In view of the problems of poor soil structure

low fertility and low plant productivity after ammonia nitrogen reduction in abandoned rare earth mining areas

soil improvement becomes the key to rapidly improve vegetation restoration.Field experiments were carried out to compare the effects of single application of different concentrations superabsorbent polymers (SAPs:S1

S2 and S3) and water and fertilizer preserving materials (WFPMs:F1

F2

F3) on soil physicochemical properties

growth of Pennisetum sinese Roxb

evapotranspiration and water use efficiency (WUE).In order to select the best soil amendment

the principal component analysis and fuzzy membership function were employed to comprehensively evaluate the relevant indicators.The results showed that:(1) The WFPMs promoted the growth of Pennisetum sinese Roxb by improving the soil physicochemical properties of the tailings soil in the abandoned rare earth mining area.The relationship between soil physicochemical properties and plant growth showed that the higher the soil pH and nutrient content

the higher the growth indicators such as tiller number

nitrogen and phosphorus content

yield and WUE.(2) Compared with the control

the WFPMs increased the plant yield and WUE by 58.13%~182.63% and 53.81%~181.54%

respectively;The effect of SAPs was limited

and its medium and high dosage of water retaining agent (S2

S3) increased the plant yield and WUE by 19.95%~77.52% and 19.54%~79.50%

respectively.(3) The principal component analysis method was used to screen out 22 soil improvement indicators

and the fuzzy membership function values of each indicator were calculated respectively.The average function value was taken as the evaluation value of soil improvement effect

and the evaluation result was as follows:WFPMs ＞ SAPs (except for S1)＞ CK.Compared with the control

the average function value of the SAPs (except for S1) only increased by 0.32~0.35 times

while that of the WFPMs increased by 0.73~1.72 times

and decreased with the increase of the application amount.Therefore

F1 was the best soil amendment treatment.The result showed that combing materials of WFPMs have a good application effect on the improvement of tailings soil in abandoned rare earth mining area.