Management › Fertilization › Type of fertilizer → Properties › Biology

Nitrogen fertilizer → Yield

A clear tendency, not consistent

69 %

of 51 studies with a clear result report a significant increase

+38 %

typical change (39 studies with numbers)

studies · 83 findings

Count each study by

58 studies · 83 findings

What the studies show

35 of 51 studies report a significant increase (69 %, 95 % confidence interval 55–80 %).

By the direction of each study’s results, significant or not: 44 of 52 studies with a direction point up (85 %, 95 % confidence interval 72–92 %; sign test p < 0.001).

↑ 35 increase
↓ 7 decrease
⇅ 1 both
= 8 no effect
? 7 unclear

How large: typically +38 % (middle half +6 % to +60 %), from 39 studies with numbers
Basis: 58 studies, 83 findings; 0 entered by hand, 58 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 69 % of the studies under nitrogen fertilizer, stays the same in 16 % and goes down in 14 %.

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…