disrupted by cuts and nicks. Develop a ratooning "algorithm" for commercially relevant baby leafy greens. An algorithm is defined as the set of plant inputs that allow for commercially successful outputs of the plants of interest. This includes seed density, germination time and conditions, growth time and abiotic conditions, harvesting method and regrowth timing. Finalize a list of engineering requirements for ratooning harvest in future farms.

Impacts
What was accomplished under these goals? Initial experimentsdemonstrated, quantified, and qualifiedthe biological possibility of ratooning for crops of interest.We tested nine diverse varieties of baby leafy greens to understand their response to ratooning in appearance and flavor.We determined the relationship between harvest blade height and regrowth rate. We determined thatit is feasible for some varieties to ratoon such that the second harvest takes place after half the number of days as the first harvest. This means that each subsequent harvest requires half of the input electricity and half of the grow tower capital utilization of the first grow.Cost-benefit analysis conducted at this time showed that this was perhaps the most important R&D initiative to increase ROI for our future farms.This enabled budgetary allocation beyond what was provided for in the SBIR phase I. In further experiments we implemented the process using commercial scale farm and harvesterin order tounderstand process limitations. Several were identified, product quality declining and the proliferation of fungal contamination below the plant canopy. Product quality came from two main areas, the first was a variety-specific biological response to ratooning where bitterness and other flavor profiles associated with plant response to stress could increase.For each variety there appears to be a different number of ratooning cycles that produce plants with acceptable flavor.The second set of product quality issues was related to growth tower and harvester issues. Un-even growth across the surface of the flat is an occasional inconvenience in current operations,howeverpresents an unmanageable burden in ratooning. When ratooning un-even growth in the first batch results in more un-even growth in subsequent batches. A result of this is that the proportion of leaves which become damaged by the harvester increases from nearly 0 to over 50%. A final notable quality issue noticed was the prevalence of mold or mildew. This issue is caused by current growth medium which is a soaking wet fleece cloth that supports some algae and other microbial growth.These observations were critical in determining future directions needed for success.Several operationaland logisticalissues were identified which can help us to better design the layout of the farm and harvest area in future farms where we will employ this method. Based on the above observations, it was decided to move experimentation to our prototype next generation farm which hasa number oftechnical improvements needed to allow ratooning to succeed. First the prototype farm has a system to create uniform airflow throughout each level of the room. This airflow should reduce the environmental moisture where microbes proliferate and allow more even growth. Secondly the prototype farm has more even spray distribution and a square drip tray to allow even growth across the surface. Thirdly, the prototype farm is currently testing future media are being developed that provide a better vapor barrier and greatly reduce surface growth.A future harvester is also being developed with technology to create a more evenharvest around the edges of the flat. Finally, the prototype farm has a new design which keeps the roots situated in the aeroponic tray during harvest, which reduces root stress observed in previous ratooning. Initial experiments at the prototype farm have focused on growth medium evaluation and iterative improvements to the harvester system.

Publications

Progress 07/15/20 to 03/14/21

Outputs
Target Audience:This report will be aimed at a technically or scientifically literate person with no assumed knowledge of commercial leafy green horticulture. The target audience of the efforts of our project will be other members of the commercial horticulture field, who will find out about our research through patent filings and later outreach. Changes/Problems:After we identified causes of initial setbacks when ratooning was first implemented, we moved work to a prototype farm which contains many improvements that may help ratooning. This represented an expansion of the planned work in Phase I. We completed all initially proposed experiments and then saw the opportunity to continue work in the prototype farm in a way that was not anticipated when submitting the initial application. What opportunities for training and professional development has the project provided?This work provided the opportunity for Jr. Scientists and research associates to practice their skills on relevant topics including machine vision, phenotyping and microbial quantification. It also served as a topic for presentations and seminars at departmental and corporate levels. How have the results been disseminated to communities of interest?The results have been disseminated internally. Weekly results are presented at the R&D departmental meeting. Longer term results have been presented to the CEO, COO, and other senior leadership at meetings such as our "Farm Economics" group meeting, in which the most impactful ways to increase profitability of leafy greens are discussed. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Background Ratooning is a technique that allows one plant to produce multiple harvests. However, ratooning has not been widely adopted in the indoor production of leafy greens. This program addresses this gap through research and implementation. Phase I research was undertaken to understand knowledge of how cultivars respond to ratooning and determine the key cultivation setpoints. The research also enabled the identification of obstacles in implementing ratooning. Technical Objectives and Accomplishments The technical objectives and accomplishments of Phase I supported the goal of demonstrating the implementation of ratooning in current and future indoor farms. For each variety of leafy green evaluated, data was collected that related to: cut height, re-growth time, and number of ratoons per tray. Therefore, three main initial experiments were proposed: • Technical Objective #1: Evaluated cut height impact on yield and re-growth for different varieties of leafy greens. • Technical Objective #2: Evaluate Re-growth time after initial harvest. • Technical Objective #3: Understand the number of ratoons per seeded tray. Proof in Principle and Accomplishments In Phase I harvester blade height was evaluated for harvesting five to ten leafy green varieties, and we achieved 77%of regrew after harvest.Harvesting blade height impacted regrowth and plant morphology after ratooning. Evaluated yield responses for varieties based on number of regrowth days after harvest and we saw positive regrowth amounts. Completed multiple growth, harvest, and re-growth trials on a seeded tray. Identification of Needed Improvements at Commercial Farm A first challenge was an increase in frequency of partially cut or torn leaves with ratooning for some varieties between the first and second ratoons using aharvester. Uneven plant growth is a potential source of cut leaves. The second challenge was that during the longer growth cycle times fungal growth.Lab tests confirmed the presence of mold, ciliates, and non-parasitic nematodes. Also, the moist cloth is exposed to light prior to canopy establishment and a layer of algae can grow. Note that this experiment was self-contained. A third challenge is mechanical damage to the roots en-route to the harvester and a greater likelihood of microbial contamination of the roots. Conclusion Overall these results provide the biological and process observations needed to further research the innovative ratooning process. All of the challenges listed above must be addressed comprehensively to succeed.

Publications