Excessive Rainfall – Why are my soybeans STILL yellow?

  • Jul 08
    Chuck Belanger
    Excessive Rainfall – Why are my soybeans STILL yellow? By Chuck Belanger on July 8, 2013
    Categories: Soybean

    A few weeks ago, most soybeans fields were going through a delay caused by the start of nodulation. They began to come out of it, but are now yellow, once again. This time it is caused by excessive rainfall. There are areas where rainfall was in excess of 5 inches in a matter of one week.

    Soils are becoming so saturated, that up to 80-85% of the field will be yellow. Soybeans require well-aerated soils to grow vigorously. Saturated soils, even if water is not present on the surface, will result in poor root development and plant growth. This will cause poor nitrogen fixation because very little oxygen is present in the soil.

    The remedy to this is sunshine, which as you all know, has been very limited for the last couple of weeks.  Even though we are getting breaks in rain, cloud cover has been thick most days with very little sunshine. Until we get sun and heat, beans will continue to stay yellow. The bottom line is that growing conditions are far from ideal for the soybean crop. Warm nighttime temperatures, bright sunny days and a few days free of rainfall will bring this crop around and change its appearance significantly. Changes need to occur shortly, since the soybeans have moved into the reproductive stages of growth with flowers starting to appear. Continued stress can begin to have an effect on yield.

    After a few field walks this past week, we noticed that rainfall is not the only problem. We are seeing Phytophthora Root Rot in some varieties. Even though these varieties usually perform very well against this disease, the excessive moisture is taking its toll. These areas are small, but be aware that this is occurring.  The following is a description from the OMAFRA webpage, under soybean diseases, “This disease will cause taproot and lateral root pruning or rotting, resulting in yellowing of the leaves, wilting and even death. Infected plants are easily pulled from the ground, since the plants are not well anchored. Older plants can be affected any time before maturity. A purple or dark-brown discoloration of the stem may extend from the roots (just below the soil line) to the lower nodes of wilted plants. Dead plants may appear a few in a row or as patches in low areas of fields. Leaves will often remain attached to the plant even after death.”

    Sorry to be a bearer of bad news, but we can’t control Mother Nature and it is just good to know what is happening. The good news is that if the rainfall relinquishes, and we get warmer sunny days, a good portion of our problem areas will come out of it, and we should not see much of a yield reduction.

    Chuck Belanger, Maizex Seeds Yield Specialist, North Essex and South Chatham-Kent Counties
    Twitter: @sprayman63