A common mistake by many lawn novices is to head to the green shed and buy a bottle of weed and feed. I mean the name says it all, it will kill my weeds and feed my lawn in one easy step, right?
Not exactly and to understand why, we need to have a look at the product analysis. A 2.4L bottle of the average Weed and Feed contains 11.5% Nitrogen from Urea, 0.13% Iron, 15g/L MCPA and 2.3g/L Dicamba. This is to cover 130sqm.
This is the equivalent of around 40ml of an 80g/L Dicamba based herbicide, 230g of Urea, a little Iron Chelate and the rest of the bottle is water. You are then further diluting the product when you hose it on.
The recommended rate of most Dicamba herbicides is 65ml per 100m2 (84.5ml for 130m2) so we can immediately see that it is around half of the recommended rate without factoring in the dilution from applying with a hose on sprayer.
On the "feed" front, 230g of Urea will provide a quick boost of growth and the iron will improve the colour slightly but it will be all over within 1-2 weeks.
If we were to compare the cost per application (over 150m2) to Contra M Duo at $3.60 and Special Fex at $9 (300ml rate when buying 2.5L), the total being a bit over $12, it is much better value than the near $20 for the weed and feed product, which is also a much lower strength.
So please, if you want better results and to save some money, keep the weeding and feeding separate.