CO2 and N2O Emissions from Spring Maize Soil under Alternate Irrigation between Saline Water and Groundwater in Hetao Irrigation District of Inner Mongolia, China

Abstract

Alternative irrigation between saline water and groundwater can alleviate shortages of available agricultural water while effectively slowing the adverse effects of saline water on the soil-crop system when compared with continuous irrigation with saline water and blending irrigation between saline water and groundwater. In 2018, we tested the effect on soil CO₂ and N₂O emissions by two types of irrigation regimes (alternating groundwater and saline water (GW-SW), and alternating groundwater, followed by two cycles of saline water (GW-SW-SW)) between groundwater and three levels of salinity of irrigation water (mineralization of 2 g/L, 3.5 g/L, and 5 g/L), analyzed the correlation between gas emissions and soil properties, calculated comprehensive global warming potential (GWP), and investigated the maize yield. The results show that, with the same alternate irrigation regime, cumulative CO₂ emissions decreased with increasing irrigation water salinity, and cumulative N₂O emissions increased. Cumulative CO₂ emissions were higher in the GW-SW regime for the same irrigation water salinity, and cumulative N₂O emissions were higher in the GW-SW-SW regime. The GW-SW-SW regime had less comprehensive GWP and maize yield as compared to the GW-SW regime. The 2 g/L salinity in both regimes showed larger comprehensive GWP and maize yield. The 3.5 g/L salinity under the GW-SW regime will be the best choice while considering that the smaller comprehensive GWP and the larger maize yield are appropriate for agricultural implication. Fertilizer type and irrigation amount can be taken into consideration in future research direction.

Keywords: alternate irrigation regime; global warming potential; greenhouse gas emission; irrigation water salinity; soil properties.

Figure 1

The location of Shuguang Experimental Station in China.

Figure 2

Irrigation and rainfall during the spring maize growth period in 2018.

Figure 3

Structure of the static closed chamber showing (A) the lid, (B) the anchor, (C) the top view of the anchor embedded in the plot, and (D) the side view of the static closed chamber working.

Figure 3

Structure of the static closed chamber showing (A) the lid, (B) the anchor, (C) the top view of the anchor embedded in the plot, and (D) the side view of the static closed chamber working.

Figure 4

Variation of (A) soil moisture, (B) electrical conductivity—(EC), (C) pH, (D) NH₄⁺-N concentration, and (E) NO₃⁻-N concentration for different irrigation water salinity (S1, S2, and S3 for 2 g/L, 3.5 g/L, and 5 g/L, respectively) and alternate irrigation regimes (L1 and L2 for one saline water cycle and two saline water cycles, respectively). Symbols represent the mean value of the three repeated tests, and error bars represent standard deviation.

Figure 5

(A) Daily CO₂ flux and (B) daily N₂O flux during the growth period of maize for different irrigation water salinity (S1, S2, and S3 for 2 g/L, 3.5 g/L, and 5 g/L, respectively) and alternate irrigation regimes (L1 and L2 for one saline water cycle and two saline water cycles, respectively). Symbols represent the mean of three repeated tests and error bars represent standard deviation. Solid arrows indicate fertigation events.