Based on early seed orders, it appears 2018 could be a banner year for soybean acres in the region. But the key to success in 2018 will be paying special attention to crop fertility following the drought conditions faced in 2017. Drought conditions led to variable crop yield in 2017 and may have lasting effects carrying over into this cropping season.

High soybean yields require well-planned crop nutrition. Since soybeans are high nutrient users, they require a multi-layered fertilizer approach. Plans usually start with phosphorus (P) and often include potassium (K) inputs up front. Maximum soybean yield requires soil phosphorus levels in the teens. It takes around 20 pounds of P₂O₅ to raise the soil test level 1 part per million (PPM) on an Olsen P test.

Nutrient uptake in soybeans generally occurs late in the season, with peak uptake occurring at the reproductive growth stages. Attempting to rely on the residual phosphorus from the previous year’s corn crop, and hoping that a good chunk of that P will be available to soybeans in the later summer of 2018, may be insufficient in achieving your yield goals. 

A relatively dry fall had multiple effects on nutrient availability for 2018. Variable harvested yields resulted in variable phosphorus and potassium uptake and removal. The release of these nutrients in crop fodder also was negatively impacted, with dry conditions resulting in lower short-term P and K recycling from crop residue after harvest and reduced nutrient cycling in the soils. The full impact likely varies from field to field and often affects soil test results.

To maximize potential ROI for 2018, careful management and interpretation of soil tests combined with solid agronomic knowledge of individual fields will be essential.

Potassium in plant residue is water-soluble and not tightly bound in tissues, meaning lack of moisture can greatly affect potassium cycling from residue to soil. Phosphorus is mostly present in organic forms, and thus is slower to release from residues. 

The effect of dry conditions is that potassium test levels may be artificially low following drought, whereas phosphorus cycling is less affected but can also be slightly low. Added spring crop nutrition may be needed to bridge the gap until residues decompose. Phosphorus and potassium recycling from soybean residue takes less moisture than from corn because most nutrients are in soybean leaves, which readily break down in the fall.

The bottom line is that there are ongoing effects of the dry conditions from 2017. Your Agtegra Cooperative agronomist can review your crop nutrition needs with you on a field-by-field basis. Together you can develop a solid crop fertility plan that places the correct nutrients on each acre to maximize your ROI in 2018. Even with dry conditions, maximizing ROI can result when the prerequisites are met for maximum yield.