Home » Wheat » Response to NPKS strips across Oklahoma

Response to NPKS strips across Oklahoma

From the fall of 2011 to about a week ago one of my grad students, Lance Shepherd, has spent A LOT of time burning up the highways and back roads of Oklahoma.  Lance’s project was titled “NPKS Strips in Oklahoma winter wheat”, basically an extension of the N-Rich Strip concept.  We wanted to see if we could or would find a response to added nitrogen (N), phosphorus (P), potassium (K), or sulfur (S) fertilizer on top of the farmer’s fertilizer applications.  Over the two crop years lance applied NPKS strip on more than 80 fields from the Kansas border to the Red River.  Of those 80+ Lance was able to collect, by hand, grain samples from 59 sites.  Over the next few weeks I will be sharing some of the juicy tidbits we are gleaming from this fantastic data set.

NPKS applicator.  Gandy boxes hold each fertilizer and a pto driven fan blew the fertilizer down the boom.

NPKS applicator. Gandy boxes hold each fertilizer and a pto driven fan blew the fertilizer down the boom.

For the project at every site Lance collected soil samples to 18”, documented soil type and collected producer fertilizer, variety, and field history information.  Over the 59 locations there were essentially 236 trials.  The yield of each strip (N,P,K, and S) was compared back to a sample collected from the field, referred to as Farmer Practice. Of the 236 comparisons there were a total of 17 positive responses.  Of these 17 responses seven were to N, seven to P, three to K, with no responses to S.

N-Rich strip very evident in field west of Alva.  N-Rich 70 bu/ac Farmer Practice 38 bu/ac.

N-Rich strip very evident in field west of Alva. N-Rich 70 bu/ac Farmer Practice 38 bu/ac.

We are learning a great deal from these 17 locations.  The biggest take home was that in most instances soil test results identified the yield limiting factors.  For example of the seven responsive P locations six had either a low soil pH or low soil P index, some both.  At only one site was there a response not predicted by soil test.  Of all 59 harvested fields more than just six had low P or pH levels however most producers had applied enough fertilizer to reach maximum yield. For nitrogen two items proved to be the most likely reason for loss of yield, under estimated yield goal or environment conducive to N loss.  As for the K responses we look at both K and chloride (Cl) as KCl, 0-0-62 potash, was applied in the K strip.  Just looking at the soils data K was not low at any of the three sites.  However, two sites are in sandy loam soils, which is conducive to Cl deficiencies.  The lack of response to S was not surprising as soil tests indicated S was sufficient at all 80 locations were strips were applied.  So again what did we learn from these plots, soil testing is key in maximizing yield and profitability and in most of the N responsive sites the N-Rich strip indicated a need for added fertilizer in February.


  1. Tom basden says:

    Brian, looks like a good study can send me your methods. We are looking for quick way to recalibrate our soil testing lab recommendations. Thanks, Tom

    • osunpk says:

      I will send you that M&M from my students thesis. I will say this was less a study and more a demo/observation. Our priority was locations over replications.

      I tried to send you an email with M&M and more info to the wvu.edu address however the delivery failed for some reason.


  2. Bill Wilson says:

    Any data from calcareous soil types?

    Any data from high shrink soil types?

    Any data from both calcareous AND high shrink soil types?

    • osunpk says:

      Very few calcareous soils. We did not venture far enough north west. However there are a few. As far as high shrink I have not looked at the data but knowing our soils my guess would be nearly 50% are high shrink swell, that’s just what we have.

  3. […] So the take home would be as this wheat season takes off and you find that DAP is hard to locate and you A) Have overall neutral (5.5+) pH levels do not hesitate using MAP. Run the normal amount of material getting a few extra lbs of P or apply less material to get the same amount of phosphate. B) Have a acidic situation and are banding to alleviate aluminum toxicity use the same amount of material or a little bit more.  Keep in mind in acidic soils with a low soil test P level you have to apply enough phosphate to take care of the Al and enough to take care of the P deficiency. Note the results of the NPKS wheat response strip (NPKS BLOG) […]

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