The most important role of agriculture is to continue to produce and supply food for us. We need to learn how to sustain the agricultural production, how to sustain soil resources for agricultural production, and how to conserve the environment exposed to human activities. Our laboratory is doing research on the nutrient cycles in the agricultural ecosystems. In these ecosystems, the inputs (fertilizer, compost, food, etc.) are identical to human activities, and the resultant leakage lead the environment pollution directly. To date we are carrying out the study on nitrogen (N), phosphorus (P) and silicon cycle by means of field-based monitoring research
[Agricultural land use in watersheds, and the resultant riverine N and P loads]
Rivers and streams is the important pathway for the transport of nutrient from terrestrial land to water reservoir, and also is the water resources for agricultural and human consumption. Nitrogen and P loads from farmland are becoming one of the important environmental issues. We are doing research on the relationship between agricultural land use and the N and P concentrations in the watershed.
[Importance of silica as an environmental capacity of hydrosphere]
Silicate is one of the essential nutrient for hydrosphere ecosystem. Silicate supply to hydrosphere potentially determine the capacity to N and P demands. Nowadays, there are concerns about the reduction of silicate in water bodies due to human activities (dam construction is a well-known example). We are doing research on silicate cycles within the terrestrial ecosystem, and the transport of silicate to the water bodies as dissolved and particulate forms.
[How much phosphorus is actually needed?]
Currently, a huge amount of P is accumulated in intensive farmlands in developed countries including Japan. It is called “legacy phosphorus”. Only a little amount of P lost in runoff water and leachate, which is negligible agronomically, could be often enough the water bodies to make eutrophic. We are studying the relationship soil P status and runoff risk, with focused on rice paddies. Simultaneously, we also study the efficient use of legacy P for paddy rice production.
[How to select and how much use the organic amendments in organic farming?]
Recently, many studies have reported that excess nutrients were accumulated due to heavy application of external compost and the other materials in organic fields in Japan. We are focused on such nutrient accumulation in terms of yields, efficiency of nutrient use, and nutrient loss into the environment, with special reference to paddy rice and leafy vegetables.
In addition, biochar is an alternative way to carbon sequestration, and also will be hopeful as a soil amendments. Focused on bamboo biochar, we try to evaluate the functions of biochar to improve soil quality.
[The nutrient cycles in regional food system]
The transport of human foodstuffs and animal feed from agricultural areas to cities, and from exporters to importers, is part of the larger picture of the transfer of nutrients. We try to quantify such nutrient flows, and are looking for scenarios that manage with respect to nutrient resources for production and the nutrient load into the environment.