The Effects Of Growing Rice On The Quantity And Composition Of Soil Organic Matter And Soil Micro-aggregate In Soda Saline-alkaline Soil

A lot of scientific researches and production practice have proved that grow rice can improve the soda saline-alkali soil effectively,but the information about the improvement and merchanism is very rare. This experiment will begin in Songnen Plain of west Jilin province.Take the soda saline-alkali soil as an object, collect the soil samples in each cultivation year and no riced(abandoned grassland) soda saline-alkali soil of the three layers(represent by Ap, P, C) in October 2010. Base on the morphological characteristics of soil profile,the feature of pH,total carbon and easy oxidation of organic carbon content,the composition of humus and the types of humic acid,the content of micro-aggregate and its organic carbon distribution, etc., to analyze the influence mechanism of soda saline-alkali soil organic carbon content and the composition of micro-aggregate by different cultivation year.In order to further enrich the mechanism of improving the soda saline-alkali soil,and provide the theoretical supports to improve the soda saline-alkali soil. The results of the study are summarized as follows :(1) Both the soils have lime reaction.The depth of Ap layer in each cultivation year are all obviously thicker than the abandoned grassland. The structure of the soil in humus layer is granular and below is prismatic.The hardness of soil has a downward trend,and has became porous.(2) Grow rice has obvious effect on pH value of the soda saline-alkali soil.After growing rice,each layer pH value of the soda saline-alkali soil have different degrees lowering.(3) Soil total organic carbon content revealed a general trend of rising with the cultivation year added, and achieve to the peak in growing rice for 40 years.Growing rice can increase the content of easy oxidation organic carbon and decrease the stability of soil organic carbon in different soil layers.(4) Along with the increasing length of cultivation year, which makes the ratio of soluble humus organic carbon content and not soluble humic organic carbon content increased. For free humus, free humic acid on the total amount is slightly lower than free fulvic acid.For combined humus, the content of combined humic acid is significantly higher than the combined fulvic acid.(5) The humification degree of free humic acid is lower than the combined humic acid. Along with the increasing of cultivation year, all levels free humic acid and combined humic acid of humification degree can be reduced. Long time growing rice can make free humic acid reduced the degree of aromatization, and the structure tend to be more simple. Combination state of humic acid remains more complex structure.(6) Soda saline-alkali soil micro-aggregate distributed mainly in the large micro aggregate(0.05 mm to 0.25 mm).And with the increasing of cultivation year, big micro aggregate decompose into small micro aggregate(< 0.05 mm). Organic carbon concentrate in small micro aggregate when growing rice in shortterm(1 year, 5 years), which will make the soil aggregate stability. Grow rice for a long time(10 to 40 years), the increasing content of organic carbon in great micro aggregate can provide carbon to the plant demand,which has played a good role.