Carbon and nitrogen cycling in food and feed systems Cycle de l'azote et du carbone dans les systèmes alimentaires

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1 Scientific registration n o : 1009 Symposium n o : 25 Presentation: Poster Carbon and nitrogen cycling in food and feed systems Cycle de l'azote et du carbone dans les systèmes alimentaires HAKAMATA Tomoyuki (1), MATSUMOTO Naruo (2), SATO Kazuyoshi (3), MIWA Eitaro (4) (1) National Institute of Agro-Environmental Sciences, Kannondai 3-1-1, Tsukuba JAPAN (2) JIRCAS, Owashi 1-2, Tsukuba 305 JAPAN (3) Miyagi Prefectural Agricultural Experiment Center, Natori , JAPAN (4) Agriculture, Forestry and Fisheries Research Council of MAFF, Kasumigaseki 1-2-1, Chiyouda-ku, Tokyo 100 JAPAN INTRODUCTION Large amounts and many kinds of organic materials derived from agriculture, fisheries and forestry flow in a food and feed system. We will state in this paper the importance of studies on carbon (C) and nitrogen (N) cycling in several scales of food and feed systems to clarify causality of global/local environmental problems and to develop effective policies. METHODS 1. Nitrogen flows in international and national food and feed systems A database for N flows and stocks in a food and feed system were constructed using data from official statistics published by FAO or the Japanese government. N flows and stocks in international and Japanese systems were estimated using the database (Hakamata, 1990; Miwa, 1990). 2. Organic materials flows, soil nitrogen mineralization and CO 2 emission in a rural system We estimated organic material flow and emission of CO 2 after application of the organic materials including manure, crop residues, etc. to farmland soil in a typical rural area in Japan, the basin of Ushiku Lake, about 70 km northeast from the center of Tokyo. We used official statistics published by a local government (Ibaraki prefecture) and a model representing the decomposition process of organic material in soil for the estimation (Matsumoto et al., 1990). 3. Quantitative Analysis of Carbon Cycle and Budget in Agro-forest

2 C cycling in three types of forest (a managed agro-forest which is cut undergrowth and raked litter, an abandoned agro-forest which is dominated by draft bamboo in the forest floor, and a natural forest) was estimated through a five-year experiment. We measured plant biomass, litter fall, litter biomass, soil C storage, and CO 2 emission in each forest, and estimated C sink using C cycle model. RESULTS 1. Nitrogen flows in international and national food and feed systems It is well known on N and other nutrients flow through the international food and feed trade that the export flow is overwhelmed by the U.S.A. and executed by a comparatively small number of countries; import of N is scattered through many countries in the world. Three major importers were Japan, USSR and west Germany in NETHERLANDS GERMANY NL MALAYSI A UK MOROCCO USSR BURKI NA FASO MALI TANZANI A CHI NA AUSTRALI A AUSTRI A USA THAI LAND DENMARK kgn/ ha Fig. 1. Net imported nitrogen per area of arable land and permanent grassland of each country.

3 Fig. 1 shows net N imported or exported per area of arable land and permanent grassland of each country. The largest exporter is not the U.S.A. but Denmark in 1985, which exports about 40 kg/ha. Norway, France, Thailand, Canada and Chile rank above the U.S.A.. Large importers in this figure are Japan, Botswana, the Netherlands, Beaux, Korea, West Germany, Switzerland, Italy, Malaysia, and so on. Generally speaking, low input to the unit area tends to mean decreasing soil fertility if without fertilization. On the other hand, high input often means environmental problems if without appropriate wastes processing. The land of Japan has been enormously loaded with N because of import of food and feed for recent three decades. Imported food and feed are stocked, processed, trades and utilized. A large part of them are wasted as animal, home and industry wastes. N wastes from the system are carried into the environment including agricultural lands. Beside these, chemical fertilizers and byproducts of crops were loaded into the environment. This causes the problems of air, water, soil and livestock pollution. Fig. 2 shows changes of a N flow in Japan from 1960 to In 1992, more than 900 thousand tons (kt) of N as imported N and about 700 kt of N as domestic food and feed were supplied to support the food life of 120 million Japanese people. More than 700 kt of N was derived from dietary habit, about 750 kt of N was from livestock industry and 160 kt of N was from food processing. More than 1,600 kt of N was inputted into the food and feed system and 1,665 kt of N was outputted from the system. Besides these, near 600 kt of chemical fertilizers and about 140 kt of by-products of crops were loaded into the environment. Eventually they make a total of about 2,400 kt of N loaded into the environment. In 1960, N flowed more through domestic production than import. About 610 kt of N were wasted to the environment through the flow of food and feed. These are about 37% of the 1992 levels. N derived from animal wastes shows remarkable increase of the wastes for these three decades. About 700 kt of fertilizer N was used in 1960 which is almost same as the amount in Larger amounts of N returned to soils as by-products of crops in 1960 than in Cropped area was larger at that time. We can see some features of changes between these years: more than 5.5 times of imported N instead of increasing in the early stages and reaching recently the upper limit of domestic crop N uptake, more than 2.5 times of environmental loads especially derived from big increase of animal wastes, and so on.

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5 Digits show nitrogen amounts (ktn) in , respectively, from top to bottom or left to right. 2. Organic materials flows, soil nitrogen mineralization and CO 2 emission in a rural system The situation is similar to it in a local area. Fig.3 shows flow of an organic material in the basin of Ushiku Lake, which is a typical arable farming area in central Japan (Matsumoto et al., 1990). Produced crops were sold and taken out from the area. On the other hand, food and feed consumed in the area were purchased from the outside of the area. The quantity of purchased food and feed were slightly greater than the sold products. A large part of crop residues and two thirds of animal wastes were recycled to the farmland. However, almost all of human wastes was not recycled. In total, 75% of the available organic matter was recycled to the farmland. And finally, 10 kt C / y (1.83 t C / ha) was emitted from the soils as CO 2. And 64 kg N / ha was mineralized in the area. Increase of nitrate N level of ground water was recently reported in the area. Fig. 3. Organic material stock (in boxes; DM kt) and flow (with arrows; DM kt / year), respired carbon from soil and mineralized nitrogen in the basin of Ushiku Lake.

6 3. Quantitative Analysis of Carbon Cycle and Budget in Agro-forest A forest part of a rural system is excepted in the above mentioned figure. Two thirds of Japan are covered by a forest. A forest ecosystem has an important role on C cycling in a rural system in Japan. The second national report of Japan for COP3 shows that the forest in Japan sequester 90,834 Gg of CO 2 in 1994 which is equivalent to 7.5 % of total emission of CO 2 in Japan. We have to clarify quantitatively C cycling in agro-forest ecosystems. The C storage in the managed agro-forest, the abandoned agro-forest, and the natural forest was estimated 43, 45, 108 tc / ha in plants, and 80, 88, 224 tc / ha in soil, respectively. The C sink in each plot was estimated 3.7, 3.5, 2.2 tc / ha / yr in plants, and -0.8, 1.3, 1.5 tc / ha / yr in soil, respectively. Raking litter and cutting undergrowth reduce C sink of forest. In the basin of Ushiku Lake, about one thirds of the basin is covered by forests, major parts of which are abandoned agro-forest. It can be estimated that the emitted C in the basin is sequestered by the forest ecosystem. DISCUSSIONS We can say from the results of our study that balanced C cycle and unbalanced N cycle of an agricultural sector in Japan should be seriously regarded. We have to realize a new balanced system of N cycling. N cycling through food and feed systems was more closed and limited in environmental loading in 1960 as we understand now. In the 1960s, the economy of Japan went into a period of high growth and introduced technological innovation even in agricultural fields. The process after that was undertaken without proper attention to the environment, and the result was serious pollution-related damage. It was only after experiencing this damage that Japan began implementing proper pollution control measures. We have to think about the best ways to balance the N cycling. Can we manage such a large amount of N in present day's agricultural lands in Japan? We had 5.2 million ha of cultivated land in If we returned whole N to the land, fertilizing rate of N would be 440 kg / ha, including N from chemical fertilizers and byproducts of crop. This level is higher than the N carrying capacity of agricultural lands in Japan, which is estimated to be 250 kg / ha. Can we secure enough area to produce the same amount of feed as imported in Japan? (Hakamata & Hirata, 1994) The necessary area of crop lands for feed can be estimated, supposing average yield of each crop equals 3 t / ha, to be 5.79 million ha. Breakdowns of them show 4.10 million ha for corn, 1.23 million ha for sorghum and 0.46 million ha for barley. Area of agricultural land, area of planted field and cropping ratio, which have been decreasing, should increase and techniques for such high yield as 4.7 t / ha for corn and 10 t/ha for sorghum which are established in Japan should be extended to realize it. Agroforestry is also useful even in Japan.

7 We can say there are two available ways, one is decrease of N entered into Japan and the other one is increase of agricultural land including efficient use of agricultural land. We can say there are capabilities to balance the N cycling only after changing not only agricultural but also many other measures to better ones in Japan. CONCLUSIONS We can address the new balanced system of nutrient cycling by learning from our history of N cycling in food and feed systems in Japan. The general necessary conditions are as following: 1) The self-sufficient ratio of food and feed should increase in not only Japan but also each other country; and after that necessary import and corresponding export should be planned. 2) Construction of toxicant free sewerage systems should be realized; or reconstruction should be done in some developed countries, like Japan. But this is also a hard work for our posterity. 3) New organic fertilizers and fertilizing technologies should be developed following the new sewerage systems. 4) All other techniques in each cropping system should be innovated in harmony with nature from nutrient cycling point of view. REFERENCES Hakamata, T. (1990) Nutrient cycling point of view for sustainable agriculture. Farming Japan, 25(6): Hakamata, T. and H. Hirata (1994) Nutrient cycling considerations for sustainable agriculture. Trans. 15th World Cong. Soil Sci., Vol.5a: 3-7. Matsumoto, N., E. Miwa and T. Hakamata (1990) Estimating method of organic material flow in rural area. J. JASS, 6(2): (In Japanese) Miwa, E. (1990) Global nutrient flow and degradation of soils and environment. Trans. 14th Intern. Cong. soil Sci., Vol. V: V271-V276.