How can we cultivate and cultivate the land? The excessive application of chemical fertilizer does serious harm.

"at present, China consumes 59 million tons of chemical fertilizer every year, accounting for 35 percent of the world's total consumption, twice as much as 30 years ago, causing serious environmental problems." Chen Wenxin, academician of the Chinese Academy of Sciences, said at the national symposium on soil microorganisms held a few days ago. In recent years, the voice of replacing chemical fertilizer with organic fertilizer is very high. So, can organic fertilizer completely replace chemical fertilizer? How to apply fertilizer to ensure the food security of our country? In this regard, a reporter from the Economic Daily conducted an investigation and interview.

The excessive application of chemical fertilizer does serious harm.

"at present, the average utilization rate of chemical fertilizer in the country is only 35 percent in that season, and the annual loss of fertilizer input caused by unreasonable fertilization is as high as 130 billion yuan. Take Shandong Province as an example, more than 400,000 tons of chemical fertilizer are wasted by leaching and volatilization every year. " Luo Wensheng, vice president of Shandong Kim Jong Da Group, said.

According to the data of the National Bureau of Statistics, in 2004, the net application of agricultural chemical fertilizer was 46.3658 million tons; in 2013, a total of 71.537 million tons of chemical fertilizer was produced and 59 million tons were applied. In the past 10 years, the use of chemical fertilizer across the country has increased by nearly 30%.

Excessive application of chemical fertilizer not only caused agricultural non-point source pollution, but also caused soil acidification and consolidation. Zhang Fusuo, a professor at the School of Resources and Environment of China Agricultural University, told reporters that nitrate ions are produced during the transformation of nitrogen fertilizer, which increases soil acidity. From 1981 to 2008, China's grain output increased by 62.8%. However, the amount of nitrogen fertilizer application has increased by nearly 200%. Excessive application of nitrogen fertilizer directly led to varying degrees of acidification of 90% of the farmland soil in the country.

Pingdu City, Shandong Province is the main ginger producing area in the country. Hao Yani, a villager in Zhujiajing Village, Liyuan Street, has planted 4 mu of ginger, which can produce more than 40,000 jin in the early years. "later, when the ground became harder and harder, the ginger seedlings always got sick, and the yield was getting lower and lower. Experts were invited to take a look at it and said that too much chemical fertilizer was used and the land was degraded. " Hao Yani said.

According to Jiang Gaoming, a researcher at the Institute of Botany of the Chinese Academy of Sciences, in the 1950s, China applied only more than 8 jin of chemical fertilizer per hectare of farmland, but now it is as high as 868 jin. The internationally recognized upper limit for the safety of chemical fertilizer application is 450 jin per hectare, and the application rate in China exceeds the safety limit by 93%. The consequence of the abuse of chemical fertilizer is the decline in the fertility of cultivated land, and the average content of soil organic matter in the country is less than 1%. Due to the excessive application of chemical fertilizer in successive years, the yield per mu of Zhangqiu scallions has dropped sharply from 20,000 jin in previous years to 10,000 jin today, and a similar situation has occurred in the black soil region of Northeast China, which is famous for its fertile soil. "the average annual application of chemical fertilizer in the region is about 80,000 tons, and the average amount of chemical fertilizer applied per mu is more than 40 jin." Hu Jiacai, general manager of Hailar Land Reclamation Group in Inner Mongolia, said that due to long-term excessive application of chemical fertilizers, the farmland ecological environment continued to deteriorate, the proportion of nitrogen, phosphorus and potassium nutrients in the tillage layer was seriously out of balance, and the supply of organic matter was seriously inadequate. The black soil, which was originally rich in organic matter, has become a thin land poor in organic matter in just a few decades.

Organic manure won't work.

Organic fertilizer is rich in a variety of nutrient elements and has a long fertilizer effect. it can effectively increase soil organic matter, improve soil physical and chemical properties and biological activity, and prevent soil consolidation. Compared with chemical fertilizer, its advantage is obvious. "however, it is only a good wish to completely replace chemical fertilizer with organic fertilizer. In fact, it will not work." Zhang Chenglin, a professor of South China Agricultural University and a member of the expert group of soil testing and formula fertilization of the Ministry of Agriculture, said.

So why doesn't it work to replace chemical fertilizer completely with organic fertilizer? In Zhang Chenglin's view, the main reason is that the nutrition is not balanced and can not meet the needs of crops. "Americans have less land and more land, so they can rest their land. Our country has a large population and little land, and the farmland is overloaded. Crops are ripe and harvested, and the soil loses corresponding nutrients, which must be replenished by fertilization. Crops need nitrogen, phosphorus, potassium and other nutrients, and relying solely on straw returning to the field is far from enough. "

Zhang Chenglin said: China's grain production has increased year after year, thanks to the contribution of chemical fertilizer. At present, China's grain supply is still in tight balance. According to common international standards, the annual per capita share of grain is considered safe only if it reaches 800 jin. China just reached the standard two years ago. In addition, natural disasters have been aggravating in recent years, and the risk of grain production is increasing day by day. Taking into account such factors as the increase in population, the reduction of cultivated land, and the shortage of water resources, the pressure to ensure national food security is still great, and the consequences of not using chemical fertilizers at all are unimaginable.

In addition, from the point of view of farmers, there is a substantial increase in the cost of using organic fertilizer instead of chemical fertilizer. "for the same kind of corn, dozens of jin of chemical fertilizer per mu is enough. If organic fertilizer is to achieve the same growth, it will take hundreds of jin. I really can't afford it! " Sun Chengli, a farmer in Shantoutun, Henan Street, Jiaohe City, Jilin Province, has interplanted Chinese medicinal materials on several mu of land, and he cannot apply chemical fertilizer. He has tried to buy commercial organic fertilizer before, and he has used it for more than NT $600, 700 or more than RMB 2000 per ton. The cost is so high that he has to accumulate farm manure on his own.

Gao Xiangzhao, director of the Water-saving Agricultural Technology Department of the National Agricultural Technology extension Service Center of the Ministry of Agriculture, said that the input of organic fertilizer is much higher than that of chemical fertilizer, because the content of effective components of organic fertilizer is low, the volume of organic fertilizer is large, and the cost of transportation and application is too high. therefore, the sale of commercial organic fertilizer is not in the doldrums. Take Shandong, a major fertilizer production province, as an example, the annual output of bio-organic fertilizer in the province is more than 12 million tons, and the actual annual sales volume is only 3.5 million tons. "there are many manufacturers producing organic fertilizer across the country, but most of them are very small and the operating rate is insufficient." Gao Xiangzhao said.