>It is often said that organic fertilizers increase soil moisture holding
>capacity. I am looking for definitive information on this. Thanks
Rob,
I'll paraphrase from "MODERN CORN PRODUCTION" by Aldrich et al., 2nd ed., 1978:
Adding o.m. raises the water-holding capacity, but most of this is in the
form of water held too tightly to be of use to crop roots. Therefore, adding
o.m. to a sandy soil which doesn't clump or aggregate does little to raise
w.h.c. In loams, silt loams, and clays adding o.m. does increase aggregation
which causes a slight rise in w.h.c. by improving total pore space. A far
more important benefit of adding o.m. to soils, especially if slope is
involved, is the large increase in soil permeability (water infiltration)
which markedly reduces water runoff from rainfall.
David Leonard
Training and extension specialist in hillside-farming systems
Tucson, AZ