Effects Of Nitrogen Fertilizer Management On The Absorption,Accumulation And Translocation Of Cd In Rice

In order to study the effect of advancement of nitrogen fertilizer on rice cadmium absorption,transportation and accumulation,early rice varieties Zhuliangyou 819 and Luliangyou 996,late rice varieties Xiangwanxian13hao and Yuzhenxiang were selected as experimental materials,and they were held in Hunan from 2019 to 2020.Field experiments were conducted in Huayuan Village(Liuyang),Yanxi Town,Liuyang City,and Tongxin Village(Fulin),Fulin Town,Changsha County,Hunan Province to study the effects of different nitrogen fertilizer application ratios and types on the absorption and transport of cadmium in rice plants.Experiment 1.The effect of different base tiller fertilizer ratios on rice cadmium uptake and transport.The total nitrogen application rate per season is 180kg/hm2,and the ratio of 3 nitrogen fertilizer application methods is set:no nitrogen fertilizer(F1),nitrogen fertilizer as tiller fertilizer and one-time application Into(F2),nitrogen fertilizer is applied as base fertilizer:tiller fertilizer at 6:4(F3);Experiment two,the effect of different nitrogen fertilizer forms and water coupling on the accumulation of cadmium in rice,nitrogen fertilizer is the main area,and water management is the sub-area.Set up 4different types of nitrogen fertilizer:no nitrogen fertilizer(N0),urea(N1),ammonium bicarbonate(N2),urea for base fertilizer,sulfur-coated urea(N3)for tiller fertilizer,and the total amount of nitrogen applied per season is 180 kghm~2,based on 6:4 application of base fertilizer:tiller fertilizer.There are two water management modes for water management treatment:W1:intermittent irrigation,and W2 flooded irrigation.The main research conclusions are as follows:1.The yield of double-cropping rice at the two experimental sites under the F2 and F3treatments increased by 7.49%-27.34%(Liuyang)and 5.48%-27.17%(Fulin),respectively.The yield of the late rice variety Xiangwanxian 13 The largest increase under F3 treatment.Compared with W1 and W2,nitrogen application can increase the number of grains per panicle and the rate of seed setting,reduce the number of effective panicles,and reduce the yield by an average of 5.55%to 17.18%.2.The cadmium content in different parts of double-cropping rice showed a decreasing trend under nitrogen treatment.The cadmium accumulation of double-cropping rice brown rice was significantly different under different base tiller fertilizer ratio,nitrogen fertilizer type,water management and water-nitrogen coupling treatment.Compared with the F1treatment,the cadmium content in brown rice of the double-cropping rice was significantly reduced under the F3 treatment,which were 41.67%～62.50%(Liuyang)and 28.57%～66.67%(Fulin),respectively,and the cadmium accumulation in brown rice was significantly reduced by 17.04～54.73%(Liuyang),8.97%～35.94%(Fulin).Under the same nitrogen treatment(N1～N3),the cadmium content and cadmium accumulation in brown rice of double-cropping rice decreased by 31.23%～54.25%and 11.14%～55.96%,respectively,compared with W1 under W2 conditions;under the same water management conditions,double-cropping rice The cadmium content and cadmium accumulation of brown rice under the treatment of nitrogen application(N1～N3)were reduced by 27.08%～42.20%and4.09%～59.69%,respectively,and the N3 treatment was the most significant.3.The transfer coefficient between various parts of rice at the maturity stage showed a decreasing trend under nitrogen fertilizer treatment.Among them,TF stems and leaves/roots were significantly reduced by 0.68%～12.25%in F3 treatment compared with F1 treatment.Under the same nitrogen treatment,TF stems and leaves/roots of early and late rice varieties under W2 conditions decreased by 0.69%～15.30%compared with W1.TF grains/stems and leaves were significantly reduced under W1 and W2 conditions,and N3 treatment was the most significant.4.The formation of iron plaque on the root surface of double-cropping rice during different growth periods showed full heading stage>booting stage.During the same period,the formation of iron plaque on the root surface of double-cropping rice had no obvious regularity under nitrogen application,which was compared with booting stage.During the full-heading stage of double-cropping rice,the amount of iron plaque formed on the root surface under the nitrogen treatment was lower than that of the non-nitrogen treatment,indicating that nitrogen application aggravated the degradation of the root surface iron plaque.The cadmium adsorption capacity of the iron plaque on the root surface of early rice was greater at the full heading stage than the booting stage.Nitrogen treatment increased the cadmium adsorption capacity of the iron plaque on the root surface,but the opposite trend was observed in late rice.In summary,in rice production,urea can be applied according to the 6:4 basic tiller fertilizer,and sulfur-coated urea applied to the tiller fertilizer,combined with flooding irrigation,can significantly reduce the transfer of cadmium from the stems and leaves to the brown rice,thereby obtaining cadmium.Rice with lower content.