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Land erosion poses threat to grain yield
HARBIN: Northeast China's Heilongjiang Province, China's biggest grain-producing area, might lose its fertile black soil within 50 years unless severe soil erosion is curbed, experts warned. A statement from the Heilongjiang Water Resources Department shows that a quarter of all the land in the province is suffering from soil erosion to varying degrees. The blame is being put on the destruction of the province's natural vegetation, which allows wind and rain to blow and wash the soil away. The province's black soil, which gets the credit for the high grain yield, is disappearing at the drastic rate of nearly 300 million cubic metres annually. The vital elements contained within the lost soil, such as nitrogen, phosphorus and kalium, would amount to 5 million tons of standard fertilizer. Each year, soil erosion causes the grain output to reduce by an estimated 2 to 4 billion kilograms. The black soil layer in the province is diminishing by about 1 centimetre every year, according to the statement. "Judging from the current exploitation and erosion rate, the soil will be wiped out within 50 years," said Liu Yan, who works in the Water and Soil Preservation Office of the department. Black soil is formed by the decay of dead plants in the earth over a long period of time and in a cold climate. It is well known for its richness in organic materials and easiness to plough. The original thickness of the soil layer in Heilongjiang before large-scale exploitation in the 1950s was around 60 to 80 centimetres. Now that figure is down to about 20 to 30 centimetres on average, according to Liu. "Black soil is one of the most valuable natural resources that cannot be reproduced because it takes 400 years to form a centimetre of the soil," he added. "We are now using the land earmarked for our grandchildren," said Guo Jingchun, deputy director of the Heilongjiang Agricultural Science Institute. "This is not alarmism," he said. "Man-made factors are causing huge land erosion." According to Guo, the damage done to the black soil by our generation through excessive exploitation is equivalent to the damage usually done by three generations. "If we let the same trend continue, our grandchildren will obviously have nothing to grow on," he said. Guo said that the wide use of artificial fertilizer is causing more "inner damage" to the black soil. Plants can only absorb about 25 per cent of the fertilizer used, the remaining is left in the earth. It will gradually harden the soil and accelerate the process of changing the land into sand. Besides the black soil belt in Northeast China, there are another two large areas of similar black soil on the Ukrainian Plain and in the Mississippi region of the US. Severe land erosion also occurred during the development of those two places. "Black hurricanes" were a common feature in the two areas in the 1920s. They both decided to plant more trees to weaken the wind, and also planted different crops in different seasons. A large-scale soil preservation campaign is kicking off in Heilongjiang Province with a series of tree planting projects along the Songhua River and Wuyu'er River, two main rivers in the province.
(China Daily 09/26/2005 page3)
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