Fall fertilization #2

I put down some more fertilizer on the front lawn on Tuesday. It has not yet been watered in. I realized that I was watering some parts of the lawn way too much by watering 5 minutes 3 times a day (I have read that over-watering can actually be more damaging to a lawn than not watering!); one area was getting soft and muddy. So I've been cutting back quite a bit, especially now that the weather has been cooler. I put down about 5 lbs of Scott's (32-0-4), which comes out to 1 lb/1000 sq. ft.

Because I always forget how to calculate how much to apply, here's the formula I used:

x = r / (n / 100) * s / 1000
(or, simplified: x = r / n * s / 10)

Where:

• x = the amount of fertilizer to apply (in pounds); this is what the formula is calculating
• r = the desired Nitrogen fertilization rate (in lbs / 1000 sq. ft.)
• n = the portion of Nitrogen in the fertilizer (the first number in the sequence found on the bag, e.g. "32-0-4")
• s = the size of the lawn being fertilized (in sq. ft.)

So, for this application:

r = 1

n = 32

s = 1600

Enter those values in the formula:

x = 1 / 32 * 1600 / 10

x = 5 lbs.

And presto, it yields the number of pounds to apply. Now all you need is a scale.

(Note that this is for granular fertilizer. You can also use this calculator, and there are probably others out there as well).

(Another side-note for myself: when putting down this amount of fertilizer, even at the lowest rate on the spreader, I'm only able to make one pass over the lawn, so it has to be done carefully in order to be dispensed evenly)

I'm attempting to follow the advice given in the Purdue Turfgrass Science publication "Fertilizing Established Lawns (AY-22-W)" (download) this year, which says this (among lots of other great information about fertilizing):

When Should You Fertilize?

The cool-season grasses (such as bluegrasses, fescues, and ryegrasses) will benefit most when you apply the majority of N fertilizer from late summer through autumn (Figure 4). This promotes summer recovery, enhances shoot density, maximizes green color, and prepares the turf for winter, all without a growth surge.

Apply less N during the spring growth flush, and then apply little to none during summer except where you frequently water and/or regularly remove clippings during mowing.

When you apply N fertilizer during the spring, use slow-release fertilizers to minimize excess growth. To promote maximum density during late summer and early fall (late August through early November), you should apply up to 1 pound of N per 1,000 square feet each month. From early October until early December, apply primarily water-soluble N fertilizers at slightly lower rates (such as 0.5 to 0.75 pound per 1,000 square feet) about every three weeks.

So my next fertilization will be sometime around mid-October.