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Objective: In order to solve the problem of inaccurate defect extraction caused by complex and variable color and irregular texture changes of tomato surface defects, the defect segmentation method based on image local variance with brightness correction was proposed. Methods: On the basis of using histogram threshold segmentation method to segment calyx and stem scar and the method of domain pixel weighted sum to replace the original pixel to complete the brightness correction, the gray image of tomato surface was divided into several image blocks, and the color of each block was characterized by image pixel variance, and then the defect and healthy area were separated. SVM model was used to detect the proportion of tomato surface defect area in the original tomato area. Results: Considering the brightness correction, the accuracy of tomato defect area extraction could be improved by 27.74%. On this basis, compared with the global threshold, dynamic threshold and regional growth algorithm, the defect extraction method based on image local variance could accurately achieve the quasi-deterministic and complete extraction of tomato surface defects, and the accuracy of the Gauss-SVM model with the defect area ratio as the input for tomato surface defect detection reached 96%. Conclusion: Considering brightness correction, the SVM defect extraction method based on image local variance is suitable for tomato surface defect detection.

Drip fertigation systems are a new technology to alleviate water shortages and improve fertilizer use efficiency. Emitter clogging is the main obstacle to their application. However, few efficient, safe, and environmentally friendly methods are available to alleviate clogging. In this study, we explored the effects of magnetized water irrigation on emitter clogging at different fertilization levels. Field experiments were conducted to study the patterns and clogging characteristics of drip irrigation systems during two planting seasons. The results showed that with an increase in fertilizer application, clogging of the emitter was aggravated. Magnetization treatment effectively relieved emitter clogging, which increased the average discharge variation rate (Dra) by 4.1–29.0% and 2.6–64.4%, respectively, and decreased the dry weight (DW) of the clogging substance by 14.0–64.6% and 15.0–75%, respectively, in the two planting seasons, compared with that of the non-magnetization treatment. The composition of the main clogging substances was estimated using X-rays; the results showed that quartz, silicate, and carbonate were the dominant substances that induced emitter clogging. Magnetization treatment can reduce the content of clogging substances and is thus a possible mechanism to alleviate clogging. Our study demonstrated that water magnetization treatment is an effective, chemical-free treatment method with great potential for clogging control in drip fertigation systems. [ABSTRACT FROM AUTHOR]