The Effect On Soil Organic Nitrogen Under The Different Tillage In Dryland

The field experimental research was conducted at the station of dry land farming of Gansu Agriculture University.The two rotation series(the rotation of spring wheat-field pea and the rotation of field pea-spring wheat)have being studied.The results were as follows: 1. Effect of no-tillage with straw cover on soil organic nitrogen fraction in dry land.the results showed that amino acid-nitrogen was the hignest content in the soil organic nitrogen in all treatment,amino sugar-nitrgen was lowest but the second organic nitrogen is different between NTS,TS and NT,T. 2.Only no-tillage and tillage with cover straw could increase the content of soil organic total nitrogen,NTS and NT was respectively higher than TS and T in 0-5cm in only no-tillage,while NTS was lower than TS in 5-10cm,NT was yet higher than T;but NTS and TS was higher than NT and T in both 0-5cm and 5-10cm in tillage with cover straw. 3. There was no big change in soil organic total nitrgen after crop reaping.NT and T have decreasing trend,while NTS and TS have inceasing trend. 4. Multiple comparison showed that there was significant in 0-5cm soil between NTS and T,and there was no significant among others,the sequencing of means of soil organic total nitrogen was NTS>TS>NT>T;but there was significant in 5-10cm soil between TS and T,and there was no significant among others,the sequencing of means of soil organic total nitrogen was TS>NTS>NT>T. 5.No-tillage with straw cover could increase the content of soil organic total nitrogen.the soil organic total nitrogen was increased by 17.18 percent in the depth of 0-5cm. 6.The mean content of NH4-N was respectively decreasing by 11.91 percent and 10.58 percent in the depth of 0-5cm and 5-10cm from Mar to Aug.the multiple comparison showed there was significant between NTS and T in the rotation series of WPW and PWP in the depth of 0-5cm,and there was no significant among others,while there was no significant in all treatments.the sequencing of the mean content of soil organic nitrogen was T>NT >TS>NTS in the depth of 0-5cm,while it was T>NT>NTS>TS in the depth of 5-10cm. 7.No-tillage and tillage with straw cover could both increase the content of amino acid-N.the multiple comparison showed that there was significant between NTS and TS in the rotation series of WPW and PWP in the depth of 0-5cm,and there was no significant among others,while there was significant between TS and T in the depth of 5-10cm,moreover the sequencing of amino acid-N was the same as total nitrogen in the depth of 0-5cm and 5-10cm. 8.Amino sugar-N was small proportion in the soil organic total nitrogen, the range of content was from 5.96 percent to 7.03 percent.no-tillage and straw cover could both increase the content of it.the mutiple comparison showed that the content of amino sugar-N was significant between NTS ,TS and T in the rotation WPW in the depth of 0-5cm, and it was very significant between NTS ,TS and T in the rotation PWP in the depth of 0-5cm , it was not significant between WPW and PWP among others;but it was very significant between TS and T in the rotation WPW in the depth of 5-10cm,it was significant between NTS and T,while it was significant between TS,NTS and T in the rotation PWP,it was not significant among others. 9.The mean content of Unkown-N was higher Aug than Mar.no-tillage and straw cover could differently increase the content of it.the mutiple comparison showed that it was significant between NTS and T in the depth of 0-5cm,and it was not significant among others;while it was not significant among others in the depth of 5-10cm. 10.The soil organic nitrogen fraction was negatively related to the depth of soil, except NH4-N.