Development of Methodologies for the Formulation of Agricultural Environment Risk Indicators in Japan

Background and Objectives

Rice paddy has multi-functions (Mie prefecture)

There is an increasing understanding that Japanfs agriculture which is characterized by strong rice cultivation in paddies is playing a multi-faceted function including not only the fundamental objective of food production, but also water purification and promotion of health and recreation. Conversely, agricultural activity affects the environment in various ways, as represented by the spread of water system eutrophication as a result of excessive use of fertilizers and organic materials, as well as the problem of agrochemical residue. Therefore, it is critically important to clarify the impact of agricultural activity on the environment and to reduce the environmental risks and evaluate the benefits, if we are to maintain agricultural activity in Japan in a sustainable manner. To do so, we need to grasp the yearly changes in the impact of agricultural activity from the standpoints of farm economy, soil management and water quality conservation. And, on the basis of such understanding, we need to formulate agro-environmental risk indicators that are useful for risk assessment, which in turn will be useful for rational decision-making for the promotion of environment-conscious agriculture.

Soil erosion potential in Japan (Yokohari et al, 1997)

Previous studies in this field were focused on small to medium river basins, which made it necessary to utilize a large amount of manpower to apply the research findings to other locations with different conditions. The present research project aims to collect and compile nationally homogenous information and to formulate indicators that will permit across-the-board assessment of the environmental impact of agriculture in Japan.

More specifically, we seek to develop new methods for indicator formulation by introducing new statistical and mathematical models on agro-environmental risks. With respect to indicators of environmental impact by soil erosion and nutrient salts balance, we will collect and compile the necessary data and draw up national maps of agro-environmental risk indicators. We will also develop methodologies for the preparation and collection of the geographical information system (GIS) data that are needed for mapping a number of agro-environmental indicators such as agricultural land use and site conditions.

Expected Outcomes

Methods for formulating agro-environmental risk indicators will be developed and national maps will be prepared. The maps will clarify the extent and location of the environmental impact of agricultural activity in Japan. Furthermore, the understanding of yearly variations will demonstrate how the extent of the impact changes from one year to another. The increased knowledge will be found helpful in the decision-making process of policies to ameliorate the environmental impact of agricultural activity.

Relevant Outcomes to Date

Fig. 1 Estimation of nitrogen concentration in animal feed field effluent

Estimation of cattle raising-derived nitrogen load on water system by the use of agricultural statistics mesh data

Using the livestock population, planted crops and other agricultural statistics, as well as fertilization standards and meteorological data in a grid of approximately 1 km square on the map, we estimated the concentration of nitrogen flowing out of an animal feed field in the northern part of Tochigi prefecture, based on the flow (stream) of cattle raising-derived nitrogen in the environment and the inflow/outflow balance (Fig. 1). The results clearly showed that the cattle raising-derived nitrogen load has a strong impact on the total nitrogen concentration in rivers in the area investigated.

Modeling of soil outflow amount from farmland to rivers

A model has been developed to compute the amount of soil outflow into rivers on a river basin level, with attention to the water flow from upland field to rivers. This model permits computation of soil outflow into rivers from different types of land use with the combined use of the AMEDAS data (Table 1). In this way, the impact on water quality by nitrogen, phosphor and other nutrients that are adsorbed in the soil can be assessed.

Table: Soil outflow in Lake Ushiku water system
River	Basin area	Outflow to rice paddy drainage					Accumu -lation in paddy drainage	Outflow from paddy drainage	Direct outflow into rivers				Total outflow into rivers
	(km²)	Upland field	Forest	Urban area	Rice paddy	Total (a)	(b)	(c = a-b)	Upland field	Forest	Urban area	Total (d)	(c+d)
Inari	27.2	38	44	87	65	230	94	140	8.0	8.9	17	34	170
Nishi Yata	59.4	77	81	76	240	480	230	250	5.7	6.9	9.9	22	270
Higashi Yata	58.5	86	58	110	330	590	270	320	9.3	6.4	19	35	350

(Unit: tons, computation period: 2002.4.2 to 2002.12.17)

A system for computation of agriculture-related nutrients balance at prefectural and municipal levels

Fig. 2 Database structure, registered information and computation of nutrients balance

We developed a database system that enables computation of the balance of agriculture-related nutrients (nitrogen, phosphor and potassium) at prefectural and municipal levels, based on an estimation of crop production, chemical fertilizer application and animal manure generation from statistical information and data (Fig. 2). This database system permits computation of the potential environmental load of each nutrient in the area.