Factors causing muddy lots in livestock farms were investigated by field research and soil analysis. The coefficient of water permeability of the top layer in muddy paddock was rather small. The top layer of soil was tight and hard and high density part was observed. This seems to be because of kneading and tamping by cattle hooves. Organic content of top layer soil was high and plugging by organic materials seems to be one of the factors of water permiability decline. Following five items are considered to be the factors causing muddy lots : soil granulation and mixture of manure by kneading of cattle hooves, decline of water permiability, high density soil caused by tamping by cattle hooves, dehydration from soil by tamping and kneading in wet condition. Prevention of kneading on top surface of soil is considered to be effective. Underdrain may have little effect to prevent lots being muddy.
    The effect to prevent muddy lots ising expanded metal and plastic net settled on the top of soil were investigated. Practical experiments were performed around a bale feeder and a hey feeder, at entrance of cattle barn and pasture for about two years. Enough efficiency of these two materials to prevent muddy lots was comfirmed. It was proved that the expanded metal should be galvanized to prevent rust. Since the durability of the plastic net was not sufficient, further investigations are needed to develop mare durable and economical materials in the future.

Keywords: stock farm, paddock, muddy lot, expanded metal, plastic net