Effects Of Fallow On Soil Carbon,nitrogen,Phosphorus And Potassium Storage Capacity In Sandy Paddy Field Lined With Film

Desertification is a phenomenon of land degradation under the influence of climatic conditions and human disturbance.It is one of the top ten environmental problems in the world.Because of desertification,the ecological environment is destroyed,sustainable economic development is hindered,and human security and health are threatened.Horqin sandy land is the largest sandy land in China,and the land degradation area accounts for 17.3% of the total land degradation area in China.Horqin sandy land,located in the impact plain at the lower reaches of the West Liaohe River,was once a grassland with lush vegetation.Horqin grassland is located in the ecotone of agriculture and animal husbandry,and the ecological environment is fragile.Since the 20 th century,the destruction of forests,over reclamation of land and over grazing have exposed the surface of sandy grassland.Under the action of light and wind,grassland is degraded rapidly,resulting in the original complete ecosystem being divided into different types of ecosystems,the edge effect of desert and grassland ecosystem being increased,causing land fragmentation and patching.In order to provide scientific basis for desertification control,soil carbon（C）,nitrogen（N）,phosphorus（P）and potassium（K）pools affected by continuous planting of film lined rice and fallow after planting film lined rice need to be studied in Horqin.Sandy soil was used as contrast.It was used to analyze the contents of total carbon（TC）,total nitrogen（TN）,total phosphorus（TP）,total potassium（TK）,available nitrogen（AN）,available phosphorus（AP）,available potassium（AK）,total organic carbon（TOC）,readily oxidized organic carbon（ROOC）and no readily oxidized organic carbon（NROOC）in 0～15 and 15～30 cm paddy and fallow soil.Meanwhile,it was used to analyze the correlation between the component content of C,N,P and K pool and the carbon pool management index（CPMI）in fallow soil.The results showed that the component contents of soil C,N,P and K pool was significantly affected by rice planting and fallow,and the contents of soil TC,TOC,ROOC,NROOC and TN and the value of C/N,ROOC/TOC and CPMI were significantly increased and then significantly decreased.The order of difference was: paddy field >fallow paddy field > sandy land.Among soil nutrients,the content of organic carbon changed the most before and after planting rice.The content of organic carbon in soil nutrients after rice planting increased by 903% compared with that before rice planting.The contents of nitrate nitrogen and AK and the proportion of AN,AP and AK in soil were significantly decreased after planting rice,but there was no obvious change before and after fallow.The contents of TP,TK,ammonium nitrogen,AN and AP in soil were not significantly different by different treatments.There was a extremely significant positive correlation of C,N,P and K pool content with C/N value and moisture content in fallow paddy soil,and CPMI of fallow soil was most affected by the content of ROOC.The study area was dominated by aeolian sandy soil,which was barren and difficult to repair.These results indicated that planting film lined rice in the desert can improve the content of soil nutrients and organic carbon in a short time,which was conducive to the continuous improvement of soil quality.However,the content of soil nutrients and organic carbon was only slightly higher than that of sandy land after one year of fallow,and the soil can not be restored to the level of grassland soil within one year after natural fallow.Therefore,it was impossible to abandon the farmland directly after the completion of sand restoration.It was necessary to intervene after the harvest of film lined rice,and a lot of grass was planted to cover the ground with plants and reduce the surface exposure rate,so that the succession was promoted from desert ecosystem to grassland ecosystem.