The key to the zero growth of chemical fertilizer use is to cure both the symptoms and the root causes of cultivated land.

"to achieve zero growth in the use of chemical fertilizer, it is still necessary to improve the fertilization structure. This can maintain stable and sustainable agricultural productivity, stable and sustainable soil fertility, a healthy and coordinated ecological environment, and the sustainable use of resources and environment. A few days ago, this reporter interviewed Zhang Shuqing, director of the Industrial extension Office of the Fertilizer Research Institute of the Chinese Academy of Agricultural Sciences.

It is understood that due to the excessive use of chemical fertilizers, the soil quality of cultivated land decreases first, resulting in pollution of heavy metals, pesticides, and inferior chemical fertilizers; secondly, soil drought, desertification, salinization and acidification are serious, and there is a general lack of organic matter, medium and trace elements; and then, due to continuous cropping, soil-borne diseases are aggravated, soil fertility decreases, microbial activity is poor, and productivity decreases.

The effect of the amount of chemical fertilizer on increasing production has reached the "ceiling"

Meng Deli, a farmer from Huanghe Village, Shuanghe Township, Keshan County, Heilongjiang Province, planted 1200 mu of land this year. Last year, he planted most of his soybeans, but this year he changed to 700 mu of corn in order to increase his yield. Talking about the input of chemical fertilizer, he said: "the input of chemical fertilizer has been increasing in the past two years, and the input of chemical fertilizer per mu has to increase by about 10 jin every year, otherwise it will feel like a decline in grain output."

Farmers seem to be caught in a prisoner's situation of using less fertilizer or more fertilizer when farming: using less fertilizer to reduce production, using more fertilizer, and production will not go up.

According to the analysis of relevant experts, there are four major problems in the application of chemical fertilizer in China: first, the average application rate per mu is on the high side. The average amount of chemical fertilizer per mu of crops in China is 21.9 kg, which is much higher than the world average (8 kg per mu), 2.6 times that of the United States and 2.5 times that of the European Union; second, the imbalance in fertilization is prominent. in the eastern economically developed areas, the lower reaches of the Yangtze River and urban suburbs, excessive fertilization is common for economic horticultural crops with high added value, such as vegetables and fruit trees; third, the utilization rate of organic fertilizer resources is low. At present, the total nutrients of organic fertilizer resources in China are more than 70 million tons, and the actual utilization rate is less than 40%. Fourth, the fertilization structure is unbalanced, the traditional artificial fertilization is still dominant, and the phenomenon of chemical fertilizer spreading and surface application is relatively common. Mechanical fertilization only accounts for about 30% of the planting area of major crops.

All kinds of experimental data show that the marginal benefit of chemical fertilizer input in China has decreased obviously. Take nitrogen fertilizer as an example, from 1998 to 2013, the nitrogen application rate of wheat in China increased by nearly 200%, but the per unit yield only increased by 50%.

This shows that the application of chemical fertilizer has reached the "ceiling", and the effect of using more chemical fertilizer on increasing grain yield is limited.

It is necessary to construct a green fertilizer system for chemical fertilizer reduction.

In order to reduce the use of chemical fertilizer, relevant agricultural departments have taken actions, such as soil testing formula projects, mechanized deep ploughing, water and fertilizer integration and other measures.

Zhang Shuqing said: "We can learn from the successful experience of foreign countries-- to build a green fertilizer system in China." First of all, it is necessary to realize the greening and high efficiency of chemical fertilizer products, to increase the efficiency and reduce the quantity of chemical fertilizer, the second is to construct the concept of integration of planting and cultivation, to realize the substitution and reduction of chemical fertilizer and organic fertilizer, and the third is to popularize the technology of precision fertilization and intelligentize fertilization mechanization. realize accurate input of fertilizer Finally, it is the legalization of management, gradually embarking on the legal track in the management of fertilizer input, and encouraging farmers to use new environmental protection planting technologies through the establishment of scientific subsidy policies. "

For example, in recent years, the rapid development of slow and controlled release fertilizers, water-soluble fertilizers, value-added fertilizers and other new fertilizers meet the needs of green environmental protection, safety and efficiency. Take the value-added fertilizer as an example, the fertilizer modified synergistic products produced by adding natural active substances such as alginic acid, humic acid and amino acid in the process of fertilizer production. Synergists such as alginic acid, humic acid and amino acid are all natural substances or plant sources, which can improve the utilization rate of fertilizer and is environmentally friendly and safe.