Effects of Organic, Inorganic and Compound Fertilizer on Growth and Quality of Water Spinach (Ipomoea aquatica) under Polyculture Condition

Fertilizer management and soil nutrient profile affect plant growth. However, each plant species is unique and may require different nutrients for best growth. This study aimed to investigate the effect of organic fertilizer, inorganic fertilizer and compound fertilizer applications on the plant growth of water spinach (Ipomoea aquatic) under polyculture system. In the present study, water spinach (Ipomoea aquatica) were grown under a polyculture planting condition with okra (Abelmoschus esculentus) and yardlong bean (Vigna unguiculata subsp. sesquipedalis), and treated with five different types of fertilizer regime (T1: without fertilizer, T2: organic fertilizer, T3: inorganic fertilizer, T4: compound fertilizer and T5: organic + inorganic fertilizer). For each treatment group, a total amount of 9 g m-2 of nitrogen, phosphorus and potassium each were applied throughout the experiment. The present results showed that under polyculture condition, no significant difference was observed in the total weight, root weight, root length and leaf number of water spinach under different treatments (p>0.05). However, significant difference (p<0.05) was found for plant height of water spinach among the five treatment groups. Furthermore, the weight of roots and shoots of water spinach was found to have positive correlation (T1: R2=0.672; T2: R2=0.799; T3: R2=0.442; T4: R2=0.779; T5: R2=0.804). In addition to crop growth, the fertilizer application also influenced the soil pH, EC, organic matter and moisture content after one cropping season. In this study, the growth of water spinach following application of organic fertilizer was found comparable to the inorganic fertilizer treatment. Incorporation of organic and inorganic fertilizer (T5) served the best condition for the growth of water spinach under the polyculture system.