Fruit quality components of balsam pear (Momordica charantia L.) and soil respiration in response to soil moisture under two soil conditions

Balsam pear (Momordica charantia L.) is an important vegetable reported to have pharmacological properties. It contains abundant bioactive compounds which can be affected by viticulture and environment factors. Identification of the optimal cultivate condition is fundamental to enhance fruit quality components of balsam pear and to decrease carbon dioxide efflux of vegetable garden. The objective of this study was to identify changes of health-promoting bioactive compounds (flavonoids and saponins) and fruit nutritional quality of balsam pear, as well as seasonal variation of soil respiration (Rs) in response to soil moisture under different soil types. A field experiment was conducted using a 3 x 2 factorial involving three levels soil moisture including 50-60% (L), 70-80% (M), and 90-100% (H) of field moisture capacity (FC) under Loessial soil (L) and Cumulic cinnamon soil (C) conditions. The results indicated that moderate soil moisture was benefit for improving quality components, 70-80% FC was benefit for accumulation of health-promoting bioactive compounds on the Cumulic cinnamon soil, and 70-80% FC was benefit for the nutritional quality of fruit on the Loessial soil; soil respiration measured in Loessial soil were always higher than that in Cumulic cinnamon soil. Air temperature, photosynthetic active radiation, soil temperature had positive correlation with Rs to some extent, while air relative humidity had a negative correlation with Rs. This study would be potentially beneficial for efficiently producing functional and high quality balsam pear.