Saline water irrigation stimulate N₂O emission from a drip-irrigated cotton field

Figures & data

Figure 1. Layout of the experimental plot (inner-row and inter-row) and location of the chambers.

Table 1. The amounts of irrigation water, N fertilizer application rates, and dates of N₂O sampling under three water salinity treatments in field experiment (2014).

Date^a	Cotton growth stage	Irrigation amount (mm)	N rate (kg ha^−1)^b		Dates of N2O sampling
			N0	N360
29–30 April	Sowing	30	–	–
15–16 June	Squaring period	45	–	–
22–23 June	Early flowering period	60	–	72	24 June, 25 June, 26 June, 27 June, 28 June, 29 June
30 June–1 July		60	–	72	3 July
9–10 July	Full flowering period	60	–	72	11 July
17–18 July	Boll setting period	60	–	72	19 July
24–25 July		60	–	–	27 July
2–3 August	Peak bolling period	60	–	72	5 August
10–11 August		45	–	–	13 August

^aDates of irrigation and N fertigation under three water salinity treatments in field experiment.

^bN0 and N360 representing 0 and 360 kg ha⁻¹ of N application rates, respectively.

Figure 2. Changes in soil moisture during one irrigation cycle from 24 June to 29 June (irrigation and N fertigation on 22–23 June). Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD.

Figure 3. Soil moisture content across the growing season (18 June–13 August) as affected by irrigation and N fertigation. Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD. Solid arrows indicate fertigation events. Dashed arrows indicate irrigation events.

Figure 4. Changes in soil salinity (EC) during one irrigation cycle from 24 June to 29 June (irrigation and N fertigation on 22–23 June). Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD.

Figure 5. Soil salinity (EC) across the growing season (18 June to 13 August) as affected by irrigation and N fertigation. Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD. Solid arrows indicate fertigation events. Dashed arrows indicate irrigation events.

Figure 6. Changes in soil pH during one irrigation cycle from 24 June to 29 June (irrigation and N fertigation on 22–23 June). Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD.

Figure 7. Soil pH across the growing season (18 June to 13 August) as affected by irrigation and N fertigation. Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD. Solid arrows indicate fertigation events. Dashed arrows indicate irrigation events.

Figure 8. Changes in soil and  concentrations during one irrigation cycle from 24 June to 29 June (irrigation and N fertigation on 22–23 June). Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD.

Figure 9. Soil and concentrations across the growing season (18 June to 13 August) as affected by irrigation and N fertigation. Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD. Solid arrows indicate fertigation events. Dashed arrows indicate irrigation events.

Figure 10. Changes in soil N₂O emission flux during one irrigation cycle from 24 June to 29 June (irrigation and N fertigation on 22–23 June). Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD.

Figure 11. Soil N₂O emission flux across the growing season (18 June to 13 August) as affected by irrigation and N fertigation. Abbreviations: FW (0.35 dS m⁻¹), BW (4.61 dS m⁻¹), SW (8.04 dS m⁻¹), N0 (unfertilized), and N360 (360 kg N ha⁻¹). Values are the mean of three replicates. Error bars represent SD. Solid arrows indicate fertigation events. Dashed arrows indicate irrigation events.

Table 2. Correlation between soil N₂O emission rate and selected soil properties (n = 72).

	Salinity	Moisture	pH			N2O
Salinity	1
Moisture	0.21	1
pH	−0.61**	0.26	1
	0.23	−0.08	−0.32*	1
	0.04	0.11	−0.26	0.12	1
N2O	0.11	0.31*	−0.23	0.65**	0.62**	1

*Significant at the .05 probability level.

**Significant at the .01 probability level.

Figure 12. Effects of irrigation water salinity and N rate on cumulative N₂O emission. Error bars indicate the standard error of the mean (n = 3). Bars with different letters are significantly different at p < .05 (Duncan's Least significant difference test).