这 Publication Issue 用你的语言不存在, 用...查看: Português (pt), Français (fr), English (en),
或使用谷歌翻译:  

Farmers in large parts of the tropics have no tradition of aiming at maximum production per hectare; their main concern was to reduce the risk of crop failure. The principal reason is that - except in the main population centres - there were no convenient markets for food surpluses. The traditional farming systems were integrated, based on self-sufficiency and hence on internal supplies and services between different farm components: mixed cropping with a legume supplying nitrogen to a cereal, field crops supplying fodder for livestock in exchange for manure, etc.

Version 4, 2007