HIGHLIGHTS:
1) Critical values focused at the groundwater depth of 50–60 cm.
2) Soil CO2 and CH4 concentrations were
affected by groundwater depth rather than fertilization level.
3)Soil CO2 concentration was significantly positively
correlated with root biomass, soil nutrients and enzyme activities.
4) Soil CH4 concentration was only correlated with soil
moist and nutrients.
Abstract
Soil CO2 and
CH4 concentrations are crucial determinants of crop
physiology and soil environment. This study aimed to investigate the
dynamics of soil CO2 and CH4concentrations and their correlations with soil nutrient content,
enzymatic activities and root biomass at shallow groundwater levels.
Lysimeter experiments were conducted at five groundwater depths (20, 40,
50, 60, and 80 cm) and three fertilizer application rates (low, 75%;
normal, 100%; high, 125%). Soil CO2 and
CH4 concentrations, physicochemical properties, and
enzymatic activities were determined in the three growth stages of
winter wheat crop, and plant biomass was measured post-harvest.
Groundwater depth significantly (P ≤ 0.001) affected
CO2 and CH4 concentrations and root
parameters, and their critical values appeared at the groundwater depth
of 50–60 cm. Soil water content presented quadratic function relation
with CO2 concentration, and exhibited the linear
correlation with CH4 concentration. As an aerobic
respiration product, soil CO2 concentration showed
significant positive correlations with organic matter and total N
levels, urease, phosphatase and sucrase activities, and root biomass in
winter wheat. Soil CH4 concentration depending on
anaerobic microbial activity showed significant correlations with soil
nutrients, such as soil organic matter, total N, and available K.
Fertilization
significantly impacted root parameters (P ≤ 0.001) and shoot
biomass (P ≤ 0.05) instead of CO2 and
CH4 concentrations. In contrast, groundwater depth
emerged as a crucial factor as it affected soil physicochemical
properties, soil enzymatic activities, root respiration, and winter
wheat growth at shallow groundwater levels.