Management › Tillage → Properties › Chemistry › Carbon compounds › Soil organic matter
A clear tendency, not consistent
73 %
of 86 studies with a clear result report a significant decrease
-32 %
typical change (57 studies with numbers)
94
studies · 168 findings
What the studies show
63 of 86 studies report a significant decrease (73 %, 95 % confidence interval 63–81 %).
By the direction of each study’s results, significant or not: 4 of 73 studies with a direction point up (5 %, 95 % confidence interval 2–13 %; sign test p < 0.001).
10 findings on relative measures (shares, stratification ratios, values per unit) or on fractions and other compartments are not counted in this answer.
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.
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.
In the top 10 cm, particulate organic carbon goes up in 2 % of the studies under conventional tillage, stays the same in 5 % and goes down in 92 %.
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…
Testing every condition on every study layer…
