5 Factors to Consider for Potassium Fertilizer

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Decisions about optimal fertilizer management can be difficult in years when commodity prices are low, says Daniel Kaiser, a soil fertility specialist at the University of Minnesota (U of M). In the article below, he gives five factors farmers should consider when making decisions about K application for corn and soybeans.

1. Focus on rhythm, not timing.

It has been shown that applying the correct rate needed over one or two years in a crop rotation is more important than when the fertilizer is applied. Most of the current U of M data has shown that the timing of application in a multi-year crop rotation is not important. Applying before the crop that will get the most benefit from the K is the best way to get your money’s worth.

2. Focus on proven performance, not a performance goal.

It can be difficult to determine which yield should be used for both a sufficiency-based or construction-and-maintenance K application strategy. Using a historical yield average is the best option. A value that you have proven can be produced is a smart way to ensure that fertilizer is not overapplied. The soil itself is not devoid of K, so it is not essential to be exact on your predicted rates. Some fertilizers are always better than none in situations where a nutrient response is likely.

3. Observe the same time of year when sampling soil.

Sampling fields at similar times of the year is essential to ensure you can accurately determine how soil test values ​​for K are changing over time. Potassium is different from other nutrients in that the soil test value is not static in the field during the growing season. It can vary from fall to spring.

4. Apply K when and where needed.

Soil testing remains the best option for deciding when and where K fertilizer should be applied. For soils richer in clay – such as loams and loamy clay soils – the chances of a cost-effective response to K fertilizer are low when soil tests are around 200 parts per million K. For soils soils that do not retain K well – such as loamy sands – high K levels may not be necessary, although soil test values ​​may be lower than those of more clayey soils.

5. Choose the right investment option.

Research has shown that K bands may be more effective in certain circumstances. Broadcast application of K in reduced tillage situations, such as ridge and strip tillage or no-till, can stratify K near the soil surface, which can lead to poor uptake in soils. dry soils. Although K-band is not always necessary, identifying situations where it is beneficial can help ensure optimal productivity.

Now is a good time to start reviewing fertilizer decisions while waiting for the fields to dry out this spring. There are situations where K may not be needed, so knowing which fields need K could save time this spring.

Support for this project was provided by the Minnesota Soybean Research and Promotion Council (MSR&PC) and the Agricultural Fertilizer Research & Education Council (AFREC).

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