P_ostBA-leaf ratio, grain production efficiency (GPE), spike partitioning index (SPI) and harvest index (HI) in the 2013–2014, 2014–2015 and 2015–2016 growing seasons.

<p>P_ostBA-leaf ratio, grain production efficiency (GPE), spike partitioning index (SPI) and harvest index (HI) in the 2013–2014, 2014–2015 and 2015–2016 growing seasons.</p

Optimizing single irrigation scheme to improve water use efficiency by manipulating winter wheat sink-source relationships in Northern China Plain

<div><p>Improving winter wheat grain yield and water use efficiency (WUE) with minimum irrigation is very important for ensuring agricultural and ecological sustainability in the Northern China Plain (NCP). A three-year field experiment was conducted to determine how single irrigation can improve grain yield and WUE by manipulating the “sink-source” relationships. To achieve this, no-irrigation after sowing (W0) as a control, and five single irrigation treatments after sowing (75 mm of each irrigation) were established. They included irrigation at upstanding (W_U), irrigation at jointing (W_J), irrigation at booting (W_B), irrigation at anthesis (W_A) and irrigation at medium milk (W_M). Results showed that compared with no-irrigation after sowing (W0), W_U, W_J, W_B, W_A and W_M significantly improved mean grain yield by 14.1%, 19.9%, 17.9%, 11.6%, and 7.5%, respectively. W_J achieved the highest grain yield (8653.1 kg ha^-1) and WUE (20.3 kg ha^-1 mm^-1), and W_B observed the same level of grain yield and WUE as W_J. In comparison to W_U, W_J and W_B coordinated pre- and post-anthesis water use while reducing pre-anthesis and total evapotranspiration (ET). They also retained higher soil water content above 180 cm soil layers at anthesis, increased post-anthesis water use, and ultimately increased WUE. W_J and W_B optimized population quantity and individual leaf size, delayed leaf senescence, extended grain-filling duration, improved post-anthesis biomass and biomass remobilization (source supply capacity) as well as post-anthesis biomass per unit anthesis leaf area (P_ostBA-leaf ratio). W_J also optimized the allocation of assimilation, increased the spike partitioning index (SPI, spike biomass/biomass at anthesis) and grain production efficiency (GPE, the ratio of grain number to biomass at anthesis), thus improved mean sink capacity by 28.1%, 5.7%, 21.9%, and 26.7% in comparison to W0, W_U, W_A and W_M, respectively. Compared with W_A and W_M, W_J and W_B also increased sink capacity, post-anthesis biomass and biomass remobilization. These results demonstrated that single irrigation at jointing or booting could improve grain yield and WUE via coordinating the “source-sink” relationships with the high sink capacity and source supply capacity. Therefore, we propose that under adequate soil moisture conditions before sowing, single irrigation scheme from jointing to booting with 75 mm irrigation amount is the optimal minimum irrigation practice for wheat production in this region.</p></div

Optimizing single irrigation scheme to improve water use efficiency by manipulating winter wheat sink-source relationships in Northern China Plain - Fig 3

<p><b>Leaf length (top), width (middle) and area (bottom) of the flag (a, d), second (b, e) and third leaf (c, f) at anthesis under six treatments in the 2015–2016 growing season.</b> Box boundaries indicate upper and lower quartiles, whisker caps indicate maximum and minimum value, black solid horizontal lines indicate medians and solid dots indicate mean value.</p

Optimizing single irrigation scheme to improve water use efficiency by manipulating winter wheat sink-source relationships in Northern China Plain - Fig 7

<p><b>Sink capacity under six treatments in the 2013–2014 (a), 2014–2015(b) and 2015–2016 (c) growing seasons.</b> Different letters in the figure indicate statistical differences among treatments (LSD_{<i>P</i><0.05}).</p

Biomass at anthesis and maturity, post-anthesis biomass and biomass remobilization under six treatments in the 2013–2014, 2014–2015 and 2015–2016 growing seasons.

<p>Different letters in the figure indicate statistical differences among treatments (LSD_{<i>P</i><0.05}).</p

Biomass at anthesis (BMA), post-anthesis (BMM) and remobilization amount (BMR) during grain filling in 3 years (2011, 2012, and 2013), under two irrigation regimes (W1 and W2), and in 3 cultivars (HS4399, JM22, WM8).

<p>Vertical bars represent standard deviations of the means.</p

Days during different growing periods of winter wheat in the 2013–2014, 2014–2015 and 2015–2016 growing seasons.

<p>Days during different growing periods of winter wheat in the 2013–2014, 2014–2015 and 2015–2016 growing seasons.</p

Optimizing single irrigation scheme to improve water use efficiency by manipulating winter wheat sink-source relationships in Northern China Plain - Fig 4

<p><b>Leaf area index (LAI) of top three leaves and total green leaves at anthesis under six treatments in the 2013–2014 (a), 2014–2015 (b) and 2015–2016 (c) growing seasons.</b> Different letters in the figure indicate statistical differences among treatments (LSD_{<i>P</i><0.05}).</p

Crop evapotranspiration (ET) in different growth periods in the 2013–2014, 2014–2015 and 2015–2016 growing seasons.

<p>Crop evapotranspiration (ET) in different growth periods in the 2013–2014, 2014–2015 and 2015–2016 growing seasons.</p

Soil water extraction (SWE) and total evapotranspiration (ET) in different growth periods during the 2011, 2012, and 2013 growing seasons, as affected by irrigation, cultivar, and year.

<p>Soil water extraction (SWE) and total evapotranspiration (ET) in different growth periods during the 2011, 2012, and 2013 growing seasons, as affected by irrigation, cultivar, and year.</p