ISSN:
1573-0867
Keywords:
Al-urea
;
Fe-urea, and Mn-urea complexes
;
free water content
;
ammonia volatilization
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract It has been the experience of the fertilizer industry that urea should not be cogranulated or blended with superphosphate because urea reacts with monocalcium phosphate monohydrate (MCP·H2O) in superphosphate to form an adduct. This reaction releases the water of hydration and causes the product to become wet and sticky or severely caked during storage. The objectives of this study were [1] to test the feasibility of preventing or retarding the reaction by complexing the urea with various salt hydrates and [2] to measure ammonia volatilization from metal salt-urea complexes on the soil surface. Three metal salt-urea complexes — Al(urea)6(NO3)3, Fe(urea)6(NO3)3, and Mn(urea)4Cl2 — were prepared and cogranulated by compaction with pure MCP·H2O or triple superphosphate (TSP) at a mole ratio of MCP:urea as 1:2. These materials were then compared with the same material without metal salts in terms of changes in free water content during a storage period of 6 weeks. Without metal salts a rapid and significant increase in free water content of the cogranulated MCP·H2O + urea or TSP + urea was observed. The increases in free water content were found to range from 1.5% to 1.8%, corresponding to approximately 63% and 78% of the added MCP·H2O that reacted with urea in the cogranulated products. On the other hand, little change or only a slight increase (less than 0.5%) in free water content was observed with the cogranulated metal salt-urea complexes. Ammonia volatilization losses from urea on the soil surface were measured in a period up to 14 d with two soils: Windthorst (pH 7.6) and Savannah (pH 7.0). The fertilizer materials used were granular. In Windthorst soil, the amounts of NH3-N lost were 25% for prilled urea, 11% for Mn(urea)4Cl2, and essentially none for Mn(urea)4Cl2 compacted with TSP at a mole ratio of MCP:urea as 1:1 or 1:2. In Savannah soil, the amounts of NH3-N lost were 39% for prilled urea, 24% for Mn(urea)4Cl2, 15% for Fe(urea)6(NO3)3, and less than 6% for each of the two metal salt-urea complexes compacted with TSP. The acidity that resulted from metal complexing of urea reduced NH3 volatilization from hydrolyzed urea in soils, and additional acidity produced from hydrolysis of MCP·H2O further reduced NH3 losses when materials were applied as multicomponent granules (metal salt + urea + TSP).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01066611
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