Suitability of Volcanic Ash, Rice Husk Ash, Green Compost and Biochar as Amendments for a Mediterranean Alkaline Soil

16 páginas.- 2 figuras.- 4 tablas.- 59 referencias.- Supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy13041097/s1

Today’s agriculture has the challenge of ensuring food supply for a growing population while human activity has already deteriorated about 40% of the world’s soils, reducing productive capacity and increasing reliance on mineral fertilizers. In this context, valorizing and recycling mineral and agricultural waste for use as substrates or soil supplements enhance a sustainable economy, as well as the development of activities focused on finishing the soil nutrients’ cycle. Looking for an effective solution to the massive waste generation and to enhance the agronomic qualities of soils, this study investigates the agronomic impact of contrasting inorganic and organic materials such as green compost (GC), wood biochar (WB), rice husk ash (RA), and volcanic ash (VA) as amendments to an alkaline Luvisol under controlled conditions. In this sense, barley seeds were planted and grown in a greenhouse under controlled conditions for 60 days on a soil amended with the aforementioned materials. The amendments demonstrated appropriate attributes for improving soil agronomic properties, enhancing the soil’s nutritional content with no effect on barley germination. The WB showed high aromaticity and abundance of refractory organic C. Both ash-rich amendments showed high P and K contents, which are important elements for plant development. The GC has high water retention capacity and an adequate C and N balance. Although the application of the amendments had no effect on barley yields, the plants from the ash-amended pots showed an increase of Photosystem II efficiency, indicative of a better physiological status. In terms of toxicological safety, the abundance of trace elements in soils and plants was investigated. All soils met the maximum allowable limits for these persistent pollutants. Nevertheless, longer-term tests on plants are required to determine the risk of Pb accumulation, particularly in soils amended with GC and compost-ash mixtures. The simultaneous combination of organic and inorganic amendments showed adequate agronomic attributes. WB analysis revealed its great recalcitrance and carbon sequestration potential. Sustainable agricultureSoil amendmentAgronomic residuesFood safetyVolcanic ash

This research was performed in the framework of the European Joint Program for SOIL “Towards climate-smart sustainable management of agricultural soils” (EJP SOIL) funded by the European Union Horizon 2020 research and innovation programme (Grant Agreement N° 862695). Sergio Prats is thanked for providing the Luvisol and Boris Durzevik from the University of Rijeka (Croatia) is thanked for providing the biochar. D. Monis, A.M. Carmona and E. Muñoz are acknowledged for technical assistance. A.Z.M. thanks her Ramón y Cajal contract, grant RYC2019-026885-I funded by MCIN/AEI/ 10.13039/501100011033. We are grateful for the work of the three reviewers who improved the original manuscript.

Peer reviewed