Management › Tillage › Tillage system → Properties › Physics

Zero tillage → Bulk density

The studies disagree

47 %

of 188 studies with a clear result report a significant increase

+4 %

typical change (119 studies with numbers)

199

studies · 299 findings

Count each study by

199 studies · 299 findings

What the studies show

88 of 188 studies report a significant increase (47 %, 95 % confidence interval 40–54 %).

By the direction of each study’s results, significant or not: 105 of 160 studies with a direction point up (66 %, 95 % confidence interval 58–73 %; sign test p < 0.001).

↑ 88 increase
↓ 44 decrease
⇅ 20 both
= 36 no effect
? 11 unclear

How large: typically +4 % (middle half -2 % to +9 %), from 119 studies with numbers
Basis: 199 studies, 299 findings; 24 entered by hand, 175 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 42 % of the studies under zero tillage, stays the same in 19 % and goes down in 32 %.

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…