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Manure → Exchangeable/available potassium

Consistent result

83 %

of 24 studies with a clear result report a significant increase

+72 %

typical change (17 studies with numbers)

studies · 27 findings

Count each study by

25 studies · 27 findings

What the studies show

20 of 24 studies report a significant increase (83 %, 95 % confidence interval 64–93 %).

By the direction of each study’s results, significant or not: 21 of 24 studies with a direction point up (88 %, 95 % confidence interval 69–96 %; sign test p < 0.001).

↑ 20 increase
↓ 3 decrease
= 1 no effect
? 1 unclear

How large: typically +72 % (middle half +23 % to +108 %), from 17 studies with numbers
Basis: 25 studies, 27 findings; 1 entered by hand, 24 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

In the top 10 cm, exchangeable/available potassium goes up in 100 % of the studies under manure, stays the same in 0 % and goes down in 0 %.

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…