Management › Fertilization › Type of fertilizer → Properties › Biology › Diversity

Nitrogen fertilizer → Species richness

The studies disagree

33 %

of 12 studies with a clear result report a significant increase

+3 %

typical change (4 studies with numbers)

studies · 14 findings

Count each study by

14 studies · 14 findings

What the studies show

4 of 12 studies report a significant increase (33 %, 95 % confidence interval 14–61 %).

By the direction of each study’s results, significant or not: 6 of 11 studies with a direction point up (55 %, 95 % confidence interval 28–79 %; sign test p = 1).

↑ 4 increase
↓ 4 decrease
= 4 no effect
? 2 unclear

How large: typically +3 % (middle half -4 % to +5 %), from 4 studies with numbers
Basis: 14 studies, 14 findings; 0 entered by hand, 14 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, species richness goes up in 14 % of the studies under nitrogen fertilizer, stays the same in 57 % and goes down in 29 %.

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…