It is always best to take a soil sample and turn it in to be analyzed for what your specific fertilizer needs are but as a general rule of thumb till in 60-90#’s of actual nitrogen (150-200#’s of urea per acre) and 200-400#’s of 6-24-24 at planting (refer to the next section down for how to read fertilizer data). Urea must be tilled in shortly after applying or before a heavy rain or you will lose most of it thru denitrication. Brassicas also prefer a PH in the 6.5/6.8 range so be sure to soil test and apply lime as needed. One can apply more dry fertilizer later on if the plants appear yellow or unhealthy. When growing long season brassicas it is a good idea to plan on applying some nitrogen during midsummer. One thing to be aware of when applying fertilizer to already growing plants, is that applying any sort of nitrogen can cause leaf burn, especially to wet plants. Thus it is best to top dress nitrogen when the plant leaves are dry. A common practice of Paul’s is to plant a plot to oats and berseem clover in the spring, then tilling it up just before planting in July to create a brassica plot. The oats and berseem clover make a great, cheap cover crop, releasing lots of natural fertilizer when tilled into the soil.
Triple 19 (19-19-19) is a fertilizer combination of nitrogen, phosphorus, and potassium. The “19”just means there is 19#’s in every 100#’s or 19%. There are common fertilizer mixes such as 6-24-24, 12-12-12, 19-19-19, 46-0-0 etc. All the “numbers” tell you is how much of each of the 3 main elements are in a bag of fertilizer. If you buy it in bulk from an ag. supply source, they can mix any combination you require. This is why we take soil tests so we know what nutrients our soils may be lacking and what might be required for the crop we’ll be growing. Sometimes you can buy fertilizers on sale at Wal-Mart, Menards, or TSI but be aware that some lawn fertilizers contain weed killers such as 2-4D and will kill your brassicas. If you mix it in the soil then it shouldn’t be a problem but it is cheaper to buy it without weed killer.