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世界上仅有三块黑土平原:美洲的密西西比平原、欧洲的乌克兰平原和我国的东北平原。我国的寒地黑土资源主要集中在黑龙江和吉林两省。寒地黑土是温带湿润、半湿润地区的黑色土壤,由于地处四季分明的寒温带,大量枯枝落叶难以腐化,历经千百年形成厚厚的腐殖质。据相关测算,黑土的有机质含量大约是黄土的10倍,是最适宜农耕的土地。在1958年的第一次全国土壤普查中,黑龙江与吉林两省的黑土总面积为约1000万公顷,而据1990年第二次全国土壤普查统计,这两省黑土总面积仅为592万公顷,减少了400万公顷。经过多年耕种和侵蚀,黑土层正在逐渐变薄。据统计,一些地方的黑土层已经由开垦初期的60-70厘米厚减少到目前的20~30厘米。同时,黑土中的有机质含量也在较快下降。我国东北地区发展生态农业、保护耕地的任务越来越迫切。
There are only three black soil plains in the world: the Mississippi Plain in the Americas, the Ukrainian Plain in Europe and the Northeast Plain in our country. China’s winter black soil resources are mainly concentrated in Heilongjiang and Jilin provinces. Cold black soil is temperate, humid, semi-humid areas of black soil, as located in the four seasons of the cold temperate, a large number of litters difficult to decay, after thousands of years to form a thick humus. According to the relevant estimates, black soil organic matter content is about 10 times the loess, is the most suitable for farming land. In the first national soil survey in 1958, the total area of black soil in Heilongjiang and Jilin provinces was about 10 million hectares. According to the second national soil survey in 1990, the total area of black soil in these two provinces was only 5.92 million hectares , A decrease of 4 million hectares. After years of cultivation and erosion, the black soil is gradually thinning. According to statistics, the black soil in some places has been reduced from 60-70 cm in the early stage of reclamation to the present 20-30 cm. At the same time, the organic matter content in black soil is also rapidly declining. The task of developing ecological agriculture and protecting cultivated land in Northeast China is more and more urgent.