Dynamics Of Population Trait For High Yielding And High Efficiency Winter Wheat And N Nutrient Regulation In The North China Plain

Understanding the high-yielding population trait and the interaction of N with other important management factors on population development will be important for achieving high wheat yield, high N use efficiency, and developing related integrated crop-N management for wheat production. The site of this study was at Quzhou town, Hebei provinece. First of all, we collected a database covering501data points from field experiment to identify high-yielding population trait in yield components and dynamics of population development and dry matter and N accumulation. Furthermore, for N regulation of high yielding population, we analyzed wheat yield, N use efficiency, and population development in relation to N management and different cultivar differing in tillering ability or spike type using3years’ field experiment; for N regulation of supra-high yielding population, we analyzed wheat yield and population development in relation to the integration of manure N management and sowing date and seeding rate with1-2years’field experiment. Finally, based on above results, we designed the integrated crop-N management for simultaneously realizing high wheat yield and high N use efficiency.The main results were concluded as follows:(I) High yields m plots (>8.5t ha’) were attributable mainly to increased spike numbers, because the variation of grains per spike and grain weight relatively decreased. To achieve>8.5t ha" high yield, the spike number should be750m-2, and grain number per spike should be32, and grain weight should be38g per1000grains. Optimal pre-winter stem number (1200stems m-2) and high productive tiller percentage (45%) were important for developing optimal population. In addition, high dry matter and N accumulation during the period from stem elongation to anthesis was crucial for ensuring high productive tiller percentage. The critical Nmin for the optimal stem number at jointing and maturity was50and90kg N ha-1, respectively, and the corresponding N target value was150and200kg N ha-1for pre-sowing and pre-jointing, respectively.(2) Under ONR treatment, the grain yield and N physiological efficiency of TN significantly increased by6and10%over the3years, respectively, compared with the multiple spike cultivar, LX. The increase in wheat yield of TN was attributed mainly to the increased grain number per spike and harvest index (7%) and similar total biomass. Compared to LX, TN decreased the number of unproductive tillers in the spring while with similar productive tillers before the winter, and thus optimized population establishment and had higher yields. The11%higher leaf N concentration at anthesis and8%greater sink strength (grain number m-2) for TN significantly increased the post-anthesis biomass by24%under ONR, which played an important role in increasing the harvest index. In both cultivars over3years, the optimal N rate (ONR) based on in-season root zone N management (INM) reduced the N rate by140kg N ha-1from300to160kg N ha-1without any yield losses, while it increased the N uptake efficiency from32%to64%compared with typical farmer’s N practice (FNP), suggesting that the ONR was optimal in practice.(3) Comparing early to late sowing, delayed sowing reduced wheat yield from9.5to7.8t ha-1 Furthermore, manure application provided a16%and11%yield compensation for the medium and late sowing date treatments, respectively, but did not significantly increase yield for early sowing. The primary reason could be that manure application increased more pre-winter stem number for medium sowing, while, for late sowing, manure application only improved partial spring stem number. High tiller mortality rate of early sowing treatment with manure application resulted in similar spike number and wheat yield as no manure treatment. Manure application improved plant N, P, and K concentration and soil temperature at a depth of5cm (0.4℃for per-winter and0.5-0.8℃for post-stem elongation), which may be important for improving population development. In conclusion, manure application could be useful for increasing wheat yield when sowing takes place on10October or later for this region.(4) Manure application increased wheat yield by10%compared with no manure treatment, due to increasing both spike number (16%) and grains per spike (11%). Under manure application, increased seeding rate from340plants m-2to520plants m-2, wheat yield significantly decreased10%due to lower thousand grain weight in spite to similar spike number. Under no manure application, increased seeding rate from340plants m-2to520plants m-2did not significantly affect wheat yield due to lower thousand grain weight and increased spike number. In addition, manure application improved plant N concentration, leaf are index, and SPAD value at anthesis.(5) An early sowing date combined with an optimal seeding rate of350seeds m2produced a higher number of spikes than the combination of an intermediate sowing date and a seeding rate of350seeds m-2or a late sowing date with a higher seeding rate of540seeds m-2. High basal N fertilizer application, typical of farmers’ standard N practices and N dressing at the re-greening stage increased spring stem numbers markedly compared to an optimal basal N rate and N dressing at the stem-elongation stage. An optimal dressing N rate of120kg N ha-1applied at the stem-elongation stage increased the spike number compared to applications of60or0kg N ha-1. Based on our results, we designed an integrated crop-N management (ICM-N) for generating high yields and high N use efficiency. The ICM-N strategy increased grain yield by38-51%(p<0.05) while using a27%lower N fertilizer rate led to an87-107%(p<0.05) increase in N use efficiency over two crop seasons compared to a standard farmers’ management strategy. The ICM-N strategy could be widely applicable for simultaneously realizing high wheat yields and N use efficiencies.