I think that's a great strategy to prevent burning your lawn. I have seen many lawns striped like a zebra's back because of uneven or excessive chemical fertilizers. Use a lower setting and criss-cross your lawn with your spreadder if you can.
Bill Hill

I agree with billhill. Just don't expand your idea to watering.

thanks for your thoughts guys.

dchall - yeah, i've been reading this forum long enough to know that watering 1/7" every day isn't quite the same as an inch a week!

It's not only a good idea...it's a great one. The boom/bust cycle of synthetic feeding is kind of hard on the lawn. It's always Thanksgiving Day or starvation level.

Spreading it out (pardon the pun) will give you a constant lower level of feeding. Your grass should enjoy that very much.

I think probably everyone else here has it right, but I'm wondering whether the recommendation of 1 lb. N per 1000 square feet assumes some level of inefficiency. I mean, if everyone knows that N will tend to leach out of the soil, but this is the recommended rate even for straight urea, then I imagine that recommendation takes this into account.

Which makes me wonder whether splitting applications like that would result in greater efficiency and, if so, whether that should either (1) cause more concern about burning, or (2) suggest that a lighter total application would be just as effective as a heavier one if done more gradually.

Thoughts?

Morpheus hit the nail on the head with the dumping effect of chemical fertilizers. Even with slow release you get a quick burst of fertilizer and than a general decline to 0. Usually when we get near to 0 we reapply again.

Without the calculus, the greatest way to minimize the dosing effect is to minimize the amount of time between feedings (i.e best case would be a continuous feed of low level fertilizer over a time period). As time between feedings approaches 0 the %NPK levels in the soil will be constant after some ramp up time . This can also be accomplished to some degree without the math by using very slow release organic fertilizers monthly.

assumes some level of inefficiency.

I'm sure it does. Fortunately, there's a pretty wide range of acceptable values, so the 1 lb per month maximum is a good guideline. There's still plenty of wiggle room.

Also, outgassing won't change, neither will leaching (a good heavy rain is still going to leach out the soil), so I'd need to sit down and think about how it could overbuild.

Offhand, I wouldn't worry about it too much.

Also, "leach out of the soil" , more correctly leach through the soil (which is a tad different from 'runoff due to rain or watering') involves certain mechanical principles, rather than theoretical principles. It's mechanical: How much is sitting there, on the surface, right now?

If the answer is 'not much', then there isn't going to be much leaching nor runoff. If the answer to 'how much is sitting there, on the surface?" is ALL of it, well, you can see runoff and leaching is bound to happen.

Let's do a little experiment: Grab a potted plant, with that hole in the bottom of the pot. Now fill a gallon milk jug with water. Over the next three weeks, you are going to pour all of that gallon of water, from that milk jug, into that pot. You will observe carefully, you will estimate (I know you will) and you'll pour a tad now, and a bigger tad later if it can absorb it, and you'll keep an eye on the situation, and you will, sure enough, pour all that water into that pot. That very minimal amount of water that flows out the bottom of the pot, or spills off the surface, is 'runoff and leaching'. It's nothing to worry about, even though it happened, as it was minimal, and nature can absorb that minimal amount, and there's nothing to have a coronary about, and there won't be an article about the sad state of affairs, due to runoff and leaching. Fact is, to some small degree, there is going to be some, no matter how careful you are. Forget about it.

Now, let's go to step two: take a different potted plant, or let that one thoroughly dry out, but 'same size', and get another gallon of water, in that milk jug. Same amount of water, eh? For purposes of our experiment, it's exactly the same plant, and exactly the same amount of water.

Now pour all the water, slowly, but all at once, all over that plant, into the pot, keep pouring, keep pouring, all at once, keep pouring, I know it's spilling, keep pouring, all of it, til all the water's gone into that pot. All of it. Hmmmm. Spilled a lot, over the edge. Hmmmm, a lot ran out the bottom of the pot. Water about everywhere, what a mess.

THAT'S runoff and leaching, babe.

I guess I must be missing the "why" part here. Of course you "can" split up fertilizer and apply part at a time. It isn't going to hurt anything. However, a bunch of highly paid scientists spent a lot of time developing coatings and binders so that the fertilizer will slowly be released over a period of time specifically so you do not have to fertilize every weekend. If you are concerned about fertilizer burn - guess what? - that means you are exceedingly unlikely to be careless and over-apply fertilizer.

Frankly, I think you will have more problems with over-applying or misapplying if you try to break 1 application up into 6. You are only applying 3 lbs or so per 1000 sq ft for most synthetic fertilizers. If you break that down to half a pound, it becomes significantly more difficult to evenly apply that over a large area.

Anyway, you sound like someone who should look into organic fertilizer. I think that could take away much of your worry about application rates and timing.