Effect of Soil Fertility and Nitrogen Application Types on Absorption and Utilization Rate of Two Types of Nitrogen Sources in Wheat at Different Growth Stages

In order to clarify the effects of soil fertility and nitrogen application types on fertilizer distribution and use efficiency at different growth stages,winter wheat were cultivated with pipe using 15N tracer technique.The results showed that: treatment A2B2C2(high soil fertility,N basal dressing depth of 20 cm,50% of N fertilizer as basal fertilizer and 50% as topdressing) of eight treatments was with the highest grain yield and balanced combination of yield components.The average percentage of absorption of nitrogen fertilizer at winter,jointing,flowering,20 d after flowering and maturity were gradually decreasing with the growth process,respectively,the proportion of uptake of soil nitrogen fertility process with progressively.Fertile soil can increase the total amount of nitrogen absorption at each growth stage,the mature season fertilizer nitrogen use efficiency increased by 10.51 percentage points,lowered loss rate by 4.6 percentage points,but reduced the absorption of nitrogen fertilizer at the middle-late growth and proportion to the distribution of grain.Only deep application of nitrogen fertilizer have the significant effect on fertilizer nitrogen uptake and accumulation before jointing and different nitrogen sources;but deep application of fertilizer can significantly increase the maturity of nitrogen utilization and reduce the loss rate.Basal dressing of nitrogen fertilizer can increase the total N uptake and reduce the proportion of soil nitrogen uptake at winter and jointing stage;50%of N fertilizer applied as basal fertilizer and 50%applied in ways that favor the accumulation of N uptake at late growth stages,the mature season nitrogen fertilizer use increased by 2.72 percentage points,the loss rate decreased by 13.5 percentage points,but the proportion allocated to the grain was significantly lower than all the basal treatment.