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Several trucks of FS were poured into a sand filter drying bed in Nungua, Accra (5 ° 33′N). The sludge was dewatered and dried under equatorial sunlight for 2–3 weeks. The DFS was processed as follows: (1) DFS irradiated by gamma radiation (20 kGy for 48 h), (2) DFS composted alone, and (3) DFS co-composted with sawdust (SD) (1:3). Composting time was allowed to continue until the compost temperature dropped to ambient temperature, which took 60 days for DFS composting and 100 days for DFS with SD co-composting. After composting, the mature composts were ground and enriched with NH4NO3 to achieve 3% N content and mixed with gamma-radiated starch or pre-gelatinized starch (3%), and finally pelletized. The pellets were sun-dried and nutrient contents were analyzed (Table 1). The formulations and procedure are described in detail by Nikiema et al. (2013).

Table 1

Chemical properties of ECO-F (agro-industrial waste compost), IN-F (mineral fertilizer as NH4NO3), I-DFS-IR (gamma-irradiated DFS, not composted, pelletized with gamma-irradiated cassava starch), EC-DFS-IR/PG (N-enriched DFS compost pelletized either with irradiated cassava starch or with pre-gelatinized cassava starch), and EC-SDFS-PG (N-enriched DFS + SD compost pelletized with pre-gelatinized cassava starch)

 Different types of fertilizers
ParametersECO-FIN-FI-DFS-IREC-DFS-IR/PGEC-SDFS-PG
Total-N (%) 3.2 35 2.8 2.6 2.5–3 
NH4 (%) NK 17.5 1.02 0.88 0.05 
NO3 (%) NK 17.5 0.48 0.61 0.03 
Available-P (%) 3.3 (P2O5NK 0.07 0.02 0.01 
Total-P (%) 1.45 NK 2.74 1.38 0.33 
Total-K (%) 3.2 NK 0.46 0.68 0.25 
Organic C (%) 30.6 70.2 65.1 71.3 
pH 7.00 NK 7.34 6.62 8.66 
EC (μS/cm) NK NK 1,690 1,100 3,050 
 Different types of fertilizers
ParametersECO-FIN-FI-DFS-IREC-DFS-IR/PGEC-SDFS-PG
Total-N (%) 3.2 35 2.8 2.6 2.5–3 
NH4 (%) NK 17.5 1.02 0.88 0.05 
NO3 (%) NK 17.5 0.48 0.61 0.03 
Available-P (%) 3.3 (P2O5NK 0.07 0.02 0.01 
Total-P (%) 1.45 NK 2.74 1.38 0.33 
Total-K (%) 3.2 NK 0.46 0.68 0.25 
Organic C (%) 30.6 70.2 65.1 71.3 
pH 7.00 NK 7.34 6.62 8.66 
EC (μS/cm) NK NK 1,690 1,100 3,050 

NK, not known.

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