An Evaluation On Soil Improvement Effect Produced By Planting Alfalfa

This literary take field investigation and laboratory analysis methods to study soilsample'S soil physical and chemical properties,soil microorganism property taken from0-30cm layer'S of different planting time alfalfa seed grounds and cotton ground planted in succession,through this method,study the influences on every soil fertility index produced from alfalfa'S planting period,and the influences on soil fertility which took from planting alfalfa or cotton,comprehensive appraised the soil fertility of different alfalfa grounds and cotton ground planted in succession by main composition analytical method. 1.the alfalfa planting time affected soil fertility,all in all,the longer alfalfa planted,the better soil quality was relatively.The period of planting alfalfa had the influences on soil physical and chemical prope N In general,the longer alfalfa planted,the more influence affected on soil chemical prope~the different alfalfa grounds had the same composition of microorganism,but the there did not have the same quantity.There were obvious difference on soil microorganism carbon and nitrogen among different alfalfa grounds.the respiration strengths and qC02 value of four years alfalfa ground were low than one or two years alfalfa grounds'S. 2.the alfalfa planting time didn't have effects on soil organic matter,but it had influences on soil available nutrient and soil bulk density,etc.it also had different influences on soil microorganism composition , soil microorganism carbon and nitrogen,respiration strengths and qMB value about vertical soil layers. 3.The soil organic matter,available nitrogen,available phosphorus content of four years alfalfa ground were even relatively high compared with cotton'S,and all indexs were highest on the top layer.Planting alfalfa Can reduce soil bulk density,increase total soil porosity,reduce soil salt content and chlorineion content,raise the capacity of holding water.But alfalfa ground soil PH value were higher than cotton ground.Planting alfalfa in succession made microorganism quantity more in field than it in cotton field , the microorganism activity is strong,and the microorganism carbon is high,the qC02 value is little.Compared with planting coRon,planting alfalfa Can improve soil quality. 4.it indicated that the four years alfalfa ground'S soil fertility was first,secondly was cotton ground,the third was the two years alfalfa ground,the last was one year alfalfa ground.