The Effect of Fulvic Acids Derived from Different Materials on Changing Properties of Albic Black Soil in the Northeast Plain of China

Despite low fertility and content of organic carbon in albic black soil, grains are grown in this type of soil in the northeast plain of China in order to find ways to improve the soil’s fertility and crop production. We carried out pot experiments of maize applied with one of three different treatments of fulvic acids (FA) derived from different parent materials: Plant-derived solid (PDSF), mineral-derived liquid (MDLF), and plant-derived liquid (PDLF) applied at respective rates of 2.5, 5, and 5 g kg(−1) as well as a control applied at 0 g kg(−1). The results showed that soil organic carbon and light fraction C was greater by 29% to 21% and 38% to 21%, respectively, among the treatments compared to that of the control. Similarly, available N content was significantly greater in the PDLF treatment, and P content was also significantly greater in the PDSF treatment. In contrast, available K and extractable Mg contents were lower, as well as organic–inorganic degree complexes and organic–inorganic composites in the PDSF, MDLF, and PDLF treatments compared with those of the control. Further results showed that MDLF and PDLF Fulvic acids (FA) accelerated plant growth, while PDSF limited plant growth. Our study provides empirical evidence that addition of fulvic acid from MDLF and PDLF had more positive effects on soil properties and plant growth than fulvic acid from PDSF. This investigation suggests that application of fulvic acid in liquid form can improve nutrient availability and affect other important chemical, biological, and physical properties of soils.