When should I fertilize my crops?
I am an avid backyard gardener and am familiar with the big three nutrients, Nitrogen, Potassium and Phosphorous, the differences between full, partial shade, etc. I also know the importance soil testing and proper pH. What I don’t know is when to fertilize? I generally buy Neptune’s Harvest and Espoma products as well as use my own compost and a neighbor’s pig manure.
Is there a schedule of some sort to make it easier to plan general fertilizing? For instance, we have some established blueberry bushes and some new ones coming in this weekend. After planting, when do I fertilize those during the season? Tomatoes? Lettuce? Perennial flower bulbs? Apple trees? Is there an easy reference guide or is it a matter of soil testing and adjusting?
Abi Griffith, Horticulture Community Education Assistant
Blueberry bushes: This fact sheet Growing Highbush Blueberries has a fertilization chart, depending on the age of your bushes. It suggests fertilizing 3 to 4 weeks after planting and has suggestions for more established bushes
Apple trees: Would want to base off of a soil test and doesn’t generally need a lot of fertilizer, but it would usually be applied in early spring if the test indicates – look at Fruit Trees – Fertilization for a more nuanced take on this. In general, you want to avoid fertilizing apples and other woody plants in the late summer/early fall because that can cause a flush of tender growth that will be more susceptible to winter damage.
Tomatoes: Again, if you have been testing your soil and making adjustments, that is a great start, but since tomatoes are a heavy feeders, they generally benefit from at least one application of fertilizer or more during the growing season (e.g. when fruits are small and just setting and perhaps again at harvest). Avoid excessive N (nitrogen) application which can cause excessive foliage.
Lettuce: should be fine if your soil is good
Perennial flower bulbs: this is a good reference – Bulbs and More – University of Illinois and they suggest “If bulbs are going to be maintained in a planting bed more than one year, it is important to supply additional fertilizer. Spring flowering bulbs should have mixed into the soil in the fall five tablespoons of 10-10-10 soluble fertilizer (or equivalent bulb fertilizer) plus two cups of bonemeal per ten square foot area. As soon as the shoots break through the ground in the spring, repeat the above soluble fertilizer application. Do not fertilize spring flowering bulbs after they have started flowering. This tends to encourage the development of bulb rot and sometimes shortens the life of the flowers.”
Since you mentioned that you use your neighbors pig manure, I just wanted to refer you to this as a reference – Guidelines for Using Manure on Vegetable Gardens as it suggests it not be used in vegetable gardens.