Influence of Inorganic Fertiliser Rates on Growth and Yield of Tiger Nut (Cyperus esculentus L.) in Two Agro-Ecological Zones

Abstract

Tiger nut (Cyperus esculentus L.) is an underutilised crop with significant economic potential, yet optimal fertiliser requirements for agronomic performance remain poorly defined across different agro-ecological zones. This study evaluated the influence of inorganic fertiliser rates on the growth and yield of tiger nut in two agro-ecological zones in Nigeria. Field experiments were conducted at Igboora and Ogbomoso using a randomised complete block design with three replications. Treatments comprised urea at 0, 30, 45, 60, and 75 kg N/ha; single superphosphate at 0, 30, 45, 60, and 75 kg P₂O₅/ha; and muriate of potash at 0, 30, 60, 90, and 120 kg K₂O/ha. Data on plant height, leaf number and tiller production were collected fortnightly, while tuber characteristics were assessed at harvest. The data were subjected to analysis of variance, with means separated using Duncan’s multiple range test at p ≤ 0.05. Fertiliser rates affected several growth and tuber characteristics at both locations, although nitrogen and potassium did not significantly affect tuber number. Plant height increased progressively with fertiliser rates up to the highest-performing tested levels, with 60 kg N/ha (80.73 cm) and 60 kg K₂O/ha (82.42 cm) producing the tallest plants at Ogbomoso. Leaf production was highest at 75 kg N/ha (67.03 leaves) and 75 kg P₂O₅/ha (77.43 leaves) at Igboora, while tiller production peaked at 60 kg N/ha (6.47 tillers) and 90 kg K₂O/ha (8.67 tillers) at Igboora. Tuber weight responses showed location-specific optimal rates: 45 kg N/ha produced the heaviest tubers at both locations (24.04 g at Ogbomoso; 36.29 g at Igboora), while the phosphorus rates associated with the highest tuber weights were 45 kg P₂O₅/ha at Ogbomoso (29.99 g) and 75 kg P₂O₅/ha at Igboora (46.06 g). The potassium rates associated with the highest tuber weight were 60 kg K₂O/ha at Ogbomoso (26.65 g) and 90 kg K₂O/ha at Igboora (39.53 g). Igboora generally recorded higher tuber weights, alongside higher initial soil organic carbon, nitrogen and available phosphorus levels. The results indicate location- and trait-specific responses to fertiliser application. These findings may inform the further evaluation of site-specific fertiliser recommendations for tiger nut production.