Hello,
My recent paper shows that organic management compared to conventional/chemical farming provides preserves the endemic earthworms and soil organic matter whilst increasing soil water storage by +28.7% on average (http://www.mdpi.com/2571-8789/2/2/33). If the soil bulk density is 1.0 g/cm3, this is directly relates to having the equivalent of 28.7% extra rainfall. These dozen or so studies were mainly from Europe and Asia.
In Africa, for example, Lal (1974) made comparisons in similar situations in Nigeria, where eudrilid earthworms are common, and found about 24 times the numbers of worm casts and infiltration rates almost doubled under zero-till plots. Also in Nigeria, Wilkinson (1975) showed a positive relationship between infiltration rates and earthworms in fallow, and Aina (1984) confirmed a 2.5 times increase in infiltrability due to earthworms in forest soils.
My recommendation would be to vermi-compost all organic wastes for return to the fields, to maintain leguminous cover-crops to fix nitrogen & to protect the soil from erosion, and to use non-chemical weed & pest control to preserve the worms.
Ref - Blakemore, R.J. (2018). Critical Decline of Earthworms from Organic Origins under Intensive, Humic SOM-Depleting Agriculture. Soil Systems. 2(2): 33. [http://www.mdpi.com/2571-8789/2/2/33].
Blog - https://vermecology.wordpress.com/2018/05/27/wormageddon-destruction-in….
Dr. Rob Blakemore