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Occurrence of Sclerotium rolfsii Inducing Sugar Beet Root Rot and its Sustainable Management by Acting on Soil Fertility in Western Morocco

Rerhou Badr, Mosseddaq Fatema, Ezzahiri Brahim, Moughli Lhoussaine, Mokrini Fouad, Bel-Lahbib Sanae, Namr Khalid Ibno

Journal of Ecological Engineering

2023

Vol. 24, nr 4

54--70

In Morocco, and particularly in the Doukkala irrigated perimeter, sugar beet rot caused by Sclerotium rolfsii is a major limiting factor for the productivity of this crop. The objective of this study was to identify the relationship between the frequency of Sclerotium rolfsii infestation and the quantity of viable sclerotia in the soil on the one hand, and with the different physicochemical parameters of the soil in cropped sugar beet fields on the other hand. In total, 1794 soil samples were collected during a four years period in the whole irrigated perimeter. These samples were analyzed for their sclerotial content. In addition, laboratory analysis of physico-chemical parameters was performed for 94 sugar beet fields in 2019. The study showed that the relative frequency of infestation by Sclerotium rolfsii and the number of viable sclerotia oscillate inversely and present a relative frequency of 45.7, 57.3, 42.3 and 49.5% for 2016, 2017, 2018, and 2019, respectively, and a number of sclerotia of 2.01, 1.65, 2.11 and 1.25 in 250 g of soil for 2016, 2017, 2018 and 2019, respectively. The study showed that the number of viable sclerotia was positively correlated with clay and silt content, soil pH, Mg, K, Fe, Cu, and Mn and negatively correlated with sand, SOM, EC, CaCO3, Zn, B, Ca, NH4 and NO3 contents. The observed decrease in viable sclerotia between 2016 and 2019 can be attributed to the decrease of Fe and Cu in the soil. It is possible that SOM intervenes with its humified fraction in the neutralization of the redox potential of Feand Cu which are involved in the production of sclerotia under oxidative stress. The good control of fertilization, especially organic, allows limiting the production of sclerotia of Sclerotium rolfsii. Data analysis allowed obtaining a significant prediction model of the number of viable sclerotia in the soil according to the physicochemical soil parameters with (R2 = 0.95 at P<0.0001) for only infested fields and (R2 = 0.87 at P<0.0001) for all the fields.

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

Rerhou Badr, Mosseddaq Fatema, Moughli Lhoussaine, Ezzahiri Brahim, Mokrini Fouad, Bel-Lahbib Sanae, Namr Khalid Ibno

Ecological Engineering & Environmental Technology

2022

Vol. 23, iss. 5

256--271

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.