Fertilizer Management to Help Maximize Soybean Yield
As fertilizer applications become more prevalent in soybean production, there are a few things producers should review to help increase the chance of getting the greatest return on each application. Before any applications are made, there should be a soil sampling program in place. Ideally every 2 to 3 years soil samples should be taken to monitor soil fertility levels to help determine application rates. The use of a grid sample followed by a variable rate fertilizer application is an efficient way of ensuring the nutrients are placed where they are needed so producers get the most bang for their buck. Different spots in the field often call for different nutrient levels. However, any sampling program whether it be composite, grid, or zone is better than none.
Fertilizer Application Timing
Research from the University of Minnesota shows that if soybean fertility is accounted for on an application, there is no dramatic impact by the timing compared to corn. Timing of the phosphate application can be an important consideration when fertilizing soybean. Many growers find applying phosphorus (P) and potassium (K) for the soybean crop ahead of a preceding crop to be more economical. However, research has demonstrated that soybean is less sensitive to application timing a two-year cropping system. Therefore, the application helps provide maximum yield potential if the P and K applied to the preceding crop is sufficient for both crops in the rotation. The exception to this practice is when soil pH is above 7.4 then soybean is more likely to respond to an application of P directly ahead of the soybean crop.
Ways to bring pH down include increasing drainage to help drain nutrients causing the high pH (excess magnesium and sodium (Na)), as well as applying elemental sulfur in the fall. The use of Iron chelate products at planting is another short-term practice many growers use as well to help increase yield potential on high pH soils. On the flip side, if pH is too low (6.0-) nutrients such as P and potassium become unavailable. Applying limestone is the most common practice to raise soil pH.
In conclusion, having a consistent soil sampling program, scouting fields for any in-season nutrient deficiencies, using adequate rates to achieve highest return on investments, and keeping a neutral pH (6.5 to 7.0) are item growers should be thinking about when it comes to managing fertility on the soybean acre.