Using surface samples, assess your soil's need for nitrogen (N), phosphorus (P), sulfur (S), potassium (K) and micronutrients necessary for wheat production. Virtually no difference exists between liquid and dry fertilizers as far as the availability of nutrients absorbed by the plants. According to Michigan State University, when choosing a fertilizer you should analyze the price of each nutrient, estimate the cost of applying the fertilizers to your specific crops and assess the difficulty of handling and application. Liquid fertilizer differs slightly from dry in several of these areas.
Fertilizers come in liquid, solid and gas. The gas, anhydrous ammonia, a liquid under pressure, is categorized as a liquid. The basic production method used in most dry fertilizers results in an orthophosphate form. The other method results in purer polyphosphates contained in most liquid fertilizers. Polyphosphates revert to orthophosphates when applied to soil. Plants absorb the majority of nutrients in the orthophosphate form.
Michigan State University states that liquid fertilizers -- anhydrous ammonia, N solutions and mixed fertilizers -- come in true solutions, which you do not need to agitate, and suspension slurry mixtures which you must stir constantly to keep the solids and liquids from separating. It maintains that bulk dry fertilizers are easier to handle, particularly in large amounts. However, Mike Rankin, crops and soils agent at UW Extension, says that liquid fertilizers are "easy to handle and meter more precisely."
Some manufacturers claim that liquid fertilizers are more absorbable than granular dry fertilizers; however, most dry fertilizers dissolve nearly 100 percent in water and complete nearly the same chemical reactions as liquid when applied to the soil.
According to Purdue University, you must inject liquid nitrogen fertilizers into the ground so the ammonia nitrogen will not dissipate, whereas you can apply dry fertilizers directly to the surface. However, on sloping land you must work even the dry fertilizer into the soil to avoid runoff.
Rankin warns that some liquid fertilizers are "grossly overpriced" and advises comparing the application price per pound of each nutrient. Michigan State says that dry fertilizer in bulk is usually cheaper and easier to handle, especially in large quantities.
Sample-testing your soil is the only way to accurately determine the optimum fertilizer for your wheat. Compost and legume crops will affect base nitrogen levels, so factor in expected nitrogen release from these sources when figuring N requirements.