Organic farming foster agroecosystem functioning in temperate soils: evidence from residue decomposition process and soil fauna communities

DOMÍNGUEZ, A. AROLFO, R. BECKER, A; BEDANO J.C.

Coimbra

Congreso; XVI International Colloquium on Soil Zoology; 2012

In recent times, the spread of croplands has been associated with an unprecedented level of environmental degradation. Organic farming has been recognized as a potential solution. However, evidence from field conditions about benefits of organic agriculture on soil ecosystem functioning are scarce. The aims of this contribution were to analyze the effect of extensive organic versus conventional farming on litter decomposition and to analyze how it is affected by soil fauna abundance. Our general hypothesis is that decomposition is driven by the interaction of management, decomposer fauna, residue type and time. Three managements were studied: (1) organic farming with conventional tillage, (2) conventional farming with agrochemical use under conventional tillage and (3) under no‐tillage. Natural grasslands were considered as reference situation. Decomposition was determined in field conditions by measuring weight loss in vegetal residues inside mesh bags. The local and also an allochthonous residue were considered. Contribution of soil mesofauna and macrofauna to decomposition was evaluated both by different mesh sizes and by assessing faunal abundances in soil. Residue decomposition and soil fauna abundances were always significantly higher in organic than in conventional farming. Both managements involving conventional tillage revealed significantly higher decomposition than no‐tillage management, but decomposition was always higher in organic farming. Macrofauna has a strong influence in residue decomposition in a first stage of the process, when residues are large. In a second stage mesofauna would be responsible of the physical degradation of the residues. Given that the organic management do not include manure use and involve high tillage intensity and low crop diversity, differing from intensive organic management, here we showed that the non‐use of agrochemicals produced substantial changes in soil fauna abundances, and that these changes produced differences in the decomposition process. Benefits of organic farming on soil fauna has been previously stated, however this study provides original, field conditions evidence, that extensive organic farming enhances decomposition process and therefore it is expected to improve soil ecosystem functioning as a whole.