Compound microorganism coated long-acting improvement fertilizer for saline-alkaline land and preparation method

The invention relates to the field of improvement of saline-alkaline land and particularly relates to compound microorganism coated long-acting improvement fertilizer for saline-alkaline land and a preparation method. The improvement fertilizer is prepared from a saline-alkaline land improvement material, a coating material, a compound microbial agent, nitrogen fertilizer as well as medium and trace elements essential to plants in the weight part ratio of 1:(0.001-0.01):(0.001-0.01):(0.1-0.5):(0.001-0.01). The improvement fertilizer can control the salinity and alkalinity in soil of the moderate and heavy saline-alkaline land in a reasonable range, so that pH and the degree of alkalization in the soil can be reduced, the release time of acidic substances is notably prolonged, the fertilizer acts in the whole growth period of crops, sustained damage of accumulation of alkali and salt on soil to the crops is effectively reduced, the crops are protected against salt damage and alkali damage in the whole growth c