**1. Introduction**

108 Soybean Physiology and Biochemistry

Zhang, C.D.; Römheld, V. & Marschner, H. (1995). Retranslocation of iron from primary

268-272, ISSN 0176-1617.

leaves of bean-plants grown under iron deficiency*. J. Plant Physiol.,* Vol. 146, pp.

Increase of the cereal production in the world is desired for increase of global food demand. The savanna agro-ecosystems of South America are one of the most important potential areas for expansion of agricultural production in the world. Therefore, the opening of some 12 million ha of this area has been conducted over the last 40 years (Kerridge, 2001). For example, in the Brazilian savanna, grain crops cover 12-14 million ha and introduced pasture area is over 50 million ha (Maceado, 2001).

However, under continuous cropping, soil productivity declines due to soil loss, soil compaction, loss of organic matter and increase in pests, diseases and weeds. For example, the soybean yield in Yguazu, Alto Parana, Paraguay, increased to over 3 t/ha after the introduction of a no-tillage cultivation system in 1983. However, the yield increase stopped in the early 1990's, and recently the yield seems to be decreasing (Seki, 1999; Shimoda et al., 2010). As a means to solve these problems, Kerridge (2001) suggested that integrated agropastoral systems with no-tillage appeared to be the key to sustainable development. But, since the period used as pasture and the pasture manegement methods have various combination in the system, few studies have been evaluated them synthetically.

The Japan International Research Center for Agricultural Socience Japan (JIRCAS) was conducted the joint reserchs of agropastoral system with the National Beef Cattle Research Center of the Brazilian Agricultural research Corporation (EMBRAPA-CNPGC) from 1996 to 2006 and many results were obtained from several experiments (Macedo et al., 2004; Kanno et al., 2004; Miranda et al., 2004 etc.). In addition, JIRCAS was conducted with the Japan International Cooperation Agency's Paraguay Agricultural Technology Center (CETAPAR-JICA) from 2003 to 2008 (Shimoda et al., 2010; 2011). In this report, I clarify the positive effects of an agropastoral system synthetically.
