It’s almost planting season! Know your ideal soil conditions before you begin

Understand your soil moisture conditions before trafficking, tilling or planting this spring.
No till corn planting in Iowa

What are exactly the right soil conditions for spring tillage, fertilizer application, spraying and planting? Farmers start going to the field in March or April when conditions are right for the task they want to do.

 Till when soil moisture is less than field capacity.

Tillage requires firmer and drier conditions than spreading fertilizer, spraying or planting. As long as soil is firm, floaters and sprayers can float across the top of the field as long as they do not cause compaction. If the machine is not making a rut or deep wheel track it is firm enough to drive a floater or sprayer across the soil surface.

Soil Ribbon Test
Soil Ribbon Test

Soil moisture status can be evaluated by taking a handful of soil from the top 6 to 8 inches to perform a ribbon test.  This will help you determine if the soil is too wet or at field capacity. As a rule of thumb, if squeezing the soil leaves water marks on the palm of your hand or if it forms a ribbon four to five inches long when pushed out between the thumb and index finger, it is too wet to start fieldwork. At field capacity soil is sticky but no free water appears on the soil when ribbon tested. Soil will ribbon easily and will form long strips two inches or more if it has a higher clay content. However wait a day or two when soil can be pressed into a ribbon between two fingers and has a slick feeling.  An ideal soil for tillage will ribbon easily but only into short strips of perhaps an inch before cracking or breaking.

Again, do not till when soil is wet or it will cause compaction and create clods that will dry out and become hard. If the soil is moist yet crumbly, it is below field capacity and fields can be worked and planted.

 Plant in ideal soil conditions.

Planting seed also requires ideal soil conditions.  If the soil is too moist, not only will wheel traffic cause compaction, but discs will smear the soil causing sidewall compaction in the V-furrow.  This compaction will impede root growth of young seedlings.

Ideal soil for planting is crumbly or friable.  This means that larger aggregates, clods or peds can be broken apart easily and moisture never glistens on your fingers. Soil moisture is the factor that affects friability the most. The moisture content for working a field varies with the soil texture and with the tool being used. Soil moisture needs to be in the right range from the surface to the depth of the soil disturbance.

Do not plant in highly saturated soil. Soil needs to be mellow and have good structure. Seed furrows need sidewall structure but not sidewall compaction.

Wait until conditions are ideal. If growers work or traffic soil with high moisture conditions, it will create a cloddy soil surface and will not be a good seedbed. Moisture is always the best indicator of when to work a soil. Soil moisture acts a lubricant, enables particles to slide and compact, raises bulk density and makes it difficult for roots to penetrate and reduces aeration and infiltration.