water Water before liquid feed?

[Mr. West]

I've heard it's good to water before giving nutrient solution. Especially if your soil is dry. Thirsty roots want water foremost.
One reason being to prevent nute burn or shock.
Another reason being to saturate the media first to allow better absorption and prevent runoff of the nutrients to follow.
There's your general topic.

Now, i will elaborate on my current method.
I know that not everyone advocates letting soil dry out between watering.
I do it to avoid fungus gnats/damping off, also I find that it helps with formation of lateral roots in search of water.
Much like nutrient deprivation. Seed starting mixes have barely any NPK. Just enough for the roots to scavenge. Side note: excess ammoniacal nitrogen attracts fungus gnats.
I have seedlings/new starts at 5 true leaf sets.
They're in MG seed starting mix and vermiculite (something like a 60/40 blend).
Started in trays (bottom-watering).
Moved plugs into cups 10 days ago.
I water-in from the top. Not to saturation, just slowly water around the plug using a fine stream at low pressure.
I gradually increase feeding fish&seaweed 2-3-1 quarter strength then half strength dose.
This provides auxins and a high relative P value to stimulate rooting.
Since potting-up, I've waited ~3 days between feeding to let the cups get almost dry. (At this stage, I will probably increase that to about every other day.)
I'll start watering further from the stem, out near the edge of the pot.
I think they're ready for full strength food now.
They've practically reached maturity and are nearly rooted in their cups.
This is probably the last time -for this round of plants- that I will bother wetting the soil first.

 

[solid7]

Fungus gnats don't bother me one bit.  I keep my plantings outside, and my media has plenty of organic material, from day one of seed planting.  If you give the pests what they REALLY want, they won't bother your roots.  Also, their microscopic poos feed your plants.  If you are strictly inorganic, fungus gnats will ruin your day, for sure.
 
I think it's pretty hard to go wrong with watering either way.  I mean, the nutrients in our liquid ferts are attracted by electro-chemical bonds.  If it's available, and needed, it's going to get grabbed.  If not, that's why you use something like compost and/or coco coir. (and let's not forget the ultimate nutrient banks - rotten fungusy wood and/or biochar)  Because in doing so, you have an increased CEC, where nutrients are held in store, for later use, and you'll worry a lot less about just dumping valuable nutrients into the runoff zone.

 

[Mr. West]

All my plants are outside too. And i have used coco for this same exercise. Haven't tried biochar.
Might try to get some mushroom compost.
You're ok with gnats, because they eat it and doodoo in the soil?
No issues with them laying eggs and the larvae eating your roots?
You figure the microbeasties in a cultivated soil will wipe them out?
Im mostly concerned for my young plants, because ive read they also carry the fungal spores that cause damping off.
Anyway, now they're grown and not so vulnerable.

I just thought I'd bring up the main topic, because I remember reading that dry rootzones are more susceptible to burn from concentrated nutes or shock from pH swing.
Plus it kinda relates to what I'm doing.
This way of top-watering sparingly, is my go-to technique for establishing a planting with shallow roots relative to its pot size. Or when i have multiple containers that are not conducive to bottom-feeding.
Mostly, I'm trying to visualize the plug's roots inside its new, larger container so that i can water/feed more precisely where it's needed for the desired stimulus.

 

[solid7]

You're ok with gnats, because they eat it and doodoo in the soil?
No issues with them laying eggs and the larvae eating your roots?
You figure the microbeasties in a cultivated soil will wipe them out?

 
I'm OK with the gnats, because they aren't really after my roots.  That is NOT their main attraction to the seed starts.  They are after organic matter.  They love peat, and they love coco coir.  Additionally, they love that fish juice and seaweed that we like to use.  As long as they have plenty else to eat, roots are not their primary meal.  I spent a lot of time observing this.  I'm looking to garden with the least amount of dickering, and the most amount of symbiosis with the nature that is present - whether I like said nature, or not.  I have not lost a plant to damping off for about 3 seasons now.  That's ONLY because I spent time observing the damn fungus gnats.
 
For me, the key is to make sure that the seed start is in a big enough container.  We joke sometimes about the Solo cup being the "only right way" to start seeds.  But for me, it's the smallest size where fungus gnats don't become a concern.  It's deep, so they can go deep down, where it's cool, and stay away from vulnerable roots in young seedlings. (can be problematic if you bottom water)

By the way, it's ONLY the larvae that are a problem.  I don't think that the adults eat at all.  I think they're just larva generators.
 
And no, I don't think the larvae get wiped out.  They go through the life cycle.  They eat the peat/coco, and poop out nutrients into the container.  Like I said, I keep them fed, so they stay off the roots.  A few fish pellets, even before the plants need it, seems to do the trick nicely.

 

[Mr. West]

Thanks for clarifying. I'll have to marinate on that a while. Sounds like you know what youre talking about. I'm used to the approach of not providing a hospitable environment for them (dry soil surface with no decaying plant matter or fungus to start out).

 

[solid7]

Well, you definitely have to beware of overwatering, because that will push them high.  Also, you have to be careful with shallow containers, because they often are just one big perched water table.  That means that the larva won't breathe well in them, so they'll move to the region where they're most likely to be able to breath.   That definitely puts them in much closer proximity with young feeder roots, closer to the mainstem.
 
I probably should have also mentioned that the kelp meal I put down at 2 sets of true leaves, needs to not touch the stems.  That can be danger.  I think it makes them gnaw at the stems/roots incidentally...  But if I keep it at least 1/4" away, no problem.

 

[Mr. West]

You weren't kidding. You've really been observing them. I'll try your process next time if i remember. I'm still clear of gnats and done germinating for a few months.

Tomorrow morning, I'm planning to hydrate the soil with plain water like I have been, then feed full strength fish&seaweed. It's about 10 minutes in between, because i have ~70 cups. (Goes along with a common tip to water partially, let it absorb, then 15 minutes later water again).

Also have 34 little square cups. Only at 3 leaf sets. Been flooding their 1020 tray alternating water and same nutes. Theyre gnat free too, but some green moss on a few (no harm, some just drink faster).

You know how they say to drink water before a meal to hydrate your stomach lining and release acids, etc. ?

 

[thefish]

I only ever get gnats inside, when I move the plants outside in the PNW i never have a problem with them. maybe they just thrive better in florida. also keep in mind that if you are providing an environment where they are thriving it is an extremely warm, moist environment and you either need to modify your watering habits or the substrate you grow in to reduce their population. there will always be a few gnats and they wont really harm your plants but if you're indoors and the only organic matter the larvae have to feed on is plant roots then you'll have problems. in a lot of cases you can dial back the water a lot more than you think you can so experiment with your watering schedule and you should be able to find something that eliminates the gnats.

 

[lek]

plant uptake increases from a dry soil to moist soil.   
 
 

One reason being to prevent nute burn or shock.

 
to avoid nute burn, calculate ppm nitrogen first.