Management › Fertilization → Properties › Biology

Organic fertilizer → Yield

A clear tendency, not consistent

67 %

of 83 studies with a clear result report a significant increase

+19 %

typical change (59 studies with numbers)

studies · 156 findings

Count each study by

91 studies · 156 findings

What the studies show

56 of 83 studies report a significant increase (67 %, 95 % confidence interval 57–77 %).

By the direction of each study’s results, significant or not: 60 of 71 studies with a direction point up (85 %, 95 % confidence interval 74–91 %; sign test p < 0.001).

↑ 56 increase
↓ 8 decrease
⇅ 4 both
= 15 no effect
? 8 unclear

How large: typically +19 % (middle half +4 % to +55 %), from 59 studies with numbers
Basis: 91 studies, 156 findings; 0 entered by hand, 91 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 layers of unstated depth, yield goes up in 68 % of the studies under organic fertilizer, stays the same in 17 % and goes down in 10 %.

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…