Evaluation Of Soil Environmental Effects Of Long-term Application Of Trace Fertilize

As an essential factor for the growth and development of plants and animals,trace elements have become the focus of attention in the field of agriculture and environmental science.Revealing the relationship between trace fertilizer application and the availability of trace elements in soil will be of great guiding significance to local agricultural production.In this paper,the effects of different trace element fertilizers on soil physical and chemical properties were studied on the basis of long-term positioning experiments conducted for 38 years in the dry land of the Loess Plateau.Meanwhile,the effects of different trace element fertilizers on the availability and morphological distribution of soil zinc,copper,manganese and iron were studied by continuous extraction and classification method.The change mechanism of availability of zinc,copper,manganese and iron in soil was discussed,and the effects of long-term application of trace fertilizer on agronomic characters and yield increase of winter wheat were analyzed.The main conclusions reached are:(1)The contents of organic matter,alkali-hydrolyzed nitrogen,total phosphorus and available phosphorus were higher than those of the control under long-term trace fertilizer application.Zinc application had the best effect on soil nutrient improvement,but trace fertilizer application had no significant effect on soil total nitrogen content.Long-term application of copper fertilizer enhanced the water holding capacity of surface soil,but the mean weight diameter(MWD),geometric mean diameter(GMD)and fractal dimension(D)of aggregates were not significantly different among different trace fertilizer application methods.The results showed that long-term application of trace fertilizer had no significant effect on the stability of soil aggregates.(2)Long-term application of copper and zinc fertilizer made the total,available and all forms of surface soil higher than the control;Application of Mn did not produce significant accumulation of Mn in soil,and the increase of total Mn and available Mn was not obvious.Among the various forms of soil copper,the oxide-bound and organic-bound copper were the sources of soil available copper,and the total copper content mainly came from the mineral form.Soil mineral state and organically bound zinc are the sources of soil available zinc,while oxide-bound zinc is the reservoir of soil available zinc.Exchange manganese is the source of soil available manganese,and oxide-bound manganese,mineral-bound manganese and carbonate bound manganese are the reserves of soil available manganese.Organic bound iron is the source of soil available iron,and oxide-bound and carbonate bound iron is the reservoir of soil available iron.(3)The grain yield increased by 14.6% and the biological yield increased by 10.6%under long-term zinc fertilization;The grain yield increased by 12.6% and the biological yield increased by 6.5%.The increase rate of grain yield of copper fertilizer was 1.4%,but there was no significant effect on biological yield.The application of borax fertilizer had no significant change in grain yield and biological yield.Under the influence of rainfall,the increase of winter wheat yield will change to different degrees under the application of different trace fertilizer.Normal years have different degrees of increase on the yield,but in dry years and wet years,the yield will fluctuate greatly.