Stacy Campbell
K-State Research and Extension
Are Liquid Fertilizers Better Than Dry Fertilizers?
Questions about the agronomic differences among the various fertilizer products found in the agriculture marketplace are sometimes raised. One of the more common questions is: “Are liquid fertilizers better than dry fertilizers?”
Liquid UAN solution (28 or 32 percent N) is simply a mixture of urea, ammonium nitrate, and a little water – and not really much water. Each gallon of 32 percent UAN solution is only 20 percent water by weight. Or, viewed another way, each gallon of 32 percent UAN solution contains roughly one quart of water by volume. The remaining weight/volume consists of dissolved urea and ammonium nitrate. Since UAN solution is mainly urea and ammonium nitrate, it is agronomically equal to dry urea and ammonium nitrate, and has the characteristics of both.
Liquid 10-34-0 is composed of a mixture of ammonium polyphosphates and ammonium orthophosphates dissolved in water. The dissolved ammonium orthophosphates are identical to dry fertilizers MAP (e.g. 11-52-0) and/or DAP (e.g. 18-46-0). The dissolved ammonium polyphosphates are quickly converted by soil enzymes to orthophosphates identical to those provided by MAP and/or DAP.
Polyphosphates were not developed by the fluid fertilizer industry because of agronomic performance issues. Instead, polyphosphates were developed to improve the storage characteristics of fluid phosphate products (and other fertilizers made from them) and to increase the analysis of liquid phosphate fertilizers. Ammonium polyphosphate (10-34-0) is equal in agronomic performance to ammonium orthophosphates MAP or DAP when applied at the same P2O5 rates in a similar manner. And liquid phosphate products are equal in agronomic performance to dry phosphate products if applied at equal P2O5 rates in a similar manner.
There is really no agronomic difference between dry and liquid fertilizers (N, P and other nutrients) – other than their physical form, how they are handled or applied, and their adaptability to the overall crop production operation. The choice of which specific fertilizer product to use should be based on:
• Equipment needed to handle and apply the product
• Logistics of hauling/nursing/applying the needed crop nutrients
• Adaptability to the overall farm operation and other cultural practices
• Personal preference
• Product availability
• Cost
With corn planting in the area underway and grain sorghum soon to follow there are always questions about placing fertilizer with seed. Some agricultural producers may consider placing fertilizer with the seed during planting. That can be a good practice, but only if done with great care.
All fertilizers are salts which can cause germination problems if too much is placed with the seed. Too much fertilizer may inhibit germination completely, which results in a stand loss.
In other instances, too much fertilizer placed with the seed may simply delay germination, or it may result in weak seedlings with poorly developed root systems. Either way, the affected seedlings will be at a competitive disadvantage, and a loss of yield potential could result.
Keep several points in mind when evaluating seed-placed fertilizer:
* The potential for injury is greater in sandy and/or dry soils.
* Nitrogen (N) and potassium (K) are the fertilizer components
responsible for seedling injury. For corn, the maximum rate to place
with seed is 6 to 8 pounds of N + K per acre.
* For grain sorghum, reduce that rate 25 to 30 percent.
* Place no fertilizer with soybean or sunflower seeds.
* Some fertilizers should never be applied with seed. Do not apply
ammonium thiosulfate by itself in direct contact with the seed. Don´t
place urea-containing fertilizers with seed.
Further details are available on Ellis County Extension web site at www.ellis.ksu.edu click onto the Crops and Livestock tab and under Hot Topics click onto K-State Agronomy e-updates; e-Update 4/17/08).
Information provided by Dave Mengel, K-State Nutrient Management Specialist.
