Objectives The physical and chemical properties of basic raw material fertilizers from different regions and manufacturers were analyzed and evaluated for the suitability of making blending fertilizers. The raw material fertilizers were classified according to their main physical properties. The values of the main factors affecting nutrient evenness distribution were tested, which would provide support for the selection of right materials for good quality belending fertilizer preparations.

Methods The common nitrogen, phosphate and potassium fertilizers were collected from markets. The average primary particle sizes (SGN), uniformity index (UI), hardness, repose angle, density, pH, and salt index were determined. According to the density, SGN and repose angle, the fertilizers were classified, and 13 blend fertilizer samples were prepared according to the principle of similarity and dissimilarity of the indexes, and the N∶P₅O₂∶K₂O ratios of the sample fertilizer were 1∶1∶1 or 2∶1∶1. An external fluted roller fertilizer distributor was used for the fertilization simulation experiment. Fertilizer samples were mixed at the rate of 6, 8, 10, 12 km/h, and the nutrient ratios of the distributed fertilizer samples were determined.

Results The SGN of nitrogen, phosphorus and potassium fertilizers were 305−469, 264−345 and 281−348, respectively. UI was 41.68−69.94, 46.03−60.08 and 40.27−47.27. Densities were 0.71−0.87 g/cm³, 0.84−1.05 g/cm³ and 1.03−1.19 g/cm³. Potassium fertilizer was generally superior to phosphate and nitrogen fertilizer in physical properties. The hardness of tested nitrogen fertilizers was generally low. Except for the ammonium chloride produced in Jiangsu, the hardness of other nitrogen fertilizers was 0.20−13.27 N. Phosphorus and potassium fertilizers have relatively high hardness, which was in ranges of 27.47−41.38 N and 23.55−48.47 N. Most urea and ammoniam phosphate were round or oval in shape, with small repose angles. The fertilization simulating results showed that the most uniform nutrient distribution was in blended fertilizer sample of F5 (N₁P₁K₅, mixed base on the principle of similar SGN), with N∶P₅O₂∶K₂O ratio of 1.64∶0.98∶1.40 after getting out of the fertilizer distributer; the most uneven nutrient distribution was F9 (N₇P₇K₅, mixed base on the principle of the SGN inequality), with N∶P₅O₂∶K₂O ratio of 2.22∶0.79∶0.78.

Conclusions More than

80% of the raw material fertilizers are suitable for making blended fertilizers. SGN and repose angle of a raw material fertilizer are the two determining factors for the quality of blended fertilizers. The SGN of 340−348 and small repose angle are required for the uniformity of nutrient distribution after blending.