Reducing quantity and increasing efficiency should settle on the green mode of increasing production.

Reporter: Corn is one of the first crops to be tested for fertilizer reduction in 2015. What problems do you think exist in corn fertilization at present?

Zhang Fusuo: Northeast China and Huanghuaihai are the main corn producing areas in China. The common problems of corn fertilization include: on the whole, the fertilizer application amount is high, especially nitrogen fertilizer; there are great differences among regions, and the fertilizer application amount in some regions is relatively high; there are great differences in fertilizer application among different farmers in the same region, and excessive fertilizer application and insufficient fertilizer application coexist. Based on the above problems and the realistic conditions of corn production in China, our team formulated the technical scheme of corn fertilizer reduction and efficiency enhancement in Northeast China and Huanghuaihai region. The main measures are as follows: establishing total amount control technical indicators for regional chemical fertilizer application to control some areas and farmers with excessive fertilizer application; vigorously popularizing regional corn formula fertilizer to reduce unreasonable phenomena such as excessive or low fertilizer application and unbalanced nutrients in farmers on a regional scale; implementing mechanized straw returning to fields, increasing organic fertilizer application, improving soil quality, replacing organic with inorganic; and applying green yield-increasing models in large areas to improve corn yield, improve nutrient efficiency and realize reduction and efficiency.

Reporter: China's main corn producing areas have a large latitude span. How can regional total amount control achieve technical indicators formulated according to local conditions?

Zhang Fusuo: The key to regional total amount control lies in "adapting to local conditions", so we divided the main corn producing areas. According to production distribution, climate conditions, cultivation conditions, topography and soil conditions, maize in Northeast China and Huang-Huai-Hai region can be divided into 6 sub-regions: Northeast cold spring maize region: most of Heilongjiang Province and eastern Jilin Province; Northeast semi-humid spring maize region: southwest Heilongjiang Province, central Jilin Province and northern Liaoning Province; Northeast semi-arid spring maize region: western Jilin Province, northeast Inner Mongolia Autonomous Region and southwest Heilongjiang Province; Northeast warm and humid spring maize region: Most of Liaoning Province, southeast of Inner Mongolia Autonomous Region, northeast of Hebei Province; summer corn area in central and northern North China: all of Shandong Province and Tianjin City, central and southern Hebei Province, central and southern Beijing City, central and northern Henan Province, Guanzhong Plain of Shaanxi Province, southern Shanxi Province; summer corn area in southern North China: north of Huaihe River in Jiangsu and Anhui provinces, southern Henan Province.

In my opinion, regional total amount control is to control the total amount of nitrogen, phosphorus and potassium fertilizer applied in a certain region in the whole growth period of crops within a reasonable range according to the characteristics of soil conditions, climatic conditions and overall stability of soil potential nutrient supply level within a certain spatial range. Total amount control is determined based on the fertilizer efficiency response results of many years and multiple points in the region, which can not only ensure crop yield, but also avoid fertilizer waste and environmental pollution caused by excessive fertilization. Based on the subdivision of production areas and the characteristics of each subregion, we have formulated specific total amount control indicators for chemical fertilizer application (Table 1), which can be further refined and applied in various regions.

Reporter: The Action Plan for Zero Growth of Fertilizer Use by 2020 regards "fine" as the first technical path of zero growth of fertilizer. After each subregion has its own "big formula", how to combine the different production conditions of each region to carry out "small adjustment" to achieve accurate fertilizer allocation?

Zhang Fusuo: To achieve accurate fertilizer, the key is to use the regional fertilizer technology of "large formula, small adjustment". The technology is based on the induction of regional crop production system and planting system characteristics and soil nutrient supply characteristics, and determines the appropriate amount and proportion of nitrogen, phosphorus, potassium and medium and trace fertilizers in the region according to the technical principles of comprehensive management of nutrient resources, and takes the process and market research and development of regional formula fertilizers as technical carriers, supporting the corresponding fertilization technology and agrochemical services, so as to achieve the goals of regional high yield, high quality, resource efficiency and environmental protection.

The application of regional formula fertilizer can reduce unreasonable phenomena such as too high or too low fertilizer application and nutrient imbalance in regional scale. On the basis of regional large-scale formula, for some regions or fields, the dosage can also be adjusted according to the yield level, climate/soil conditions, crop growth, soil testing and plant nutrition diagnosis, etc., or a certain amount of simple fertilizer can be applied. This is a "small adjustment" to achieve more accurate phased nutrient management. The regional large-scale fertilizer formula and fertilizer recommendation for corn fertilization in Northeast China and Huang-Huai-Hai region (Table 2) have also been issued. All localities should strengthen soil testing and monitoring of crop growth conditions to ensure that fertilizer production enterprises allocate fertilizer according to the formula, and provide small-scale formula fertilizer according to local conditions while providing large-scale formula fertilizer.

Reporter: At present, the utilization rate of organic fertilizer resources in China is low, and the content of organic matter in soil needs to be improved urgently. For corn planting, how to realize the combination of organic and inorganic, land and fertilizer?

Zhang Fusuo: About 35% of nitrogen, 20% of phosphorus and 80% of potassium in corn nutrient absorption are in straw. Straw returning to field is of great significance for returning nutrients, improving soil quality and partially replacing chemical fertilizer.

In recent years, with the rapid development of mechanized corn harvesting, the proportion of corn straw returned to the field has increased significantly, especially in Huang-Huai-Hai area. At present, on the basis of continuing to expand the area of corn straw returning to field in Huanghuaihai area, we should focus on improving the technical links of deep ploughing and improving the quality of next wheat sowing; Northeast China should support and popularize corn mechanized harvest in order to drive straw returning to field, and advocate autumn soil preparation to facilitate straw decomposition and water storage and moisture preservation.

On the basis of straw returning to field, the fertilizer application scheme of next crop should be adjusted appropriately, among which, the amount of potassium fertilizer should be reduced by 15~30 kg K 2O/ha, and the proportion of base fertilizer nitrogen should be increased appropriately on the basis of total nitrogen fertilizer amount stability to facilitate nitrogen supply in early stage.

Conditional areas, but also vigorously promote the application of organic fertilizer, such as livestock manure compost, biogas residue biogas slurry, etc. In such cases, fertilizer use may be adjusted downwards as appropriate.

Reporter: The excessive application of chemical fertilizer is due to the need to increase production. How to further improve corn yield and achieve the goal of reduction and efficiency under the condition of fertilizer reduction?

Zhang Fusuo: Insufficient fertilizer or excessive fertilizer will reduce yield. Nutrient management techniques must be combined with high-yield cultivation techniques to increase yield and save fertilizer and increase efficiency. In recent years, the research and practice of high yield and high efficiency of maize carried out in China show that only by combining fertilization technology with high yield cultivation technology can the good effect of large increase in yield and large reduction in chemical fertilizer be achieved.

On the basis of implementing the above-mentioned total amount control, regional fertilizer application and organic substitution, all localities should be closely combined with high-yield mechanized cultivation techniques of dense planting, integrate high-yield and high-efficiency green yield-increasing mode, carry out large-area and whole-system demonstration and popularization application, so as to improve corn yield, improve nutrient efficiency and realize reduction and efficiency.