Effect of planting density, training method, and soil moisture on the yield and the quality of bitter gourd (Momordica charantia)

Bitter gourd (Momordica charactia) is a highly nutritional, health-promoting vegetable and has recently increased in consumption and planting area. Bitter gourd was newly introduced as a summer vegetable into the Miura peninsula district. However, its cultivation method has not been fully established yet. Bitter gourd tends to bear many stems and leaves, which shade fruit to cause problems such as fruit quality deterioration due to uneven coloration and pest damage. Hence, to improve the yield and quality of bitter gourd, studies were conducted on planting density, training method, and soil moisture. [1] Yield increased but work efficiency decreased with increasing planting density. [2] The following three training methods were tested after pinching the primary vine at the seventh node : (1) secondary vine pinching culture, in which the harvest was obtained only form tertiary vines that were allowed to grow semi-naturally after four secondary vines grew 1.5 meters long and were then pinched; (2) tertiary vine pinching culture, in which the harvest was obtained only from four secondary vines allowed to grow to main branches and all tertiary vines were pinched; (3) semi-natural culture, in which the harvest was obtained from both tertiary and secondary vines by allowing four secondary vines to grow to main branches and leaving intact some of tertiary vines with many female flowers. A comparison of the three test plots revealed that the training method for harvest only from secondary vines (tertiary vine pinching culture) was excellent in work efficiency and lighting and suitable for bitter gourd cultivation. [3] Controlled watering to pF 2.5 was good for initial growth. Ample watering tended to increase weight per fruit but decrease the number of fruit. On the other hand, somewhat controlled watering was good for growth later in the harvest season but excessive watering weakened stocks, decreased harvest, and inhibited root growth. Excessive watering was considered likely to create an environment favorable for root-knot nematode.