How can reduction and efficiency gains be put into practice? The green yield-increase model is key
Reporter: As one of the crops in the first pilot program for fertilizer reduction in 2015, what problems do you think currently exist in corn fertilization?
Zhang Fusuo: Northeast China and the Huang-Huai-Hai region are China's main corn-producing areas. The common problems in corn fertilization are: overall chemical fertilizer application rates are on the high side, especially nitrogen fertilizer; there are large differences between regions, with some regions applying relatively high amounts; within the same region, fertilization varies greatly among different farmers, with over-fertilization and under-fertilization coexisting. Based on the above problems and the actual conditions of China's corn production, our team formulated a technical plan for reducing chemical fertilizer and increasing efficiency in corn production in Northeast China and the Huang-Huai-Hai region. The main measures are: establish regional technical indicators for total chemical fertilizer application control, so as to control regions and farmers with excessive fertilization; vigorously promote regional corn formula fertilizer to reduce unreasonable phenomena such as excessively high or low fertilization and unbalanced nutrients at the regional scale; implement mechanized straw return, increase the application of organic fertilizer, improve soil quality, and substitute organic for inorganic; and integrate and apply the green yield-increase model over large areas to raise corn yield per unit area, improve nutrient efficiency, and achieve reduction and efficiency gains.
Reporter: China's main corn-producing areas span a large range of latitudes. How can regional total control formulate technical indicators according to local conditions?
Zhang Fusuo: The key to regional total control lies in “adapting measures to local conditions,” so we divided the main corn-producing areas. According to production layout, climatic conditions, cultivation conditions, topography and soil conditions, the Northeast China and Huang-Huai-Hai region corn areas can be divided into 6 sub-regions: the Northeast cold spring corn region: most of Heilongjiang and eastern Jilin Province; the Northeast semi-humid spring corn region: southwestern Heilongjiang Province, central Jilin Province and northern Liaoning Province; the Northeast semi-arid spring corn region: western Jilin Province, northeastern Inner Mongolia Autonomous Region, and southwestern Heilongjiang Province; the Northeast warm and humid spring corn region: most of Liaoning Province, southeastern Inner Mongolia Autonomous Region, and northeastern Hebei Province; the North China central-northern summer corn region: all of Shandong Province and Tianjin Municipality, central and southern Hebei Province, central and southern Beijing Municipality, central and northern Henan Province, the Guanzhong Plain of Shaanxi Province, and southern Shanxi Province; the North China southern summer corn region: the area north of the Huai River in Jiangsu and Anhui Provinces, and southern Henan Province.
In my view, regional total control is based on the characteristic that under certain soil conditions, climatic conditions and within a certain spatial range, the potential soil nutrient supply level is generally stable, and it controls the total application amount of nitrogen fertilizer, phosphate fertilizer and potassium fertilizer during the entire crop growth period within a certain region to a reasonable range. Total control is determined based on the results of multi-year, multi-site fertilizer response trials within the region, which can both ensure crop yield and avoid fertilizer waste and environmental pollution caused by excessive fertilization. On the basis of subdividing production areas and combining the characteristics of each sub-region, we have already formulated specific total chemical fertilizer application control indicators (Table 1), and localities can further refine and apply them on this basis.
Reporter: The Action Plan for Zero Growth in Chemical Fertilizer Use by 2020 takes “precision” as the first technical path for zero growth in chemical fertilizer. After each sub-region has its own “major formula,” how can “minor adjustments” be made in combination with different local production conditions to achieve precise fertilizer blending?
Zhang Fusuo: To achieve precise fertilizer blending, the key is to make good use of the regional fertilizer blending technology of “major formula, minor adjustments.” This technology is based on summarizing common patterns such as the characteristics of regional crop production systems and cropping systems and the characteristics of soil nutrient supply, and determines the appropriate amounts and ratios of regional nitrogen, phosphorus, potassium and secondary and micronutrient fertilizers as well as corresponding fertilization technologies according to relevant technical principles of integrated nutrient resource management. It uses regionally formulated fertilizers developed through technology and market research as the technical carrier, and is supported by corresponding fertilization technologies and agrochemical services, so as to achieve the goals of regional high yield, high quality, efficient resource use and environmental protection.
The large-scale application of regional corn formula fertilizer can reduce unreasonable phenomena such as excessively high or low fertilization and unbalanced nutrients among farmers at the regional scale. On the basis of the regional major formula, for some regions or fields, the amount can also be adjusted according to yield level, climate/soil conditions, crop growth, soil testing and plant nutrient diagnosis, or certain single-element fertilizers can be applied in combination. This is the “minor adjustment,” so as to achieve more precise stage-based nutrient management. The regional major formulas and fertilization recommendations for corn in Northeast China and the Huang-Huai-Hai region (Table 2) have also been issued. Localities should strengthen soil testing and monitoring of crop growth conditions, ensure that fertilizer production enterprises blend fertilizers according to the formula, and provide locally adapted minor formula fertilizers while providing major formula fertilizers.
Reporter: At present, China's utilization rate of organic fertilizer resources is low, and soil organic matter content urgently needs to be improved. For corn planting, how can the combination of organic and inorganic be achieved, and the combination of land use and land nurturing?
Zhang Fusuo: Of the total nutrients absorbed by corn, about 35% of nitrogen, 20% of phosphorus and 80% of potassium are in the straw. Straw return is of great significance for returning nutrients, improving soil quality, and partially replacing chemical fertilizers.
In recent years, with the rapid development of mechanized corn harvesting, the proportion of corn straw return has increased substantially, especially in the Huang-Huai-Hai region. At present, on the basis of continuing to expand the area of corn straw return in the Huang-Huai-Hai region, the focus should be on improving the technical links of deep plowing into the soil and improving the sowing quality of the following wheat crop; in Northeast China, mechanized corn harvesting should be strongly supported and promoted to drive straw return, and autumn land preparation should be advocated to facilitate straw decomposition and water storage and soil moisture conservation.
On the basis of straw return, the fertilization plan for the following crop should be appropriately adjusted. Among these, the potassium fertilizer amount should be reduced by 15~30kgK2O/ha, and while the total nitrogen fertilizer amount remains stable, the proportion of nitrogen in the base fertilizer should be appropriately increased to facilitate nitrogen supply in the early stage.
In areas with the conditions, the application of organic fertilizers such as livestock and poultry manure compost, biogas residue and biogas slurry should also be vigorously promoted. In this case, the amount of chemical fertilizer can be reduced as appropriate.
Reporter: Excessive application of chemical fertilizer is driven by the need to increase yield. Under the condition of reducing chemical fertilizer, how can corn yield be further increased to achieve the goal of reduction and efficiency gains?
Zhang Fusuo: Insufficient or excessive chemical fertilizer will both reduce yield. To increase yield while saving fertilizer and improving efficiency, nutrient management technology must be combined with high-yield cultivation technology. In recent years, our nationwide research and practice on high-yield and high-efficiency corn have shown that only when fertilization technology is well combined with high-yield cultivation technology can a good effect of large yield increases and substantial chemical fertilizer reduction be achieved.
On the basis of implementing the above reduction fertilization technologies such as total control, regional fertilizer blending, and organic substitution, localities should closely combine them with dense planting high-yield mechanized cultivation technology, integrate a high-yield and high-efficiency green yield-increase model, and carry out large-area, whole-system demonstration and promotion applications to increase corn yield per unit area, improve nutrient efficiency, and achieve reduction and efficiency gains.