[Industry Horizons] Marching Towards the Ideal Complete Fertilizer

One of the problems existing in the use of chemical fertilizers in China is the "over-refinement" of chemical fertilizer varieties. In 2012, China produced 62 million tons of urea, 28 million tons of ammonium phosphate fertilizers, and the total supply of soluble potash salts was 16.6 million tons. That is, in 2012, there were 100 million tons of high-concentration basic fertilizers available as raw materials for compound (mixed) fertilizers. With 290 kilograms of urea, 410 kilograms of monoammonium phosphate, and 300 kilograms of potassium chloride, it is easy to produce a high-concentration compound fertilizer with a ratio of 18-18-18, which contains 18% nitrogen, 18% phosphorus pentoxide, 18% potassium chloride, and 13.5% chlorine.

Professor Xu visits and inspects the production situation in the company's workshop

In 2012, according to the statistics of the China Phosphate Fertilizer Industry Association, among the 55 large and medium-sized compound fertilizer plants across the country, the total output of compound fertilizers was 32.6 million tons. The average nutrients were 15.77% nitrogen, 16.53% phosphorus pentoxide, 13.55% potassium oxide, and the total nutrient content was 45.35%. To produce this compound fertilizer with average nutrients, 241 kilograms of urea, 370 kilograms of monoammonium phosphate, and 226 kilograms of potassium chloride can be used. Considering that the compound fertilizer contains 20 kilograms of water, there is still a surplus of 137 kilograms. How to make up for these remaining amounts? Currently, the common practice is to replace urea with cheap ammonium chloride, or use inert materials (such as clay, kaolin, bentonite, attapulgite, stone powder, zeolite powder, sepiolite powder, etc.) as fillers to adjust the components to the required proportion. Only a few factories use low-concentration fertilizers containing nutrient elements such as calcium magnesium phosphate fertilizer, superphosphate, and ammonium sulfate to fill the remaining amounts.

Crops need 17 essential nutrient elements for growth: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, iron, chlorine, boron, manganese, copper, zinc, molybdenum, and nickel. Most of the high-concentration compound fertilizers sold on the market only provide nitrogen, phosphorus, potassium, chlorine, and sulfur. This leads to nutrient imbalance in crops, a decline in their resistance to diseases and adverse climatic conditions, and makes them more vulnerable to pest and disease attacks. High-yield crops are prone to lodging during the mature period, and lodging is one of the limiting factors affecting the further increase in yield.

Extensive research at home and abroad has shown that unbalanced fertilization is likely to lead to the occurrence of pests and diseases. Excessive application of nitrogen makes the leaves thick and fleshy, making them more attractive to pests; the leaves are weak, the stems and leaves have poor erectness, the area exposed to sunlight becomes smaller, and the air permeability is poor; the contents of calcium and silicon, which play an important role in disease resistance in plants, are relatively reduced. All these affect the increase in yield and lead to an increase in the use of pesticides.

The reasonable application of medium and trace nutrient elements helps to reduce the occurrence of pests and diseases. Applying calcium can reduce the ulcer disease of tomatoes, the black mold disease of onions, the gray mold disease of lettuce, and the root rot of cabbages; applying silicon can inhibit the blast and sheath blight of rice, the powdery mildew of wheat, and the wilt of cucumbers. Nutrient elements such as potassium, silicon, and calcium are often called functional elements, which can improve the stress resistance of crops.

Magnesium is the core element of chlorophyll. The combined action of nitrogen, magnesium, and iron elements can significantly increase the green color of the leaves. Chlorophyll synthesizes carbohydrates through photosynthesis, which is the basis for high crop yields; the joint action of magnesium and sulfur can increase the oil content in seeds.

Sulfur is an essential component of proteins, and almost all proteins in crops contain sulfur. The mustard oil in cruciferous seeds and the garlic oil in onions and garlic are all thioester compounds. Sulfur is a flavor element that gives many crops a special pungent and fragrant smell.

According to the latest estimation by the Ministry of Agriculture, among the cultivated land soils in China, the proportions of trace elements below the deficiency critical values are: calcium 63%, magnesium 53%, sulfur 40%, boron 84%, iron 31%, manganese 48%, copper 25%, molybdenum 59%. Compared with the second national soil survey, the area of cultivated land lacking medium and trace elements has nearly doubled.

Zhengzhou University decomposes phosphate rock with urea sulfuric acid without discharging phosphogypsum, and adds calcium magnesium phosphate fertilizer and molten phosphate potassium fertilizer during the fertilizer manufacturing process to form a medium-concentration, multi-nutrient, and functional compound fertilizer. This fertilizer contains nitrogen, phosphorus, and potassium, with a total nutrient content of 36% to 42%, contains more than 2% of calcium and magnesium nutrient elements, and more than 5% of sulfur and silicon, with comprehensive functional nutrient elements; the fluorine in the phosphate rock exists in the compound fertilizer in the form of urea fluorosilicate, which can partially replace pesticides; urea exists in a complex state, and the nitrogen has a moderate slow-release effect; phosphorus and potassium exist in both water-soluble and citrate-soluble forms, improving the fertilizer utilization rate.

The urea sulfuric acid functional compound fertilizer process is a new compound fertilizer process with low cost and no pollution. This medium-concentration, multi-nutrient, and functional compound fertilizer has shown excellent fertilizer effects in the field trials of rice in Hubei and Henan provinces and wheat in Henan and Shandong provinces. It not only increases the yield by 5% to 20%, but also has the additional functions of enhancing lodging resistance and reducing pests and diseases. The field trials of Luxi Chemical Industry have shown that under the same application amount, the fertilizer effect of the urea sulfuric acid functional compound fertilizer with a total nutrient content of 40% is higher than that of the ordinary compound fertilizer with a total nutrient content of 45%, and the incidence of pests and diseases is low. This is due to the synergistic effect of multi-nutrients such as calcium, magnesium, sulfur, and silicon and the additional functions of silicon and calcium. The medium-concentration, multi-nutrient, and functional compound fertilizer has good economic and environmental benefits.

General Manager Liu takes a group photo with Editor-in-Chief Feng of China Chemical Industry News in the company

Hubei Yishizhuang Agricultural Technology Co., Ltd. has, for many years, used calcium magnesium phosphate fertilizer, superphosphate, and ammonium sulfate as nutrient regulators to produce medium-concentration, multi-nutrient, and functional compound fertilizers with a total nutrient content of 30% to 40% of nitrogen, phosphorus, and potassium. These fertilizers are used for the cultivation of citrus, leafy vegetables, rape, corn, rice, etc. When applied in the same weight, their fertilizer effects are equivalent to or exceed those of ordinary compound fertilizers with a total nutrient content of 45%, and they also improve the quality of crops.

Professor Xu visits the company and takes a group photo with General Manager Liu of the company

Abroad, the concept of the "ideal complete fertilizer" has been proposed. This means that when applied once, it can supply all the nutrients necessary for crops in the current season; the release of nutrients should be adapted to the fertilizer requirements of crops at different growth stages; to save labor, the fertilizer should contain herbicides, insecticides, and fungicides; it should contain substances for drought resistance, cold resistance, lodging resistance, and plant growth regulation; and it should have the function of improving the soil, especially the lower layer of the soil. And the medium-concentration, multi-nutrient, and functional compound fertilizer is approaching this concept of the "ideal complete fertilizer".

(Authors: Xu Xiucheng, Hou Cuihong, Zhao Bingqiang, Zhang Weifeng. Date: April 4, 2014. Source: China Chemical Industry News)

Xu Xiucheng: A nationally renowned chemical process expert, a senior professor at Zhengzhou University, the editor-in-chief of the journal Phosphate Fertilizer & Compound Fertilizer. He has won 2 national technological invention awards and several provincial and ministerial awards; he has obtained 5 Chinese invention patents and 1 US patent, among which he has won 1 Chinese Patent Excellence Award and 1 Chinese Patent Gold Award.

Zhao Bingqiang: A researcher and postdoctoral fellow at the Institute of Soil and Fertilizer, Chinese Academy of Agricultural Sciences, the leader of the innovation team of the Ministry of Agriculture. He is responsible for the research and management of the "National Long-term Monitoring Base Network for Soil Fertility and Fertilizer Efficiency", a national key field experimental station. He is also the secretary-general of the Chinese Society of Plant Nutrition and Fertilizers.