Organic and inorganic fertilisers influence sweet potato (Ipomoea batatas L.) performances under BRIS, peat, silty clay and clay soil

NurulNahar, E.¹*, Engku Hasmah, E. A.², Erwan Shah, S.¹, Mohd Rani, A.³, Khairol, I.⁴ and Rosnani, A. G.⁵

Abstract
The sweet potato is one of the most economically important food crop and is recognised as a highly nutritious food. Sweet potatoes with purple flesh are richer in anthocyanins. This study evaluates the purple sweet potato, namely Kedudut 2, Kedudut 5 and Kedudut 6 varieties under silty clay, clay, BRIS and peat soil with three levels of organic fertiliser (0, 5 and 10 t/ha) and four levels of NPK 12:12:17 (0, 200, 400 and 600 kg/ha) on yields and total anthocyanin content (TAC). The results indicated that Kedudut 2 (560 mg/kg) produced the highest TAC compared to Kedudut 5 (276 mg/kg) and Kedudut 6 (252 mg/kg). Even though Kedudut 5 and Kedudut 6 had greater tuber yields, both had very low TAC, which may not be favourable to farmers and industries. Generally, Kedudut 2, Kedudut 5, and Kedudut 6 produced anthocyanin yields of 2.29 kg/ha, 1.24 kg/ha and 1.73 kg/ha, respectively. The tuber yields and anthocyanin yields in Bagan Datuk (silty clay) and Serdang (clay) were low. Soil with a high clay content is naturally compacted, which results in low fertiliser effectiveness and consequently reduces the tuber yield potential. It can be concluded that planting Kedudut 2 with a rate of 5 t/ha organic fertiliser and 200 kg/ha inorganic fertiliser (NPK 12:12:17) is recommended for sweet potato cultivation in Bachok, while 5 t/ha organic fertiliser and 600 kg/ha inorganic fertiliser are recommended in Pontian for maximum marketable yield and consequently maximise the anthocyanin yields.

Keywords: sweet potato, nutrient management, tuber yield, Ipomoea batatas, total anthocyanin content

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