Runoff a major concern after heavy rain?

[Green]

An inch and a half of rain was forecast. I put down fertilizer and pre-M. Of course, we get almost 3.75 inches.

For areas that border roads, what happens after that much rain? Environmental activists want you to believe that everything in the soil solution (or a portion) will tend to move with the water and go into the street, storm drain, and waterways.

But what is actually likely to happen? I did put down wetting agent (e.g. SLS) along the edges after about the first 1/3 inch of rain.

[MorpheusPA]

It does depend. If the fertilizer was water-soluble urea, it's most likely gone, although it depends on your undersoil and whatnot. And yes, it went into runoff, street, storm drain, and waterways. Not great. Water-soluble phosphorus, ditto, and that's actually worse (a shot of N in the water isn't wonderful; phosphorus is in very short supply planet-wide and causes a major blossom when it's available). If it had time to bind, it bound strongly. If it dissolved later (the stuff not being the most water-soluble, either), it can run off fairly easily in significant rainfall.

Potassium nobody cares about, it's available by the metric ton, as long as it wasn't enough to make the water salty. In most decent amounts it's not considered a major pollutant.

Organics could erode off and wash into storm drains, but that should be minimal except in severe flooding.

Most pre-emergents are easily dissolved and extremely strongly soil-binding and washed in with the first quarter inch, found their home, and bound. Barring erosion, they'll stay put.

[Green]

The pre-M is the most important part. Good to hear it probably bound.

The fertilizer was a mix of urea, polymer coated urea, and Milorganite. Mostly water soluble urea at 70%. I applied no more than 0.25 lb of N per thousand, total, counting all three sources.

On the sloped portion in the front, I applied and watered it in a day or two before. Would that help? But with all the extra water from the rain, whatever was in soil solution sounds like it probably washed out of the soil and off the lawn from what you're saying. Not what I was hoping.

Would the SLS have helped, or did I likely lose that, too?

In the back, the fertilizer would have washed into my low input area...yikes. I did not want to fertilize that area.

What soil conditions would help urea and Potassium to bind better? Given my soil, do you think it might be ok? I'll gladly answer any questions about it.

Also, in addition to what I recently applied, am I also likely to lose stuff that was already in the soil for a long time as well, like Potassium, Phosphorus, and Nitrate N reserves, from this type of rain event?

Thanks!

[Green]

I also sprayed an 8% humic product. On some areas, I did it right before the rain; other areas got it a week ago.

Saw this quote: "The organic combination of humic acid (HA) and urea can form stable chemical bonds, which decreases the nitrogen release rate and increases utilization efficiency of fertilizer by crops (Liu et al.)"

But I wonder how long that binding takes to occur, and whether it normally happens with urea directly, or if it has to undergo hydrolysis to ammonia/um N first. If it could bind the urea within hours, maybe this binding saved me, dunno.

[MorpheusPA]

What bound to humate and attached to soil could have stayed put, but that's not going to be a vast amount. But some, sure. Anything that was in soil solution at the time is gone.

Urea is a salt; it doesn't bind and washes out very easily--overapplication of urea on grass can be solved by watering it through the root zone to avoid a burn. Nitrogen forms that include negative ions don't bind. Positive ones do, but nitrogen shifts forms very easily via the nitrogen cycle, so you never really know what you're going to get, and no preferential form as applied will stay put (except organics, in their original forms. Once decayed, however, they're moving into more basic and more soluble forms). While not great, minimal nitrogen into water isn't a huge problem and home lawns aren't a major source of it (fields overfertilized with pig residue are the primary source).

Ammonium sulfate (a positive nitrogen form) do soil bind very nicely...so when that urea breaks down, and releases ammonium ions, they'll bind to the soil...until they flip forms again. But the soil has limited binding capacity (often happily filled with calcium and magnesium and potassium anyway), and most simply sits in soil solution as a salt and washes out if water's moving through.

Potassium, when applied, is in salt form, so ditto, it washes. Given time, it does soil bind strongly, and you'll only lose what's in soil solution to rainfall. But again, potassium isn't a water pollutant in any large measure and isn't considered a problem. Phosphorus is the issue.

Phosphorus strongly soil-binds very quickly, with very little in solution at any one time; usually you only lose that tiny bit during drenching rains. Post application, however, you have much, much more in solution that can wash through (and again, it's not exactly the most water-soluble stuff in some forms so it won't go in the first quarter inch, either). This is the one you don't want to be dumping into waterways.

The way you change it is by monitoring rainfall and applying appropriately, regrettably. The soil will only bind what its EC can manage; anything else washes out.