RESPONSE OF TWO SWEET POTATO (Ipomoea batatas L.) VARIETIES TO DIFFERENT LAND PREPARATION METHODS AND FERTILIZER TYPES IN ABUJA, NIGERIA

Abstract

In sub-Saharan Africa, soil acidity, low fertility, and Cylas weevil infestation limit sweet potato output in degraded savanna soils. A three-year field experiment (2023–2025) was conducted in Abuja to evaluate the interactive effects of different cultivars, tillage practice, and fertilizer type on soil chemical properties, growth, root yield, and Cylas incidence. Treatments consisted of two cultivars (white-fleshed ‘TIS-87/0087’ and orange-fleshed ‘UMUSP3’), three tillage systems (flat, mound, and ridge), and four fertilizer treatments (control, green manure from Hyptis suaveolens, NPK 15:15:15, and poultry manure) arranged in a randomized complete block design with three replications. The experimental soil was strongly acidic (pH 4.5) with low organic carbon (0.31%), total nitrogen (0.011%), and available phosphorus (4.40 mg/kg. Significant three-way interactions influenced root yield. The white-fleshed cultivar under mound cultivation with NPK fertilizer produced the highest root yield (41.53 t/ha), representing a 279% increase over the control. Mound and ridge tillage improved soil pH (6.2–6.3), organic carbon, and effective cation exchange capacity relative to flat tillage. Poultry manure recorded the highest improvement in soil pH (6.5), organic carbon (1.63%), and ECEC (9.56 cmol/kg). Cylas incidence declined by 73–80%, with orange-fleshed plants showing the greatest suppression. Root yield was strongly correlated with fresh biomass (r = 0.98). Orange fleshed sweet potato achieved its highest yield (36.15 t/ha) under ridge cultivation with poultry manure. White-fleshed cultivars with mound + NPK maximized caloric yield, while orange-fleshed cultivars under ridge + poultry manure are suitable for biofortification.