Effect of Crop Residues Management on Soil Fertility and Sugar Beet Productivity in Western Morocco

The competitiveness of sugar beet in the Doukkala irrigated perimeter makes this crop the main one compared to wheat, vegetables and forage. However, the dominance of small plots drives farmers to practice 2 to 3 years rotation of sugar beet. This work, carried out on contrasting and representative soils between 2012 and 2019, aims to study the effects of sugar beet residues incorporation on the soil organic matter, soil properties, and sugar beet root yield and sugar content under reel field conditions and actual rotation system. The results showed that the rate of soil organic matter (SOM) increased by + 28.8% during eight agricultural seasons. Plots that never received crops residues experienced an average decrease in SOM rate of -19%. The maximum average increase in the SOM rate of + 194% was observed at the level of the plots, where sugar beet residues were incorporated six times. This variation in SOM is more marked in coarse-textured soils. The variations of Mg, K, P, Ca, Zn, B, CaCO3, soil pH, CEC are positively correlated with statistical significance with SOM variation. The multiple linear regression model for predicting the variation in SOM content, depending on soil texture, initial SOM content and number of residue incorporations, with (R2 = 0.81, RMSE=26.15) shows that this variation is significantly favored by coarse soil elements and the number of residues incorporation and that it is unfavorable in soils with a dominant fine texture and initially rich in organic matter. Yield and sugar content were improved by 31% (67,45 Mg. ha-1 in 2012 and 86,38 Mg. ha-1 in 2019) for root yield and by 4% (16.68% in 2012 and 17,37% in 2019) for sugar content in plots with six residues incorporations. Data from this study suggest that the use of sugar beet residues is benefical for improving soil properties and thus increasing soil organic status and crop performances.