Evaluation of Soil Water Management Difference in Mango Orchards between Thailand and Japan

The objective of this study is to evaluate the difference of the soil water management in mango orchards between the varieties of “Irwin” in Japanand “Nam Dok Mai” inThailand. Field observations were conducted in mango orchards in Okinawa, Japan and Phrao, Thailand to clarify the water management practices. Measurement of the hourly soil water content in Phrao indicated that the irrigation was scarce and the volumetric water content in the soil was maintained almost constant. in the flowering season. This can be the farmers’ practice for flower induction. After the flowering season, irrigation was frequent in order to produce the large fruit. In the harvest season, the soil water content was relatively high because of frequent irrigation and rainfall. In Okinawa, the volumetric water content was maintained at the same level in a relatively deep layer. The result at the5 cmdepth indicated that the farmer carefully controlled the soil water content. In the flowering season, the soil water content was relatively low. While the orchard was managed empirically, the volumetric water content near the soil surface was maintained over 25% during the harvest season. This result indicates that the farmer performed the good soil water management to enhance mango fruit quality even without technical measurement. A numerical model describing the soil water and heat transfers was introduced to predict the farmer’s empirical soil water management in Okinawa. Using the meteorological data in March 2010, the irrigation regime was predicted using the simulated soil water content. In the flowering season, the farmer irrigated when the soil surface water content reached 14%. Based on this criterion for the empirical soil water management, the simulation result indicated that the farmer irrigated four times in this period. The numerical model presented here can be useful for evaluating the differences in water management practices of local farmers.

Determination of surface color of‘all yellow’mango cultivars using computer vision

Image processing techniques are increasingly applied in sorting applications of agricultural products.This work has assessed the use of image processing for inspecting surface color of two Thai mango cultivars.A computer vision system(CVS)was developed and experiments were conducted to monitor peel color change during the ripening process.Conversion of RGB to CIE-LAB values was done via image processing and prediction models were developed to estimate color parameters from CVS data.Performance evaluations showed insufficient prediction for L values(R2=0.42-0.58),but better results for A and B values(R2=0.90-0.95 and 0.80-0.82,respectively).Compared to the calculated color values hue angle and chroma,a yellowness index computed from intermediate XYZ values was found to be much more adept at accurately predicting peel color from CVS data.Correlations were strong for both cultivars(R2=0.93 for‘Nam Dokmai’and R2=0.95 for‘Maha Chanok’).Results from classification analysis indicated satisfactory results for classifying fruits according to ripeness based on yellowness.Success rates of true positives in the categories unripe,ripe and overripe ranged 72%-92%for‘Nam Dokmai’and 98%-100%for‘Maha Chanok’.Therefore,it was shown that the CVS was capable of producing accurate color values for the two mango cultivars investigated.The findings of this study can be incorporated for development of a robust system for quality prediction and establishment of a CVS for automatic grading and sorting of mangos.