Liquid fertilizers containing phosphorus (P) and potassium (K) have grown in popularity among farmers in recent years. Proponents claim these products can wholly or partially replace traditional granular P and K fertilizers. However, not everyone is convinced of their efficacy and value. This article examines the pros and cons of using liquid P and K fertilizers.
What Are Liquid P and K Fertilizers?
Liquid P and K fertilizers are fertilizer products containing phosphorus and potassium in a liquid form. They are designed to provide crops with these essential nutrients through either soil or foliar application.
Some common types of liquid P and K fertilizers include
- Liquid phosphorus fertilizers like ammonium polyphosphate
- Liquid potassium fertilizers like potassium carbonate
- Blended NP or NPK mixtures in liquid form
These products come in a concentrated liquid form and are diluted with water before application They can be applied via ground spray equipment, through irrigation systems, or mixed into liquid starter fertilizers
Potential Benefits of Liquid P and K
1. Flexible application methods
Unlike granular fertilizers which must be incorporated into the soil, liquid P and K products can be foliar applied or fertigated through irrigation systems. This provides more flexibility in timing and placement of nutrients.
2. Faster nutrient uptake
Foliar-applied liquid P and K can be rapidly absorbed by plant leaves and utilized by the plant. This is especially useful for addressing in-season nutrient deficiencies.
3. Lower application rates
Some research suggests liquid P and K fertilizers provide equal crop response at lower application rates compared to granular fertilizers. This improves nutrient efficiency.
4. Good tank-mix compatibility
Liquid P and K fertilizers can often be mixed and applied together with other crop inputs like pesticides. This reduces passes across the field.
5. Convenience
Liquid fertilizers are easier to handle, transport, and apply compared to bulk granular fertilizer. This improves convenience for the grower.
Potential Drawbacks of Liquid P and K
1. Higher cost per pound of nutrient
On a per pound of nutrient basis, liquid P and K fertilizers typically cost significantly more than traditional granular fertilizers.
2. Questions about efficacy
University research on the crop response and performance of liquid P and K fertilizers has been mixed. Their ability to wholly replace granular P and K is debated.
3. Potential for foliar burn
High application rates or concentrations of some liquid P and K products may cause foliar burn or leaf damage. Proper rates and dilution is key.
4. Limited soil residual
Unlike granular P and K fertilizers which provide residual soil nutrition, liquid products generally have no residual value. Their impact is only from the current application.
5. Storage and handling challenges
Liquid fertilizers require specialized storage, transfer equipment and may have a short shelf life compared to dry granular products.
Liquid vs Granular P and K: Key Considerations
When evaluating liquid P and K fertilizers, here are some key factors to consider:
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Soil test levels – Are soil test P and K levels already sufficient for your crop’s needs? Liquid fertilizers are best suited for supplemental fertility, not building low soil nutrients.
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Application timing – Foliar liquid P and K works best for addressing in-season deficiencies. For preplant fertility, granular broadcast may be better.
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Application method – If you don’t have sprayers or irrigation to apply liquids, granular may be a better fit.
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Cost per pound of nutrient – Liquid products often cost over 2-3X more per pound of P or K than granular fertilizers. Consider the value.
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Crop nutrient removal – Liquids may not supply adequate P and K for high-removal crops. Granular often makes more sense for corn, potatoes, etc.
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Local research – Consult university research in your region on liquid P and K performance to make the best choice.
Best Practices for Using Liquid P and K Fertilizers
If you do choose to use liquid P and K fertilizers, here are some tips:
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Start small – Use liquids to supplement, not completely replace, your granular P and K program initially.
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Soil test regularly – Monitor soil nutrients to determine if liquid P and K is maintaining adequate levels.
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Follow label rates – Only use liquid fertilizers at labeled rates to avoid crop damage.
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Target deficiencies – Use foliar liquid P and K to address deficiencies or stress periods for crops.
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Avoid excessive N – Select low-N or no-N formulations when applying liquid P and K foliarly.
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Use surfactants – Add recommended surfactants to improve leaf coverage and nutrient absorption.
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Rotate chemistry – Rotate between different liquid fertilizer formulations for resistance management.
The Bottom Line
Liquid P and K fertilizers can be a viable option for supplementing crop nutrition programs. However, questions remain about their ability to completely replace traditional granular P and K fertilizers, especially at current prices.
Like any crop input decision, fully evaluate these products in the context of your specific farming operation. Local on-farm trials, soil tests, and university data will provide the best information to find your optimal combination of liquid and granular P and K fertilization.
In Furrow Field Fertilizers
Liqui-Grow makes a line of “low-salt” fertilizer products for growers who use planters that put liquid starter fertilizer in the furrow, also known as “pop-up” placement. These products can be placed directly on the seed at 3-to-5 gallons per acre. These clear, “true solutions” are manufactured from super-phosphoric acid, potassium hydroxide, and urea or anhydrous ammonia.
Products available include:
Fall Nitrogen Fertilizer vs Spring Nitrogen Fertilizer
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Organic Liquid Phosphorus Fertilizer, Pro Phos™ 0-20-0
FAQ
When should p and K be applied?
What fertilizer is high in P and K?
What does NP and K do in fertilizer?
Should I prioritize P & K fertilizer?
If you cannot afford all the fertilizer P and K you think you need or there is not enough fertilizer to be had, you might want to prioritize their use on your farm. The key to prioritizing P and K use is to have recent soil test information for your fields. Now is a great time to find out what P&K is out there! (Photo Credit: John Obermeyer)
What is primagro K potash biofertilizer?
The potassium solubilizing bacteria contained in PrimAgro K potash biofertilizer help to break these bonds apart and make potassium mobile and usable in the soil. PrimAgro K potash biofertilizer is best used across multiple applications and in combination with other potash fertilizer products.
When should I use banded P & K fertilizer?
Banded P and K applications are best suited for specific situations, including soils that are slow to warm in the spring and soils that are managed under no-till or conservation tillage. Nutrient removal due to silage or crop residue harvest should be considered when determining fertilizer rate recommendations.
Are phosphorus & potassium fertilizers causing price volatility?
Recent years have seen increased price volatility for both farm inputs and products. Few inputs have experienced such dramatic price fluctuations relative to grain as have phosphorus (P) and potassium (K) fertilizers (Figure 1).
Can precision soil sampling improve phosphate and potash fertilizers?
Figure 1. Monthly price ratios for phosphate and potash fertilizers over the course of the last decade. Research has shown that precision soil sampling can improve P and K management and return on fertilizer investment when combined with variable rate application technologies (Ferguson and Hergert, 2009).
How does primagro K biofertilizer work?
This means the potassium accumulates in the soil in an insoluble form, which contributes to soil over-salinization. The potassium solubilizing bacteria contained in PrimAgro K potash biofertilizer help to break these bonds apart and make potassium mobile and usable in the soil.