Weird soil test Phosphorus results

[Rosie318]

I have a 37ac field that P levels in 2015 were fairly high (average P was 50 and max was 114) and now in 2020 it has lowered significantly (average P is 35 and max is 98). I haven’t changed my fertility practices at all and the rainfall was not above average in 2020. I have no clue what could have caused it to drop so drastically. Please help!!

 

[Almost Eden]

Is that really a drastic drop? It doesn't seem that way to me over a five-year spread if you're actively using those fields. Do your plants show signs of phosphorus deficiency? I guess it's possible that one of your tests was incorrect, but that doesn't seem like a drastic change to me. Some plants take up a lot of phosphorus. What were you growing?

 

[Rosie318]

Is that really a drastic drop? It doesn't seem that way to me over a five-year spread if you're actively using those fields. Do your plants show signs of phosphorus deficiency? I guess it's possible that one of your tests was incorrect, but that doesn't seem like a drastic change to me. Some plants take up a lot of phosphorus. What were you growing?

I switch the field every season from corn to beans. 2016 was beans and 2020 was corn. I always put on removal every season and all of my other fields are consistent with the 2016 test levels which is why it seems like a major drop to me.

 

[The Big Cowhuna]

Although beans aren't heavy feeders, corn will take up the phosphorus. However, that does seem like a big dip if your remaining fields aren't showing similar numbers and they were treated the same. How was your plant vigor and yield in 2020? Could this one test be off? It's important to take the sample from the right depth. You probably already knew that though, and if you took the sample, I don't doubt you did it correctly. Adding usable phosphorus to the soil is an easy fix at least. Usually it's erosion that leeches phosphorus, but you've already said that it didn't rain more than usual. I'm at a loss.

 

[Henderson]

Have you asked your local extension office? I say that because they might know something that's happened local to your area that we don't. I agree with you that it's unusual and I hope you get to the bottom of it. I can't come up with a reason beyond wind, rain, and erosion.