I agree with daninthedirt.

The steps that they give mention the addition of compost to improve the soil so I think their comment avoid high nitrogen Fertilizer refers solely to any chemical fertilizer that a person might consider using.

I like all their instructions. Looks like a good company.

The only thing that I might add is to possibly not mulch in early Spring until the soil is warm enough.

It appears to be just a generic instructions sheet, a preparing your garden guide. It is not one specific to spinach or any other crop. Probably comes on all their seed packets.

Recommends standard fertilization it appears to me but I'd prefer less phosphorous in mine. It is usually wasted anyway. I guess it all depends on how you define "high nitrogen". Excess nitrogen can easily burn roots and even kill plants.

Dave

Thanks folks. I masterblend 4-18-38 for fruiting veggies and add calcium nitrate during growth stage or always for leafy veggies. I am assuming that I can continue that regimen? Sorry, I should have added this in the OP. I use the soluble form of each through Drip.

FWIW, Stover (the seed company) produces a nice one page "Vegetable Growing Guide" for spinach, and nowhere in that guide is there any special reference to nitrogen. They recommend fertilization with some all-purpose fertilizer. I think the folks composing the seed packet text just were flailing a bit.

4-18-38?? That's sure not an all-purpose fertilizer. Maybe your soil analysis calls for it, but that's hitting potassium pretty hard. What is your rationale for that?

Oh so this is hydroponic growing. Totally different ballgame, different situation than the average in ground vegetable gardening.

Folks over on the Hydroponics Gardening forum would be much more helpful for you then as 4-18-38 would have no role in soil based operations.

Dave

Thanks! I'll check out that forum as well. While we are talking about this, I also want to fertilize my soil (potted) vegetables through drip and for that I am going to use Miracle Gro All purpose plant food, which is 24-8-16. I use the gritty mix and since there is pretty much no organic matter available to the plants, I would fertilize while watering through a Venturi injector (so need a 100% water soluble fertilizer) . I use this fertilizer to manually fertilize for now for.

I tried the organic route but didn't have much success with the amount of time I have to dedicate to gardening and the plants didn't get what they needed at fruiting time.

Any opinion / advice on the NPK ratio or my method?

You should avoid high nitrogen fertilisers as spinach is high in nitrates - high nitrogen fertilisers add nitrates, which are potential carinogens.

It is true that high nitrate fertilizers make for more nitrates in greens. But actually, nitrates are not really all carcinogenic. The ones in vegetables much less than in meats. The reason is that nitrates can convert to nitrosamines, which are the real carcinogenic compounds, and that conversion doesn't happen much in the absence of proteins. Also, vegetables have other chemicals that prevent that formation.

https://www.bbc.com/future/article/20190311-what-are-nitrates-in-food-side-effects

Eat greens! More nitrogen fertilizer makes more greens.