| In order to explore the effects of the mixing ratio of controlled release nitrogen and common nitrogen on soil nitrogen content,winter wheat growth,development,and quality under different nitrogen application rates.Reveal the physiological and ecological mechanisms of controlled release mixed nitrogen fertilizer regulating winter wheat growth,development,and nitrogen absorption and utilization,and determine the optimal mixing ratio and nitrogen application rate of controlled release nitrogen for winter wheat in the Guanzhong Plain.In the experiment,two nitrogen application rates of 192(N1)and 240(N2)kg/hm~2 were set,and under the two nitrogen application rates,five different mixing ratios of controlled release nitrogen and common nitrogen were set.The proportions of controlled release nitrogen were 0%(F1),30%(F2),50%(F3),70%(F4),and 100%(F5),respectively.The effects of changes in soil nitrate concentration at various growth stages of winter wheat on dry matter accumulation,nitrogen uptake and transportation,yield,and quality of winter wheat were analyzed,and the following conclusions were drawn:(1)With the increase of the proportion of controlled release nitrogen,the content of soil nitrate nitrogen in the jointing and flowering stages can be increased,and the accumulation of nitrate nitrogen in the 1-2m soil layer at the mature stage can be reduced.When the proportion of controlled release nitrogen is 70%,the soil nitrogen supply is more stable during the growth period of winter wheat.Compared with the full application of controlled release nitrogen,the content of soil nitrate nitrogen and ammonium nitrogen in the overwintering and rejuvenating stages of winter wheat can be increased.When the nitrogen application rate was increased to240 kg/hm~2,the nitrate nitrogen content in the soil at the turning green,jointing,and flowering stages of winter wheat could be significantly increased.When the controlled release nitrogen ratio was 70%and 100%,the nitrate nitrogen content in the 1-2 m soil layer at the mature stage of winter wheat did not significantly decrease under the two nitrogen application rates,reducing the downward leaching of nitrate nitrogen in the soil.(2)The changes of soil root morphology between different treatments were mainly manifested in the root length density and root surface area density.Increasing the proportion of controlled release nitrogen could increase the root length density and root surface area density in the 0-60 cm soil layer from the jointing stage to the mature stage of winter wheat.There were no significant differences in the average root diameter,root length density,and root surface area of winter wheat from flowering to maturity between the 70%controlled release nitrogen treatment and the full controlled release nitrogen treatment.However,the root length density of 0-40 cm at the jointing stage significantly increased,and the average root diameter of 10-20 cm soil layer significantly decreased.The 70%controlled release nitrogen treatment was more able to regulate the root morphology of winter wheat from the jointing stage to the flowering stage.(3)Increasing the proportion of controlled release nitrogen can increase the population number of winter wheat at flowering and ripening stages,and increase the dry matter accumulation and distribution ratio of grains by increasing the dry matter transport amount before and after a thesis.The population number at the turning green stage and the jointing stage is high significantly and positively correlated with the population number at the flowering and mature stages,and the soil nitrate nitrogen content during the overwintering stage is highly significantly and positively correlated with the population number at the turning green stage.Compared with the treatment with a controlled release nitrogen ratio of 70%,the total application of controlled release nitrogen treatment increases the population number at the turning green stage and the jointing stage by increasing the soil nitrogen content during the overwintering and turning green stages.thereby increasing the population number at the flowering and mature stages,Laying a high yield foundation for winter wheat.(4)Increasing the proportion of controlled release nitrogen can increase the nitrogen accumulation of winter wheat by increasing the nitrogen transport from pre anthesis to grain;There was a significant positive correlation between the soil nitrogen content at the turning green stage and the jointing stage and the nitrogen accumulation amount at the flowering stage of winter wheat.The treatment with controlled release nitrogen fertilizer accounting for 70%significantly increased the nitrogen accumulation amount at the flowering stage by increasing the soil nitrate concentration at the turning green stage and the jointing stage.There is a significant quadratic equation relationship between the nitrogen accumulation amount at flowering stage and the contribution rate of nitrogen to grains before and after flowering.When the nitrogen accumulation amount at flowering stage is 272.8 kg/hm~2,the contribution rate of nitrogen to grains before flowering reaches the maximum,and when it is lower than272.8 kg/hm~2,the nitrogen accumulation amount at flowering stage will promote the contribution rate of nitrogen to grains before flowering.(5)Increasing the proportion of controlled release nitrogen can improve grain yield by increasing the number of spikes in winter wheat;Compared to N1 nitrogen application,when the controlled release nitrogen ratio is 0%,30%,and 50%,there is no significant difference in yield.When the controlled release nitrogen ratio is 70%and 100%,the yield is significantly increased,and there is no significant difference in nitrogen utilization efficiency.N2F4 has an average increase of 15.6%in net benefits compared to N1F4,and an average increase of 2.8percentage points in nitrogen utilization efficiency.(6)Increasing the proportion of controlled release nitrogen can improve the grain quality characteristics of winter wheat.When the proportion of controlled release nitrogen is 70%and100%,it can significantly improve the protein,wet gluten,and sedimentation value of the grain,and mainly reduce the total starch content by reducing the amylose content.Compared with other treatments,controlled release nitrogen at 70%can improve the farinographic characteristics of the grain,significantly increase the dough formation time and stability time,and significantly reduce the degree of weakening.When the nitrogen application rate was increased to 240 kg/hm~2,the protein and wet gluten content,dough formation time,and stability time significantly increased,and the degree of weakening significantly decreased.In summary,when the nitrogen application amount is 240kg/hm~2 and the controlled release nitrogen accounts for 70%,it can significantly increase the number of panicles and thereby increase the yield by increasing the soil nitrogen supply after the turning green stage and increasing the population number at the jointing and flowering stages.Moreover,by increasing nitrogen accumulation at flowering stage,significantly increasing nitrogen transport before flowering,significantly increasing nitrogen accumulation and distribution ratio in grains at maturity stage,significantly increasing protein and wet gluten content in grains,and improving grain characteristics.it is a controlled release mixed nitrogen fertilizer application scheme for achieving high yield and efficient nitrogen utilization of winter wheat in the Guanzhong Plain region. |
