Relationship between environmental factors, tapping dates, tapping intensity and gum arabic yield of an Acacia senegal plantation in western Sudan

Gum arabic yield, from Acacia senegal, and yield trends were studied at the Demokeya (13° 16′; 39° 29′E; Alt.560 m) experimental site in Western Sudan. The effects of the date and intensity of tapping, rainfall and the minimum and maximum temperatures at tapping and gum collection on gum arabic yield were examined for eight years (1992-1999/2000) in a 12-year-old plantation. The objective of the study was to establish an understanding of the causes of variability in gum arabic yield and yield trends as a basis for yield control, prediction and stability. The results showed tapping dates produced roughly similar gum production patterns across years. Yield was found to be positively correlated with tapping intensity, rainfall and the minimum and maximum temperatures at tapping time, and negatively correlated with tapping time and the minimum and maximum temperatures at gum collection. The time of tapping, tapping intensity, rainfall and the maximum temperature at gum collection were found to explain 85% of the total variability in gum yield per unit area. The gum yield (g) of the first pick was highly correlated (r=0.93) with total yield (g/tree). The simple regression model based on this relationship was highly significant (p=0.008). These models could help in understanding the causes of yield variability in gum arabic and can be used for estimating the yield of a current year based on the rainfall of the previous year under a prescribed plan of tapping. The yield of the current year can also be predicted using simple models based on the commencement of tapping and the yield of the first pick. In addition, the results can help to predict future gum yield depending on rainfall, temperature forecasts and the average tapping date and intensity used by gum farmers in western Sudan.