Abstract
Impacts of biochar application in combination with organic fertilizer, such as compost, are not fully understood. In this study, we tested the effects of biochar amendment, compost addition, and their combination on lettuce plants grown in a soil poor in nutrients; soil microbiological, chemical, and physical characteristics were analyzed, together with plant growth and physiology. An initial screening was also done to evaluate the effect of biochar and compost toxicity, using cress plants and earthworms. Results showed that compost amendment had clear and positive effects on plant growth and yield and on soil chemical characteristics. However, we demonstrated that also the biochar alone stimulated lettuce leaves number and total biomass, improving soil total nitrogen and phosphorus contents, as well as total carbon, and enhancing related microbial communities. Nevertheless, combining biochar and compost, no positive synergic and summative effects were observed. Our results thus demonstrate that in a soil poor in nutrients the biochar alone could be effectively used to enhance soil fertility and plant growth and biomass yield. However, we can speculate that the combination of compost and biochar may enhance and sustain soil biophysical and chemical characteristics and improve crop productivity over time.
Highlights
Soil fertility degradation, caused by erosion and depletion or imbalance of organic matter/nutrients, is affecting world agricultural productivity [1]
Biochar and compost used for the experiment were previously analyzed by Amendola et al [31] and Alfano et al [30], respectively
Stomatal conductance showed no significant differences between control and treated plants (Figure 5), while transpiration rate was slightly increased in plus compost and biochar (PSCB) and unchanged in plus compost (PSC) and plus biochar (PSB) compared to pH values from 6.9 (PS) (Figure 5)
Summary
Soil fertility degradation, caused by erosion and depletion or imbalance of organic matter/nutrients, is affecting world agricultural productivity [1]. Long-term overuse of mineral fertilizers may accelerate soil acidification, affecting both the soil biota and biogeochemical processes, posing an environmental risk and decreasing crop production [4]. Organic amendments, such as compost and biochar, could be useful tools to sustainably maintain or increase soil organic matter, preserving and improving soil fertility and crop yield. Biochar is a carbon-rich material obtained from thermochemical conversion (slow, intermediate, and fast pyrolysis or gasification) of biomass in an oxygen-limited environment It can be produced from a range of feedstock, including forest and agriculture residues, such as straw, nut shells, rice hulls, wood chips/pellets, tree bark, and switch grass [5]. Biochar has been described as a possible tool for soil fertility improvement, potential toxic element adsorption, and climate change mitigation [6,7,8]
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