Effects of agronomic practices on the yield, composition and quality of ginger

Ginger is an important culinary spice and has been known from ancient times for its medicinal value and many health benefits (Rahmani et al., 2014, Malu et al., 2009). The effectiveness of ginger ranges from prevention of nausea and vomiting to prevention and treatment of many types of cancer (Ravindran and Babu, 2016). The increased interest in health and wellbeing in developed countries has led to increased demand for good quality products of this spice crop. Ginger has many quality characteristics that need to be considered by producers when targeting both fresh produce and health related markets. In addition to characteristics such as appearance, smell, taste and colour, the concentration of bioactive chemical compounds in the plant is important as it determines efficacy in health products. There are certain agronomy practices as well as climatic factors that have been shown to affect the quality of ginger (Nair, 2013, Ravindran et al., 2007), although most research has examined fresh market quality attributes. The effects of different agronomic practices on chemical composition remains a poorly researched field. This research project investigated the effects of agronomic practices on yield and the quality of ginger. Factors examined in the project were: • harvest times of ginger from the field and greenhouse in different seasons, • source of the rhizome pieces used for planting, • effect of light intensity, • manipulation of rootzone microbial populations or diversity • effect of storage conditions Parameters measured were growth rate and yield; pattern of development of the rhizome, and the concentration of gingerols and shogoals of fresh ginger. Significant changes in plant biomass, ginger rhizome morphology, and the concentrations of chemical components [6]-gingerol, [8]-gingerol, [10]-gingerol and [6]-shogaol in different regions of the ginger rhizome were recorded in response to crop agronomic and production environment treatments. The treatments of growing ginger in the greenhouse environment and harvest at 185 days after planting and reducing the light intensity at 30%, have resulted in the biggest responses in fresh weight of rhizomes, fresh weight of shoots, number of fingers present on the rhizome and number of buds present on the fingers of rhizome, as well as the greatest responses in the concentration of the components in mother and in lower order fingers on rhizomes. No significant changes in plant yield or quality attributes were found following use of microbial products and between plants grown from rhizome pieces that were sourced from different position on the mother rhizome. Furthermore, the agronomic practices of storage initial quality categories and storage durations of ginger rhizomes; in various environmental conditions, and constant storage conditions of temperature and relative humidity, resulted in a significant difference in fresh and dried weight as well as the concentrations of chemical components. This study provides new knowledge of factors that affect the quality of ginger crop that will benefit commercial ginger producers and processors. Ginger crop growth management and storage programs need to be carefully managed to achieve the quality required for specific end uses, such as the ginger processing market. An understanding of the factors that affect plant growth and rhizome composition are integral to the development of these management and storage programs, and this project has contributed to that knowledge base.