Effect of Climate Variability and Degree-Day on Development, Yield and Quality of Shogun (Citrus reticulata Blanco) in Southern Thailand

Abstract

Climatic factors and degree-days are normally important in the development, yield and quality of fruits leading to commercial value. However, there has been no investigation of this aspect for shogun (Citrus reticulata Blanco). Hence, the fruit development, yield and quality of shogun under the influence of climatic factors were investigated using the framework of a quadrat cube (0.5 × 0.5 × 0.5 m) during two consecutive years (2011–2012). Forty 8-year-old uniform trees, field grown in Yala and Pattani provinces were used. The experiment was designed as a completely randomized design. It was evident that the weather conditions between 2011 and 2012 were different, with the rainfall in 2012 lower. The results showed that fruit yields in Pattani in 2011 and 2012 (38.89 and 36.69 kg per tree, respectively) were significantly (P ≤ 0.01) higher than those in Yala (27.74 and 18.53 kg per tree, respectively). Comparing 2011 and 2012, fruit yields in Pattani and Yala decreased 5.65 and 33.20%, respectively. The fruit diameters of shogun fruit in Pattani in 2011 and 2012 were 5.63 and 5.62 cm, while in Yala they were 5.02 and 4.98 cm, respectively, with growing degree-days of 3,387 and 2,989, and 3,153 and 2,780, respectively. The fruit quality in Pattani in 2011 and 2012 was better than in Yala based on the weight of fruit, peel and juice and peel thickness, whereas the total soluble solids in Pattani were lower than in Yala. Furthermore, the color of the rind in Pattani was greener than that in Yala. It was suggested that a decrease in the rainfall and soil moisture caused a negative impact on the fruit development, yield and quality of shogun in Yala. Hence climatic variability and degree-days influenced the development, yield and quality.