Benvolio is right on this one. Let's say the chipper cost $6,000. (I really have no idea, I'm just using an example.) Let's also say that your marginal tax rate, at your income level, was 25% that year.
That means that you saved $1,500 on your taxes. However, you spent $6,000. (This $6,000 is still within the amount that the IRS allows you to write off, in its entirety, in the year of acquisition - without having to do those pesky depreciation calculations spread over multiple years.)
If you hadn't bought the chipper, you'd have $4,500 more in your account (all other things being equal).
You're thinking of a tax CREDIT, which is an entirely different animal; if you spend $1,000 on something that gives you a tax CREDIT for the amount you spend, you can "turn around" and deduct $1,000 from your taxes in return...THEN it's as though you didn't spend the money at all. There aren't many arrangements of this sort, that exist.