Comparative effects of soil organic amendments on the growth, yield and antioxidant content of ampalaya (Momordica charantia L.)

A field experiment was conducted to determine the effects of different soil organic amendments [vermicompost, commercial compost and Bio-N] and inorganic fertilizer on the growth, yield and antioxidant content (total phenolics, flavonoids, total tannins, % lipid peroxidation and vitamin C) of ampalaya (Momordica charantia L. var. 'Makiling'). Ampalaya responded favorably to application of different soil organic amendments like vermicompost, Bio-N and commercial compost as reflected in the enhanced growth, yield antioxidant contents of the plant compared to those under the no fertilizer treatment. Plant height, number of leaves, total leaf area, herbage yield and vine vigor increased significantly when plants were applied with different soil organic and inorganic fertilizers as compared with those of the unfertilized plants. The number and ratio of male and female flowers and the total number of flowers did not significantly vary among the various fertilizer treatments. The total number and weights of fruits, and total number and weight of both marketable and non-marketable fruits were highest in plants given inorganic fertilizer. The following trend in fruit yield was observed among organic amendments: commercial compost vermicompost Bio-N. In terms of fruit size, the unfertilized ampalaya plants produced the smallest fruits as shown by the data on length, diameter and weight of individual fruits. The incidence of deformed fruits was also noted in the control plants despite the bagging done on the fruits. The length, diameter and weight of fruits raised from the different soil-amended treatments were comparable with one another. The level of antioxidants (total phenolics, total flavonoids, total tannins and vitamin C) was generally higher in ampalaya plants fertilized with organic composts compared with those applied with inorganic fertilizer. In both treatments, the concentration of antioxidants was higher in the fruits than in the leaves. Fruits harvested 64 days after planting (middle harvest) contained higher levels of these compounds than those picked from the first and last harvests. Considering the position in the stem where the leaves were taken, the leaves collected from the middle position (120 cm from the shoot tip) had, in general, higher antioxidant contents than those obtained from the upper position (60 cm from the shoot tip). The antioxidant levels of ampalaya fruits harvested from vermicompost treated plants were at par with those obtained from Bio-N treatment particularly in terms of total phenolics, tannins and flavonoid contents. In the leaves, the antioxidant contents were generally higher in plants grown with Bio-N fertilizer than those supplied with either vermicompost or commercial compost.