Management → Properties › Biology › Diversity

Cover crops → Shannon index

The studies disagree

50 %

of 4 studies with a clear result report a significant increase

+7 %

typical change (3 studies with numbers)

studies · 6 findings

Count each study by

5 studies · 6 findings

What the studies show

2 of 4 studies report a significant increase (50 %, 95 % confidence interval 15–85 %).

By the direction of each study’s results, significant or not: 2 of 4 studies with a direction point up (50 %, 95 % confidence interval 15–85 %; sign test p = 1).

↑ 2 increase
↓ 1 decrease
⇅ 1 both
= 0 no effect
? 1 unclear

How large: typically +7 % (middle half -6 % to +9 %), from 3 studies with numbers
Basis: 5 studies, 6 findings; 0 entered by hand, 5 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…