Compared impact of compost and digestate on priming effect and hydrophobicity of soils depending on textural composition

Abstract

Summary Digestates and compost are used as valuable fertilizers in agriculture because of their benefits for plant nutrition and carbon sequestration potential. These amendments are also suspected to interfere negatively with the soil. To compare their relevance for priming effect and hydrophobicity of soils, two amounts of digestate or compost, respectively, were mixed with a homogenized cambic Luvisol and a Podzol. The basal respiration rate (BAS), the repellency index (RI) and organic carbon content (Corg) of pre-dried mixtures were investigated. The podsolic mixture showed quantitative reduction of Corg and increased BAS (this effect was not statistically significant) due to priming effect through microbial stimulation. As a result of enhanced organic substance (OS) protection in the cambic Luvisol mixture, constant amounts of Corg and declined BAS could be detected. The wettability was reduced in both soils: either directly by the supply of amphiphilic components or indirectly by increased incorporation of microbial exudates. This reduction was not statistically significant. Higher contents of available organic compounds in digestates and higher amounts of hydrophobic humic acids in the compost could be assumed to be decisive for generation of hydrophobicity. Also the soil texture controlled the microbial decomposition by higher incorporation of OS in finer pores and contributed to the protection against microbial decay.

Effect of pre-treatment processes of organic residues on soil aggregates

“…During incubation, soils treated with digestate and the fermented product formed a hydrophobic layer covering the soil surface. This process has been reported previously for digestate (Voelkner et al, 2019), and it has been associated with high fatty acid content (Bayer and Schaumann, 2007). The production of water-repellent substances can be induced by the addition of nutrients (Hallett and Young, 1999) that exacerbate the exudates production by soil microorganisms (Navarro and Navarro, 2003).…”

Analysis of Spatiotemporal Variability of Corn Yields Using Empirical Orthogonal Functions

“…Dependencies of EC2 and EC3 on time may reflect differences in nutrient management, surface slope, and field geometry. Coarse-textured soils of the study site could develop some degree of hydrophobicity and water repellency after a multiyear manure application [28][29][30]. No data were available to distinguish the effects of the aforementioned water availability factors.…”