Buz Kloot

Buz Kloot

Sep 20, 2016

Group 6 Copy 110
1

Soil Test Results - Phosphorus

While we already have talked corn yield (see Figure 2 for reference) I wanted to touch on soil test phosphorus.  The standard narrative is that the corn takes nutrients out of the soil we have to replace.  Once again our phosphorus data (Figure 1) goes against this conventional thought.

Figure 1:Soil test Phosphorus Before and after Corn

We took samples (10 samples per treatment) before and after corn, one in December 2015 an one in September 2016 just after the harvest.  In each case we are actually seeing and increase in phosphorus. Corn grain P removal in the grain for 140 bu/ac is ~ 21 lbs/ac P and for 100 bu/ac is ~ 15 lb/ac P.  Let alone the P that's still sitting in the corn stover on the surface of the soil.  Extractant was Mehlich 1, Clemson Soil test Rating for P>81 lb/ac is high. Soil series is an Orangeburg loamy sand, depth to clay ~10 inches.    

In case this experiment was considered a fluke, we have 97 sample (representing about 1,000 acres of corn) points that were sampled pre- and post corn and we looked at them again after corn harvest and we see we went from 81 to 86 lb/ac.  Now I am not saying this is an increase - it's definitely not statistically significant, but  we are not seeing a drop from expected P removal.

By the way, the manganese the folks are telling you to add?  Soil test Manganese increased from 12.5 lb/ac to 21.5 lb/ac.  A statistically significant increase - how do we explain this if we haven't added manganese for 5 years?

Don't get me wrong, P removal is happening, please understand that, but obviously a lot more is going on here, remember soils are deeper than 6".  

Rather than my carrying on, I invite you to search "mycorrhizae" and  "legacy phosphorus".  

Clearly our data are from the Southeastern Coastal Plain, but if you are a farmer, I urge you to rethink the narrative you are being told on phosphorus addition as I am reminded of the Capital One catch phrase: "What's in your wallet?". 

Figure 2: Corn Yield by Treatment

1 comment

Join the conversation!Sign In
  • Jim Tate
    Jim TateBacker
    To me this is further evidence of what Dr. Ingham has been saying for years... There is plenty of phosphorous in the soil but we have to get the microbial life balance right in order for them to break down the mineral fraction to an absorb-able form.
    Sep 21, 2016
  • Buz Kloot
    Buz KlootResearcher
    Indeed Jim. My passion/aim is to take that kind of science and make it available/demonstrable at a farm scale.
    Sep 21, 2016

About This Project

This is a follow-up project to our first experiment.com project "How much fertilizer do we really need?" where it was difficult to find any response to phosphorus (P) or potash (K) fertilizer inputs, suggesting that, in a healthy, cover cropped soil, legacy P and K may be untapped resources, while economic nitrogen rates seemed to be lower than initially thought. Soil test P in our 40 plots is in the "High" range, so we will concentrate on the effect of nitrogen and potassium in this research.

Blast off!

Browse Other Projects on Experiment

Related Projects

Can Thailand be a hub for cultured protein production?

Demand for protein is growing in emerging economies fastest. Producing cultured protein (CP) is one approach...

Supporting Women's Economic Entrepreneurship in Abuja, Nigeria: An Economic Experiment.

About 41% of women in Nigeria are informal entrepreneurs. There are still about 17 million women who are...

How can white-rot fungi transform agro-industrial waste ?

France and Europe's first agricultural region, Nouvelle Aquitaine, generates an excessive flux of lignocellulosic...

Backer Badge Funded

An economics project funded by 68 people

Add a comment