Biochemical Processes Controlling Soil Nitrogen Mineralization under Waterlogged Conditions

Abstract

Changes in precipitation patterns in recent years have resulted in flooding or ponding of many farmlands in the North Central region of the United States. In this work, 11 field‐moist surface soils (0–15 cm) and their air‐dried counterparts were incubated at 30°C under waterlogged conditions for times ranging from 3 to 15 d, and the amounts of NH4–N released were determined. Results showed that, presumably because of slaking effects, the rates of NH4–N release were greater in air‐dried than in field‐moist soils. The mineralization rates of the field‐moist soils were significantly correlated with organic C (r = 0.59, P < 0.05), organic N (r = 0.69, P < 0.05), and microbial biomass C (r = 0.62, P < 0.05) and N (r = 0.63, P < 0.05). The corresponding r values for the air‐dried soils were 0.76 (P < 0.01), 0.87 (P < 0.01), 0.84 (P < 0.01), and 0.85 (P < 0.001), respectively. Estimation of the amounts of N mineralized per hectare of field‐moist soils in 1 d ranged from 2.2 to 4.9 kg (average = 3.3). Those values for air‐dried soils ranged from 5.2 to 26.2 kg (average = 15.5). The rates of hydrolysis of six enzyme substrates studied were significantly correlated with the rates of NH4–N release in the field‐moist soils. The relationships were amidase (r = 0.82, P < 0.01), arginase (r = 0.90, P < 0.001), asparaginase (r = 0.86, P < 0.001), glutaminase (r = 0.88, P < 0.001), β‐glucosidase (r = 0.83, P < 0.01), and β‐glucosaminidase (r = 0.84, P < 0.01). Temperature coefficient (Q10) values ranged from 1.2 to 1.4 (average = 1.3) for the field‐moist soils and from 1.0 to 1.3 (average = 1.1) for their air‐dried counterparts. This study showed that microbial biomass, a number of hydrolases, and slaking seem to play a significant role in hydrolysis of N in temporarily flooded soils.

High Temperature and Salinity Enhance Soil Nitrogen Mineralization in a Tidal Freshwater Marsh

“…Nitrification could be inhibited in high moisture environments, especially in submerged conditions [28] , [30] – [32] . Therefore, ammonium ought to reflect N mineralization [33] , [34] .…”

Denitrification and Nitrous Oxide Emissions in Annual Croplands, Perennial Grass Buffers, and Restored Perennial Grasslands

“…Consistent with previous work (Davis et al, 2008), we also observed a positive correlation between TOC and DEA as well as NH 4 + -N and DEA. The positive relationship between NH 4 + -N and DEA could be due to (i) NH 4 + -N regulation of NO 3 − -N consumption and production (Davis et al, 2008) or (ii) it can be an indirect relationship resulting positive correlations among TOC, NH 4 + -N, potentially mineralizable C, and N mineralization (Schomberg et al, 2009;Haddad et al, 2013). Opposite patterns of in situ N 2 O fluxes and DEA across the watershed treatments led us to pursue denitrification measurements.…”

Potassium Humate Application and Cutting Immature Flowers affect Soil Properties, Microbial Activity and Jerusalem Artichoke Yield Components

“…The hydrolysis of ρ _ nitrophenyl _ β _ D _ glucopyranoside was determined as described by Tabatabai, 1994 andHaddad et al, 2013. The same method used for determination of the rate of hydrolysis of p _ nitrophenyl _ β _ D _ glucopyranoside was used for determination of the hydrolysis of p-nitrophenyl _ N _ acetyl _ β _ D _ glucosaminide.…”

“…Microbial biomass C and N are the most important biochemical pools that affect the nitrogen mineralization process in soils, and early indicator of changes in total soil organic carbon (Haddad et al, 2013). Humic substances are the largest constituent of soil organic matter (∼60%) and are considered as a key component of the terrestrial ecosystem, being responsible for many complex chemical reactions in soil (Stevenson, 1994).…”