Just a couple of points in addition to what rgreen posted. Yes, leaching does apply to organics just as to synthetics but with N it is primarily volatility - it vaporizes into the air - more than leaches.

If N is your primary concern, and assuming your soil has an active micro herd to pre-digest it for the plant use, then rather than 10-10-10 you can simply side dress with more alfalfa meal or one of the other N organic supplements.

Ditto what was said about the many advantages of liquid supplements vs. granular supplements. Already pre-digested and ready for plant use and easier to adjust dosage.

"Now I've heard that such inorganics can burn the roots of the plants but am assuming that only happens if the fertilizer granules contact them. (True? False?)"

True but the same can be said about organics. Too many wrongly assume that just because something is "organic" it can't harm plants, it can't be abusive or excessively applied. Not true.

Lastly, be sure to keep in mind the very different nutrient needs of your various plants. Assuming those needs are the same for all plants leads you down a road full of potholes. ;-)

Dave

Thanks for the responses. The garden contains various varieties of broccoli, collards, kale, lettuce, mustard and 'Jade Cross' brussels sprouts. Figured nitrogen would be a major nutrient for these leafy guys. I had soil tests done last fall and applied the suggested amounts, where needed, of rock phosphate and greensand, this past spring. After the summer harvest, I went back in and added a bit more alfalfa meal (about three weeks ago).

Don't know if this forum permits the use of name brands; if it does, would you be willing to recommend a good liquid supplement?

Again, thanks!

Organic solubles are available. Fish emulsion is the first to come to mind, but there are a couple of available options. An easy one for a quick boost is just diluted urine. Lay off the salt for a day and dilute with a gallon or 2 of water. I think the most common dilution ratio is like 10 parts water to 1 part urine.

As for inorganic solubles, I've never seen a problem mentioning brands, but in my experience, there's really no need... any of the water soluble, crystal type products are easy to work with.

A good organic liquid supplement for the veggies on your list would be one of the Fish Emulsions (Alaska brand or Neptune harvest). For my greens and brassicas I add Garden Tone at planting time and then supplement with granular urea either side dressed prior to a good rain or dissolved in a watering can at a rate of 1.5 Tbsp. per gallon of water. Urea is pretty potent stuff at 46-0-0 so best to take it easy and apply less more often.

Once the nitrogen is in the form of nitrates, yes it can leach and, of course, as noted, when released as ammonia, it can outgas before it gets nitrified. If the nitrogen is in the form of undigested plant proteins, it will not leach, but of course is not in a plant-usable form. Bacterial action will release that nitrogen gradually. Slow-release inorganic fertilizers release nitrogen in plant-usable form, and won't leach effectively.

As noted, urea is potent stuff, but if you use it, by all means dig it in. If you leave it on the surface, the nitrogen will be released as ammonia, and will float away instead of getting nitrified into soil nitrates.

Naming brands is no issue and you'll find many discussions here containing recommendation of the many various liquid ferts, both organic and inorganic. The search bar will pull them up for you.

Plus a Google search for 'liquid organic garden fertilizer' or 'water soluble organic fertilizer' will get you links to the numerous brands and sources available.

If you have alfalfa meal already available then you can make a liquid tea out of some of it by just soaking it in water overnight and then diluting the mixture further to the color of very weak green tea before applying to plants.

Dave

As noted, urea is potent stuff, but if you use it, by all means dig it in. If you leave it on the surface, the nitrogen will be released as ammonia, and will float away instead of getting nitrified into soil nitrates

Dig it in or water it in well - no difference.

I think that's true. Dissolving it by watering it in with a half-inch or so will do the trick. But just moistening it on the surface is a waste. Moist urea on the surface is mostly gone in a few weeks. Poof.

When urea breaks down, the soil around each urea crystal is saturated with ammonia, and is highly alkaline. That can be quite toxic for a few hours. All the more reason for completely dissolving the urea crystals, and distributing it under the surface.

In fact, Lone Jack, you're exactly right. At least for a small residential garden, it seems more practical to dissolve the urea in water, and then just irrigate with it. Of course, you can't dissolve the urea in water and store it. You'd need to use it right away.

Just picked up a quart of Alaska Fish Fertilizer. Will dilute and apply tomorrow morning. Will probably drive Fleabag (local cat) wild!

Thanks everyone.