Changes in winter wheat spike N concentration with time under different N application rates in the 2009 and 2011 seasons.

<p>a: 2009–2010 NM13, b: 2010–2011 NM13, c: 2009–2010 YM16, d: 2010–2011 YM16. Data are presented as days after sowing. The vertical bars represent standard error of the mean value on each sampling date. The vertical dotted bars without line end represent LSD values (<i>P</i><0.05) on each sampling date.</p

Critical N data points used to develop spike N_c curves.

<p>a: 2009–2011 NM13, b: 2009–2011 YM16. The symbols (◇) and (○) represent the data points obtained from the N-limiting treatments for YM16 and NM13, and (×) and (+) represent the data points obtained from the non-N-limiting treatments for YM16 and NM13. The symbols (●) represent the calculated N_c points for each sampling date. The solid line represents the spike N_c curve that describes the relationship between spike N_c concentration and SDM of winter wheat.</p

The relationship between RY and NNI for winter wheat in 2009–2011.

<p>The NNI value was averaged over all sampling dates.</p

Changes of spike dry matter (t ha^-1) for winter wheat with time (days after sowing) under different N application rates in experiments conducted during 2009–2011 seasons.

<p>Changes of spike dry matter (t ha^-1) for winter wheat with time (days after sowing) under different N application rates in experiments conducted during 2009–2011 seasons.</p

The basic information about the four experiments conducted in present study.

<p>The basic information about the four experiments conducted in present study.</p

Comprehensive validation of the spike N_c curve using the independent data set from the experiment conducted during 2007–2008.

<p>Data points (□) and (△) represent N-limiting and non-N-limiting treatments, respectively. The solid line in the middle represents the critical N curve (N_c = 2.85×SDM^-0.17) that describes the relationship between the critical N concentration and spike dry matter of rice. The data points (●) and (○) that were not used for establishing the parameters of the allometric function (2009–2011) were used to develop two limit curves (--------): minimum limit curve (N_min = 1.86×SDM^-0.41) and maximum limit curve (N_max = 3.57×SDM^-0.12).</p

Critical N data points used to develop spike N_c curves.

<p>a: 2009–2011 NM13, b: 2009–2011 YM16. The symbols (◇) and (○) represent the data points obtained from the N-limiting treatments for YM16 and NM13, and (×) and (+) represent the data points obtained from the non-N-limiting treatments for YM16 and NM13. The symbols (●) represent the calculated N_c points for each sampling date. The solid line represents the spike N_c curve that describes the relationship between spike N_c concentration and SDM of winter wheat.</p

Critical N data points for spike N_c curve definition using pooled data from two cultivars.

<p>The solid line represents the critical N dilution curve (N_c = 2.85×SDM^-0.17, <i>R</i>^<i>2</i> = 0.8) that describes the relationship between the N_c concentration and SDM of wheat. The dotted lines represent the 95% confidence interval (<i>P</i> = 0.95).</p

Changes in the N nutrition index for YM16 and NM13 during the reproductive growth period.

<p>a: 2009–2010 NM13, b: 2010–2011 NM13, c: 2009–2010 YM16, d: 2010–2011 YM16. The vertical bars represent standard error of the mean value on each sampling date. The vertical dotted bars without line end represent LSD values (<i>P</i><0.05) on each sampling date.</p

Changes in winter wheat spike N concentration with time under different N application rates in the 2009 and 2011 seasons.

<p>a: 2009–2010 NM13, b: 2010–2011 NM13, c: 2009–2010 YM16, d: 2010–2011 YM16. Data are presented as days after sowing. The vertical bars represent standard error of the mean value on each sampling date. The vertical dotted bars without line end represent LSD values (<i>P</i><0.05) on each sampling date.</p