Kinetics and Leaching Study of Nitrate and Nitrite on Urea Hydrolysis in Alkaline Soil

Aims: The present research study describes leaching kinetics of NO2- and NO3- at different added urea concentrations on undisturbed columns of agriculture soil.
Study Design: This study design to understand solute transport in soil.
Place of Study: Samples are collected from the agriculture fields of Kota region and research work related to analysis is carried out at University of Kota. Rajasthan. India.
Methodology: The clay loam soil collected from agriculture fields of Kota, Rajasthan. India was dried and sieved for uniform particle size. Initial leaching rates of NO2- and NO3- ions have been calculated at different added urea concentrations and linear dependence of LRobs and [ion]i has been derived. The leaching kinetics of nitrate and nitrite have been studied by determining the concentrations of NO2- and NO3- in the leachate with time using standard spectroscopic method by measuring the wavelength at 520 nm and 410 nm respectively. The leaching was carried out till ions are completely removed. Effect of Na and Ca level of percolating water have been studied on nitrate and nitrite leaching. Graphical equation of different kinetic models applied on results were tested with least square regression analysis.
Results: The log-log plot of [ion]i vs LRobs are found to be second order for NO2- leaching and fractional order of more than one for NO3- leaching. On increasing Ca level of percolating water LRobs found to decrease while in case of Na results are found to be reverse.
Conclusion: It is evident that urea-soil interaction generate nitrate and nitrite but initially soil was dried and incubation period of urea is only 24 hours therefore the conversion of added urea N into NO3-N and NO2-N is only less than 2 and 0.2% respectively. Fraction order rate in case of nitrate suggest that another path of conversion of nitrate into nitrite simultaneously occurs with its generation. Effect of irrigation water quality is also found to have significant effect on leaching rates of both the ions.