Raindrops impact the soil surface with a surprising amount of force, and will often destroy soil structure on and within the top few millimeters of soil. This layer can then become compacted and much denser than the underlying soil. Bright sunshine and strong winds, which often follow a storm front, can exacerbate this process resulting in a layer that is virtually impenetrable to emerging alfalfa, corn and soybean seeds.
With the recent rains, and many fields already planted, it is especially important to walk your fields and check for soil crusting. As long as the surface retains some moisture, the seedlings should be able to push themselves through the crust; but as the surface dries and hardens, reduced stands are possible. Traditionally, this is especially problematic in conventionally tilled fields and fields which have been overworked with secondary tillage. In heavy clay soils and with very heavy rainfall events, no-till fields should be checked as well.
The sooner crusting is identified, the better your chance of physically breaking up the surface without damaging emerging seedlings. Rotary hoes, field cultivators and or cultipackers can all be used to break up a developing crust. Try to run them as deep as the compacted layer but no so deep as to uproot and damage developing seedlings. If significant rainfall is in the near forecast, you can also take a chance and let Mother Nature soften the surface and allow those shoots to emerge and establish themselves.
This year we are hearing reports of significant crusting which is negatively impacting the establishment of alfalfa and orchardgrass fields, and soybeans seeded in tilled fields.