Management › Tillage → Properties › Physics

Conventional tillage → Bulk density

The studies disagree

40 %

of 198 studies with a clear result report a significant decrease

-2 %

typical change (124 studies with numbers)

211

studies · 322 findings

Count each study by

211 studies · 322 findings

What the studies show

79 of 198 studies report a significant decrease (40 %, 95 % confidence interval 33–47 %).

By the direction of each study’s results, significant or not: 72 of 166 studies with a direction point up (43 %, 95 % confidence interval 36–51 %; sign test p = 0.103).

↑ 59 increase
↓ 79 decrease
⇅ 22 both
= 38 no effect
? 13 unclear

How large: typically -2 % (middle half -7 % to +3 %), from 124 studies with numbers
Basis: 211 studies, 322 findings; 30 entered by hand, 181 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 conventional tillage, stays the same in 21 % and goes down in 36 %.

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…