Comprehensive Analysis of the Influence of Fulvic Acid from Paper Mill Effluent on Soil Properties, Soil Microbiome, and Growth of Malus hupehensis Rehd. Seedlings under Replant Conditions

Abstract

In this study, the potential regulatory effects of fulvic acid extracted from paper mill effluent (PFA) in apple replant disease (ARD) were investigated through a comprehensive experimental evaluation of the effects of PFA on soil properties, growth inhibition of apple replant pathogens, and growth of replanted Malus hupehensis Rehd. seedlings. PFA with a relatively lower molecular weight was mainly composed of carbohydrates, lignin derivatives, and polysaccharides and was rich in functional groups such as carboxyl and phenolic hydroxyl groups. Treatment with PFA dosages ranging from 2 to 3 g/pot significantly increased available phosphorus (P) in soil by 47.5 to 57.5% when compared with the control without PFA, indicating that PFA had a positive effect in activating P. In addition, PFA stimulated the growth of replanted seedlings by promoting root elongation, enhancing leaf photosynthesis, and increasing the activity of root antioxidant enzymes including superoxide dismutase, peroxidase, and catalase. However, no convincing evidence was found that application of different dosages of PFA had remarkable effects on soil pH, inorganic nitrogen, available potassium, organic matter, and the numbers of bacteria and fungi. Notably, PFA had no effect on the copy number of the main pathogenic fungi causing ARD, including Fusarium oxysporum, Fusarium solani, Fusarium proliferatum, and Fusarium moniliforme. Overall, PFA can alleviate ARD to a certain extent mainly through its effects on improving the resilience of replanted young seedlings rather than by affecting soil microorganisms or providing nutrients. ■ HIGHLIGHTS• Apple replant disease (ARD) can be partly mitigated by the application of fulvic acid extracted from paper mill effluent (PFA). • PFA exhibited a positive effect on root development and leaf photosynthesis, as well as the protective enzyme activity of the replanted seedlings. • PFA alleviated ARD mainly through its biostimulation rather than by increasing the nutrient supply or affecting soil microorganisms.

Cooperative Action of Fulvic Acid and Bacillus paralicheniformis Ferment in Regulating Soil Microbiota and Improving Soil Fertility and Plant Resistance to Bacterial Wilt Disease

“…Fulvic acid application also increased soil N, P, and K contents. At 36 days posttransplantation, application of fulvic acid powder increased available phosphorus in soil by 185.69% compared with that of soil untreated with fulvic acid, which had better effect than the fulvic acid extracted from paper mill effluent used in a previous study (47.5 to 57.5% increase of phosphorus) ( 18 ). At 36 days posttransplantation, IBP, BP, and FA treatments increased alkali-hydrolyzable nitrogen in soil by 101.25%, 127.07%, and 90.43%, respectively.…”

“…Fulvic acid could provide potassium necessary for the growth of crops. However, Wang et al ( 18 ) found that application of fulvic acid extracted from paper mill effluent had no remarkable effects on soil pH, inorganic nitrogen, available potassium, and organic matter. The effects of fulvic acid from different sources on soil nutrition varied, and the fulvic acid extracted from yeast fermentation broth had a better effect of improving soil fertility.…”

Orchard Management and Incorporation of Biochemical and Molecular Strategies for Improving Drought Tolerance in Fruit Tree Crops

“…Fulvic acid is a type of organic acid that plays an important role in increasing plant growth and plant drought resistance [ 161 ]. In grape berries, fulvic acid improved fruit quality and calcium absorption [ 162 ].…”

Effect of Hydrogen Peroxide on the Soil Microbial Community Structure and Growth of Malus hupehensis Rehd. Seedlings under Replant Conditions

“…Due to frequent tree species optimization, but limited land resources, it is difficult to avoid replanting cultivation in the original site during orchard renovation, which in turn leads to the widespread occurrence of ARD, and significantly restricts the sustainable development of the apple industry . Replanted young apple trees usually exhibit such phenomena as show delayed root extension, slow plant metabolism, poor resistance to stress, and even death of the whole plant . ARD causes serious economic losses throughout the whole life cycle of an orchard .…”

“… 2 Replanted young apple trees usually exhibit such phenomena as show delayed root extension, slow plant metabolism, poor resistance to stress, and even death of the whole plant. 3 ARD causes serious economic losses throughout the whole life cycle of an orchard. 4 Thus, it is urgent to develop alternative clean and green measures to control ARD.…”