Assessment of the synergistic effectiveness of aqueous extract of plants (Sarcocephalus latifolius, Curcuma longa, Azadiractha indica) and soil solarization on some growth, yield and disease parameters of onion (Allium cepa L.) in the field (Far-North Cameroon)

Abstract

To increase onion yield in the Far North of Cameroon using environmentally friendly methods, plant responses to solarization and field application with aqueous neem seeds extracts, Sarcocephalus latifolius roots and Curcuma longa rhizomes extracts were analyzed during the 2022 and 2023 cropping seasons. The experimental design was a completely randomized block with 9 treatments, each of which was triplicated: negative control (T-); S. latifolius extract (Sa); solarization (S); C. longa rhizome extract (C); positive control (T+); solarization + S. latifolius (S+Sa); aqueous neem seeds extract (N), solarization + C. longa (S+C); solarization + aqueous neem seeds extract (S+N). Investigations consisted of evaluating their effectiveness, alone or combined with solarization on agronomic and phytopathological parameters of onion (Allium cepa) of the Goudami variety. Obtained results revealed that treatment solarization + aqueous neem seeds extract (S+N) stimulated better leaf formation, leaf elongation, and enhanced plant collar diameter and significantly (p<0.0001) increased yield compared to other treatments during the first cropping season, although it was 2.71 t/ha lower than that of the chemical treatment in the second year. As for phytopathological parameters, biological treatments (solarization + neem seeds extract, S. latifolius extract, and solely neem seeds extract) significantly reduced (p<0.0001) the incidence of onion pathogen attacks compared to the negative control. Single or combined treatments with C. longa extracts resulted in a reduction in development and/or inhibition of diseases on infested plants. As the outcomes, treatment solarization + aqueous neem seeds extract could be recommended for sustainable onion (A. cepa) production in the Far North of Cameroon, if pollution risks due to chemical inputs are to be alleviated. Key words: Solarization, plant extracts, onion, growth, yield, disease management, sustainable agriculture. phosphorus, potassium, calcium, magnesium.