Determination of harvesting time and quality of kesum (Persicaria minor) in different cultivation systems

Various planting techniques and systems have been studied and practised to produce high quality and yield crops. Among the cultivation systems that are widely used in agriculture are open-field planting, fertigation, and hydroponic systems. Harvesting at the optimal maturity stage is a vital approach to obtaining crops with high quality and nutrient content. Kesum (Persicaria minor) is an aromatic herb that is very native to Southeast Asian countries and is synonymous with Asian cuisine because of its ability to enhance flavour in dishes and is also used as a traditional medicine. This study was conducted to evaluate the optimal harvesting time and quality of kesum in different cultivation systems, which were open field planting, fertigation, and hydroponic systems (controlled and semicontrolled environment). In an open field and fertigation system, kesum were planted on soil but with different fertilizer rates and applications. While for the hydroponic system, kesum were planted in 156 cm × 63 cm polystyrene boxes filled with water in a controlled and semi-controlled environment (closed and opened rain shelter structure, respectively). Samples were harvested at different maturity stages 8, 12, 16, and 18 weeks after planting. The postharvest quality of the samples was measured at every harvesting time. The plant fresh weight was found to increase at every harvesting week in all cultivation systems, whereas optimal weight was reached at week 16 after planting (296.18 g in controlled hydroponic, 509.45 g in semi-controlled hydroponic, 639.20 g in fertigation and 751.5 g in open field). Meanwhile, the total phenolic content (TPC) was found to increase to optimal content at week 12 for kesum planted in semi-controlled hydroponic (183.47 mg/g), fertigation (333.30 mg/g) and open field (435.32 mg/g) system but at week 16 in controlled hydroponic (207.43 mg/g). Ascorbic acid and water content showed a decreasing trend throughout the harvesting weeks, in contrast to the total soluble solids content, total titratable acidity, and pH value, which increased in all four cultivation systems. Based on the data obtained, the optimal harvesting time for kesum planted in either fertigation, conventional or hydroponic systems is at week 16 after planting for obtaining kesum with high yield and quality.