Dynamics of 14C-labeled glucose and ammonium in saline arable soils

Alma Vuelvas-Solórzano,Rosalina Hernández-Matehuala,Marcela Cárdenas-Manríquez,Luc Dendooven,Marco L Luna-Guido,Eloy Conde-Barajas

doi:10.1590/s0100-06832009000400010

Abstract

Organic matter dynamics and nutrient availability in saline agricultural soils of the State of Guanajuato might provide information for remediation strategies. 14C labeled glucose with or without 200 mg kg-1 of NH4+-N soil was added to two clayey agricultural soils with different electrolytic conductivity (EC), i.e. 0.94 dS m-1 (low EC; LEC) and 6.72 dS m-1 (high EC; HEC), to investigate the effect of N availability and salt content on organic material decomposition. Inorganic N dynamics and production of CO2 and 14CO2 were monitored. Approximately 60 % of the glucose-14C added to LEC soil evolved as 14CO2, but only 20 % in HEC soil after the incubation period of 21 days. After one day, < 200 mg 14C was extractable from LEC soil, but > 500 mg 14C from HEC soil. No N mineralization occurred in the LEC and HEC soils and glucose addition reduced the concentrations of inorganic N in unamended soil and soil amended with NH4+-N. The NO2- and NO3- concentrations were on average higher in LEC than in HEC soil, with exception of NO2- in HEC amended with NH4+-N. It was concluded that increases in soil EC reduced mineralization of the easily decomposable C substrate and resulted in N-depleted soil.

Highlights

Nowadays, there is an environmental and economic need to understand the role and destiny of N in different ecosystems
Mineralization of maize and glucose were inhibited in alkaline saline soils with electrolytic conductivity (EC) > 10 dS m-1 and large amounts of NH4+ and NO3- were immobilized within short periods of time, reducing N availability (Conde et al, 2005)
The CO2 production rate was significantly higher in LEC soil amended with NH4+ than in the unamended soil, but lower than in soil amended with 14C labeled glucose or 14C labeled glucose plus NH4+ (p < 0.05) (Figure 1a, Table 2)

Summary

Introduction

There is an environmental and economic need to understand the role and destiny of N in different ecosystems. Nitrogen cycling is mostly controlled by biological activity and at the same time biological processes are affected by climate and physicochemical soil characteristics. In some extreme environments, such as saline soils, the high electrolytic conductivity (EC) inhibits microbial activity and organic matter decomposition and affects N cycling 1980; Bandyopadhyay & Bandyopadhyay, 1983; Zahran, 1997; Pathak & Rao, 1998). Mineralization of maize and glucose were inhibited in alkaline saline soils with EC > 10 dS m-1 and large amounts of NH4+ and NO3- were immobilized within short periods of time, reducing N availability (Conde et al, 2005). Pathak & Rao (1998) reported that ammonification and nitrification were inhibited by high salt concentrations and that, the latter, was very sensitive to the presence of salts When were added (Vega-Jarquin et al, 2003). Pathak & Rao (1998) reported that ammonification and nitrification were inhibited by high salt concentrations and that, the latter, was very sensitive to the presence of salts

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Conclusion