Biochar and Sulphur Enriched Digestate: Utilization of Agriculture Associated Waste Products for Improved Soil Carbon and Nitrogen Content, Microbial Activity, and Plant Growth

Tereza Hammerschmiedt,Jiri Holatko,Petr Skarpa,Maja Radziemska,Pavel Ryant,Jan Vopravil,Antonin Kintl,Martin Brtnicky,Oldrich Latal,Marek Sudoma

doi:10.3390/agronomy11102041

Abstract

A number of agriculture residues may be used either directly or after suitable treatment as amendments to improve soil quality. Such materials include biochar made of agriculture residues, digestate or elemental sulphur obtained from biogas desulphurisation. The joint use of these materials via pre-incubation may be more advantageous than only mixing prior the application to soil. In this study, digestates were mixed with amendments and incubated for 6 weeks before application to soil in a short-term pot experiment with lettuce (Lactuca sativa). The following treatments were tested: control digestate, digestate + biochar, digestate + elemental sulphur, digestate + biochar + elemental sulphur. The biochar-enriched digestate significantly increased soil microbial biomass, soil C:N, fresh above ground biomass, fresh and dry root biomass. Elemental sulphur-enriched digestate caused highest arylsulfatase and phosphatase, increased urease, microbial biomass in soil and fresh root biomass. Amendment of digestate + biochar + sulphur led to the significantly highest total soil carbon, microbial biomass, β-glucosidase, urease, and increased C:N ratio, arylsulfatase in soil and root biomass. It mitigated the adverse effect of either biochar or elemental sulphur on soil respiration. Properties of digestates were apparently affected by pre-incubation. This approach in digestate fertilizer production may contribute to sustainable farming.

Highlights

The increasing use of renewable energy facilities, including biogas plants, leads to the growing interest in digestate—a by-product of anaerobic digestion usually used as an organic fertilizer
Digestate was amended by biochar and S, as it is shown in Table 1, the ratios were determined on the basis of required doses of components in field conditions: 50 m3·ha−1 of digestate, 20 t·ha−1 of biochar, 40 kg·ha−1 of sulphur
There could be seen, that biochar amendment led to increased dry matter and nutrient (Ca, P, Na, K, Mg, Mn, B) content in BC and BC + S treatments as compared to control and S treatment

Summary

Introduction

The increasing use of renewable energy facilities, including biogas plants, leads to the growing interest in digestate—a by-product of anaerobic digestion usually used as an organic fertilizer. The digestate is a suitable supplement to mineral fertilizers providing a readily available nitrogen (N), phosphorus (P) and potassium (K) source [1]. By providing macro- and micro-nutrients to the soil, it can effectively promote plant growth. Digestate positively affects soil microorganisms [3] which play vital roles in the soil ecosystem functioning. They are responsible for nutrient cycling, mineralization of organic matter, synthesis of new compounds (immobilization), humus formation, maintenance and stability of soil substructure and influence soil fertility and crop yields. Microorganisms are sensitive to soil nutrient availability as well, enabling their use as indicators of ecosystem changes [4]. The postulate is that the disrupted microbial enzymatic activity may indicate potential harmful impacts of anthropogenic stress [5]

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Conclusion