Dynamic Changes of Humus in Inland Saline-alkali Soil in Field with Post-harvest Crops Returning

This paper studied the dynamics changes of soil humus and its composition〔humic acid(FA)and fulvic acid(FC)〕in the field with post-harvest crops returning.The results showed that humus,fulvic acid and humic acid contents in the saline-alkali soil increased by 112.5%,269.54%and 92.9%respectively after the decomposition of the straws.The content of fulvic acid was 3~10times of humic acid.HA/FA of salinealkali increased at first and then decreased with the highest value of 0.283on the 90th day.Humus content was between 0.19%and 0.38% with the fastest straw decomposition treatment of adding 7.2g urea.The content of humus and fulvic acid increased at the beginning,then decreased and increased at the end with increase of urea addition.The humus content increased 46.7% while the fulvic acid increased 55.3%and humic acid was quite opposite and decreased by 14.3% on average.HA/FA decreased but was not obvious.