Survey on Weed Management on Levee of Paddy Fields in the Okitama Area and Shonai Area in Yamagata Prefecture

Abstract

abstrFrom 2020 to 2021, we investigated levee management conditions in Nagai City in the Okitama area and Tsuruoka City in the Shonai area of Yamagata Prefecture. In Nagai City, herbicides were used on the levees of 80% of the paddy fields surveyed. In Nagai City, the slope angle between fields in the survey area is 5.5 per mil, single paddy fields are small, levees are numerous, and the area of the levee slopes is large, which means that the work-load required for weed control is high. It was considered that herbicide might be used to reduce labor. The results of an interview-based survey, showed that many farmers cited “a reduction of working hours (60%)” and “a reduction in labor load (60%)” as reasons for using herbicides. On the other hand, in order to prevent the levees from collapsing, 64% of the levees were coated with soil. In contrast, in Tsuruoka City, no herbicides were used on any of the levees surveyed, and weeds on the levees were managed by mowing. The slope between fields in the survey area of Tsuruoka City is as gentle as 0.54 per mil, which is classified as flat land. The number of levees and the cumulative area of levee slopes is low, which means that the total area requiring weed management is smaller than that in Nagai City. In addition, numerous farmers have introduced self-propelled mowers to reduce the workload associated with mowing, making it easier to manage levee weeds by mowing. Interestingly, the results of the interview survey, revealed that many of the farmers (54%) cited “local customs and climate” and “conservation of environment” as the reason why weeding was performed by mowing without using herbicides. The motivation of farmers in Tsuruoka City to perform weed management by mowing is a topic for future study.act