Stabilized Fertilizers: Master Core Technologies, Regulate Market

By Shi Yuanliang, Li Jie, Wang Lingli, Li Zhong, Wei Zhanbo, CAS Shenyang Institute of Applied Ecology

China’s fertilizers industry developed in three stages, for which straight fertilizers, compound fertilizers and slow/controlled-release fertilizers/stabilized fertilizers can be taken as respective representatives. Commercialization of stabilized fertilizers in China already has a history of over 30 years. Their sound agronomic effects and environmental benefits back cost reduction and efficiency improvement in big ways.
Urease inhibitors and nitrification inhibitors are core technologies for stabilized fertilizers. Research into urease inhibitors started rather late in China. Globally, many varieties of urease inhibitors are patented and in customary use in agricultural production, mainly in Germany, India and the United States.
In the present century, China has invested a great deal in researching the improvement and application of inhibitor synergy technology. Owing to their synergistic effect, the consumption of inhibitors has been considerably reduced. The technology has gained extensive applications. Slow-release urea, stabilized compound fertilizers and stabilized compound nitrogen fertilizers have been put on the domestic market, becoming mainstream new-type fertilizers.
Research on new inhibitor materials is also unfolding in China, mainly aiming to discover new inhibitor materials and research inhibitor protection technologies. Root exudates of plants have also been found to be useful to inhibit nitrification.

Commercialization status
of stabilized fertilizers

With the R&D of urease inhibitors and nitrification inhibitors, long-acting urea developed by CAS Institute of Applied Ecology has been produced in Liaohe Chemical Fertilizer Plant, Panjin Chemical Fertilizer Plant, Daqing Chemical Fertilizer Plant and Haolianghe Urea Plant since the early 1980s. Products have been used extensively in Northeast China, North China and East China. At the beginning of the 21st century, CAS Shenyang Institute of Applied Ecology developed inhibitor synergy technology and used it in fertilizer modification. Commercial production ensued in collaborations with SKF Chemical Co., Ltd., Shenyang Zhongke New Fertilizer Co., Ltd., Jinxi Natural Gas Chemical Co., Ltd., and Heilongjiang Beifeng Agricultural Production Means Group. Commercialization of NAM (a product compounded by urease/nitrification inhibitors) and Zengan series products has enabled stabilized fertilizer production to thrive in China. Researchers have used the technology to make compound fertilizers (special fertilizers) according to the need of individual fertilizer applications to simplify the process of farming, so stabilizer fertilizers have a widening application range.
Using the synergistic function of urease inhibitors and nitrification inhibitors to control nitrogen conversion in fertilizer modification, problems such as the short acting period of single inhibitors and the unfavorably rapid conversion and release of nitrogen fertilizers are solved. One-time base application of long-acting compound fertilizers and slow-release urea with no need of topdressing is also achieved. There are more than 40 producers of stabilized compound (mixed) fertilizers, including Shandong SKF Chemical Co., Ltd., Kunming Agricola Compound Fertilizer Co., Ltd., Heilongjiang Beifeng Agricultural Production Means Group, Hebei Zhongjia Chemical Fertilizer Co., Ltd., and Chongqing Jiangbei Chemical Co., Ltd. Output and sales exceed 1.0 million tons a year. Producers of stabilized urea include Liaoning Huajin Chemical (Group) Co., Ltd., Shandong Luxi Chemical Group Co., Ltd., Sichuan Meifeng Chemical Industry Co., Ltd., SinoChem Jilin Changshan Chemical Co., Ltd., Shaanxi Fengxi Chemical Group Co., Ltd., Jilin Longyuan Chemical Fertilizer Co., Ltd., Hubei Xiangyun (Group) Chemical Industry Co., Ltd., Jiangsu Huachang Chemical Co., Ltd., SinoChem Group and Jinzhou Chemical Co., Ltd. Output and sales exceed 300 kt a year. Production processes for stabilized fertilizers have also benefitted from technical R&D. In making stabilized urea, biochemical inhibitors are compounded with solvent carriers and then dissolved with urea melt. The production process for stabilized macro urea has also been developed. The process of continuous degradation and spontaneous addition, developed in the production of stabilized urea, has solved problems with inhibitors such as long dissolution period, slow decomposition and melt pump corrosion. The ammonia-acid process is a new compound fertilizer production technology that appeared in China in the past decade. It has reduced the loss of inhibitors in high-temperature and acidic conditions.
Domestic output of stabilized fertilizers in 2016 was around 1.45 million tons, of which stabilized urea was 330 kt and stabilized compound (mixed) fertilizers was 1.22 million tons. There were more than 60 varieties.

Problems in the development of stabilized fertilizers

Environment-friendliness, great stability, high efficiency and convenient application will now be the main goals in development. Development of stabilized fertilizer technologies is booming, with constant integration and innovation. There are however still some problems such as the high production cost of fertilizers and the short acting period of inhibitors. The path for stabilized fertilizer development in China is to take the R&D results for green, low-price and high-quality inhibitors as a breakthrough point, produce new varieties of stabilized fertilizers through upgrading large-scale, continuous and automatic processes and equipment, achieve commercial and large-scale production of new-type fertilizers, guarantee the safety of the environment and the quality assurance of agricultural products and promote the sustainable development of agriculture.

Technology:

Focuses in technology include: durable action of both urease inhibitors and nitrification inhibitors; mechanisms and technologies for compatibility between different inhibitors and for composite action between inhibitors and synergists; control of nutrient conversion biochemical processes for different nitrogen fertilizer special inhibitors; technologies for screening and synthesizing new efficient urease/nitrification inhibitors and configuring special urease/nitrification inhibitors; protection technologies for improving the stability of urease/nitrification inhibitors and extending their acting period. Inhibitors used in stabilized fertilizers today have different effects in different regions. Researchers have already worked a great deal to screen inhibitors for suitability to soil conditions and weather conditions. They have also done a lot of research on the combined use of inhibitors, making remarkable advances. Research on the adaptability of different types of inhibitors to different soils and crops is however yet to be intensified.

Market and legislation:

Quite a few institutions in China do technology R&D for new-type fertilizers such as stabilized fertilizers. Markets of related sectors are not yet well developed though, impeding development of the stabilized fertilizer sector. For example, chaotic market, counterfeit products and unsound laws and regulations constrain widespread application of related technologies and products. Urgent efforts should be made to establish management standards and guide development of this sector to benefit farmers and the environment.
So we should work harder to increase the utilization rate of chemical fertilizers, reducing the overall application volume of chemical fertilizers and innovating stabilized fertilizers, further the R&D of environment-friendly new inhibitors, high effect and low cost, develop protection technologies and efficient addition processes for inhibitors, combine technologies to control stabilized fertilizers with technologies for promoting the enrichment and absorption of synergists according to the specific features of a crop or a region, and develop functional and special stabilized fertilizers that are well targeted and suit specific regions or crops. Producers should not only master the core technologies for chemical fertilizers but also improve product R&D capabilities and adapt their marketing mode.