Quantifying the relative importance of soil moisture, nitrogen, and temperature on the urea hydrolysis rate

Abstract

Urea hydrolysis is a complicated process influenced by multiple factors. Most previous studies only examined the causative factors of the process without ranking these factors' relative importance quantitatively. In this work, the experimental analysis method, ANOVA method, and backpropagation (BP) neural network method were used to rank the effects of moisture content (W), nitrogen amount (F), and temperature (T) on the urea hydrolysis rate. A group of 22 artificial neural network structures with different numbers of neurons in the hidden layer (2 ≤ L ≤ 12), different initial connection weights, and different learning algorithms was trained and validated using the data set. The relative importance of the factors that affect urea hydrolysis was studied on the basis of information on the weight and threshold value. Results showed that the individual factors and the interaction between any two factors exerted an extremely significant effect (p < 0.01) on the hydrolysis rate, except for the interaction among the three factors. The ANOVA method achieved the importance ranking of T > for the hydrolysis rate. The incremental backpropagation-BP-K model with the topological structure of 3-6-1 expressed the relationship between the input variables and the output variable accurately. All of the methods indicated that the degree of influence of the factors on urea hydrolysis followed the descending order of T > F > W. Temperature was the key factor in the hydrolytic process. The results of the importance analysis of the three methods were consistent. ARTICLE HISTORY

Nitrate leaching and NH3 volatilization during soil reclamation in the Yellow River Delta, China

“…However, Sun et al (2017) found that the peak values of NH + 4 − N concentrations were delayed approximately 20 days after fertilizer application due to irrigation after fertilizer application. Others have found that high soil moisture limits urease activity (Du et al, 2007) and decreases the urea hydrolysis rate (Lei et al, 2017), which may have contributed to the differences seen in our study. An incubation experiment showed that the NH + 4 − N concentration reached its peak in the first week , which was similar to the results of this study.…”

The effect of metal oxide coating of urea on mineralization in two contrasting soils

“…This is consistent with similar studies for urea applied to soil as granules (Lasisi & Akinremi, 2020; MacLean & McRae, 1987) or in solution (Moawad et al., 1984). However, a direct comparison of the rate of urea hydrolysis with past research is difficult as it is dependent on various factors such as the concentration of urea applied, soil temperature, soil moisture, and soil type (Broadbent et al., 1958; Lei et al., 2017), and for this sandy soil with low soil carbon and presumably low microbial biomass, urease capacity would be relatively low and/or the localized high concentration of ammonium near the fertilizer granule may have inhibited the rate of ammonification. The conversion of urea‐N, applied at a rate of 285 mg urea‐N kg −1 (Figure 3D) to NO 3 − was only ∼60% complete by 30 days for the sandy soil, with the remainder present as NH 4 + (Figure 1).…”

Recent trends in nitrogen cycle and eco-efficient nitrogen management strategies in aerobic rice system

“…As soil saturation increases, ammonia volatilization of synthetic N fertilizers can either be increased because of the faster hydrolysis process or decreased due to dilution in the soil solution. Moreover, high temperature encourages the hydrolysis process of synthetic N fertilizers and the rate of NH 3 diffusion from soil solution to the ambient environment ( Lei et al, 2017 ).…”