Do your transplants have enough fertility?
Posted: April 1, 2012
Broccoli in four different transplant media. Potting mix to the right does not provide sufficient nutrients. Photo March 28th three weeks after potting up.
In a demonstration at the Seed Farm New Farmer Training Program as part of an upcoming Introduction to Organic Vegetable Production class I grew broccoli seedlings in four different potting mixes. All plants were potted up the same day (March 7th). You can see that plants to the left are healthy and almost ready to transplant out. Plants to the right in potting mixes without sufficient nutrients are stunted. To the far right they are beginning to show purple potassium deficiency symptoms.
If you are not sure if your potting mix has sufficient nutrients you can send a sample to Penn State Ag Analytical Laboratory. You might also try growing plants in a few different mixes to see how they compare. Another option is applying a foliar fertilizer. For organic growers there are fish and kelp based products that are applied in the irrigation water. Make sure to follow the label and not apply fish products when it is too hot. The oil can burn the leaves. To see what effect the foliar has try applying it to some but not all flats.