Prediction of root zone water and nitrogen balance in an irrigated rice field using a simulation model

Field analysis of water and nitrogen fate in lowland paddy fields under different water managements using HYDRUS-1D

“…Dash et al (2014) simulated that the mineralization and bio-fixation N amounted to 75.6 kg ha −1 in paddy fields with N application of 120 kg ha −1 , which is similar to our results on plots with N application of 135 kg ha −1 . Gaydon et al (2012) summarized that estimates of mineralized and fixed N vary from a few to 80 kg ha −1 .…”

“…These characteristics resulted in the extremely low N content in the leaching water and relatively low N leaching losses. The N leaching losses in two years, 12.8 kg ha −1 on average were both significantly lower than that the reported value (120 kg ha −1 ) that Chowdary et al (2004) and Antonopoulos (2010) obtained, and 28.5 kg ha −1 simulated by Dash et al (2014). Their high N leaching losses were resulted from the high hydraulic conductivity of the plow pan soil.…”

“…Our modeling approach, to some extent, suggests the inappropriateness of using the same N transformation parameters for N regime simulation in plots with different N treatments. However, the same N transformation parameters were usually applied to model the potential N regime and balance under different N fertilization scenarios, such as Dash et al (2014). The N transformation process is extremely complicated in paddy fields, using the zeroand/or first-order decay reaction cannot fully describe this timevarying process.…”

“…During the simulation, identical averaged soil hydraulic parameters were used for all experimental plots under AWD or CF irrigation, respectively, since the area of the fields is small and the spatial variability of soil hydraulic properties on water flow and N transport can be neglected. NH 4 + N was assumed to be adsorbed by the paddy soil to the solid phase with the distribution coefficient of 3.5 cm 3 g −1 (Dash et al, 2014;Hanson et al, 2006;Ling and El-Kadi, 1998;Lotse et al, 1992;Ramos et al, 2011). The N transport parameter, longitudinal dispersivity (D L ), as well as N transformation parameters including w,1 (hydrolysis), w,2 and s,2 (nitrification in the liquid and solid phases), w,2 and s,2 (volatilization), w,2 and s,2 (mineralization and bio-fixation) and w,3 and s,3 (denitrification) cannot be easily measured in laboratory or on field.…”

“…It is needed to understand the differences of water and N distributions in lowland soil profiles between paddy fields under AWD and CF irrigation for better practice of AWD irrigation. HYDRUS (Simunek et al, 2008) have been widely used to analyze the multi-layer soil water flow in paddy fields for preferential flow (Dash et al, 2014;Garg et al, 2009;Sander and Gerke, 2009;Tan et al, 2014), seepage across paddy fields bunds (Janssen and Lennartz, 2009), and heavy metal transport (Nguyen Ngoc et al, 2009). However, transport and transformations of N or other decayed chemicals in paddy fields were seldom investigated by HYDRUS modeling (Patil and Das, 2013), although it was popularly used for the analysis of N transport and transformations in dry land fields cultivated with other crops, such as maize (Crevoisier et al, 2008;Ramos et al, 2011;Ramos et al, 2012), wheat (Wang et al, 2010), onion (Ajdary et al, 2007), and corn (Mailhol et al, 2007).…”