Fig 1.
Chronological representation of soil collection and orchard management over the experimental period.
Fig 2.
Monthly global radiation, potential evaporation, precipitation and mean daily air temperature of 2013, 2014 and 2015.
Bars denote the monthly global radiation and precipitation, respectively. Lines represent the monthly potential evaporation and mean daily air temperature, respectively.
Fig 3.
Schematic view of PC (black plastic mulch with weed control) and PGC (black plastic mulch combined with cover crop) treatments.
Fig 4.
0–200 cm soil water storage in each stage for 2013, 2014 and 2015.
Lowercase letters denote significant differences between PC and PGC for the inter-row or in-row (p ≤ 0.05). “*” indicates that the differences between the inter-row and in-row (connected by lines) of the PC or PGC treatment were significant (p ≤ 0.05). Bud formation means the bud formation stage of apple trees (in late March). Before sowing the cover crop refers to the time before sowing the rape (in mid-June). The apple harvest always occurs in early October in this region. Error bars were the standard deviations.
Fig 5.
0–200 cm soil moisture (layer by layer) in each treatment (inter-row and in-row) at different stages.
Fig 6.
The evapotranspiration during the grass cover period (July-September) in 2013, 2014 and 2015.
Lowercase letters denote significant differences between PC and PGC for the inter-row or in-row (p ≤ 0.05). “*” indicates that the differences between the inter-row and in-row (connected by lines) of the PC or PGC treatment were significant (p ≤ 0.05). Error bars were the standard deviations.
Fig 7.
The total evapotranspiration during the growing period (late March to September) of apple trees in 2013, 2014 and 2015.
Lowercase letters denote significant differences between PC and PGC for the inter-row or in-row (p ≤ 0.05). “*” indicates that the differences between the inter-row and in-row (connected by lines) of the PC or PGC treatment were significant (p ≤ 0.05). Error bars were the standard deviations.
Fig 8.
The proportion of evapotranspiration during the grass cover period (ETg) in total evapotranspiration (ETg/ET) in 2013, 2014 and 2015.
The red arrow shows the deviations of ETg/ET between PC and PGC for the inter-row and in-row.
Table 1.
Yield, water use efficiency during the cover crop period (WUEg), and total water use efficiency (WUE) under different treatments in the apple orchard.
Fig 9.
Hourly soil temperature (0–25 cm) during bud formation stage, grass cover period and harvest time in 2015.
The soil temperature was recorded from 8:00 to 18:00 every two hours. Bars show standard deviation of the means. Error bars were the standard deviations.