Crusts are created by the breakdown of the soil's structure by flowing water, raindrops or through freeze-thaw action. In the freeze-thaw action, crusts are created with the puddling effect as ice forms, melts and reforms. Crusts are usually less than two inches thick, but are massive because individual soil particles fill pore spaces on the surface and prevent water movement, air entry and seedling emergence from occurring. Nodulation, the symbiotic relationship of bacteria on the soybean roots, can be seen shortly after emergence, but the plant is not actively fixing nitrogen until the V2 to V3 stages. The number and nodules formed on the soybean roots along with the amount of nitrogen fixed increases until the R5.5 stage.
Nodules actively fixing nitrogen for the plant are pink or red inside.
White, brown or green nodules indicate that nitrogen-fixation is not occurring. Soil nitrogen is utilized over fixed nitrogen, if available in large amounts. Check the health of your soybean nodules and check root proliferation. At V2, soybeans should be rooting down six inches into the soil and by V5 will completely reach between 30- inch rows, making any cultivation at V5 needing to be very shallow.