Yield and water use efficiency of dryland potato in response to plastic film mulching on the Loess Plateau

Figures & data

Figure 1. Flowchart of the process of obtaining data from the literature to build a database for this study.

Figure 2. Map of the Loess Plateau. The locations of the potato field experiments reported in the peerreviewed literature are shown on the map.

Table 1. Brief descriptions of the materials and methods associated with the different mulching methods, mulching areas and colors of plastic film used in potato field experiments on the Loess Plateau.

Item	Mulching practice	Brief description
Mulching method	Conventional tillage (CT)	The soil was plowed without mulching until the next sowing (no mulching)
	Flat mulching (FM)	Flat planting and mulching with plastic film 7 or 8 μm thick
	Ridge-furrow mulching (RFM)	Ridge-furrow planting with plastic film mulching; the ridge height was 10–30 cm, and the ridge breadth was 40–80 cm
Mulching area	Full area mulching (FAM)	The entire planting area (flat or ridge-furrow) was mulched with plastic film
	Partial area mulching (PAM)	Alternating strips (flat or ridge) mulched with plastic film and bare land
Color of plastic film	Black plastic mulching (BPM)	Mulching with black plastic film 7 or 8 μm thick
	White plastic mulching (WPM)	Mulching with white plastic film 7 or 8 μm thick

Table 2. Actual values of potato yield, water use efficiency (WUE), and evapotranspiration (ET) under plastic mulching on the Loess Plateau.

Item	Categorical variable	Yield (kg ha^−1) range	WUE (kg ha^−1 mm^−1) range	ET (mm) range
Mulching method	FM	11300–43845	74.3–111.4	275.1–432.9
	CTFM	9600–30248	41.5–90.7	285.1–439.9
	RFM	9975–47588	32.9–138.3	142.8–442.6
	CTRFM	9600–34991	24.3–103.2	216.7–439.9
Mulching area	FAM	10575–47588	36.5–138.3	235.3–435.4
	CTFAM	9600–34991	24.3–103.2	253.8–439.9
	PAM	9975–45060	32.8–130	142.8–442.6
	CTPAM	9600–34991	24.3–103.2	216.7–439.9
Color of plastic film	BPM	14371–47588	36.5–138.3	202–442.6
	CTBPM	10583–34991	24.3–103.2	219–439.9
	WPM	9975–45060	32.9–116.4	142.8–436.1
	CTWPM	9600–33199	24.3–90.7	216.7–436.1
Precipitation	< 400 mm	9975–47422	59.3–138.3	142.8–413.7
	CT< 400 mm	9600–34991	31.2–103.2	216.7–385.6
	> 400 mm	13394–47588	32.9–122.2	235.3–442.6
	CT> 400 mm	10583–33199	24.3–90.7	306.5–439.9

Notes: FM: flat mulching, RFM: ridge-furrow mulching, FAM: full-area mulching, PAM: partial-area mulching, BPM: black plastic mulching, and WPM: white plastic mulching.

Figure 3. Results of the comparison of plastic mulching and conventional tillage. (a) Potato yield, (b) water use efficiency (WUE), and (c) evapotranspiration (ET). In the Figure, each black point represents the result of one individual comparison between plastic mulching and the control. The points lying on the 1:1 line indicate that the corresponding values responded similarly to plastic mulching and the control, whereas the points distributed above or below the line indicate positive or negative effects, respectively, under plastic mulching.

Figure 4. The relative effect sizes for potato yield, water-use efficiency (WUE), and evapotranspiration (ET) under different plastic mulching methods, mulching areas, colors of plastic mulch and annual precipitation on the Loess Plateau. Error bars represent the 95% CI, and values close to the bars represent the corresponding numbers of observations. FM: flat mulching, RFM: ridge-furrow mulching, FAM: full-area mulching, PAM: partial-area mulching, BPM: black plastic mulching, and WPM: white plastic mulching.

Table 3. Results of the meta-analysis (heterogeneity analysis) of the effects of plastic mulching on the yield, water-use efficiency (WUE), and evapotranspiration (ET) of potato on the Loess Plateau using random-effects models.

Item		Categorical variable	Number of observations	P-value of effect size	Heterogeneity analysis
					chi-square	df	P-value of chi-square test	Heterogeneity (I^2) (%)
Yield	Mulching method	FM	46	0.0002	26.52	13	0.23	17
		RFM	294	< 0.0001	175.75	40	0.05	17
	Mulching area	FAM	164	< 0.0001	103.81	32	0.04	22
		PAM	176	< 0.0001	103.14	39	0.11	16
	Color of plastic film	BPM	150	< 0.0001	82.65	21	0.23	10
		WPM	190	< 0.0001	115.91	31	0.06	19
	Precipitation	< 400 mm	104	< 0.0001	78.17	17	0.009	35
		> 400 mm	236	< 0.0001	121.99	26	0.36	4
WUE	Mulching method	FM	18	0.72	8.35	3	0.4	4
		RFM	136	< 0.0001	93.27	19	0.02	28
	Mulching area	FAM	82	< 0.0001	51.37	14	0.11	22
		PAM	72	< 0.0001	52.25	15	0.03	33
	Color of plastic film	BPM	92	< 0.0001	51.47	11	0.24	13
		WPM	62	0.0002	52.92	11	0.006	43
	Precipitation	< 400 mm	52	0.002	50.45	10	0.002	50
		> 400 mm	102	< 0.0001	53.51	9	0.34	7
ET	Mulching method	FM	18	0.62	6.52	3	0.59	0
		RFM	136	0.06	86.64	19	0.05	23
	Mulching area	FAM	82	0.74	45.72	14	0.25	13
		PAM	72	0.12	49.12	15	0.06	29
	Color of plastic film	BPM	92	0.8	34.45	11	0.87	0
		WPM	62	0.03	56.56	11	0.002	47
	Precipitation	< 400 mm	52	0.9	41.46	10	0.02	40
		> 400 mm	102	0.1	52.12	9	0.39	4

Notes: FM: flat mulching, RFM: ridge-furrow mulching, FAM: full-area mulching, PAM: partial-area mulching, BPM: black plastic mulching, and WPM: white plastic mulching.

Figure 5. Potato yields (a), WUE (b), and ET (c) under plastic mulching and conventional tillage.

Figure 6. Yields under plastic mulching and conventional tillage. (a) Mulching method, (b) mulching area, (c) color of plastic film, and (d) precipitation. FM: flat mulching, RFM: ridge-furrow mulching, FAM: full-area mulching, PAM: partial-area mulching, BPM: black plastic mulching, and WPM: white plastic mulching.

Figure 7. Water-use efficiency (WUE) under plastic mulching and conventional tillage. (a) mulching method, (b) mulching area, (c) color of plastic film, and (d): precipitation. FM: flat mulching, RFM: ridge-furrow mulching, FAM: full-area mulching, PAM: partial-area mulching, BPM: black plastic mulching, and WPM: white plastic mulching.

Figure 8. Evapotranspiration (ET) under plastic mulching and conventional tillage. (a) Mulching method, (b) mulching area, (c) color of plastic film, and (d) precipitation. FM: flat mulching, RFM: ridge-furrow mulching, FAM: full-area mulching, PAM: partial-area mulching, BPM: black plastic mulching, and WPM: white plastic mulching.

Table 4. Analyses on economic benefits of potato.

Item	Output (RMB/ha)	Input (RMB/ha)	Net revenue (RMB/ha)	Output/Input (O/I)	Increase in Net revenue (%)	Increase in O/I (%)
No mulching	26296	7515	18781	3.50
Plastic mulching	34005	8758	25247	3.88	34.43	10.86

Figure 9. Relationships among the yield, water-use efficiency (WUE), and evapotranspiration (ET) of potatoes under plastic mulching on the Loess Plateau. (a) Relationship between ET and yield, (b) relationship between ET and WUE, and (c) relationship between yield and WUE.