Seeding was done by hand into pre-moistened 1” x 1” x 1 ½” cubes of three different media (Grodan 200 ct rockwool, Oasis XL 162, and GrowTech 162). Seeds were germinated in clear water in seeding trays, and were transferred to the nursery and nutrient solution 3 to 5 days after seeding. Seedlings were produced in flowing nutrient solution in the nursery for an additional 10 to 12 days before transplanting. Due to the season, no supplemental lighting was provided during the seedling phase. After transplanting, plants were grown out in the channels for 25 to 28 days until harvest. The nutrient solution was continually cycled through the Fertroller where automatic pH and EC adjustments met programmed solution set points. The pH was maintained at 5.8 by the addition of dilute sulfuric acid. EC was maintained at 1.7 by the addition of concentrated fertilizer solution and source water. Tank changes were carried out every two weeks.
Some comments on the trial
Looking over the environmental and yield data, there are some interesting points and items that I would like to pull out and discuss a bit.
- I haven’t really focused often on the environmental data in previous blogs- mostly saying that through a four run trial, there was quite a bit of environmental variability. This trial, though, I want to point out that over a four month period in northeastern OH, we probably won’t find many data sets with this similar a set of conditions. Carbon dioxide stayed quite consistent and especially across the last three runs, the temperature and light were also quite similar. Humidity did increase under warmer summer conditions as the wet wall ran for longer periods of time to reach cooling set points. Due to similar environmental conditions, we also followed fairly consistent transplant and harvest schedules through the four runs I comment on the environmental conditions because it is clear that some variability still exists in crop growth rates and final yield even with reasonably similar temperature and light conditions (similar for a greenhouse meaning outside a growth chamber, etc.).
- Having discussed the reasonably similar environments, this leads to some serious questions about why there was so much variability in the weights reported in earlier tables. One key reason is that we experienced some seed quality and germination issues. This was most clear in the Panisse and Oscarde cultivars where germination was inconsistent in the first three runs (we switched to a new seed lot in the 4th run). This led to uneven growth or not even having enough seedlings to provide the 15 plants of each cultivar in each media. A glance at the standard deviations in the previous slides illustrates that these two cultivars were generally more variable than the other three. Germination and plant stand likely had a strong influence on those deviations.
- The third and final thing I want to talk about is related to the other two points of discussion. The use of three different growing media had some interesting general impacts. I inserted runs 1 and 4 into the above table because they represent the most complete data sets. Overall, for the Kireve, Rouxai, and Rutiali cultivars, peat cubes tended to show the potential for yield increases. These trends were not repeated and were in some cases reversed in the cultivars where germination and plant stand were less consistent (Panisse and Oscarde). Does that suggest that peat performs differently in some cultivars over others? I cannot say that this is not the case, but I can put forth another idea. It may be that in seed lots and cultivars with strong vigor and rapid germination, peat can be an asset to seedling production and plant growth. However, rockwool and/or oasis may be providing better environments for germination and early growth in less high quality seeds. More investigation is certainly needed as there is definitely room for improvement in our seedling production, and further work will help us better understand whether we are dealing with a seed, media, or environmental issue.
|Kireve- Run 4|
|Oscarde- Run 4|
|Panisse- Run 4|
|Rutilai- Run 4|
|Rouxai- Run 4|