Development of a sustainable evaluation indicator for livestock farming system on the basis of nitrogen flow: a case study on the material flow in livestock farming along with fodder crop production and grazing on abandoned paddy fields

摘要

This study was conducted to identify the differences of characteristics of nitrogen flow on the cattle fattening breeders in different types of feeding system. Targeted breeders were classified into fodder-product type and grazing type. In both types, the nitrogen flow during livestock farming was estimated based on the inputs and outputs of materials, and summarized with following three indicators: (1) Flow-Drive Indicator (FDI), indicator for the amplified nitrogen flow per unit of external commercial materials, (2) Artificial Resources Utilization Indicator (AUI), indicator for effects of the inputs of artificial resources on nitrogen flow, and (3) Sustainability Indicator (SI = FDI/AUI), indicator for sustainability of resource utilization. As the results of nitrogen flow analysis, higher average FDI value in the grazing type (2.09) than in the fodder-product type (1.90) showed that the nitrogen from external commercial materials contributed efficiently to increase the nitrogen flow in the grazing type. The average AUI value in the fodder-product type (24.27) was clearly higher than in the grazing types (1.90). It is suggested that fodder-product type was operated by higher dependency of the inputs of utilization of artificial resources. The value of SI was less than 0.2 in the fodder-product type, and it ranged from 1.00 to 1.36 in the grazing type, respectively. It was suggested that the nitrogen flow was completely different in both types of systems, and the grazing type well utilized natural process. Moreover, by comparing the AUI and SI values, it was found that the fodder-product type was operated depending on nitrogen inputs from commercial products. In contrast, the grazing type operated well utilization of nitrogen from natural resources with less input from commercial feed.