Effects of different rotation sequences on the distribution of soil organic matter and available micronutrients
were studied using potassium dichromate volumetric method and DTPA extraction － atomic absorption method
on the basis of long-term experiment of Shilipu village of Changwu county． The results showed that the distribution of
soil available micronutrients not only effected by the total amount of soil micronutrients，but also related with the crop
rotation sequences． From surface soil to deep soil of different rotation sequences，the content of soil organic matter
decreased first and then increased slowly，it continuously increased of the content of soil available Fe，the content of
soil available Mn and Zn decreased gradually，the content of soil available Cu increased first and then decreased slowly．
In the 80 ～100 cm soil layer，the content of organic matter of the cereal-forage rotation ( CFR) was 11． 08 ～11． 89
g·kg － 1 and the clover-legumes rotation( CLR) was 11． 04 ～ 11． 72 g·kg － 1 ． The content of soil available Fe and
Mn were lower than other crops of the CFR in the third years of wheat，planting alfalfa and potato could effectively increase the content of soil available Mn in CFR，continuous wheat cropping and alfalfa cropping could decrease the content
of soil available Zn and Mn． The content of soil available Fe was higher than that of the CLR in the crops of wheat
with broomcorn millet and the content of soil available Mn was the lowest of the CLR in the crops of wheat，and it average
lower 7． 73% ～30． 55% the crops of wheat with broomcorn millet and the crops of legumes． It was higher than CLR
of the soil available micronutrients of CFR，there were great difference of the soil available micronutrients in CFR and
CLR above 80cm soil layers，but the difference between CFR and CLR was reduced below 80 cm soil profiles．
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