INTERACTIVE EFFECTS OF TILLAGE AND FERTILIZER TYPE AND  APPLICATION ON CYLAS WEEVIL, SOIL PROPERTIES, AND ORANGE-FLESHED SWEET POTATO YIELD IN SOUTHERN GUINEA SAVANNA, NIGERIA.

N.E.,  Ilozobhie; P.O., Anyaegbu; D.O.,  Aihebhoria; U.A., Agha; A.A., Salawu; F .A. Awojemila; S. Aliyu; T.P.,  Chorio; M. Baba-Nitsa; H.C.L. Okosieme

N.E., Ilozobhie National Biosafety Management Agency (NBMA), Plot 3, Kalahari Close, OﬀICS Drive, Dakibiyu, Jabi, FCT- Abuja, Nigeria. Department of Agronomy, Faculty of Agriculture, University of Abuja, Nigeria
P.O., Anyaegbu Department of Agronomy, Faculty of Agriculture, University of Abuja, Nigeria.
D.O., Aihebhoria Agronomy Department, International Institute for Tropical Agriculture (IITA), Kubwa, FCTAbuja, Nigeria.
U.A., Agha National Biosafety Management Agency (NBMA), Plot 3, Kalahari Close, OﬀICS Drive, Dakibiyu, Jabi, FCT- Abuja, Nigeria. Department of Agronomy, Faculty of Agriculture, University of Abuja, Nigeria
A.A., Salawu Department of Agronomy, Faculty of Agriculture, University of Abuja, Nigeria.
F .A. Awojemila Federal Ministry of Environment, Plot 444, Aguyi Ironsi Street, Maitama, Abuja.
S. Aliyu Department of Agronomy, Faculty of Agriculture, University of Abuja, Nigeria.
T.P., Chorio National Biosafety Management Agency (NBMA), Plot 3, Kalahari Close, OﬀICS Drive, Dakibiyu, Jabi, FCT- Abuja, Nigeria.
M. Baba-Nitsa Department of Agronomy, Faculty of Agriculture, University of Abuja, Nigeria.
H.C.L. Okosieme National Biosafety Management Agency (NBMA), Plot 3, Kalahari Close, OﬀICS Drive, Dakibiyu, Jabi, FCT- Abuja, Nigeria.

Keywords: Cylas weevil, orange-ﬂeshed sweet potato, poultry manure, soil health, tillage

Abstract

Orange-ﬂeshed sweet potato (OFSP) is a biofortiﬁed crop crucial for addressing vitamin A deﬁciency in sub-Saharan Africa. Yet, yields remain constrained by poor soil fertility, suboptimal tillage, and pest pressure. This two-season (2024–2025) study evaluated the interactive eﬀects of three tillage systems (mounds, ridges, ﬂat beds) and four fertilizer treatments (NPK 20:10:10 at 200 kg/ha, poultry manure at 5 t/ha, urea at 200 kg/ha, and an unfertilized control) on Cylas weevil infestation, soil properties, and tuber yield of the OFSP variety ‘Mother’s Delight’ in Abuja, Nigeria. The experiment was a 3 × 4 factorial in a randomized complete block design with three replications, analysed using combined ANOVA (α = 0.05). NPK signiﬁcantly increased root yield (35.5 t/ha) relative to the control (21.7 t/ha; +63.6%) but also raised weevil infestation by 84.3%. Poultry manure produced a moderate yield (28.9 t/ha; +33.2%) with reduced infestation. Mound tillage gave the highest mean yield (29.4 t/ha), although infestation exceeded that of ﬂat beds. The mound × NPK combination achieved the maximum yield (38.5 t/ha; +91.5% over ﬂat/no fertilizer). Seasonal eﬀects were not signiﬁcant (p > 0.05), indicating stable treatment performance. Poultry manure improved soil pH (4.6–6.7), organic carbon, exchangeable K, and cation exchange capacity, whereas NPK reduced soil pH (to 4.4). Root yield correlated strongly with fresh biomass (r = 0.971) and weevil infestation (r = 0.877). Mound tillage with NPK maximises yield but increases pest risk and soil acidiﬁcation, underscoring the need for integrated nutrient and pest management.

INTERACTIVE EFFECTS OF TILLAGE AND FERTILIZER TYPE AND APPLICATION ON CYLAS WEEVIL, SOIL PROPERTIES, AND ORANGE-FLESHED SWEET POTATO YIELD IN SOUTHERN GUINEA SAVANNA, NIGERIA.

Abstract

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