Rubber tapping of Yunyan 77−4 rubber tree in winter and dry season: research on rubber properties

The triploid rubber tree cultivar Yunyan 77−4 is widely planted for quick growth and resistance to cold in Yunnan, China. However, during the regular tapping rubber period from April to November or December, the heat can cause latex flow obstruction, significantly reducing the tree’s yield. Tapping rubber during the winter and dry season may become a feasible option because low temperatures encourage latex flow. This study used Yunyan 77−4 natural rubber trees stimulated by irrigation and ethephon stimulation to examine changes in the qualities of natural rubber (NR) during the winter and dry season. According to the experimental results, the dry rubber content, total solid content, Mooney viscosity, and P₀ all showed a trend of decreasing and then increasing under the influence of temperature and humidity. The lowest values occurred in the control group at the lowest temperatures in December or January of the following year at 30.56%, 35.39%, 54, and 30, respectively. These values could be suitably increased by irrigation and chemical stimulation treatments. Ash, nitrogen content, and mechanical characteristics tended to rise and then fall, with maximum values of 0.49%, 0.62%, and 20.16 MPa, respectively, and the two treatments had little effect on them. The molecular weight appeared to peak during the first month of tapping rubber, the volatile component decreased as a whole, and the dirt content fluctuated little during the entire trial. The experiment also found that the two treatments would reduce the antioxidant properties of NR. The results of this study provided information about the properties of the NR of Yunyan 77−4, which served as a theoretical foundation for the popularization, application, and performance regulation of tapping rubber in the winter and dry season.