Influence of Fertiliser Packages on Yield and Quality of Lembayung Sweet Potato Grown in BRIS Soil

Abstract

Lembayung is a purple-fleshed sweet potato (Ipomoea batatas L.) variety with potential for fresh consumption and food processing. However, its production on BRIS (Beach Ridges Interspersed with Swales) soils is constrained by low soil fertility, poor nutrient-retention capacity, and rapid nutrient leaching. Appropriate fertiliser management is therefore required to improve crop performance and storage root quality under these marginal soil conditions. This study evaluated the effects of different fertiliser packages on the growth, yield, tuber quality, and sensory attributes of the purple-fleshed sweet potato (Ipomoea batatas L.) variety Lembayung cultivated under nutrient-deficient BRIS (Beach Ridges Interspersed with Swales) soil conditions. The field experiment was conducted at the Malaysian Agricultural Research and Development Institute (MARDI) Bachok Research Station, Kelantan, Malaysia, using a Randomised Complete Block Design with three replications. Eight fertiliser treatments comprising conventional NPK fertiliser, specially formulated fertiliser, and two biofertiliser formulations were evaluated. Growth performance, storage root weight, total soluble solids (TSS), total sugar content, and sensory attributes were assessed at harvest. The results showed that fertiliser package composition significantly influenced crop performance and tuber quality. T7 (900 kg ha⁻¹ NPK 13:13:21 + Formulated fertiliser) produced the highest plant weight (1106.7 g plant⁻¹) and total sugar content (5.69 g 100 g⁻¹), indicating enhanced vegetative growth and carbohydrate accumulation under higher nutrient availability. However, the highest storage root weight was recorded in T4 (special formulation fertiliser), reaching 937.4 g per tuber, suggesting that a balanced nutrient supply was more effective in promoting storage root bulking. Although TSS did not differ significantly among treatments, T2 and T3 recorded the highest value of 12.2 °Brix. Sensory evaluation showed that T2 (600 kg ha⁻¹ NPK 13:13:21 + Formulated fertiliser) achieved the highest scores for aroma, texture, taste, sweetness, and overall acceptability. The findings demonstrate that moderate fertiliser application combined with biofertiliser supplementation can provide a favourable balance between crop productivity, tuber quality, and consumer acceptance. Overall, integrated nutrient management using biofertilisers and specialised fertiliser formulations shows strong potential for improving nutrient use efficiency and supporting the sustainable production of high-quality Lembayung sweet potato under marginal BRIS soil conditions.