By Jacob Schmitt, Operations Agronomist

 

How important are sulfur applications to soybean yield? This is a question we hear often. In fact, we talk a lot about sulfur. Sulfur applications have become much more prominent in the past few years. In fact, it may be a nutrient we need to consider with the same level of importance as N, P and K.

Sulfur plays an extremely important role in nitrogen fixation in the soil. In a test at the North Central Research Station in 2020, the addition of sulfur from several different sources generated a positive ROI across the entire trial.

Some of the key takeaways from this trial:

• Adding an application of sulfur generated a positive yield response across the entire experiment
• A Y-drop application of 2 gallons of accesS increased soybean yield by 3.7 per acre
• A Y-drop application of CalSip at R2 increased yield 3.2 bushels per acre

Check out all of our research results on our website at research.agroliquid.com.

Want to learn about the importance of sulfur? AgroLiquid Agronomist John Leif penned this blog post, discussing why sulfur is so important to a crop.

Soybeans require large amounts of potassium (K), sulfur (S), and calcium (Ca). They also require micronutrients such as manganese and iron to meet their yield potential. In addition to soil applications of those nutrients, soybeans often respond to foliar applications. Sure-K® and fertiRain® products are well suited to provide cost-effective crop nutrition when applied as foliar treatments.

Sure-K

Sure-K was applied for 10 consecutive years in a corn-soybean rotation as a soil applied treatment and as a foliar treatment. Over the 10 years of the trial, the foliar application of Sure-K at 3 gal/A consistently performed as well as Sure-K applied at 5 gal/A in-furrow.

fertiRain

When applied alone, fertiRain provides excellent potassium nutrition along with nitrogen, phosphorus, and sulfur. Application timings are flexible, and it can be tank mixed with many crop protection products.

The Right Mix

Sure-K and fertiRain can be applied alone, or in combination with each other or other crop nutrients. Soybeans will often require more potassium than fertiRain alone can provide, and fertiRain can provide additional nitrogen, phosphorus, and sulfur to Sure-K.

Performance Consistency is Key

Product performance consistency is as important as individual trial results. AgroLiquid has evaluated yield response to foliar applied Sure-K across 165 locations from 1998 – 2019. Those trials showed a high level of performance consistency and economic benefit. The economic response was calculated using the soybean market price and fertilizer costs appropriate for the year each trial was conducted.

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Just 3 gal/A at planting nets more than 3.5 bu/A increase at harvest!

Planter-time phosphate sources like springuP can supply a young crop’s immediate needs, while slow release sources of P, such as Pro-Germinator®, sustain a season-long feeding.

With adequate phosphate levels in the soil, highly available early season ortho-phosphate sources can start a crop on the right path.

As evidenced in this trial, with plenty of phosphorus and potassium already applied (all treatments included 100 lbs/A DAP and 100 lbs/A 0-0-60), all the crop needed was a product with readily available orthophosphate to get ahead. In fact, the stand count on the plot treated with springuP and Micro 500® had nearly 6,000 more plants per acre than the plot that received only DAP and 0-0-60. This was reflected in the additional 3.7 bu/A yield.

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SpringuP is a liquid phosphorus fertilizer starter designed to give plants a jump-start on the growing season. The combination of phosphorus, nitrogen and potash sets the stage for strong, early growth. SpringuP liquid phosphorus fertilizer can help plants emerge faster, giving them an early start on the growing season.

 

Pro-Germinator uses a blend of phosphate, nitrogen, potash, and iron to maximize crop response at critical growth stages. The combination of quick-release phosphates with slow-release, carbon-protected, polymer phosphates, promotes exceptional growth early on, and plants continue flourishing through reproductive stages.

Soybean fertility programs have long been a focus of AgroLiquid’s crop nutrient research.

Sure-K is one of AgroLiquid’s flagship products. Many years of research, as well as grower experience, have proven its performance.

Knowing that soybeans utilize a lot of potassium and understanding the low soil potassium (K) levels in many parts of the soybean growing areas, Sure-K was a perfect fit for a soybean fertility program. In the late 1990’s the North Central Research Station (NCRS) began testing Sure-K as a foliar application on soybeans. These foliar applications are especially beneficial, as they can be made in conjunction with most post-emergence pesticide applications.

Since 1998, 165 comparisons have been completed across the US. This data helps us determine both the yield and economic benefit of a soybean foliar fertility programs. As shown in the data below, over these 24 years Sure-K has provided a positive yield return 90% of the time with an average yield increase of 4.5 bu/A, returning an average of more than $22/A for the fertilizer dollars invested.

*ROI calculated on current CBOT soybean price and fertilizer price.

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Sure-K is a high-efficiency product that provides plants the nutrients they need to thrive at key reproductive stages. The unique formula provides increased utilization at lower concentrations, providing the same or better results than standard potassium fertilizers while using less. In addition, Sure-K uses no chlorides or hydroxides, so it preserves soil health long-term.

 

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Foliar applications of Sure-K when soybeans are beginning to flower (R1) have a proven yield benefit. This timely application of Sure-K provides available liquid potassium at peak usage.

This trial from 2019 in LyCene, KS shows an increase of 3.4 bu/A with just 2 gal/A of Sure-K added to the grower’s standard treatment of 100# MAP and 100# potash.

All treatment: 100 lb/A potash + 100 lb/A DAP

Additional benefits of working with Kalibrate:

• Low use rate
• Ease of application
• High average return on investment
• Mixes with many other fertilizers and crop protection
• Proven response on high potassium soils

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Research trials at the North Central Research Station (NCRS) have long shown that foliar fertilizers can push several more bushels of soybeans per acre. But like anything dealing with plant nutrition, it should be “customized” to plant and soil needs. See trial results below from the NCRS .

Because of the wet spring that we all remember from last year, these soybeans were planted late. Thanks to an extended warm and dry fall, yields were surprisingly very good. The low soil phosphorus made the application of Pro-Germinator at planting necessary. Additionally, we often have not shown a response to foliar-applied potassium if another nutrient like phosphorus is limiting, like Liebig’s Law says.

The soil potassium level was not bad, but the % Base Saturation indicated that there could be a response to added potassium. Sure-K is AgroLiquid’s best nutrient product for foliar-applied potassium, and it did result in a yield increase. FertiRain is an excellent foliar product, but is not as effective as Sure-K for feeding potassium. There has been some suggestion of yield response with foliar-applied C-Tech due to the carbon and biologicals. But there was not much response in this experiment where potassium was the missing link.

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