Effects of nitrogen reduction on trace elements and crop quality in typical lime concretion black soil under straw returning modes
The effect of reduced nitrogen fertilizer application on trace elements and crop quality in typical lime concretion black soil was studied through long-term straw returning field positioning test.Four treatments were set up:nitrogen,phosphorus and potassium conventional(N100PK),reduced nitrogen fertilizer application by 30%(N70PK),no nitrogen application(N0PK)and no fertilization(CK)under double cropping of wheat and corn with straw returning to the field.The results showed that there was no significant change in the total amount of trace elements in the topsoil(0-20 cm).The avaible Fe content was 8.5-11.0 mg·kg-1,the avaible Mn content was 15.5-19.0 mg·kg-1,the avaible Cu content was 1.6-2.0 mg·kg-1,and the avaible Zn content was extremely low,ranging from 0.1 to 0.4 mg·kg-1.With the reduction of nitrogen fertilizer application,the content of available Fe and Mn decreased by 26.04%and 9.46%,respectively,while there was no significant change in available Cu and Zn.The Cu content in corn grains decreased by 12.5%-24.9%with the reduction of nitrogen fertilizer application,while the Fe content in corn straw decreased by 50.0%-61.4%due to the absence of nitrogen fertilizer application.The Zn content in wheat grains showed a trend of first decreasing and then increasing,while the Fe content in wheat straw decreased by 63.7%to 71.1%.Nitrogen fertilizer reduced corn albumin by 14.0%and wheat prolamin by 25.6%.In conclusion,under the straw returning mode,reducing nitrogen fertilizer application reduced soil available Fe and available Mn trace elements and their bioavailability,and might affect crop quality by inhibiting protein synthesis.
long term positioning testreduction of nitrogen fertilizerreturning straw to the fieldtrace elementscrop quality
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