Soil Moisture and Temperatures

This is the time of year when we are trying to get ready to plant corn and the question always comes up about when to plant.  Most everybody wants to plant as early as possible to avoid as much hot summer weather as possible and increase yields in the process.  But this is also true with almost all crops, the earlier you plant the higher the yields and the least amount of stress in the growing season.  

The first thing to think about is Summer Solstice on June 20 at 10:31 pm.  This is the date when the day length is the longest of the year and after that date every day gets shorter by nearly 2 minutes a day.  This lengthening of days and the shortening of days has an effect on plant growth - can you figure out which is better?  Of course, longer days are better for crops and we do see plants begin some change after summer solstice.  

That said we know to plant as early in the spring as possible to take advantage of longer days but if our soils are cold then the seed won’t come up.  So, we spend a lot of time looking at soil temperatures to plant corn, sorghum, cotton and peanuts.  Corn is 50⁰, sorghum 60⁰, cotton is 65⁰ and peanuts is 65⁰ degrees F taken at planting depth at 8am for 4-5 days.

So, what is the current soil temperature?  During the coldest part of the polar vortex it was right around 35⁰ at the 2-4 inch depth, so too cold to plant anything.  But the last several days it has been above 50⁰ and the weather should stay warm enough to keep soil temperatures rising enough that the corn planters will be running soon.

What about soil moisture?  Well we are dry and have been for some time.  Soil moisture at the end of January was 30% at 4 inches and 16% at 40 inches.  Today it is 24% at 4 inches and still at that 16-17% at 40 inches.  Ideally we want the 4 inch to be at 35% now and the 40 inch to be at 50% to give the deep moisture we need to grow any crop through the hot summer days.