Effect Of Long-term Phosphorus Fertilization On Fluorine Accumulation In Farmland Soil And Fluorine Absorption By Wheat And Resistance Control Measures

Fluorine has a double threshold effect on human body,and excessive fluorine has a bad effect on human health.Diet is the main channel for human to intake fluorine,and the excessive fluorine accumulation in crops is harmful to the human body.Based on the long-term experiment under the wheat-maize rotation system in Guanzhong Plain,by comparing seven treatments for 30 years of fallow(FL),un-amended control(CK),nitrogen fertilizer(N),nitrogen and phosphorus fertilizer(NP),nitrogen,phosphorus and potassium(NPK),straw retention with NPK(SNPK)and manure application with NPK(MNPK).To study the effect of the long-term application of phosphorus fertilizer on fluorine accumulation in soil and wheat fluorine absorption,and the resistance effect of straw retention and manure application.To clarify the characteristics of fluorine accumulation in arable layer and profile(0～100 cm)soil in long-term application of phosphorus fertilizer.Understanding the accumulation of fluorine in wheat organs during each growth stage,and the resistance control effect of straw retention and manure application on phosphorus applied soil.The main conclusions are as follows:(1)The application of phosphorus fertilizer significantly increased the fluorine content of the arable layer,total fluorine content was increased by 20.48%～26.79% compared with the treatment of non-phosphorus fertilizer,the water-soluble fluorine content by 1.37～2.82 times,and the exchangeable fluorine content by 0.82～1.48 times.The soil content of fluorine in 0～10 cm layer is higher than 10～20 cm layer.The fluorine content of 0～40 cm layer is greatly affected by the application of phosphorus fertilizer,and the lower layer is mainly affected by natural factors.The water-soluble fluorine content in arable layer is high,then decreases along the soil profile;the exchangeable fluorine content decreases greatly in arable layer than that of deeper soil.The fluoride content in groundwater is less likely to be affected by the application of phosphorus fertilization.(2)The fluorine content of each growth stage of wheat is: root > leaf > stalk.The fluorine is mainly enriched in the root,with the interception of other organs,the transfer to the grain is relatively small.Due to the lager biomass in phosphorus fertilizer treatments,the content of grain is less than that of non-phosphorus fertilizer treatments,but the accumulation of fluorine in the grain was nearly more than 4～8 times of non-phosphorus fertilizer treatments.(3)With straw retention and manure application,the total fluorine of soil was significantly reduced by 5.93% and 4.29%,and the water-soluble fluorine content decreased by 2.95% and 59.53%.Straw retention and manure application effectively reduced the total fluoride content in deeper soil;manure application significantly reduced the water-soluble fluorine content of phosphorus soil profile.Fluorine was mainly intercepted by wheat root with straw retention and manure application,the transfer andenrichment rate was reduced,so the fluorine content in grain decreased by 9.80% and3.92%,respectively.Generally,long-term application of phosphorus fertilizer can lead to a large increase of total fluorine,water fluorine and exchangeable fluorine content of arable soil,but has less impact on soil layer below 40～60 cm;using organic fertilizer can significantly reduce water-soluble fluorine content of arable soil.The absorption and accumulation of fluorine in wheat is mainly in the roots.Long-term application of phosphorus fertilizer did not cause the excessive fluorine content of wheat grain,but Straw retention and manure application can reduce the absorption of fluorine in wheat.