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Slow-release fertiliser production

The aim is to produce slow-release (sr) fertilisers from urea-formaldehyde containing solid wastes from the tanning industry and to apply the sr fertiliser for growing diverse agricultural products.

Efficient use of N fertilisers by crops has been, and continues to be, of major agronomic interest. 50% of applied fertiliser N is taken up by the plants, 25% is lost by different mechanisms and 25% remain in the soil in relatively stable forms. According to a number of studies, these losses are due primarily to lixiviation, denitrification, volatilisation and immobilisation in organic matter. Nitrogen use is also adversely affected by sudden changes in the available soil nitrogen and by non-optimal synchronism between nitrogen supply and demand of the plant. These problems can be alleviated by the use of controlled-release fertilisers (CRF) whose major advantage is to provide a continuous and regular supply of nitrogen for the whole growth season with a consequent saving in spreading costs. They also promise to avoid the need for repeated applications, to minimise excessive consumption of N, to avoid disturbing the nutrient balance, as well as to reduce N losses by leaching, to decrease gaseous losses of N, and to reduce the risk of injury resulting from over-application, particularly with seedlings. Information regarding the nutrient release patterns from controlled-release fertilisers are often difficult to interpret due to differences in methodology used by various manufacturers and investigators. Urea form is one of the controlled-release N fertilisers produced by the reaction of urea with formaldehyde in aqueous solutions in the presence of acid which catalyses the reaction. The degree of polymerisation depends on the molar ratio of urea to formaldehyde and on the pH, time and temperature of reaction. A typical urea-form may contain 30% of its nitrogen in forms that are soluble in cold water (25 degrees Celsius). The quality of the remaining 70% is judged by the percentage that is soluble in hot water. At least 40% of the nitrogen insoluble in cold water should be soluble in hot water for an acceptable agronomic response; typical values are 50% - 70%. Urea-forms tend to vary in composition due to the method of manufacture; therefore, they are characterised by using an activity index (AI) as defined by: AI = CWISN - HWISN / CWISN x 100 CWISN is the percentage of N that is insoluble in cold water (25 degrees Celsius), and HWISN is the percentage of N that is insoluble in hot buffer solutions (98-100 degrees Celsius). UF is mainly used on turfs and lawns, where the growing season is long and the rate of nitrogen consumption is fairly steady. It has no residual salt effect and does not scorch foliage. The synthesis of 15N labelled fertilisers will permit more accurate evaluations of the contributions of the fertiliser N than either yields or total nitrogen uptake of the crops. Labelling also permits direct measurement of the amounts of fertiliser N taken up by crops or left in the soil at the end of the cropping season. Availability of N to plants from applied inorganic or organic fertilisers using 15N isotopes has been investigated in much detail; however, among the numerous agronomic studies, few of them use 15N label controlled-release N fertilisers. The objective of this research is to determine the effects of the urea-formaldehyde (15N-labeled) containing tannery solid wastes as a controlled-release fertiliser having a high activity index (AI > 60) and other N fertilisers (Urea, ammonium sulphate) on growth characteristics (dry matter, N content, N uptake, fertiliser use efficiency) at different growth stages for different plants and soil types under growth room and field conditions. Keywords: leather, waste, fertiliser.
Acronym: 
SRF
Project ID: 
3 519
Start date: 
01-03-2005
Project Duration: 
64months
Project costs: 
3 200 000.00€
Technological Area: 
Water Pollution / Treatment
Market Area: 
Textiles (synthetic and natural)

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