Short-term response of soil greenhouse gas fluxes to alfalfa termination methods in a Mediterranean cropping system

Figures & data

Table 1. Type and timing of the management practices applied for the two alfalfa termination methods

Alfalfa termination		Days after alfalfa	Management practice
Method	Date	Termination	Operation	Soil depth (m)
Tillage	11 October 2017	0	Spading	0.20
	16 October 2017	5	Harrowing 1	0.15
	21 November 2017	41	Harrowing 2	0.15
No tillage plus herbicide	11 October 2017	0	Herbicide	na

na, not applicable.

Table 2. Mean data and results of repeated measures ANOVA for the soil parameters following the Tillage and No tillage plus herbicide alfalfa termination methods over the study period

Variable	Termination method (mean ±SE)		Source of variation	Statistic
	Tillage	No tillage plus herbicide		DF	F-value	P-value
Soil temperature	10.9 ±0.3	11.3 ±0.3	Time	1.58	1257.45	0.00
(°C)			Termination method	1	62.370	0.02
			Time × termination method	1.58	3.221	0.17
Water-filled pore	66.5 ±0.8	75.4 ±0.2	Time	1.38	21.93	0.02
space (%)			Termination method	1	146.77	0.01
			Time × termination method	1.38	2.30	0.25
Soil N2O flux	0.16 ±0.03	0.14 ±0.03	Time	1.73	3.71	0.14
(N g ha^−1 h^−1)			Termination method	1	1.51	0.34
			Time × termination method	3.46	1.12	0.41
Soil CH4 flux	−0.10 ±0.02	−0.03 ±0.01	Time	1.61	2.81	0.19
(C g ha^−1 h^−1)			Termination method	1	11.92	0.07
			Time × termination method	1.61	1.95	0.27
Soil CO2 flux	0.59 ±0.02	0.37 ±0.02	Time	1.89	34.98	0.00
(C kg ha^−1 h^−1)			Termination method	1	19.85	0.05
			Time × termination method	1.89	3.45	0.14

DF, degrees of freedom; SE, standard error.

Figure 1. Seasonal variations as days after alfalfa termination (day 0) for the soil temperature (ST) and water-filled pore space (WFPS) at 0.10 m depth (a), and of the soil nitrous oxide (N₂O, b), methane (CH₄,c) and carbon dioxide (CO₂, d) fluxes. Data are means ±standard error (n = 3). *, P < 0.05, alfalfa termination by Tillage versus No tillage plus herbicide.

Figure 2. Soil total greenhouse gas (N₂O + CH₄ + CO₂) emissions over the 71-day study period following alfalfa termination by Tillage and by No tillage plus herbicide. Inset: The weight of each gas compared to the total soil greenhouse gas emissions following each alfalfa termination method. Positive values represent losses; negative values represent uptake. Data are means ±standard error (n = 3). *, P < 0.05, alfalfa termination by Tillage versus

Figure 3. Relationships between the variations in soil GHG emissions (N₂O, CH₄, CO₂) and soil temperature at 0.1 m depth (a) and soil water-filled pore space (WFPS) at 0.1 m depth (b), following the alfalfa termination by Tillage (dashed line, open circles) and by No tillage plus herbicide (continuous line, closed circles). Data are means ±standard error (n = 3). *, P < 0.05.