Fractions of particulate organic matter in soils depending upon farmyard manure and mineral fertilization

Summary

In a long-term fertilization trial particulate organic matter (POM) was investigated after 20 years of farmyard manure vs. mineral fertilization at different levels with the method of Meijboom et al. (1995). The organic matter was separated with sodium polytungstate (Magid et al., 1996; Six et al., 1999) into a light (p <1.13 g cm-3), medium (1.13-1.37 g cm-3) and heavy (p >1.37 g cm-3) fraction.
The organically fertilized plots had lower contents of the light fraction (0.73 - 0.78 g kg-1 dry matter on average of all fields) compared to the mineral treatment (0.95 g kg-1 TS). This gives a hint that organic residues are decomposed faster in the manure fertilized soil, according to the higher biological activity found earlier in this treatment. The heavy fraction of POM showed the same distribution as the Corg values being higher with manure fertilization (10.7 - 11.5 g kg-1 dm) than with mineral fertilizer (7.8 g kg-1).