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Description
INTRODUCTION
Recovery of environments altered by human activities can be hampered by the lack of stockpiled soils, which are required for restoration work and planting. However, large amounts of by-products are produced during the treatment of solid urban waste and construction and demolition waste. Many of these secondary products can be recycled to create Technosols. Soil health management is one of the most effective methods for the sustainable maintenance of productive soils. Typical soil fertility analyses often do not include physical or biological soil indicators that could provide insights into soil health, help explain problems related to crop growth and reduce the need to use synthetic fertilisers and plant protection products (Oliveira et al., 2020). The aim of this research was to evaluate three soil health indicators in six types of Technosols sown with diverse Atlantic grassland species.
MATERIALS AND METHODS
Six different Technosols were created by mixing Recysoil (made with sewage sludge compost and fine aggregates obtained from recycling construction waste) (70%) and stockpiled soil (TA) (28%) with 2% by volume of different organic amendments. The following six Technosols were created: T1=Recysoil+TA; T2=Recysoil+TA+Biochar; T3= Recysoil+TA+Sludge hydrochar; T4= Recysoil+TA+Hydrochar organic fraction; T5= Recysoil+TA+Hydrochar paper-cardboard; and T6= Recysoil+TA+Worm humus.
The experimental design was completely randomised, with 6 treatments (Technosols) replicated 3 times. The Technosol plots (3 m x 4 m) were established between 15/3/2023 and 4/4/2023. The plots were then left for a period of 1 month to allow stabilisation of the organic material.
On 4/5/2023 the plots were sown with diverse (37 species) Atlantic grassland seeds (6 g/m2).
Soil sampling (upper 20 cm layer) was carried out at three different times (on 5/5/2023, 29/9/2023 and 21/12/2023) in each plot.
The following soil health indicators were analysed, in two replicates of the soils sampled at the three different times: soil microbial respiration (CO2-C, ppm), potentially mineralizable organic nitrogen (SLAN, ppm) and stability of soil aggregates to water (VAST, %) (Solvita Kit, Woods End Laboratories Inc., Mt. Vernon, ME, USA).
An analysis of the variance (ANOVA) was performed to check the effects of Technosols and sampling time.
RESULTS
The Technosols were characterized by neutral pH and high contents of organic matter and main nutrients.
There were no statistically significant differences between the Technosols in regard to the three soil health indicators assessed but there were differences between sampling dates (Figure 1).
Figure 1. Mean values of CO2-C, SLAN and VAST at three sampling times (± SE). Bars with different letters (a>b) indicate significant differences at p < 0.05 (Tukey's test).
The values obtained for microbial respiration were intermediate decreasing between first and third sampling time, potentially mineralizable nitrogen was intermediate-high increasing between first and third sampling (Brinton 2019a, 2019b) and aggregate stability to water was low although it increased between the first and the third sampling (Brinton, 2016).
DISCUSSION
The lack of significant differences between the Technosols may be due to the short time since establishment, so that the microorganisms had not yet been able to mineralize the organic matter present in the Technosols and form stable aggregates. Three soil health indicators will continue to be monitored every 2-3 months, until the end of the project (at the end of June 2025), to enable calculation of an overall health and fertility index for each Technosol.
ACKNOWLEDGEMENTS
We are grateful for the funding obtained within the "Gijón Ecoresiliente" project financed by the Biodiversity Foundation of the Ministry for Ecological Transition and the Demographic Challenge (MITECO), within the framework of the Recovery, Transformation and Resilience Plan (PRTR), which in turn is financed by the European Union - NextGenerationEU.
REFERENCES
-Brinton, W., 2016. Volumetric Aggregate Stability Test (VAST). Official Solvita® instructions. Version 2016:2.0. Woods End Laboratories Inc., Mt. Vernon, ME.
-Brinton, W., 2019a. Soil CO2 Respiration. Official Solvita Instructions (CO2-Burst), SOP 2019 Rev. 1 (DCR Models 701.2+). Woods End Laboratories Inc., Mt. Vernon, ME.
-Brinton, W., 2019b. SLAN-Solvita Labile Amino Nitrogen. Official Solvita® instructions. Version 2019/N. Woods End Laboratories Inc., Mt. Vernon, ME.
-Oliveira, J.A., Epelde, L., Afif, E., Palencia, P., Lastra, J.J., 2020. Biological indicators of soil health in meadows and fodder crops. Book of abstracts XVI European Society for Agronomy Congress. Smart Agriculture for great human challenges. Sevilla 1-3 September 2020, pp. 150-151.
| Keywords | Circular economy; Microbial respiration; Organic nitrogen; Gijón Ecoresiliente; Soil amendments |
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