Effects of biochar derived from the pyrolysis of either biosolids, manure or spent coffee grounds on the growth, physiology and quality attributes of field-grown lettuce plants

Anastasis Christou,Costas Michael,Vasileios Fotopoulos,Panos Papanastasiou,Marinos Stylianou,Andreas Ioannou,Stella Gedeon,Egli C. Georgiadou,Despo Fatta-Kassinos

doi:10.1016/j.eti.2021.102263

Abstract

The positive effects of biochar applied as soil conditioner for boosting soil fertility and thus plant growth are sufficiently documented, mostly through in-situ experimentation. This field study evaluated the effects of soil amendment (5% v/v) with distinct types of biochar (biosolids-derived biochar, BDB; cattle manure-derived biochar, MDB; spent coffee grounds-derived biochar, SCGDB) on the growth, physiology and quality attributes of lettuce ( Lactuca sativa L.) plants grown in sandy clay loam-textured soil, under temperate climatic conditions. Peat moss (PM) was also used, to serve as internal control due to its wide use. Plants grown on MDB-amended soil showed a significant increase of biomass production rate, evident through elevated mean fresh and dry weight values compared with all other treatments. Increased growth was also found in BDB treatment, though failed to reach significance. None of the treatments impacted the photosynthetic pigment content, however they did reduce the nitrates content in leaves. Leaves sampled from BDB and MDB treatments showed reduced soluble solids content (SSC) and titratable acidity (TA), and increased sucrose content. MDB-treated plants showed increased fructose content while BDB-treated plants showed increased total soluble sugar and total phenolics content. Moreover, plants grown in MDB- and BDB-amended soil showed increased total antioxidant capacity, despite maintaining ascorbic acid content in values similar to control. SCGDB and PM treatment did not affect any of the parameters tested. Overall, results showed that BDB and MDB applied as soil amendments may serve as means for enhancing the growth, and partially the nutritional value of lettuce plants. • Distinct biochars were used as soil amendments in lettuce grown in low fertile soil. • Lettuce plants in soil amended with manure-derived biochar had increased biomass. • Applied biochars did not impact the photosynthetic pigment content of leaves. • Manure- and biosolids-derived biochar enhanced the antioxidant capacity of plants. • Manure- and biosolids-derived biochar performed better compared with peat moss.

Highlights

Experience obtained from agricultural applications, along with data derived from experiments performed either in situ or in control environment over the last years has render biochar a promising material for boosting the agricultural productivity, tackling the challenges of securing food supply, in climate change and circular economy conditions (Maroušek et al, 2019)
This study aimed to explore the effects of the application of three different types of biochar applied in soil as conditioners on the growth, physiology and quality attributes of field-grown lettuce (Lactuca sativa L.) plants
Weight measurements confirmed macroscopic observations, as plants in MDB treatment had 60% higher mean weight per plant compare with control samples, and their weight was almost doubled compared with samples in SCGDB and Peat moss (PM) treatments (Table 1)

Summary

Introduction

Experience obtained from agricultural applications, along with data derived from experiments performed either in situ or in control environment (greenhouse and lab) over the last years has render biochar a promising material for boosting the agricultural productivity, tackling the challenges of securing food supply, in climate change and circular economy conditions (Maroušek et al, 2019). Surface area and poresize distribution, along with its neutralizing and cation exchange capacity (among other properties), enable biochar to be used as soil amendment for the improvement of degraded soils (saline, sandy soils), the enhancement of nutrient availability, the increase of water use efficiency, the remediation and/or protection from organic or inorganic pollutants, and the mitigation of greenhouse gasses (nitrous oxide, methane) emissions (Ali et al, 2017; Kamali et al, 2020). Biochar derived from the pyrolysis of pistachio shell managed to mitigate the Ni-mediated stress in lettuce and mungbean plants grown in pots by boosting their antioxidant defense system, while improving their nutritional quality (Turan, 2019, 2021a)

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