Effects Of Long Term Fertilization On Zn,Cu Transformation And Crop Uptake In Brown Soil

The study is carried out in a long-term located experiment in brown soil,which has a history of 37 years from 1979 to 2015.The experiment includes 15 treatments which are divided into three regions,chemical fertilizer plot,low amount organic fertilizer plot and high amount organic fertilizer plot.The soil pH,organic matter,various forms of nitrogen,available Zn and available Cu were measured at different growth stages during the period of 2015.Zn and Cu contents in soil from six-year samples,as well as in corn and soybean grains from three-year samples were measured.The purpose of this study was to reveal the effects of pH,organic matter and nitrogen on the contents of Zn and Cu in soil and in plants,and further to explain the rule and influencing factors on the transportation of Zn and Cu in soil-plant system.The results are as follows:1 Long-term application of chemical fertilizers reduced the soil pH.The application of nitrogen fertilizer pH decreased more significantly;the application of organic fertilizer increased soil pH,and alleviated the N-induced decrease of pH.Application of chemical fertilizers can increase soil ammonium nitrogen and nitrate nitrogen contents;the application of organic fertilizer can delay the migration of ammonium nitrogen to the lower soil layer.With the deepening of the soil layer,the contents of ammonium nitrogen and nitrate in the chemical fertilizer zone decreased gradually,while ammonium nitrogen in the organic fertilizer zone did not obviously change and the nitrate nitrogen showed a decreasing trend.Application of organic fertilizers can increase the contents of organic matter,total nitrogen and available Zn and Cu which decreased with the deepening of soil.2 Long-term no using of any fertilizer make total and available Zn and Cu lower.Long-term application of chemical and organic fertilizers increased the contents of total and available Zn,Cu in every selected year.The latter had a more significant effect.Long-term application of different fertilizers increased the contents of WS-Zn,EX-Zn,OM-Zn,while decreased the contents of the FeMnO-Zn;Long-term application of different fertilizers increased the content of EX-Cu.Other forms of Cu had no significant changes under different fertilization conditions.3 Long-term no using of any fertilizer make Zn accumulation in maize and soybean grains lower.The use of chemical fertilizers increased the Zn accumulation in maize and soybean grains at early years,but decreased the accumulation at later years.The use of organic fertilizer showed a reverse influence on the Zn accumulation in maize.The treatments of N1PK and N2 had a more significant effect on the Zn accumulation in maize grain regardless of whether the orgainic fertilizer was used or not.The Cu accumulation in maize and soybean grains was lower when no useing of fertilizer and only using of organic fertilizer.The use of chemical fertilizers increased the Cu accumulation in maize and soybean grains at early years,but decreased the accumulation at later years.The use of organic fertilizer never increased the Cu accumulation in two kinds of grains,and inversely decreased the Cu accumulation at later years.4 There was a significant negative correlation between pH and available Zn and Cu in chemical fertilizer and low amount organic fertilizer plots.The correlation between organic matter,total nitrogen and available Zn,Cu showed significantly positive.5 WS-Zn and available Zn had a positive effect on the Zn accumulation in corn grain.Available Zn increased zinc accumulation in soybean grain,while EX-Zn,FeMnO-Zn had an opposite effect.WS-Cu and OM-Cu contributed to the increase of copper accumulation in maize grain.WS-Cu can increase the copper accumulation in soybean grain,while the EX-Cu has an opposite effect.