Physical Properties of Fertilizers

The consumer cannot detect whether a fertilizer actually meets the guaranteed nutrient content however, federal or state laws normally regulate the nutrient content and thereby give some protection to the consumer. In contrast, physical condition usually is a matter only of agreement between purchaser and supplier. Normally, fertilizer regulatory laws do not regulate fertilizer physical properties. However, the consumer can certainly evaluate the physical condition of a fertilizer. Simply by observation, he can see whether a fertilizer is caked or free-flovnng, dusty or dust-free, wet and sticky or dry. 

The most frequently encountered problems resulting from deficiencies in physical properties are caking (agglomeration or lump formation), dustiness, poor flowalnlity, excessive hygroscopicity (moisture absorption characteristics), and segregation (nonuniformity of composition throughout a fertilizer lot). 

The physical quality of a fertilizer can be evaluated by many different methods. These methods of measure- 

This chaptar defines the various physical properties discusses the effects arxl importance of these physical properties on product quality briefly reviews the types of methodology used in measuring these properties and gives some typical values for most of these properties for various fertilizers. Literature references are given, indicating where more detailed information can be obtained. 

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Hofstee, J. S., Physical Properties of Fertilizer in Relation to Handling and Spreading, Wageningen Agricultural University, Wageningen, The Netherlands (1993). 

Hoffmeister, G. 1979. Physical Properties of Fertilizers and Methods for Measuring Them, TVA Bulletin Y-147, Tennessee Valley Authority, Environmental Research Center, Muscle Shoals, AL, U.S.A. 

S. Rutland, David W. 1993. Manual for Determining Physical Properties of Fertilizer, Reference Manual lFDC-R-10, Second Edition, International Fertilizer Development Center, P.O. Box 2040, Muscle Shoals, AL, U.S.A. 

In Japan, ureaform is also produced as a component of compound fertilizers by the addition of formaldehyde solution to the urea solution fed to the granulator.49 In one process a methylene urea reactor is used to react urea and formaldehyde solution to produce a slurry that feeds directly to a granulation plant with other materials to make compound fertilizers.50 Some slow-release nitrogen is formed, and the physical properties of the products are improved. 

The quality of a fertilizer product is basically judged by two criteria chemical properties and physical properties. The chemical properties (nutrient content, form, and availability to the crop) and their effectiveness for crop growth are the main reasons for using a fertilizer. In contrast, physical properties of a fertilizer product are important with respect to processing, handling, storage, and field application. 

Seawater contains about 3.5% salts, in which the content of sodium chloride is about 80%. The concentration of dissolved salts as well as temperature and pressure influence the physical properties of seawater. The total salt concentration is usually called salinity . Salinity is generally measured by the electrical conductivity or determination of chloride content. At present, salinity(S) is defined as S = 1.80655 Cl (Cl is the concentration of chloride in seawater) [5]. Dissolved oxygen and silica are usually measured as additional parameters to characterize seawater. The concentrations of nitrogen and phosphorus are the indices of nutrients and measure the fertility and production of the oceans. 

Fertilizers are packaged in a variety of different forms including solids, liquids (solutions and suspensions), and gas (anhydrous ammonia). The important physical properties of solid fertilizers are particle size, particle strength, caking tendency, chemical stability, and hygroscopicity. 

The soil pH considerably affects soil characteristics. It is important for many soil-forming processes and it also affects the biological activity of soil organisms. The soil pH directly affects particularly the solubility of many substances, ion adsorption and desorption, coagulation and peptization of colloids and chemical reactions. By its action on the soil structure it also affects most of the physical properties of the soil. Thus, the soil pH is an important parameter of the soil fertility. 

The foregoing are the principal Immediate conversion products of ammonia. There are however, a large number of combinations of nitrogen materials now being worked up for fertilizer use. The physical properties of most of the fixed nitrogen products which contain nitrogen as the only fertilizer ingredient are far from satisfactory In that they readily absorb moisture from the air, and cake or pos-... 

In the following section, most of the physical properties of solid fertilizers will be discussed. 

There are a number of other physical properties of solid fertilizers which are of importance for various reasons. These physical properties are briefly discussed below. 

Table 18.14. Typical Physical Properties of Various Solution Fertilizers ...

Other physical properties of fluid fertilizers that may have some specific importance are vapor pressure, specific heat, wettability, surface tension, refractive index, and conductivity. 

Hoffmeister, George, and C. P. Harrison. 1977. Physical Properties of Granular Urea-Based NP and NPK Fertilizers, Proceedings of the 27th Annual Meeting of the Fertilizer Industr , Round Table, pp. 162-170, Washington, D.C., U.S.A. 

Tennessee Valley Authority. 1970. Effect of Aluminum and Iron on the Physical Properties of Ammonium Phosphate Fertilizers, IN Neuj... 

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