Farmyard manure, plant based organic fertilisers, inorganic fertiliser - which sustains soil organic matter best?

Summary

Legume biomass or pulse meal may be considered as alternatives to farmyard manure (FYM) in organic farms with small scale animal husbandry or in stockless organic farms. From 1996 a field trial was established on a poor sandy soil to compare plant based organic fertilisers, FYM and inorganic fertilisers, each applied at 100 kg ha-1 N. Additionally, FYM was tested at a higher rate of 170 kg ha-1 N. Average soil organic carbon content in topsoil (Corg) of the last crop rotation period (2002-05) is compared to that in 1996. Corg remained at the same level of 0.78 % only with FYM, while plant based and inorganic fertiliser decreased carbon contents to 0.74 and 0.72 % Corg, respectively. The higher FYM rate increased Corg up to 0.84 %. Based on these results, for soil organic matter maintenance, plant based organic fertilisers can not be recommended generally.