Suspension Fertilizers

Use of suspensions has grown very rapidly in the United States during the past 5 years. Some of the main reasons for their increased popularity are the same as for other fluids. However, some of the reasons they are used in preference to solution-type mixtures are  

The most popular phosphate material for suspensions is still ammonium polyphosphate solutions. However, 

In using this process rapid cooling to 60°C is effected -by-the evapoTative-cooler. The mixture is redrculated with the pump while gelling clay. Add is ammoniated to an N P20s weight ratio of 0.33 1. With this procedure aD of the crystals in the suspension are small DAP crystals. An example of the formulation for a 12-12-12 suspension produced in this type of plant is given in Table 10.9. 

The use of granular material for the production of suspensions is well established. Granular material such as MAP, DAP, and urea have been used. 

Probably the main reason for using the granular materials is that they are usually the most economical source of phosphate delivered to the use areas. Also, when ammonia is added to the suspension the material cost usually is less than the comparable cost for bulk-blended (dry mix) materials. Other reasons given for the conversion of granular materials to fluids are  

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When 20% of the phosphoms was polyphosphate, the compounds ia the product were ia the ratio of 3.5 mole MAP per mole of the pyrophosphate. The principal use of the material was ia the production of suspension fertilizers. In this appHcation the polyphosphate content imparted improved storage properties to the suspensions. The granular soHd APP, however, also had excellent storage properties and was a good material for use ia bulk blends and for direct appHcation. 

Suspension Fertilizers. Suspension fertilizers were developed chiefly as a means of... 

Young, R. D., Providing Micronutrients in Bulk-Blended, Granular, Liquid and Suspension Fertilizer, Comm. Fert., 118(1), 21-24 (Jan. 1969). 

Suspension Fertilizer (ISO) - A two-phase fertilizer in which solid particles are maintained in suspension in the aqueous phase,... 

Suspension Fertilizer (AAPFCO) - A fluid containing dissolved and undissolved plant nutrients. The suspension of the undissolved plant nutrients may be inherent with the materials or produced with the aid of a suspending agent of nonfertilizer properties. Mechanical agitation may be necessary in some cases to facilitate uniform suspension of undissolved plant nutrients. 

Suspension Fertilizer - A liquid (fluid) fertilizer containing solids held in suspension, for example, by the addition of a small amount of clay. The solids may be water-soluble in a saturated solution, or they may be insoluble, or both. 

When micronutrients are incorporated in suspension fertilizers, solubility is not a technical problem although it may be an agronomic problem. Soluble or insoluble compounds of micronutrient elements are added to suspension fertilizers using materials of small enough particle size that they are easily suspended and will not clog spray nozzles. Production of suspension fertilizers containing micronutrients has been described by Silverberg et al. 123]. 

Typical density values for some common fluid fertilizer grades are listed in Table 18.14 (solution fertilizers) and Table 18.15 (suspension fertilizers). 

Typical viscosity values for some common fluid fertilizer grades are listed in Table 18.14 (solution fertilizers) and Table 18.15 (suspension fertilizers). For fluids that are to be applied directly to the soil, the viscosity must not exceed 800 MPa s at 27 C and 900 MPa s at 0°C. The viscosity of base grades that are primarily for use in -productiorvof-fluid-blends-mustmot exceed 1,000 MPa s at 27°C and 1,500 MPa s at 0 C. Field tests have shown that fluid blends that do not meet the above viscosity criteria usually cannot be uniformly applied to the soil, and base grades that do not meet these viscosity criteria usually cannot be satisfactorily drained from storage tanks... 

Table 18.15. Typical Properties of Various Suspension Fertilizers ... 

Suspension Fertilizers. Suspension fertilizers were developed chiefly as a means of breaking the grade barriers imposed on solution fertilizers by solubility limitations. The low solubility of potassium chloride was particularly troublesome, in that high-potash solution grades were not possible. 

There is considerable variety in the types of fertilizer raw materials used commercially in preparation of suspension fertilizers. This is indicated in Fig. 11.21, where some of the more popular materials are listed. Likewise, production procedures and equipment vary considerably. Provision of a high-shear mixer is essential not only for gelling of the suspending clay but also for disintegration of... 

FiQ-11.23. Suspension fertilizer production using solid feeds (1-3% gelling clay also included in mix). 

Uses Dispersant In wettable powds. In water-sol. pl., suspension cones, with mean particle size < 2.0 p, and water-dlsp. granules mlg. by spray drying, compaction granulation, and extrusion dispersant or codispersant for fomnulations applied In high hardness water and liq. or suspension fertilizer Properties Free-flowing bm. powd. complete sol. in water m.w. 4200 bulk dens. 34 Ib/ft (packed) surf. tens. 42.1 dynes/cm (1 % aq.) pH 11 (2% aq.) 12.5% total suitor 1.6% Na2 03 8% moisture... 

Chem. Descrip. Elhoxylated sodium salt of highly sulfonaled krafi lignin Uses Agrochem. dispersant which can tolerate high ionic sir. conditions of liq. and suspension fertilizers and high hardness waters Properties Free-flowing powd. complete sol. in water bulk dens. 35 Ib/fP (packed) surf. tens. 42 dynes/cm (1% aq ) pH 11.5 (2% aq ) 11% sulfur 8% moisture Use Level 1-2%... 

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