What Is Pop-Up Fertilization?
“Pop-Up” fertilization is the process of putting the fertilizer in at the time of planting the seed. The alternative is starter fertilization, in which the fertilization is done near but not with the seed.
Ammonium sulfate [(NH4)2 SO4] has been a fertilizer of choice for over 150 hundred years. In one configuration or other, it has served world agriculture and its economy very well. It serves needs from the common front lawn to major farm lots. Broadcast or applied as liquid or granule, it meets almost every fertilizer need. But, as agricultural application technology improves, users needs to understand its use in pop-up fertilization. As growers pursue early planting in cool soils that inhibit early root growth, they have to consider their options.
Once There Was The Starter Fertilizer
The so-called “starter fertilizers” place nutrients in bands 2-inches below and 2-inches to the side of the seed. Starter applications place more Nitrogen (N), Zinc (Zc), and micronutrients near the seed. Common liquid sources are ammonium polyphosphate solution and urea ammonium nitrate solution. Dry materials include urea, ammonium sulfate, and diammonium phosphate. Higher rates may be applied at further distance from the seed.
Now There Is The Pop-up Fertilizer
The increasingly popular “pop-up fertilizers” are placed directly with the seed at planting. Fertilizer placement has been engineered into the seed farmers used on more modern planters, allowing precise placement of seed and fertilizer. This single operation fertilization process saves time, energy, and fertilizer.
- There is no requirement for a separate, specific, distribution opener on the planter, so pop-up fertilizing lowers costs by reducing the rate of starter fertilizer.
- It reduces the amount of fertilizer handled during starter fertilizing and the quantity of necessary phosphorus in soils already high in phosphorus.
- It suppresses weeds by not broadcasting fertilizer near weeds.
- It reduces power consumption and the need for separate deep-band openers or planter modifications.
- It eliminates nutrient erosion by precise placement.
However, there are some considerations regarding use of pop-up fertilization:
- There is a risk of leaching losses of N during the winter following fall pop-up fertilization.
- Pop-up fertilization may effectively override the natural organic mineralization of previous crops.
- High concentrations of nitrogen, sulfur (S), and potassium (K) in soils with low water content present a dander of salt or ammonia injury to the seeds. Limiting N and potassium oxide (K2O) to 10 pounds/acre is a good bet.
The active ingredients of ammonium sulfate are intended to correct the nitrogen levels in soil and the pH balance in alkaline soils. It is an odorless, tan, water-soluble, sand-like crystal produced by combining ammonium with sulfuric acid. Mixed with water in the soil, it releases nitrogen for plant growth and acid-forming ammonium ions for soil alkalinity. It is a non-hazardous and non-flammable byproduct of nylon production.
- The nitrogen is slower to release than in nitrate forms, so it works throughout the growth season. Its nitrogen will produce healthy plants, but overuse may over stimulate growth and invite disease and pests.
- Alfalfa crops and soybeans produce oil and benefit from the sulfates. And, as sulfur has been removed from the atmosphere and acid rain, farmers find pH deficiency which can be helped by the sulfates in the fertilizer.
Ammonium sulfate continues to prove indispensable, and advances in application technologies like pop-up fertilization will continue to require its ready accessibility.