Management › Tillage → Properties › Physics

Conservation tillage → Bulk density

The studies disagree

44 %

of 220 studies with a clear result report a significant increase

+3 %

typical change (132 studies with numbers)

231

studies · 360 findings

Count each study by

231 studies · 360 findings

What the studies show

97 of 220 studies report a significant increase (44 %, 95 % confidence interval 38–51 %).

By the direction of each study’s results, significant or not: 113 of 184 studies with a direction point up (61 %, 95 % confidence interval 54–68 %; sign test p = 0.002).

↑ 97 increase
↓ 56 decrease
⇅ 24 both
= 43 no effect
? 11 unclear

How large: typically +3 % (middle half -3 % to +8 %), from 132 studies with numbers
Basis: 231 studies, 360 findings; 35 entered by hand, 196 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, bulk density goes up in 37 % of the studies under conservation tillage, stays the same in 22 % and goes down in 33 %.

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…