Serious harm from excessive fertilizer use: how can we farm the land and nourish it at the same time?

“At present, China consumes 59 million tons of chemical fertilizer each year, accounting for 35% of the world's total consumption, a 2-fold increase over 30 years ago, causing serious environmental problems.” Chen Wenxin, an academician of the Chinese Academy of Sciences, said at the national soil microbiology academic symposium held a few days ago. In recent years, calls to replace chemical fertilizer with organic fertilizer have been very loud. So, can organic fertilizer completely replace chemical fertilizer? How should fertilizer be applied to ensure China's food security? On this matter, a reporter from Economic Daily conducted an investigation and interview.

Serious harm from excessive fertilizer use

“At present, the average seasonal utilization rate of chemical fertilizer nationwide is only 35%, 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 each year through leaching and volatilization across the province.” said Luo Wensheng, vice president of Shandong Kingenta Group.

Data from the National Bureau of Statistics show that in 2004, the national application amount of agricultural chemical fertilizer in pure nutrient terms was 46.3658 million tons; in 2013, the country produced 71.537 million tons of chemical fertilizer, with an application amount of 59 million tons in pure nutrient terms. Over 10 years, the national application amount of chemical fertilizer increased by nearly 30%.

Excessive application of chemical fertilizer has caused agricultural non-point source pollution and also triggered soil acidification and hardening. Zhang Fusuo, a professor at the College of Resources and Environmental Sciences at China Agricultural University, told reporters that during the transformation of nitrogen fertilizer, nitrate ions are produced, increasing soil acidity. From 1981 to 2008, China's grain output increased by 62.8%, while nitrogen fertilizer application increased by nearly 200%. Excessive application of nitrogen fertilizer directly caused varying degrees of acidification in 90% of the country's farmland soil.

Pingdu City in Shandong Province is a major national ginger-producing area. Hao Yani, a villager in Zhujiajing Village, Liyuan Subdistrict, grows 4 mu of ginger at home, which in earlier years could produce more than 40,000 jin. “Later, the soil became harder and harder, the ginger seedlings kept getting diseased, and the yield became lower and lower. Experts were invited to take a look and said too much chemical fertilizer had been used and the land had 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 a little more than 8 jin of chemical fertilizer per hectare of farmland, while now it is as high as 868 jin. The internationally recognized safe upper limit for chemical fertilizer application is 450 jin per hectare, and China's application amount exceeds the safe upper limit by 93%. The consequence of fertilizer abuse is a decline in cultivated land fertility; at present, the average organic matter content of soil nationwide is less than 1%. Due to years of excessive chemical fertilizer application, the per-mu yield of Zhangqiu scallions has plunged from 20,000 jin in previous years to 10,000 jin today, and similar situations have appeared in the black soil region of Northeast China, which is known for fertile soil. “The annual average chemical fertilizer application in the whole area is about 80,000 tons, and the average application per mu exceeds 40 jin.” said Hu Jiacai, general manager of Inner Mongolia Hailar State Farms Group. Due to long-term excessive application of chemical fertilizer, the farmland ecological environment has continued to deteriorate, the proportions of nitrogen, phosphorus, and potassium nutrients in the plow layer soil have become seriously unbalanced, and the supply of organic matter is seriously insufficient. The black land originally rich in organic matter has, in just a few decades, become thin land poor in organic matter.

Making organic fertilizer the mainstay will not work

Organic fertilizer is rich in multiple nutrient elements, has a long fertilizer effect, can effectively increase soil organic matter, improve the soil's physicochemical properties and biological activity, and prevent soil hardening. Compared with chemical fertilizer, its advantages are obvious. “However, completely replacing chemical fertilizer with organic fertilizer is only a good wish; in reality, it will not work.” said Zhang Chenglin, a professor at South China Agricultural University and a member of the expert group on soil testing and formulated fertilization of the Ministry of Agriculture.

So why will completely replacing chemical fertilizer with organic fertilizer not work? In Zhang Chenglin's view, the main reason is that the nutrients are unbalanced and cannot meet crop needs. “The United States has few people and much land, so it can practice fallow farming. China has many people and little land, and farmland is all under overloaded production. When crops mature and are harvested, the soil loses corresponding nutrients, which must be replenished through fertilization. Crops need nutrients such as nitrogen, phosphorus, and potassium in various aspects, and relying only on methods such as returning straw to the field is far from enough.”

Zhang Chenglin said that China's grain output has increased year after year, and chemical fertilizer has played an indispensable role. At present, China's grain supply is still in a tight balance. According to generally accepted international standards, an annual per capita grain possession of 800 jin is considered safe, and China only reached that standard two years ago. In addition, in recent years natural disasters have shown a worsening trend, the risks to grain production have been increasing day by day, and considering factors such as population growth, reduction of cultivated land, and tight water resources, the pressure to ensure national food security remains very great. The consequences of completely not applying chemical fertilizer would be unimaginable.

⟦NL> In addition, from the farmers' perspective, replacing chemical fertilizer with organic fertilizer also involves the problem of a substantial increase in cost. “For growing corn, using a few dozen jin of chemical fertilizer per mu is enough. To achieve the same growth with organic fertilizer, several hundred jin are needed. It is really unaffordable!” A few mu of land belonging to Sun Chengli, a farmer in Shantou Village, Nianzigou Village, Henan Street, Jiaohe City, Jilin Province, are intercropped with Chinese medicinal herbs and cannot be treated with chemical fertilizer. He had previously tried buying commercial organic fertilizer, using both those costing six or seven hundred yuan per ton and those costing more than 2,000 yuan per ton, but the cost was really too high, so he had to make farmyard manure himself again.

Gao Xiangzhao, director of the Water-Saving Agriculture Technology Division of the National Agricultural Technology Extension Service Center of the Ministry of Agriculture, said that the input for applying organic fertilizer is much higher than for chemical fertilizer. This is because organic fertilizer has low effective component content and large volume, and the cost of transportation and application is too high. Therefore, sales of commercial organic fertilizer are not brisk. Take Shandong, a major fertilizer-producing province, as an example: the province's annual production capacity of bio-organic fertilizer exceeds 12 million tons, but actual annual sales are only 3.5 million tons. “There are many manufacturers producing organic fertilizer nationwide, but most are very small in scale and operate below capacity.” Gao Xiangzhao said.