Baby Spinach Research Yield Update
Growcer’s R&D team sharing how we seed baby spinach during Rootcamp.
Sharing the results of Growcer’s baby spinach experiments
As previously discussed, Growcer is experimenting with baby spinach.
1. Spinach is well loved, delicious, and full of nutrients. It's a no-brainer why it's in the crop rotation for so many growers.
2. Adult spinach (the big spinach you're used to) comes with its own challenges when trying to grow it in a vertical modular farm like Growcer's.
What if I told you, you could eliminate those challenges (of low germination and bolting) and double your yield (and better your ROI) with baby spinach?
Theoretically, you can grow MORE baby spinach *faster* than you can adult spinach, with less hassle.
But you can't simply plant spinach seeds in a Growcer farm and get baby spinach, there were several modifications the team made to optimize for baby green production. Let’s see how they fared when put to the test.
Improving Germination Rates
If you’re not ready to abandon adult spinach yet, you can see the multiple ways Growcer’s R&D improved germination for regular spinach production.
The lessons gained from the spinach germination trials were adapted to the new baby spinach cultivation system.
Specifically, spinach seeds underwent hydropriming. Then following a 24-hour drying step, the seeds were planted into the new cultivation blocks filled with loose substrate. Remember, baby spinach cultivation blocks have a higher planting density and require a loose substrate to fit into the smaller planting slots.
The R&D team measured average germination rates at 2 days after seeding (2DAS) and 6 days after seeding (6DAS) for each spinach cultivar, Sunangel and Space.
The target for germination rates was 80%. Why not 100% you might ask? Well, germination is the sprouting process where a plant grows from a seed into a seedling. Germination in spinach is particularly poor because of its thick seed coat, so 100% germination usually does not happen. A batch of seeds is a mixed bag. Within a batch of seeds, you can get seeds that are not fully mature or some that are damaged, so they take a longer time to germinate or do not germinate at all. Plus, nothing in science is ever 100% guaranteed.
Figure 1: Average germination rates for both batches of Space (Spa) and Sunangel (Sun) spinach at two and six days after seeding (DAS). Data points are presented as means of ten replicates with 77 seeds each. Bars and limit lines represent the standard error of the mean.
As you can see from the graph, both cultivars of spinach failed to meet the 80% germination target.
Growcer’s R&D team found that the time it took to seed at a higher density increased because of imbibition (that’s when you wet the seeds with a wet paper towel) which left “sticky” seeds that were harder to handle. The failure to hit the germination target and the lengthy seeding process prompted the team to revise how we seed baby spinach.
Measuring Baby Spinach Yields
Before revising the germination process, the R&D team wanted to collect some yield data (never miss an opportunity to collect data!).
The yields for the two spinach cultivars were assessed at three separate harvest intervals: 2, 3, or 4 weeks after seeding. The result was that for both Sunangel and Space cultivars, the yield in kg/m2/week at the 3-week mark was higher than at the 2 or 4-week mark.
Or put in other words, not too little time, not too much time, but just right.
Figure 2 : Average yield of Space and Sunangel spinach at 14, 21, and 24 days after seeding (DAS). Data points are presented as means of 6-7 replicates with 308 seedlings each. Bars and limit lines represent the standard error of the mean. Harvest times followed by the same upper-case letters within each cultivar and cultivars followed by the same lower-case letters within each harvest time are not statistically different at P ≤ 0.05.
A Second Look at Germination
Improving the rates of germination in baby spinach requires a different approach. The team looked at ways to simplify the process and hit our goal of >80% germination. This was done in two stages by testing out light and humidity variations.
Loose substrate covering freshly planted baby spinach seeds.
Let there be light?
The team conducted an experiment to test the effect of light exposure at different stages of the germination process.
“G” Treatment
Day One: Seed imbibition
Day Two: Seed drying
Day Three: Seeding and incubation in the dark in an enclosed “germination rack” prototype
Day Four: Unsealed blocks placed in light
“L” Treatment
Day One: Seed imbibition
Day Two: Seed drying
Day Three: Seeding and incubation in the dark in sealed covers
Day Four: Sealed blocks placed in light
“D” Treatment
Day One: Seed imbibition
Day Two: Seed drying
Day Three and Four: Seeding and incubation in the dark in sealed covers
The “L” treatment had significantly less germination, so it was dropped from further assessment.
The “D” treatment showed the highest germination rate, but the results produced were not significantly different from the “G” treatment.
Contrary to some existing protocols for baby spinach production, it became clear that initial light exposure was not necessary for proper germination and development. In other words, the dark side wins this one.
Then, looking at the procedure with a full system viewpoint, one treatment stood out as the best one.
Treatments “G” and “D” had similar germination rates. The extra space required and upfront costs of a “germination rack,” meant that “G” and “D” were equal for hitting our germination goals but “G” was more resource-intensive. We decided to abandon the “G” approach because it did not amount to improved germination rates or translate into higher harvestable yields.
In other words, the “D” treatment won because it achieved our germination goals with less resources (space, money, and time).
Figure 3 : Germination rates and resulting yields of light exposure and germination rack testing
Let there be humidity?
The baby spinach is planted into blocks that it stays for the duration of its plant cycle.
The data decided that no, there will be no light, because germination in full dark conditions works. Following this, the team set out to investigate alternatives to hydropriming (keeping the seeds in a wet paper towel for 24 hours) the spinach seeds prior to planting.
Remember: Typically, you transplant a seedling into the main growing area, but this step is also eliminated for baby spinach. The baby spinach blocks can simply be placed into the cultivation area directly. This - the act of putting the blocks directly into the main growing area - is called “floating.”
“D” Treatment
Day One: Seed imbibition
Day Two: Seed drying
Day Three: Seeded and incubated in sealed bags at high humidity, with no light until floating
“U” Treatment
Day One: Seeding untreated seeds and incubation on the same day
Day Four: Blocks remained in sealed bags at high humidity and no light exposure until floating on day 4.
“E” Treatment
Day One: Seed imbibition
Day Two: Seed drying, and an extra drying step where the germination dome was removed 1.5 hours to seeding to allow for better handling
Day Three: Seeded and incubated in sealed bags at high humidity, with no light until floating
All treatments had germination rates close to or above 85% with the “U” treatment having the highest germination rate.
The success of the “U” treatment is exciting (truly!), because it demonstrated the potential impact of the new substrate type. Because the “U” treatment performed the best, and also coincidentally took the least amount of steps, we were able to reduce the labour needed for this new cultivation method while increasing yield. So we got higher yields with a less labour intensive process.
Figure 4 : Germination rates and resulting yields (kg/m2/week) of seed pre-treatment testing
*The C in the first figure above should be a D
Benchmarking Yields and Labour
After determining which treatments (“D” and “U”) gave us the highest germination rates and yields for baby spinach production, we benchmarked both the yield and labour for the Sunangel spinach cultivar.
*Drum roll please*
When compared to standard adult spinach production, we increased the yields of baby spinach by up to 115% per year of cultivation. We can produce 115% more spinach in the same farm area in a year, compared to adult spinach benchmarks.
However, there are some tradeoffs when it comes to the time required. The labour required for seeding at a high density and how often you would have to seed (because remember, you harvest in 3 weeks instead of 5!), means that baby spinach production takes 16% more time on an annual basis compared to adult spinach.
However, we are still very excited about the potential to produce 3.6 metric tons (7,937lbs) of baby spinach per year in a single Growcer farm (if you’re growing spinach throughout the entire farm).
Next Steps
Now that the team has eliminated the potential for bolting because of the shorter cultivation cycle, a whole new world of possible cultivars has opened up! The next steps in our research will be to look into alternative spinach cultivars, including those that have a tendency to grow and bolt much faster, and see if we can adapt what we learned with baby spinach to other leafy crops.