Part 1, Section 2: Soil Fertility Management
Soil Fertility Management
Fluid fertilizers are becoming more and more common. Recent fertilizer statistics for Pennsylvania indicate that nitrogen solution (UAN) is the most common source of nitrogen used in the state. Multinutrient fluid fertilizers also are becoming more popular. The fluid fertilizers may be categorized into two groups: clear solutions and suspensions.
In clear solutions, which are the most common fluid fertilizers used in Pennsylvania, nutrients are dissolved completely in water. The major advantage is in handling. The disadvantages are the generally higher price and lower possible analysis compared to dry fertilizers, especially when the material contains potassium.
Suspension fertilizers, which are much less common, are fluids in which the components’ solubility has been exceeded and in which very fine undissolved particles are kept from settling out by the inclusion of clay. Again, the major advantage of these materials is in handling. Suspensions also can be formulated at much higher analyses than can the clear solutions. Analyses similar to those for dry materials are possible. The major disadvantage of suspensions is that they require constant agitation, even in storage. Furthermore, suspension fertilizer cannot be used as a carrier for certain other chemicals.
The bottom line in comparing fluid fertilizers with dry fertilizers on the basis of amount of plant food, is that they are equal in agronomic effectiveness when each is used properly.
Remember, when making calculations of fluid fertilizers, that the analysis is given as a weight percentage, not on a volume or “per-gallon” basis. Most fluids weigh between 10 and 12 pounds per gallon. The following is an example to illustrate the calculations.
One gallon of the 10–34–0 liquid weighing 11.68 pounds per gallon contains:
11.68 lb Fertilizer/gallon × .10 N = 1.17 lb N/gallon
11.68 lb Fertilizer/gallon × .34 P2O5 = 3.97 lb P2O5/gallon
If 5 gallon per acre of this fertilizer is used as a corn starter fertilizer, this would apply the following nutrients:
5 gallon/A × 1.17 lb N/gallon = 5.85 lb N/A
5 gallon/A 3.97 lb P2O5 per gallon = 19.85 lb P2O5/A
It would take a little less than 9 gallons of this liquid to equal 100 pounds of a dry material with the same analysis.
For comparing fluids with dry fertilizers, divide the weight per gallon into 2,000 to get the number of gallons per ton.
In the above example, the calculation is:
2,000 ÷ 11.4 = 175 gallons per ton