Patience can be the best practice when it comes to spring field work, despite how tempting it can be to get into fields as soon as the frost is out of the ground.
But getting out too early comes with threats like nutrient runoff, soil compaction and poor seed germination, according to UW-Madison Extension Soil Specialist Francisco Arriaga.
Even when things are starting to look good, conditions can change in a hurry in spring, and a few days of chilly rain can have a big impact on soil temperatures, as evidenced by the second week of April, Arriaga said April 14 during a UW-Extension Badger Crop Connect webinar.
“The temperature was starting to look pretty good, but then we got a little bit of cool weather, we got some cool rain, and it cooled off the soil 6 or 8 degrees,” he said. “So conditions can change quite fast.”
Prior to cooler air and slow, soaking rains moving through the state, some farmers were able to get into the fields early in the week ending April 11, according to the U.S. Department of Agriculture’s National Agricultural Statistics Service. Tillage, manure and fertilizer applications were underway in many areas and some farmers were planting small grains, potatoes and alfalfa before more than an inch of precipitation total fell over multiple days.
Temperatures early in the month were well above normal, with daytime highs ranging from the 50s to low 80s, according to the NASS Wisconsin Crop Progress and Condition report.
UW-Extension Lafayette County Agriculture Educator Josh Kamps said he was watching the soil temperature, which in early April was up close to 50 degrees, using a a weather station that was put in place because of a UW Discovery Farms research farm in the Lafayette County and left in place to aid the local agriculture industry.
“Now with some of the colder rains in the colder weather it is starting to go down,” he said.
Kamps said he was also watching the weather station for its soil tension reading.
“A soil tension reading really speaks to whether we can be out on the soils with our equipment,” he said. “Are we doing any damage, any compaction to that soil structure.”
Before beginning field work, Arriaga recommended checking resources like the Runoff Risk Advisory Forecast, which also has a tab for soil temperature, at www.manureadvisorysystem.wi.gov/runoffrisk/index. But even better, he said, is to use tools like a digital meat thermometer to check soil temperatures and moisture meters or grabbing a handful of soil to know exactly what conditions are like in your fields.
“Your farms conditions are going to vary field to field,” he said. “So getting out there and measuring it is probably a worthwhile thing to spend your time to do.”
When testing moisture in fields by grabbing clumps of soil, Arriaga said farmers should look for soil that is somewhat moist but drier than field capacity that can be formed into a weak ball. It should be a little dark in color but not leave staining on hands and have very few aggregates that break away.
“Moisture is going to affect the compactability of the soil,” he said. “Soils that have better soil health, have better aggregation, are going to have a lower risk for soil compaction. As the water content of the soil increases, at a certain point, that risk of compaction increases. And once you get to a point where you’re getting close to saturation, the risk of compaction goes down, but then you’re creating ruts and other other issues and messes.
“Be patient and wait for good conditions.”
Arriaga said the main concern with soil temperature is seed germination. Most seeds have an optimum range for germination between about 75 to 80 degrees, he said, but most crops can germinate at about 50 degrees.
“Having said that, that doesn’t mean those seed and those plants, once they germinate, will be thriving,” he said. “We should be thinking more about these optimum range.
“The reason for it is optimum range is that stand evenness can be affected by the temperature of the soil. That can affect how well those plants grow once they germinate.”