The behaviour of nitrogen fertilizers in neutral and acid loss soils
1981
Onyiego Benson Mochoge(Kenya Agricultural Research Institute, Nairobi (Kenya). National Agricultural Research Laboratories)
A study to quantify the transformations of two nitrogen fertilizers (N15 - tagged Ca(N03)2 and (NH4)2S04) during their passage in undisturbed soil columns was conducted in the laboratory. The upper 30 cm of two types of soils i.e. neutral agricultural and acid forest loess soils, were used and two temperatures, 40C and 230C were employed in the study. A steady-state water flow condition of 0.5 cm/day was established.It was found that there was higher N-immobilization after the application of NH4-fertilizer than N03-fertilizer. The forest soil exhibited higher immobilization than the agricultural soil and an increase in temperature increased N-immobilization in all cases. Nitrification rates and amounts were much higher in the agricultural than in the forest soil. In both soils, the nitrification rates were clearly influenced by temperature. Denitrification was higher after NH4- than after N03-application, and losses were generally higher in the forest soil. The temperature did not affect the amount of denitrification except in one treatment. After N03-application, the losses increased considerably at 230C treatment of the forest soil. The transport mainly took place in form of nitrates. NH4+ was submitted to exchange and fixation. Dispersion of the applied fertilizer was higher in the well-aggregated forest soil than in agricultural soil. This soil also exhibited anion exchange, leading to a slight retardation of nitrates. The study also showed that over the period of the experiment, no priming effect was noticed. Simulating the transport of N03-N through the soils using Continuous System Modeling Program (CSMP), the results obtained were in good agreement with the measured ones.
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