Along with increasing livestock products via intensive rearing, the accumulation of livestock manure has become a serious issue due to the fact that there is finite land for livestock manure recycling via composting. The nutrients from livestock manure accumulate on agricultural land and the excess disembogues into streams causing eutrophication. In order to systematically manage nutrient loading on agricultural land, quantifying the amount of nutrients according to their respective sources is very important. However, there is a lack of research concerning nutrient loss from livestock manure during composting or storage on farms. Therefore, in the present study we quantified the nutrients from dairy cattle manure that were imparted onto agricultural land by investigating 41 dairy farms, taking into consideration weight reduction and nutrient changes during the storage and composting periods. In order to support the direct investigation and survey on site, the three cases of weight reduction during the storing and composting periods were developed according to (1) experiment, (2) reference, and (3) theoretical changes in phosphorus content (ΔP = 0). The data revealed the nutrient loading coefficients (NLCs) of volatile solids (VS), total nitrogen (TN), and total phosphorus (TP) on agricultural land were 1.48, 0.60, and 0.66, respectively. These values indicated that the loss of nitrogen and phosphorus was 40% and 34%, respectively, and that there was an increase of VS since bedding materials were mixed with excretion in the barn. The NLCs obtained in this study may assist in the development of a database to assess the accurate level of manure nutrient loading on soil and facilitate systematic nutrient management.