Effect of plant waste-derived organic fertilizer on soil quality and vegetation restoration in rocky desertification sloping lands

To investigate the effects of plant waste-derived organic fertilizer on soil quality and vegetation restoration during the ecological rehabilitation of karst rocky desertification slopes， and to determine the proportion of organic fertilizer added and the application effect under different slope gradients， a study was conducted involving both pot and field experiments on rocky desertification slopes in Qianxi， Guizhou Province. Each experiment comprised 5 test groupes. The pot experiment included a control （CK） group and groupes with organic fertilizer addition ratios of 10% （T1）， 20% （T2）， 35% （T3）， and 55% （T4）. The effects of pot treatments on soil properties and the growth of alfalfa （Medicago sativa） and ryegrass （Lolium perenne） were studied. Based on the pot experiment results， the optimal organic fertilizer addition ratio of 35% was selected for the field experiment. The field experiment involved 5 slope gradient groupes：1°-5°（T-5）， 6°-10° （T-10）， 11°-15° （T-15）， 16°-20° （T-20）， and 21°-30° （T-30）. This experiment aimed to study the differential effects of organic fertilizer （at 35%） on soil properties and spontaneous vegetation regeneration across these slope gradients. The results indicated that in the pot experiment， all organic fertilizer treatments significantly improved soil physicochemical properties， the growth of alfalfa and ryegrass， and plant regeneration compared to the CK group （PP>0.05）， and the magnitude of change in all measured indicators was significantly lower than that in the other three treatment groupes （T-5， T-10， T-15）. This indicates that the effectiveness of organic fertilizer is greater on rocky desertification slopes with gradients below 15°.In conclusion， plant waste-derived organic fertilizer， as a fertilizer source for soil ecological restoration on karst rocky desertification slopes， significantly improves soil physical structure and nutrient content， while promoting the spontaneous regeneration of vegetation. However， its effectiveness is constrained by nutrient addition ratios and slope conditions.