Why Are My Soybeans Growing So Slowly?

Did Soybeans Make Any Progress in May?

2025 has had challenges like any other crop year in Iowa. The single biggest question I have received this year compared to other seasons is the lack of growth on soybean in the month of May this year. For the answer to this question, we need to ask ourselves field specific questions related to planting date and weather conditions that followed  While it is true that soybean can germinate with cool soil temperatures (36F to 39F) at planting, the optimum temperature is 65F. Soybean need three things for growth, those are moisture, heat, and sucrose. All these factors are important for early growth for soybeans. One factor that is interesting is the fact that while we often do not use growing degree days for stages of growth with soybean, it does give us a weather trend for the year. Growing degree calculations in Red Oak, Iowa shows we only had one, 7-day period where the daily GDDs were over 15 GDDs. So, this indicates the roller coaster of temperatures which drives the other key plant functions. We also need to consider the cloudy days which can impact photosynthesis which is the driver of early plant growth. Soybeans are resilient and will rebound as summer takes hold and normal temperatures return. Most soybean fields should at least now be in the early vegetative stages and lateral root growth should be taking over and be prevalent in the top 6 inches of soil and rapid growth should be occurring.  When scouting soybean this time of year we should also notice nodule formation and look for internal pink coloration. This indicates the presence of oxygen carrying leghemoglobin  If you are finding very few nodules this may indicate the presence of excess nitrate in the soil, since soybeans will utilize soil nitrate first before using fixation from nodules.