Reducing the sorting of soil clods and green potatoes on the potato harvester is effective in reducing labor in potato harvesting. In this study, we focused on the passage of tractors and sprayer wheels and their soil compaction during spraying as factors in the production of soil clods and green potatoes. In conventional spraying practices, the tractor and sprayer wheels pass through the valley positions between ridges, and wheel passage lines affect four ridges (sprayer-passed ridge) on both sides of the wheels. In Experiment 1, we investigated the sites of frequent soil clod occurrence during harvest. The results showed that the sites of frequent soil clod production were the sprayer-passed ridges. In Experiment 2, we investigated the effect of improving the tractor and sprayer-passed lines on soil clods and green potato production. Improved passage lines were not set on planted rows to widen the distance between the tractor runway and the improved ridges. The potato yield of the processing standard and the quantity of the soil clods and green potatoes in both ridges were compared with that in the control ridges (no effect of passage). The quantity of soil clods and green potatoes in the sprayer-passed ridge plot increased significantly compared to the control ridge. In contrast, those in the improved ridge plots were not significantly different from the control plots. These results suggested that the improvement of the tractor and sprayer-passed lines was effective as a cultivation method for reducing the quantity of soil clods and green potatoes. Moreover, the yield of potatoes suited for processing standard in the sprayer-passed ridge plot was significantly lower than that of the control plot, whereas the yield of the improved ridge plot was significantly higher.

This study focused on GNSS-based rowing and mulching for effective herbicide application to furrows in the soybean production with black film mulch. An operator, experienced in GNSS-guided operations, mulch rows with equal width of furrow. Meanwhile, the operator who is inexperienced at GNSS-guided system, meandered the mulched rows so that equal furrows between mulched rows were not realized. In mulch rows with equal width of furrow, the boom sprayer could work with almost no steering operation. On the other hand, in the meandering mulch rows, frequent steering was necessary to drive the boom sprayer. It was observed that the spray height of the sprayer was not constant when the handle was frequently operated in the meandering mulch rows. Straight rows formed by GNSS-based operation equalized the width of furrow, allowing for efficient herbicide application to furrows from the sprayer, reducing herbicide application amount by 45%.

This study examined a thermal infrared camera-based method to detect the early stage of foot rot disease in sweet potatoes. A pot experiment was conducted to investigate the effects of the surrounding environment on the increase in leaf temperature due to disease infection and its cultivar （variety） difference. In cv Koganesengan which has a weak resistance to foot rot disease, the leaf temperature increased under air temperature more than 30℃ when such disease was infected. The Koganesengan plant which showed the increase more than 1.4℃ in leaf temperature was recognized as infected one. These findings were verified by field experiment. Our study suggested that thermal cameras can be potentially used for early detection of foot rot disease, although it is necessary to focus on the growth stage and observation environment.