It is beneficial if you have a sustaining bacterial/fungal colonization. Kelp continuously feeds microbes which in turn feed the plant more efficiently
If you feed a compost tea once during veg on each plant then you can feed kelp to your soil every other feeding or every feeding in small amounts
the compost tea will start your "living" soil, then you just need to feed it to sustain the colonization
A good compost tea will have
Microbe food ( kelp meal, Molasses)
Bacterial Compost ( earthworm castings)
Fungal Food (Humic Acids & yucca)
Rock Dust
Forest soil (outdoors soil increases fungal and bacterial diversity)
if you wanna know more there are some great articles and books on Compost Tea
