ROLE DE LA COMPOSITION CHIMIQUE ET BIOCHIMIQUE DES RÉSIDUS DES CULTURES ET DE FUMIER DE FERME DANS LA DÉCOMPOSITION DES SOLS DÉGRADÉS SOUS CLIMAT ARIDE TUNISIEN

Abstract

Four crop residues (tops and roots) of sulla (Hedysarum coronarium L.), rapeseed (Brassica napus L.), faba bean [Vicia faba L. var. Minuta (Desf. Ex. Alef.) Mansf.] and durum wheat (Triticum durum Desf.) were chemically characterized and compared against the bovin manure used as a Control. Residues and manure were applied in a minimum amount restituted or supplied in unproductive year under natural conditions, on two different Tunisian soils: a clay loam soil from the Mornag Region belonging to the Ben Arous governorate in the north of Tunisia and a sandy soil from the region Benikhdech belonging to the governorate of Medenine in southern Tunisia. Aerobiosis incubation was realized at a constant temperature of 28°C during 90 days with a humidity adjusted to 2/3 of field capacity (Θcc). The analysis of the fibers showed that the Fabaceae residues (sulla and field bean) were characterized by the highest cellulose levels corresponding to 35.43% and35.50% of organic matter (OM); compared to manure that is distinguished by a lower rate of 2.35%. The lignin contents ranged from 7.03 to 19.30% in both residues and manure. The neutral detergent soluble fraction rate was clearly lower at a rate of 26.04% for the Fabaceae and 24.96% for wheat and rapeseed, against 70.10% for the manure. At the end of incubation, results showed that the amount of C-CO2 emitted from the clay soil was between 23.91 and 91.51 percentage of total organic carbon (TOC %) of organics products added. while the amount emitted from the sandy soil varied between 6.48 and 57.24% COT. The contribution of Fabaceae residues and manure has mineralized amounts of carbon significantly higher (P <0.05) than the control and significantly lower than both the mixture of soil-rape and the soil-wheat. The decomposition of the organic tested products (residues and farm manure) is closely related to their chemical and biochemical compounds. More organic residues are rich in it lignin, more their biodegradation is difficult.