Soil Health, Crop Productivity, Microbial Transport, and Mine Spoil Response to Biochars

Abstract

Biochars vary widely in pH, surface area, nutrient concentration, porosity, and metal binding capacity due to the assortment of feedstock materials and thermal conversion conditions under which it is formed. The wide variety of chemical and physical characteristics have resulted in biochar being used as an amendment to rebuild soil health, improve crop yields, increase soil water storage, and restore soils/spoils impacted by mining. Meta-analysis of the biochar literature has shown mixed results when using biochar as a soil amendment to improve crop productivity. For example, in one meta-analysis, biochar increased crop yield by approximately 10 %, while in another, approximately 50 % of the studies reported minimal to no crop yield increases. In spite of the mixed crop yield reports, biochars have properties that can improve soil health characteristics, by increasing carbon (C) sequestration and nutrient and water retention. Biochars also have the ability to bind enteric microbes and enhance metal binding in soils impacted by mining. In this review, we present examples of both effective and ineffective uses of biochar to improve soil health for agricultural functions and reclamation of degraded mine spoils. Biochars are expensive to manufacture and cannot be purged from soil after application, so for efficient use, they should be targeted for specific uses in agricultural and environmental sectors. Thus, we introduce the designer biochar concept as an alternate paradigm stating that biochars should be designed with properties that are tailored to specific soil deficiencies or problems. We then demonstrate how careful selection of biochars can increase their effectiveness as a soil amendment.

Surface oxygenation of biochar through ozonization for dramatically enhancing cation exchange capacity

“…As a soil amendment, the use of biochar with high CEC has been shown to improve soil properties such as the ability to retain soil nutrients, which is an important attribute for agronomic purposes in that it reduces the nutrient leaching. However, it must be understood that not all biochars behave in a similar manner when used as a soil amendment, as it has been shown that while some biochars will increase crop yields, other biochars either have no effect, or a negative effect on crop yields (Jeffery et al 2011;Spokas et al 2012;Novak et al 2016). The conventional biochar material in the current market typically has quite low cation exchange capacity (CEC), a key property that is central to help retain soil nutrients and water.…”

Effect of biochar application on the content of nutrients (Ca, Fe, K, Mg, Na, P) and amino acids in subsequently growing spinach and mustard

“…Nutrient composition of BC depends on the feedstock material and conditions of pyrolysis (Mukherjee and Zimmerman 2013). However, many studies described a positive effect of BC application to soil, whereas the responses on crop yields are not consistent (Novak et al 2016). According to Břendová et al (2015) BC ability to increase pH value is probably one of the crucial factors of reduction of element leachability.…”

Negative emissions—Part 3: Innovation and upscaling

“…Recurring R&D topics in prominent articles include: the amount of soil carbon retained by agricultural practices (Piccoli et al 2016), the corresponding amount lost (Sanderman et al 2017), and the impacts of tillage (Sohi et al 2010). Effects on carbon content and the overall health of soil from application of biochar is a large focus area (Fang et al 2016, Novak et al 2016, Pandian et al 2016, including for example N content (Prommer et al 2014). Temperature for pyrolysis is an important topic among biochar articles (Sohi et al 2010).…”