ISHS Acta Horticulturae 143: VIII African Symposium on Horticultural Crops
UREA HYDROLYSIS AND SUBSEQUENT TRANSFORMATIONS IN THE GEZIRA SOIL |
| Author: | A.T. Ayoub |
| Abstract:
The staple isotope N-15 was used to study urea transformations and the fate of nitrogen fertilizers applied to the Sudan Gezira soil. Eighty percent of the urea nitrogen applied to the Gezira soil was converted to ammonium-nitrogen within a week. The ammonium-nitrogen was converted into nitrate-nitrogen at an approximate rate of 1.0 ppm N/day under drying and rewetting conditions as compared to a rate of 3.5 ppm N/day for the soil moisture conditions. In a glasshouse experiment where 220 kg N/ha as NH4 NO3 was applied to Sudan grass, only 12.8 % of the total plant nitrogen came from NH4-N and 21.4 % came from NO3-N. Gaseous nitrogen losses amounted to 54 % of the added ammonium and 25 % of the added nitrate nitrogen. The low percentage of the nitrogen derived from the fertilizers and the high gaseous nitrogen losses, specially from the ammonium form, are noteworthy. Certain physical and chemical soil conditions had limited early plant growth and reduced its efficiency to absorb available nitrogen and compete efficiency with these losses mechanisms. | |
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