黑土地,并不仅仅因土壤的颜色而得名,而是一个特定的概念。黑土层形成于几百万年甚至上亿年以前,其典型特征是有一个厚达七八十厘米甚至1米的肥沃的腐质层,有机质含量通常在3%～10%,最高可达15%。如今,在全世界能称得上黑土区的地方只有三大块:一块是乌克兰大平原;一块是密西西比河流域;再一块就是我国东北 Black land, not just because of the color of soil named, but a specific concept. The formation of the black soil millions of years or even billions of years ago, the typical feature is a fertile humus layer thickness of seventy or eight centimeters or even 1 meter, organic matter content is usually 3% to 10%, up to 15 %. Nowadays, there are only three major places in the world that can be regarded as black areas: one is the Great Plains of Ukraine; one is the Mississippi River Basin; another is the north-eastern part of our country