Humic balance of soils under intensive farming: the case of soils irrigated perimeter of Doukkala in Morocco [Bilan humique des sols sous intensification agricole: Cas des sols du périmetre irrigué des Doukkala au Maroc]

In the irrigated perimeter of doukkala in morocco,soils are subjugated to an agricultural intensification and a mineral fertilization coupled to a non restitution of crop residues; which contributes to a depletion of soil organic matter. this study aims to assess the fertilizer value of seven crop residues and their biochemical composition and to determine the overall soil humic balance of the irrigated perimeter of doukkala. the results show that the crop residues are rich in major elements. the nitrogen is especially brought by soybean residue (37,37 kg/ha) followed by sugar beet (22,91 kg/ha). for chemical elements,soybean cultivation is the one that brings the most with amounts of 7,76; 11,96; 23,52 and 67,66 kg/ha,respectively for p,k,mg and ca. sugar beet residues provide the highest quantities of na (37,07 kg/ha). the crop residues are rich in cellulose,hemicellulose and soluble fractions and low in lignin. the wheat residues have the highest rate of cellulose (40,63%) followed by sorghum and maize with 30,37% and 28,53%,respectively. the hemicellulose rate varies between 10,02% (tomato residues) and 23,49% (wheat residues). the lignin rate varies between 4,61% (tomato residue) and 9,55% (sorghum residues). tomato residues have the highest soluble fraction (65,30%) and wheat residues have the lowest one (29,78%). an imbalance of humic level was observed for all soils studied (vertisol,fersiallitic,changed little and isohumic). this imbalance is due to the strong mineralizing power of these soils,particularly the fersiallitic one and the low return of crop residues.