Nutrient enhancement potentials of moringa (Moringa oleifera), neem (Azadirachta indica), and pawpaw (Carica papaya) fortified composts in contaminated soils

This study assessed the nutrient enhancement potentials of moringa ( Moringa oleifera ), neem ( Azadirachta indica ), and pawpaw ( Carica papaya ) fortified composts in contaminated soils. The composts were formulated from poultry manure; leaves of moringa, neem, and pawpaw; and sawdust for a period of 8 weeks. Contaminated soil samples were collected from a dumpsite in Abeokuta, Ogun State. The contaminated soils were treated with the stabilized composts for a period of 4 weeks. Castor oil plants were introduced to assess the nutrient quality of the composts. Soil and compost parameters (pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), C/N ratio, P, K, Na, Mg, and Ca) were determined using the standard procedures. Data collected were evaluated for simple descriptive and inferential statistics. Results showed non-significance ( p > 0.05) of C/N ratios that ranged between 12.75 ± 2.43 and 12.96 ± 1.49. The pH values of moringa- and neem-fortified composts were slightly acidic, while the pawpaw-formulated compost was slightly alkaline. The levels of TN and OC were three times higher in moringa- and pawpaw-fortified composts than in the neem compost. Introduction of the composts to the contaminated soils decreased the soil pH but increased the nutrient quality parameters such as TN (33–50%), OC (56–77%), P (7–20%), Na (89–91%), K (12–25%), and Mg (10–13%). The three compost types increased the physiological properties of the castor oil plants. The study indicated the promising potentials of the three composts for nutrient enhancement of soil.