Background: In Morocco, phosphate processing generates large quantities of sludge which amass, form fillings, reduce arable land and distort the landscape. Phosphate wash sludge is rich in mineral elements. In order to recover some of these mineral elements including phosphorus, we considered using this sludge in a nursery as a substrate. Objective: The aim of the study was to check the effect of solid phosphate sludge amendment on some of the main soil-borne pathogens: Verticillium dahliae Kleb. and Rhizoctonia solani Kühn. Materials and Methods: The pathogens have been isolated and identified in the laboratory of Plant Pathology and Postharvest Quality of INRA-Kenitra. Phosphate wash sludge used was originated from the Khouribga phosphate treatment sludge disposal site. Different concentrations of phosphate sludge (0, 10, 30, 50, and 100 g/l) were tested on a PDA-based medium, in three replicates. The inhibitory effects on mycelial growth were measured and compared with those on the soil used by nurseries (Maamora forest soil). Petri dishes with PDA alone were used as control. The same concentrations (10, 30, 50 and 100 g/kg) were tested in vivo on two varieties of tomato and on Faba Faba bean for Verticillium dahliae and Rhizoctonia solani, respectively. Results: The results of this study showed that there was significant growth inhibition at different concentrations of solid Phosphate sludge amendments in vitro. The highest inhibition percentage was observed at 100 g/l of phosphate sludge amendments with 42% and 75% for Verticillium dahliae and Rhizoctonia solani. The high concentrations of phosphate sludge have shown lower disease severity of Verticillium dahliae on the tomato plants and a disease index of Rhizoctonia solani on the Faba bean plants. Conclusion: Based on these results, we can recommend that solid phosphate sludge can be used or mixed with other substrates in nurseries.

Phosphorus deficiency is a major limiting factor in horticultural production. One potential solution can be restoring soil phosphorus from mineral resources, such as solid phosphate sludge (SPS) generated from phosphate treatment processes at mining sites in agriculture. This study explores the possibility of using this sludge in nurseries to produce fruit and forest plants. We tested six mixtures of SPS with the sandy soil of the Maamora forest on ten plant species. In the second experiment, we tested the same mixtures with sea sand. In addition, one concentration of four composts based on phosphate sludge was also tested on two citrus rootstocks and carob. The first experiment’s results showed significantly higher growth with the control mixture for pomegranate, acacia, and C. volkameriana plants. The relative growth was higher at SPS concentrations of 20% to 30% for the other plant species, although there was no significant difference between treatments. The estimations of AUGPC (area under the growth progress curve) showed no significant difference in most species. In the second experiment, the relative growth in the M4 (30% of SPS + 70% of sand) mixture was higher, and the AUGCP showed a significant difference compared to the M1 control mixture. The application of solid phosphate sludge positively affects and improves the growth of fruit and forest trees in the nurseries, especially when the concentration is between 20 and 30%. For this purpose, the phosphate sludge could have great potential to be used in nurseries and create a favourable soil condition as a cultivation substrate.

Grapevine (Vitis spp.) is a major crop, which has a great socio-economic importance worldwide, nevertheless it remains susceptible to several diseases. The International Organization of Vine and Wi...