Differences Of Nitrogen Utilization And Yield Formation In Wheat Fields With Different Yield Levels

The field experiment was conducted in Shijiawangzi village,Xiaomeng Town,Yanzhou District,Jining City,Shandong Province,in 2019-2020.Two yield levels of super high yield(11 000 kg·ha^-1)and high yield(9 000 kg·ha^-1)were selected.Using wheat variety Yannong1212 as material,the difference and mechanism of nitrogen utilization and yield formation in wheat fields with different yield levels were studied.1 Differences in soil nitrogen supply capacity of wheat fields with different yield levelsThe contents of soil total nitrogen,organic matter,alkaline nitrogen,available phosphorous and available potassium in the 0～40 cm soil layer all decrease with the deepening of the soil layer.The soil nutrient content of the super-high-yield wheat field was significantly higher than that of the high-yield wheat field at each growth stage of wheat.The content of soil total nitrogen,organic matter,available phosphorous and available potassium is the highest during the winter,and slowly decreases with the growth of wheat.However,maintaining a stable state,the soil alkaline hydrolyzable nitrogen content first decreased during the wheat growth period,then increased and then decreased,and the anthesis period was the highest.The activities of soil urease,sucrase,catalase,alkaline phosphatase and protease in the0～40 cm soil layer all decrease with the deepening of the soil layer.The soil enzyme activities in super-high-yield wheat fields were significantly higher than those in high-yield wheat fields at each growth stage of wheat.During the wheat growth period,the soil urease and alkaline phosphatase activities increased first and then decreased,and reached the maximum during the anthesis period.Soil catalase activity increases slowly with the postponement of the growth period,and reaches the maximum in the mature period.The activities of soil sucrase and protease decreased slowly with the postponement of the growth period,and the most during the wintering period.The soil nitrate nitrogen content in the super-high-yield wheat field is significantly higher than that in the high-yield wheat field in the 0～100 cm soil layer from the wintering period to the anthesis period of wheat.20 d and 30 d after anthesis,the high-yield wheat field in the 40～100 cm soil layer is significantly higher than the super-high-yield wheat field.In the mature period,the super-high-yield wheat field in the 0～40 cm soil layer is significantly higher than the high-yield wheat field,and the 40～100 cm soil layer is significantly lower than the high-yield wheat field.The content of soil ammonium nitrogen in each soil layer during each growth period of wheat was at the super-high-yield wheat field,which was significantly higher than that in the high-yield wheat field.The growth period of wheat and the depth of the soil layer have little effect on the ammonium nitrogen content of the soil,and the ammonium nitrogen content remains in a stable state.The soil microbial biomass nitrogen content in the 0～100 cm soil layer decreases with the deepening of the soil profile,and the super-high-yield wheat field in the 0～60 cm soil layer is significantly higher than the high-yield wheat field in the various growth stages of wheat.The soil microbial biomass nitrogen content decreased from the wintering stage to the jointing stage,increased from the jointing stage to the anthesis stage,decreased from the anthesis stage to the mature stage,and reached the maximum value at the anthesis stage.The content of soluble organic nitrogen in the soil layer of 0～100 cm decreases with the deepening of the soil profile.The super-high-yield wheat field in the 0～80 cm soil layer was significantly higher than the high-yield wheat field in the various growth stages of wheat.The change during the growth period is consistent with the change of the microbial biomass nitrogen content.2 Differences in dry matter production and yield of wheat in wheat fields with different yield levelsThe total number of stems,dry matter accumulation from overwintering to maturity,distribution of dry matter in grains during maturity,assimilation after anthesis,and their contribution to grains in super-high-yield wheat fields are all significantly higher than those in high-yield wheat fields.The grain filling rate of wheat in the super-high-yield wheat field was significantly higher than that in the high-yield wheat field at 14～21 d,21～28 d and 28～35 d after anthesis.Super-high-yield wheat fields extend the duration of wheat grain filling,the active filling period and the time required to reach the maximum grain filling rate,and increase the grain weight at the maximum filling rate,the maximum filling rate and the average filling rate.The number of wheat spike per unit area,thousand-grain weight,spikelet seed rate,grain yield and harvest index in super-high-yield wheat fields were significantly higher than those in high-yield wheat fields.3 Differences of nitrogen accumulation,translocation and nitrogen use efficiency in wheat fields with different yield levelsThe accumulation of nitrogen from winter to maturity in the super-high-yield wheat field,the distribution of nitrogen in the grain during the mature period,and the contribution rate of the nutrient organ nitrogen before anthesis to the grain were significantly higher than those in the high-yield wheat field.Flag leaf nitrate reductase activity and glutamine synthetase activity in super-high-yield wheat field were 14 d,21 d and 28 d after anthesis.The super-high-yield wheat field was significantly higher than the high-yield wheat field;The endopeptidase activity,soluble protein content and free amino acid content of wheat flag leaves were significantly higher than those of high-yield wheat fields at 21 d and 28 d after anthesis.Nitrogen uptake efficiency,nitrogen use efficiency,nitrogen utilization efficiency,nitrogen partial factor productivity,and nitrogen physiological efficiency for biomass formation are significantly higher than those of high-yield wheat fields,while the nitrogen requirement for producing 100 kg of grain is significantly lower In the super high-yield wheat field.