Early In Crop Sampling – a new tradition for soil sampling in the Upper Midwest

Article by Craig Struve, SoilView, LLC

The use of commercial fertilizer became more popular in the United States after World War II when manufacturing changed from munitions and military equipment to meeting the needs of a growing agriculture system. Horses were replaced with steel and nitrogen began being used as a fertilizer rather than an explosive. In the late 1950’s & early 1960’s fertilizer plants where being built across much of the U.S. grain belt and commercial fertilizer production was increased to supply more intense cropping practices – hybrid corn, increases in plant populations, and tractor power. Consolidating farms operated by young veterans of both the depression & WWII soon learned the value of commercial fertilizers to increase yields and accelerated the use of fertilizer.

University Extension Programs helped pave the way with agronomy research programs and rural classes that taught young new farmers about the adoption of new farming practices. As part of this education the benefits of taking a soil sample started to become popular in the late 1960’s – most often just 1 sample on a field represented the entire farm! By the late 70’s and 80’s some growers were having a sample or 2 pulled on a few fields. Almost all samples were taken in the fall after all of the field work was done for one very good reason:  That is when someone had time to walk out and spade some soil into a bucket, if the soil wasn’t frozen or if the snow wasn’t too deep.  The trend was set: Soil sampling was to be done in the fall, not for agronomic reasons, but because someone had time and the fertilizer would be applied in the spring before plowing.

Growers knew that some fields – even some areas of a field – were higher yielding than others. Growers and agronomists also started to realize crop removal across a field varied considerably with yield but it was very difficult to determine what factors were the most yield limiting. The 1990’s and early 2000’s changed all of this: The rapid adoption of GPS technology, yield monitors, and more intense soil sampling changed the rate and placement of fertilizer applied across the landscape with the use of variable rate application technology. GPS technology allowed for intensive grid sampling to increase geometrically in both acres and number of soil samples taken.

Growers of course changed farming and fertilizing practices as well. When fertilizer was used during the early 60’s the nitrogen was sidedress and P & K often went on with the corn planters. As yields increased, fertilizer rates also increased and broadcast applications became more popular – much was farmer applied with pull type spreaders, most often in the spring. Fall tillage became the norm and allowed growers to have the big part of their time consuming tillage work done before spring. More fall fertilizer also started being applied and became known as fall plow-down, “getter on before I plow”. This wasn’t a huge problem at first but as farms (and equipment) grew and the farmers turned to custom applied fall fertilizer, the tillage was right behind the combines in many fields making it impossible to get quality grid soil samples taken, results reviewed, and applications made before fall tillage.

As a result of the changes in farming practices and the speed at which field operations take place many agronomists have switched to early in crop sampling. This sampling period has become so popular we have branded it EIC for Early In Crop.  There are many reasons that both the grower and agronomist should consider EIC sampling.

Soil conditions are the most perfect for quality cores during EIC sampling.

  • Able to plan a better program from better soil results.
  • Soil sample results are much more consistent & repeatable on unworked soils.
  • Nutrients have released from previous crop residue and soil nutrients are at consistent plant availability.
  • More reliable soil nitrate & sulfur analysis.
  • Tissue tests correlate better to EIC sample results.

Added time to review soil test results and plan your fall fertilizer program.

  • Time allows for better agronomy programs to be developed.
  • Spend quality time planning with growers in July, August, or September.
  • Have a known plan of inventory needs for fall application.
  • Allows better planning for lime application if needed.

Apply fall fertilizer without waiting for sample results or fertilizer recommendations and do fall tillage without delay.

  • When the harvest starts fertilizer application can start with sound recommendations.
  • Apply the correct fertilizer before ground is worked.
  • Lower application cost on unworked ground.
  • Much easier on the application operator and equipment.
  • EIC sampling is less expensive than sampling worked fields.

As with any change there can be grower concerns when considering a switch to EIC sampling. These are all easily addressed and we’ve found that most growers agree EIC is a good idea after discussing the value of it with their trusted advisors. Here are a few of the most common concerns:

The sampler’s equipment will run over my crop.  SoilView samplers are trained to be careful and respectful in all seasons, and special care is taken during EIC sampling.

  • SoilView’s equipment footprint is light and small, similar to the growers 4-wheeler.
  • Contour fields are most often completed before emergence.
  • Corn is done early and rows are never crossed except when turning on end rows.
  • In areas of corn-bean rotation it is often the current bean field that gets sampled – beans are very forgiving and this also normally avoids recent fertilizer or manure application as well.

Will the current crop removal affect my P & K test levels? Typical application plans already allow for VR nutrient application to account for crop removal based on anticipated or desired yield plus a build. Most often current crop removal was accounted for in a previous application. The actual pounds of nutrients removed in one year has minimal impact on soil test PPM, for example:

  • a 60 Bu/A soybean yield removes 44 lbs. of P2O5 which affects the soil test by approximately 2 PPM.  K removal at 60 Bu/A is 72 lbs. affecting the soil test approximately 5-6 PPM.
  • a 200 Bu/A corn yield removes 70 lbs. of P2O5 which affects the soil test approximately 3 PPM. K removal at 200 Bu/A is 50 lbs. affecting the soil test approximately 3-4 PPM. 1

Everything I read recommends to sample during the same time period each time I sample.  This is true even in the fall when results can vary a great deal from harvest to freeze up because of nutrient tie up in residue without rain events. Variations in seasonal sample results are typically very small and can be accounted for when changing to EIC.  Seasonal variations for soil test K can be the most different, but the results from EIC are often a closer measure of plant available nutrients. University and soil laboratory research actually shows that EIC sampling can eliminate many problems created by fall nutrient tie-up in residue and sampling in tilled fields. 2

Agronomists that have made the transition to EIC really appreciate the additional time they have to review the data during the summer and develop a plan for delivery to the growers before harvest. Growers are much more receptive to making a quality plan when not feeling the pressure of harvest and a short fall season. Not every grower will change, but offer it to a few growers at your location and it will grow annually. Every year we see more and more growers changing their practices to take advantage of the many benefits of Early In Crop sampling, especially once they see that there is really only one reason to sample in the fall:




  1. IPNI Nutrient Removal Calculator
  2. Agvise Laboratories Presentation – Early Summer Sampling