Urea

About: Urea is a research topic. Over the lifetime, 21394 publications have been published within this topic receiving 382444 citations. The topic is also known as: carbamide & carbonic acid diamide.

Loss of nitrogen and phosphorus in tile drainage as influenced by urea application and grazing animals

Abstract: The effects of urea fertiliser and grazing dairy cattle on the amounts of N and P forms transported in tile drainage from permanent pasture were investigated. In 4 weeks after an application of urea (60 kg N/ha) in July 1975 the increased loss of nitrate (NO3) and total nitrogen (TN) in tile drainage accounted for 2.0 and 2.3% respectively, of the applied fertiliser N. Grazing resulted in a dramatic increase in the concentrations of dissolved inorganic P (DIP) and particulate P (1.5- and 40-fold increases respectively). Concentrations of both NO3 and TN increased 5-fold immediately after grazing, although this effect was less sustained than that caused by urea application. Grazing was of comparable importance to urea application of the loss of NO3 and TN in tile drainage. The greater increase in the loss of particulate P (46.9 g/ha/4 weeks), compared to that of DIP (23.1 g/ha/4 weeks), resulted from a 50% increase in the amount of sediment carried. A 17% reduction in the amount of water discharged after g...

Cyclic urea-formaldehyde prepolymer for use in phenol-formaldehyde and melamine-formaldehyde resin-based binders

Abstract: The preparation of phenol-formaldehyde and melamine-formaldehyde resin-based binders extended with a cyclic urea-formaldehyde prepolymer and to products prepared using the binders. More particularly, the invention relates to a cyclic urea prepolymer comprising urea, formaldehyde, and ammonia or a primary amine which, when added to a phenol-formaldehyde or melamine-formaldehyde based resin, results in a useful binder for the manufacturer numerous articles.

Volatilization of ammonia from urea applied to soil: Influence of hippuric acid and other constituents of livestock urine

Abstract: Ammonia volatilization from five nitrogenous constituents of urine, assessed over 8 days following their application to columns of soil, and expressed as a proportion of the N applied, decreased in the order: urea, allantoin, creatinine, creatine, hippuric acid. However, hippuric acid, when mixed with urea in solution at a concentration such that hippuric acid-N = 2.5% of urea-N, substantially increased the volatilization of ammonia from the urea, particularly during the first 2 days after application to soil. The presence of the hippuric acid also enhanced the increase in soil pH, measured 24 h after application of the solution, in comparison with urea alone. A concentration of hippuric acid twice that indicated above appeared to exceed the optimum for increasing volatilization. The other constituents of urine listed above had little if any effect on the volatilization of ammonia from urea. Volatilization was greatly influenced by the concentration of total N in solutions of urea plus hippuric acid: the proportion of the N that was volatilized increased with increasing concentration over the range 1–10 g N 1 −1 but declined at the highest concentration examined, 15gNl −1 . With urea (10 gNl −1 ) plus hippuric acid (0.23gNl −1 ), the pH of the solution over the range 5.0–9.0 had no appreciable effect on the extent of volatilization, or on the pH of a soil-solution mixture measured 24 h after the addition. Salt concentration in the solution, examined as potassium chloride and potassium acetate, also had little, if any, effect. A solution containing urea (10 g Nl −1 ) plus hippuric acid (0.25 g Nl −1 ) and adjusted to pH 8 was much closer to cattle urine in the extent and pattern of ammonia volatilization over 8 days than was urea alone.