The 2015 Lawn and Garden Soil Test program began March 16, assuming the ground eventually thaws.  Let’s take some time to remember why we promote this program: to keep track of and lower unnecessary fertilizer usage.  While some may not think that their little garden is contributing to the white elephant in the room (aka, the lake), let’s talk about monitoring and reducing fertilizer from the stance of the plants.
Fertilizer is not plant food. Plants make their own food.
Fertilizers should be used to supplement the nutrients plants need to grow.  Adding more nutrients is not going to make your plants use more sun, water, and CO2 to make your plants bigger.  Plants have a threshold, just like people.  If I shove a bunch of multivitamins down your throat, you’re not going to grow bigger in one season either. 
This being said, test you soil and fertilize – or supplement – as necessary.  This is not going to be the same rate year to year.  Different practices (when you fertilize, if you use cover crops in your garden, how long you cut your grass, etc.) and the type of plants will uptake nutrients at different rates.
It is better to under-fertilize than over-fertilize.  Some symptoms of over-fertilization include: crust of fertilizer on the soil surface; yellowing and wilting of lower leaves; browning of leaf tips; browned or blackened limp roots; defoliation; very slow or no growth; and death of seedlings.
Now you’re wondering, “I’ve got a soil test, how do I know if I need fertilizer?” Our soil test program is a partnership between the Grand Lake/Wabash Watershed Alliance, the Lake Improvement Association, and Helena Agronomic Center.  Helena provides recommendations based on set of standards.  There ideal limits are: pH of 6.5-6.8, phosphorus at 30 ppm, % potassium of 2.6-3.6%, and nitrogen of four pounds/1000 sqft per year.  They have a variety of fertilization programs available to make the best out of your soil.  Please be aware that you are not required to have one of their programs in order to get a soil test.  
Doing some internet searching, here are some additional guidelines for your gardens and lawns.
The Basics of Fertilizing; Bonnie Plants
  • Light nutrient needs:  bush beans, mustard greens, peas, turnips
  • Moderate nutrient needs:  beets, carrots, okra, pole beans, potatoes, sweet potatoes
  • Heavy nutrient needs:  broccoli, Brussels sprouts, cabbage, cantaloupe, cauliflower, corn, cucumbers, eggplant, kale, kohlrabi, onions, peppers, rhubarb, squash, tomatoes, watermelon
Fertilizing Lawns; University of Minnesota Extension
  • Nitrogen needs: high-maintenance lawn (irrigated lawns) between 3 and 4 pounds N/1000 sqft
  • low-maintenance lawn (non-irrigated lawns) between 1 and 2 pounds N/1000 sqft
  • If grass clippings are not removed, less nitrogen is required than if grass clippings are removed.
  • Phosphorus needs: no phosphorus is needed on soil tests greater than 25 ppm.
If you use fertilizer, make sure the fertilizer is used on a plant of some kind because the lake doesn’t need it.