CHEMICAL AND BIOCHEMICAL CHARACTERIZATION OF FOUR CROP RESIDUES AND FARMYARD MANURE

Farming techniques intensification in recent decades has raised many questions about soil fertility louse. Monoculture of cereals and intensive tillage have led to soil a rapid degradation of organic matter (OM), followed by compaction and reduction of the capacity of mineralization. Therefore a lost of productivity of farming systems was observed. The use of bioressources such as crop residues in soil fertilization is a technique for bio-remediation of degraded land. Four residus (Root and foliage) of sulla (Hedysarum cornarium L.), rapeseed (Brassica napus L.), faba bean (Vicia faba L. var. Minuta (Desf.ex.Alef.) Mansf)) and durum wheat (Triticum durum Desf.) were analyzed in comparison with cattle manure as control. All crop residues were taken in June 2009, from an experimental plot located in the experimental station of the Institut Nationl Agronomic of Tunisia INAT, at Mornag (Ben Arous/Tunisia). All plant residues were characterized by a high level of organic carbon (40-44%) while that of manure was 31.75%. In the other hand, the concentration in total nitrogen was very significant for manure (2.33%) compared to the other residues which did not exceed 1%. Consequently, the C/N ratio of manure was 13.62 while the average for the other residues was about 59.62. Residues Fabaceae (sulla, faba bean) were characterized by the highest cellulose rates, respectively 35.4 and 35.5% of the OM, compared to manure which was distinguished by the lowest rate (2.35%). The lignin content varied from 7 to 19 % in the residues and manure. The neutral detergent soluble fraction has an average of 26 % for Fabaceae and 24 % for wheat and rape, whereas it was 70 % for manure. Rapeseed residues were characterized by the index of biological stability ISB lowest of 0.11 % against a rate of 0.34 % for other residues.