Management › Fertilization › Type of fertilizer → Properties › Chemistry

Nitrogen fertilizer → Exchangeable/available potassium

A clear tendency, not consistent

71 %

of 7 studies with a clear result report a significant decrease

-23 %

typical change (6 studies with numbers)

studies · 10 findings

Count each study by

9 studies · 10 findings

What the studies show

5 of 7 studies report a significant decrease (71 %, 95 % confidence interval 36–92 %).

By the direction of each study’s results, significant or not: 2 of 9 studies with a direction point up (22 %, 95 % confidence interval 6–55 %; sign test p = 0.18).

↑ 2 increase
↓ 5 decrease
= 0 no effect
? 2 unclear

How large: typically -23 % (middle half -30 % to +17 %), from 6 studies with numbers
Basis: 9 studies, 10 findings; 0 entered by hand, 9 read by the library

Every study counts once, however many findings it reports: one with 40 sampling dates does not outvote ten others. A study with a significant increase and decrease (say at different depths) counts as "both". A first synthesis for orientation, not a substitute for a systematic review.

Where the studies are

goes up
stays the same
goes down
both ways

Through the soil profile

Each layer on its own: a study that reports the topsoil and the subsoil counts in both. Choose a layer to see what goes with it.

goes up
stays the same
goes down
both ways

What makes a difference

The conditions whose levels differ most clearly, each with the outcome that differs most between its levels of at least 10 study layers. Choose a layer in the profile to see them for that layer alone, or a level here to filter by it.

Testing every condition on every study layer…

Along the conditions

Testing every condition on every study layer…