Effects of foliar topdressing of labeled urea(15N)on nitrogen absorption,distribution and utilization of peanut
Foliar topdressing is a common field management technique for crop high-yield cultivation in mod-ern agriculture.In order to investigate the effects of times and concentration of leaf nitrogen application on nitrogen uptake,accumulation,distribution and utilization of plant,and reveal the nutritional mechanism of foliar topdress-ing nitrogen on the establishment and function maintenance of different organs in peanut.the experiment was con-ducted with 5 treatments:T0 was the control;T1 urea concentration was 1%,with one-time topdressing of 35 days before harvesting;T2 urea concentration was 3%,with the same topdressing time as T1;T3 urea concentration was 1%,with three-time topdressing of 50d,35d and 20d before harvest;T4 urea concentration was 3%,with the same topdressing time as T3.The 15N-labeled urea and common urea were used in this experiment.The dry matter mass,nitrogen content,nitrogen accumulation amount and 15N abundance of each plant organ were determined after har-vesting.The results showed that:(1)The nitrogen content of foliar nitrogen application increased by 0-0.22 percent-age points,and T4>T3>T2>T1,in which the content of nutrients(roots,stems,leaves)increased by 0.17-0.45 per-centage points compared with the control,while the content of reproductive bodies(fruit needles,fruit shells,seeds)increased less.The nitrogen accumulation of plants increased by an average of 19.8%under nitrogen application treatment,with an average increase of 42.1%in nutrient bodies and 12.7%in reproductive bodies.(2)The distribu-tion ratio of nitrogen through foliar application in different organs were quite different,with an order of kernel>leaf>stem>shell>needle>root,among which kernel and leaf accounted for about 60%and 30%,respectively.The proportion of other organs was less.Topdressing time had a certain effect on nitrogen distribution.Application 35d before harvest was more favorable for the distribution of reproductive bodies,which was 7.9%on average higher than that of 50d and 20d before harvest.(3)The plant nitrogen efficiency decreased with the increase of the amount of foliar nitrogen application.Fewer nitrogen application times or low nitrogen fertilizer concentration had high fertil-izer utilization rate.The average nitrogen fertilizer utilization rate with one time topdressing was 70.6%,which was 37.7 percentage points higher than that of three time topdressing,and was the highest in treatment of application 35d before harvest,which was 1.8 and 3.9 percentage points higher than that in treatments of application 50d and 20d before harvest,respectively.In conclusion,leaf nitrogen source can significantly improve the level of plant nitro-gen metabolism,promote nitrogen absorption and accumulation,especially in nutritive bodies,which is the physio-logical mechanism of"root and leaf protection"and the technical measure that root nitrogen source is difficult to re-place in late growth stage of peanut.Nitrogen from leaf topdressing was mainly distributed in pod and leaves,which was the physiological mechanism of peanut to increase yield and leaf photosynthesis.The utilization rate of leaf ni-trogen fertilizer was significantly higher than that of root fertilizer,which was an effective way of economic fertiliza-tion for peanut.The plant N efficiency decreased with the increase of leaf N application amount,and the fertilizer utilization rate was higher with less application times or lower nitrogen concentration.This study could provide theo-retical basis and technical support for peanut foliar fertilization.
peanutfoliar applicationnitrogenaccumulation and distributionnitrogen utilization rate
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